Emerging roles of α/β hydrolase domain (ABHD) proteins in S-palmitoylation modification: molecular mechanisms, structural features, and pathological implications

Abstract

S-palmitoylation, a reversible post-translational modification, regulates critical biological processes and represents a promising therapeutic target for diverse human diseases. Over the past decade, human α/β hydrolase domain (ABHD) proteins have emerged as key regulators of the dynamic S-palmitoylation/depalmitoylation cycle, yet a systematic overview of their roles in this modification remains lacking. This review provides a comprehensive summary of the functions of emerging ABHD proteins—including ABHD17A/B/C, ABHD16A, ABHD10, ABHD7, and ABHD8—in the dynamics of S-palmitoylation and depalmitoylation cycle, along with their molecular mechanisms, structural features, and substrate specificities. Associations between dysregulated ABHD protein-mediated S-palmitoylation and various diseases, including cancers, neurological disorders, degenerative diseases, viral infectious diseases, metabolic diseases, and reproductive disorders are discussed. Predictive criteria for uncharacterized ABHD proteins and prospective targeted therapeutic strategies are also proposed. This review provides mechanistic insights into emerging ABHD proteins in S-palmitoylation/depalmitoylation, and lays a foundation for developing novel diagnostic markers and precision therapies for S-palmitoylation-related diseases.

Graphical abstract

Introduction

Post-translational modifications (PTMs) orchestrate a wide spectrum of physiological and pathological signaling pathways through the precise regulation of protein activity, membrane trafficking, and signal transduction [1, 2]. Among the diverse types of PTMs, protein S-palmitoylation (also known as S-acylation) is a lipid-based modification, in which a 16-carbon palmitoyl group is covalently attached to cysteine residues of proteins (Fig. 1). Notably, it is the only reversible type among three canonical palmitoylation types (O-, N-, and S-palmitoylation). Over the past 5 years, a growing number of in-depth studies have identified the key regulatory molecules involved in S-palmitoylation, and further elucidated the pleiotropic roles of the dynamic S-palmitoylation cycle in the progression of various human diseases [3–6], making S-palmitoylation regulators promising therapeutic targets for the intervention of diverse pathological conditions.

Fig. 1.

A schematic representation of the S-palmitoylation–depalmitoylation cycle and currently characterized ABHDs that modulate this cycle. The structural model of human ABHD protein was predicted by AlphaFold. ABHD10 (AF-Q9NUJ1-F1), ABHD16A (AF-O95870-F1), ABHD7 (AF-Q8IUS5-F1), ABHD17A (AF-Q96GS6-F1), ABHD17B (AF-Q5VST6-F1), and ABHD17C (AF-Q6PCB6-F1)

S-palmitoylation is catalyzed by palmitoyl transferases (PATs), which consist of 23 members in mammals and all harbor the conserved Asp-His-His-Cys (DHHC) domain [7]. Conversely, depalmitoylation is predominantly mediated by members of the serine hydrolase superfamily. Among these, palmitoyl-protein thioesterase 1 (PPT1) and acyl-protein thioesterases (APT1 and APT2) represent the earliest characterized depalmitoylating enzymes, which govern substrate depalmitoylation within the lysosome, mitochondria, and Golgi apparatus, respectively [4, 8]. APTs were initially considered the core depalmitoylating enzymes. However, subsequent studies have demonstrated that numerous recently identified S-palmitoylated substrates are not regulated by APTs. Moreover, the classical depalmitoylation inhibitor Palmostatin B also targets additional serine hydrolases [8, 9], indicating the existence of uncharacterized depalmitoylase members.

Human α/β-hydrolase domain (ABHD) proteins comprise twenty-three members (Fig. 2), which exert serine hydrolase or acyltransferase activities through their conserved catalytic triad, and selectively metabolize diverse lipid substrates [10]. ABHD proteins maintain cellular lipid homeostasis and membrane structural integrity by modulating the synthesis and degradation of lipids such as medium-chain phospholipids, lysophosphatidylserine, and N-acyl phosphatidylethanolamine. Meanwhile, by fine-tuning the intracellular levels of signaling lipids, such as 2-arachidonoylglycerol, phosphatidic acid, and lysophospholipids, ABHD proteins regulate multiple pivotal pathways involved in endocannabinoid signaling, immune inflammation, insulin transduction, anoikis, and tumor metastasis. Dysregulation of ABHD proteins is closely linked to lipid metabolism disorders, neurodegeneration, malignancies, and rare hereditary syndromes [11]. Besides their well-established roles in lipid metabolism, research over the past decade has progressively uncovered the molecular mechanisms by which ABHD proteins orchestrate multiple signaling pathways and disease pathogenesis through modulating the S-palmitoylation status of protein substrates.

Fig. 2.

Evolutionary relationships and domain characteristics of ABHD proteins. a The amino acid sequences of 23 ABHD proteins were aligned and the phylogenetic tree was constructed via the maximum likelihood method. The numerical values along the branches denote evolutionary distances. The bold numbers represent bootstrap values. b The evolutionary relationships and domain characteristics of depalmitoylases APT1, APT2, and PPT1

ABHD17A/B/C were first identified as capable of regulating depalmitoylation reactions in a screen for serine hydrolases targeted by Palmostatin B [9]. In the following decade, ABHD10, ABHD16A, ABHD7, and ABHD8 were sequentially reported to regulate multiple biological processes, including mitochondrial oxidative stress, innate immunity, myoblast differentiation, and inflammation, by modulating substrate palmitoyl binding in S-palmitoylation and cleavage in depalmitoylation (Fig. 1) [12–15]. Owing to the high conservation of sequences and catalytic sites among ABHD proteins [10, 11, 16], the sequence and structural features of identified ABHD proteins governing S-palmitoylation/depalmitoylation can be utilized to predict other potential ABHD proteins that modulate this post-translational modification.

Over the past decade, several groups have reviewed the regulatory roles of S-palmitoylation in disease pathogenesis [4, 6], summarized the biological functions of palmitoyltransferases and depalmitoylases [7, 8], and discussed ABHD proteins in lipid metabolism [10, 11]. However, the fine-tuning roles of emerging ABHD proteins in S-palmitoylation have not yet been systematically elucidated. The current review comprehensively summarizes the biological functions of emerging ABHD proteins involved in S-palmitoylation/depalmitoylation and their correlations with disease progression, analyzes their sequence and structural commonalities to further explore the potential of other members of ABHD proteins in regulating the dynamic S-palmitoylation/depalmitoylation reaction, and finally proposes therapeutic strategies for diseases targeting the ABHD-mediated S-palmitoylation process.

Emerging functions of ABHD proteins in S-palmitoylation/depalmitoylation

This section elaborates on the regulatory roles of characterized ABHD proteins in the dynamic S-palmitoylation/depalmitoylation cycle. For each member, the coverage moves from enzymatic identification, substrate regulation, and disease pathology as well as targeted therapies, linking functional characterization with translational implications.

Identification of ABHD17A/B/C as depalmitoylases and their functional diversification in mammalian physiology

ABHD17A, ABHD17B, and ABHD17C are different isoforms of the ABHD17 subfamily. While research on the direct regulation of lipid metabolism by ABHD17A/B/C remains very limited, these proteins have been extensively documented to mediate a broad range of biological processes through their depalmitoylase activity, including tumorigenesis [9, 17–23], synaptic function, and neuronal polarization [24–26], GPCR signaling [27], inflammasome activation [28], as well as the progression of inflammatory bowel disease and degenerative disorders [29, 30]. To date, ABHD17A/B/C are the most thoroughly investigated ABHD proteins in the context of depalmitoylation.

Enzymatic identification

In 2015, Lin et al. conducted a screening assay using two highly S-palmitoylated proteins—oncogenic N-Ras and postsynaptic density protein 95 (PSD-95)—as targets [9], and identified ABHD17A/B/C as candidate depalmitoylases. Overexpression of ABHD17A, or ABHD17B, or ABHD17C markedly reduced the S-palmitoylation of PSD-95 and N-Ras, confirming that ABHD17 proteins constitute a novel group of depalmitoylases. The functions of ABHD17A/B/C are redundant, and knocking down ABHD17A alone has a modest effect on N-Ras S-palmitoylation, whereas simultaneous knockdown of all three isoforms significantly suppresses this process. Collectively, Lin et al.’s study was the first to delineate the role of ABHD17 isoforms in mediating depalmitoylation, thereby initiating the study of key regulatory roles of ABHD proteins in S-palmitoylation.

Substrate spectrum and molecular mechanisms

Substrates regulating tumor progression across multiple malignancies

Subsequent investigations have progressively unraveled the multifaceted roles of ABHD17 proteins in the progression of hepatocellular carcinoma (HCC), colorectal cancer (CRC), nonsmall cell lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDAC) (Fig. 3). For instance, ABHD17A functions as a depalmitoylase that counteracts zDHHC3-mediated S-palmitoylation of SREBP cleavage-activating protein (SCAP), thereby promoting SCAP degradation and decreasing cholesterol biosynthesis, which reduces cholesterol accumulation in the tumor microenvironment and preserves CD4⁺ T cell cytotoxicity, limiting HCC immune escape [17]. Additionally, during the progression of CRC, ABHD17A catalyzes Ras superfamily member Rap2b depalmitoylation, relocating Rap2b from the plasma membrane to the cytosol. This blocks the activation of the AKT/GSK3β signaling pathway, thereby suppressing the metastasis of colorectal cancer cells [18]. In contrast to the tumor-suppressive function of ABHD17A, ABHD17B plays multifaceted roles during the oncogenesis of diverse cancer types. Hexokinase 1 (HK1) secreted by hepatic stellate cells (HSCs) via large extracellular vesicles (lEVs) enhances glucose uptake and glycolysis in HCC cells. ABHD17B mediates the depalmitoylation of HK1, which blocks the efficient secretion of HK1 and thereby suppresses HCC proliferation [19]. However, during the progression of NSCLC, ABHD17B depalmitoylates the neutral amino acid transporter ASCT2, thereby suppressing the lysosomal degradation of ASCT2. This process anchors ASCT2 stably to the plasma membrane, boosting glutamine uptake and glutamate production in NSCLC cells to sustain the rapid proliferation of tumor cells [20]. Current studies on ABHD17C in cancer progression have predominantly focused on its proproliferative effects in cancer cells. During PDAC progression, KRAS mutation enhances ABHD17C-Arachidonate 15-lipoxygenase (ALOX15B) binding, resulting in decreased S-palmitoylation and degradation of ALOX15B, which diminishes the ferroptosis sensitivity of PDAC cells, enabling tumor cells to evade ferroptosis [21]. Wang et al. further identified the pro-tumorigenic role of ABHD17C during HCC progression. Specifically, ABHD17C mediates the depalmitoylation of N-Ras, which induces N-Ras activation and thereby triggers the PI3K/AKT signal cascade to promote HCC cell proliferation [22].

Fig. 3.

Molecular mechanism underlying ABHD17 proteins-mediated regulation of cancers and neurological disorders via depalmitoylation. During tumor progression, ABHD17A suppresses immune escape in HCC and metastasis in CRC via selective depalmitoylation of SCAP and Rap2b, respectively. By contrast, ABHD17B plays tumor-suppressive roles in HCC but tumor-promoting roles in NSCLC. ABHD17C promotes progression of PDAC and HCC by depalmitoylating ALOX15B and N‑Ras, respectively. In addition, ABHD17A/B/C mediates the depalmitoylation of MAP6 and PSD-95, thereby orchestrating the progression of neuronal polarization and synaptic function, respectively

Substrates governing synaptic function and neuronal development

The depalmitoylating enzymes of ABHD17 isoforms also play indispensable regulatory roles in synaptic function and neuronal polarization processes (Fig. 3). Yokoi et al. found that overexpression of ABHD17B reduced synaptic aggregation of PSD-95, leading to decreased spine density and abnormal dendritic spine morphology [24]. Treating cells with Palmostatin B, an inhibitor of ABHD17A/B/C, could alleviate the depalmitoylation of PSD-95, increase the stability of PSD-95 at synapses [25]. Besides, Tortosa et al. revealed that ABHD17B regulates axon maturation by controlling the S-palmitoylation of microtubule-associated protein 6 (MAP6), mediating its transport between secretory vesicles and axonal microtubules [26].

Substrate mediating inflammasome activation and pyroptosis

NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) belongs to the pattern recognition receptor family, which initiates inflammasome assembly and induces pyroptosis [31, 32]. ABHD17A serves as the primary depalmitoylase of NLRP3. It binds to the LRR domain of NLRP3 and removes S-palmitoylation at Cys837 and Cys838, thus negatively regulating NLRP3 inflammasome activation. The autoinflammatory disease-associated NLRP3 R920Q mutation disrupts this interaction, resulting in NLRP3 hyper-palmitoylation and aberrant inflammasome activation [28].

Substrate involved in innate immune signal transduction

As an intracellular innate immune receptor, nucleotide-binding oligomerization domain-containing protein 2 (NOD2) requires S-palmitoylation to localize to the plasma membrane and endosomes, which enables it to recognize bacterial peptidoglycan and activate the NF-κB and MAPK signaling pathways, thereby inducing the release of antimicrobial peptides and pro-inflammatory cytokines. Dixon et al. demonstrated that ABHD17 isoforms (A, B, and C) function as specific depalmitoylating thioesterases for NOD2. Pharmacological inhibition or RNA interference-mediated knockdown of ABHD17 significantly elevates the S-palmitoylation levels, membrane targeting capacity and signaling function of NOD2 [29].

Substrate regulating cartilage homeostasis and chondrogenic differentiation

As a pivotal RNA N⁶-methyladenosine (m⁶A) methyltransferase, methyltransferase-like 3 (METTL3) acts as an essential regulator of cartilage development and joint homeostasis. Of note, S-palmitoylation serves as the core post-translational modification that governs METTL3 activity and stability. ABHD17A functions as the specific depalmitoylase for METTL3, which catalyzes the removal of the S-palmitoylation modification at Cys376 of METTL3. ABHD17A-mediated METTL3 depalmitoylation disrupts the formation of cytoplasmic phase-separated condensates of METTL3, reducing METTL3 protein stability, ultimately triggering defective chondrogenic differentiation, diminished cartilage matrix synthesis [30].

Indirectly modulated substrate in innate antiviral immunity

Interestingly, ABHD17A has also been shown to upregulate the S-palmitoylation modification of proteins through other ABHD protein (Fig. 4) [33]. Shi et al. unexpectedly found that overexpression of ABHD17A enhanced the S-palmitoylation and antiviral ability of interferon-inducible transmembrane protein 1 (IFITM1). Since ABHD17A lacks the conserved DHHC motif, Shi et al. hypothesized that it indirectly regulates IFITM1 S-palmitoylation. Screening of zDHHC and depalmitoylation enzymes revealed that ABHD17A overexpression significantly reduced ABHD16A transcription, impairing ABHD16A-mediated IFITM1 depalmitoylation and thereby increasing IFITM1 S-palmitoylation [33]. This study reveals for the first time the role of crosstalk among ABHD proteins in the dynamic regulation of protein S-palmitoylation.

Fig. 4.

ABHD16A, ABHD7, and ABHD10 regulate distinct biological processes via depalmitoylation. ABHD16A regulates innate immune function and antiviral activity by depalmitoylating IFITM proteins, which is modulated by RNF5-mediated ubiquitination and proteasomal degradation. ABHD7 functions as the depalmitoylase of Lamin A, but its binding affinity to Lamin A is weakened under lactate-induced metabolic stress. As a mitochondrial depalmitoylase, ABHD10 has substrates including PRDX5, SPATA19, GK2, and PDHX, which are involved in regulating mitochondrial redox homeostasis, fibrosis in alcoholic liver disease, and sperm mitochondrial sheath formation

Disease involvement and therapeutic strategies

The S-palmitoylation status of the ABHD17A/B/C substrates is closely implicated in the pathogenesis of diverse human diseases. Accordingly, targeting ABHD17 isoforms for diagnostic biomarker identification and drug discovery has emerged as a promising novel avenue for disease treatment and prevention.

Cancers

Wei et al. recently performed a single-cell RNA sequencing experiment and revealed that ABHD17C is specifically upregulated in the aggressive epithelial subset (subtype C4) of lung adenocarcinoma (LUAD). Its expression level correlates with clinical stage progression and immune evasion, indicating that ABHD17C serves as a robust biomarker for identifying LUAD patients at high metastatic risk [34]. Conversely, in clear cell renal cell carcinoma (ccRCC), downregulation of ABHD17C is significantly associated with tumorigenesis, and its expression constitutes a reliable diagnostic index for discriminating tumor tissues from normal counterparts [35]. Collectively, ABHD17C may serve as a new diagnostic biomarker for the screening of multiple cancers.

Tumor cells commonly lose contact inhibition, which constitutes a core molecular phenotype of unlimited tumor cell proliferation. The Hippo signaling pathway acts as the central cascade that modulates contact-dependent proliferation inhibition in cells [36]. TEA domain family members (TEADs) within this pathway drive cell proliferation, and the stability and biological activity of TEADs are precisely controlled by their S-palmitoylation modification [37]. Kim et al. have verified that ABHD17A together with APT2 regulate the S-palmitoylation level of TEADs. Under high cell density conditions, ABHD17A and APT2 expression are significantly upregulated, which promotes TEADs depalmitoylation, in turn attenuating TEADs activity and participating in the establishment of contact inhibition [38]. Accordingly, induction or potentiation of ABHD17A expression and function in tumor cells to mimic the regulatory mechanism under high-density microenvironments can effectively suppress TEADs activity, thereby restoring contact inhibition and arresting tumor cell proliferation. Future studies may focus on screening small-molecule activators of ABHD17A or upregulating its expression in tumor cells through genetic regulation approaches, aiming to inhibit TEADs activity and block tumor progression.

The enzymatic activity of ABHD17 isoforms is amenable to specific inhibition by small-molecule agents. ABD957 partially abrogates ABHD17-mediated N-Ras depalmitoylation, retains N-Ras at the plasma membrane, and thereby attenuates oncogenic activity [23]. In addition to direct enzymatic inhibition, targeting upstream regulators provides an alternative therapeutic strategy. For example, activation of transcription factor Nur77 to upregulate ABHD17B expression effectively suppresses HCC progression [19]. Furthermore, natural products targeting ABHD17 can also be utilized for cancer therapy. In pancreatic cancer progression, the methyl protodioscin disrupts the interaction between ABHD17C and ALOX15B, restoring ALOX15B membrane localization and S-palmitoylation status. This reinstates ferroptosis induction and effectively impedes the progression of pancreatic cancer [21].

Neurological diseases

Alzheimer’s disease (AD) is pathologically characterized by synaptic loss and neuronal damage, ultimately leading to comprehensive cognitive decline [39]. Synaptic PSD-95 is significantly downregulated in AD patients, and this reduction acts as a causal mediator of Aβ-induced synaptic damage rather than a passive correlate. Mechanistically, PSD-95 binds NMDA receptors and constrains conformational changes of their C-terminal domain, blocking Aβ-triggered metabotropic NMDA receptor signaling, protein phosphatase 1 activation, and synaptic depression. This protection is independent of the AMPA receptor subunit GluA1 (which mediates PSD-95-dependent synaptic potentiation), excluding the confound that PSD-95 rescues synapses merely by compensating for Aβ-induced depression via enhanced transmission, and confirming its direct interference with Aβ’s pathogenic cascade. Dore et al. reported that Palmostatin B, an inhibitor targeting ABHD17A/B/C, sustains S-palmitoylation of PSD-95 at Cys3 and Cys5 residues and retains its postsynaptic membrane localization. Such effects rescue Aβ-triggered synaptic depression and dendritic spine loss, thereby mitigating Aβ-mediated synaptic toxicity [25]. Collectively, these findings indicate that selective suppression of ABHD17 depalmitoylase activity to boost synaptic PSD-95 stability represents an effective strategy for ameliorating AD-associated pathological manifestations.

Schizophrenia is a severe chronic mental disorder characterized by significant abnormalities in thinking, emotion, and behavior [40]. During neuronal polarization, MAP6 is responsible for stabilizing axonal microtubules, regulating organelle trafficking, and promoting axon maturation. MAP6 knockout mice exhibit schizophrenia-like behaviors, including short-term memory deficits. Dysregulated S-palmitoylation cycles mediated by ABHD17A/B/C result in failed targeting of MAP6 to axonal microtubules or defective detachment from vesicles, which further causes abnormal axon maturation. The loss of functional MAP6 ultimately gives rise to schizophrenia-like behaviors in mice [26]. However, for schizophrenia, the expression of ABHD17 isoforms needs to be precisely regulated—both excessive and insufficient expression will lead to abnormal S-palmitoylation of MAP6 [26]. Therefore, for the development of ABHD17-targeted drugs for Schizophrenia, key priorities include identifying which specific ABHD17 isoform exerts a dominant effect in the MAP6 localization, while accounting for potential side effects such as MAP6 abnormalities resulting from excessive ABHD17 inhibition.

Autoinflammatory diseases

Autoinflammatory diseases (AIDs) represent a group of rare hereditary disorders characterized by systemic multisystemic inflammatory abnormalities [41]. The pathogenesis of AIDs is directly associated with abnormal S-palmitoylation of NLRP3 and excessive activation of downstream inflammasomes. AIDs-associated NLRP3 mutations induce S-palmitoylation imbalance: these mutations impair the binding of ABHD17A to NLRP3, preventing effective depalmitoylation of NLRP3 [28]. Zheng et al.’s experimental results on in vitro-cultured THP-1 macrophages demonstrated that ABHD17A knockout significantly enhances inflammasome activation (including caspase-1 activation and IL-1β/IL-18 release), while ABHD17A overexpression reverses this effect, confirming its core role in the negative regulation of inflammation [28]. These findings suggest that we can directly enhance the depalmitoylase activity of ABHD17A using agonists to efficiently remove the excess palmitoyl groups from NLRP3 and restore its homeostasis. Subsequent work may focus on identifying small-molecule compounds that boost ABHD17A enzymatic activity through high-throughput screening.

Inflammatory bowel disease

Crohn’s disease is an inflammatory bowel disease that can involve the entire gastrointestinal tract, with core clinical manifestations including abdominal pain, diarrhea, weight loss and fatigue [42]. NOD2 gene mutations represent a major genetic contributor to Crohn’s disease. A subset of Crohn’s disease-linked NOD2 variants exhibit impaired S-palmitoylation and subsequent receptor inactivation, making targeted ABHD17 inhibition a rational therapeutic strategy to correct this pathogenic defect. Dixon et al. showed that targeting ABHD17 isoforms using the small-molecule inhibitors ABD957 and Palmostatin B or siRNA-mediated silencing significantly elevated the S-palmitoylation levels and plasma membrane localization efficiency of wild-type NOD2, enhanced the activation of its downstream signaling pathways and cytokine secretion, and restored the membrane targeting and ligand-induced signaling function of Crohn’s disease-associated hypo-palmitoylated NOD2 variants including L248R, R702W, and A755V [29]. These findings indicate that ABHD17 targeting offers a novel approach for precision therapy and disease prevention in patients with Crohn’s disease. However, this intervention has only been validated in cellular models to date, and its in vivo efficacy, off-target safety profile, and clinical translational potential remain to be further comprehensively investigated.

Degenerative disease

Osteoarthritis is a degenerative joint disorder characterized by progressive articular cartilage degeneration, cartilage matrix degradation, and aberrant subchondral bone remodeling [43]. Notably, the reversible S-palmitoylation of METTL3 at cysteine 376 is markedly suppressed under osteoarthritic conditions, which drives chaperone-mediated autophagic degradation of METTL3 and impairs its cytoplasmic translational regulatory function, representing a core pathological mechanism underlying cartilage degeneration. Through artificial intelligence (AI)-guided screening targeting the METTL3 depalmitoylation pathway, Qin et al. identified the small-molecule compound isoborneol. Isoborneol binds to the depalmitoylase ABHD17A to disrupt its interaction with METTL3, thereby specifically restoring the S-palmitoylation of METTL3 under osteoarthritis pathological conditions. In addition, both in vitro and in vivo experiments validate that isoborneol significantly downregulates the expression of cartilage-degrading enzymes and pro-inflammatory cytokines, while upregulating core cartilage matrix proteins including type II collagen and aggrecan. Collectively, these findings demonstrate that isoborneol—by targeting the ABHD17A-METTL3 interaction—serves as a pivotal regulatory agent for osteoarthritis treatment [30]. As a natural small molecule, isoborneol possesses superior cell permeability and convenient administration properties, providing a novel epitranscriptomic regulatory therapeutic strategy for osteoarthritis and shedding new light on drug development for degenerative skeletal disorders.

Regulatory mechanisms of ABHD16A in antiviral immunity via IFITM1 depalmitoylation

ABHD16A (also termed BAT5) has been demonstrated to preferentially hydrolyze medium- and long-chain unsaturated monoacylglycerols and prostaglandin glycerol esters, with negligible activity toward diacylglycerols, triacylglycerols and lysophospholipids [44]. Subsequent functional studies have confirmed that ABHD16A serves as the principal phosphatidylserine lipase, hydrolyzing phosphatidylserine to produce the immunomodulatory lipid lysophosphatidylserine (Lyso‑PS), which in turn participates in the release of inflammatory cytokines from macrophages [45]. Dysregulation of ABHD16A is not only closely associated with the pathogenesis and progression of the neurodegenerative disorder [45], but also leads to Lyso‑PS accumulation, which subsequently activates the RhoA/LIMK/Cofilin signaling cascade and thereby promotes gastric cancer metastasis [46]. The regulation of Lyso-PS production by ABHD16A implicates its potential modulatory function in immune signaling pathways.

Enzymatic identification

The gene encoding ABHD16A is located within the human major histocompatibility complex class III (MHC III) [16], suggesting a potential relationship between ABHD16A and the immune system. Lehner et al. performed high-throughput yeast two-hybrid screening to dissect protein interaction networks targeting the MHC III region and demonstrated that ABHD16A may interact with innate immune factors such as IFITM1 and E3 ubiquitin ligase ring finger protein 5 (RNF5) [47]. In 2022, Shi et al. demonstrated that ABHD16A directly interacts with and depalmitoylates IFITM members, formally identifying it as a protein depalmitoylase. Mutagenesis experiments further confirmed that its conserved HXXXXD motif and Ser355 are essential for depalmitoylase activity [13].

Substrate spectrum and molecular mechanisms

Shi et al. subsequently adopted Japanese encephalitis virus (JEV), vesicular stomatitis virus (VSV) pseudotypes, and hepatitis B virus (HBV) as research objects to investigate the effect of ABHD16A depalmitoylation on IFITM1 in antiviral immunity. Mechanistically, ABHD16A downregulates IFITM1 S-palmitoylation, which disrupts IFITM1 membrane localization and its viral inhibition capacity, ultimately facilitating JEV, VSV, and HBV infection [13, 48]. Based on the ABHD16A interaction network characterized by Lehner et al. [47], Shi and colleagues further discovered the ubiquitination modification of ABHD16A. The E3 ubiquitin ligase RNF5 directly targets ABHD16A for ubiquitination and subsequently proteasomal degradation. This process can effectively alleviate the effect of ABHD16A depalmitoylation on IFITM members, which is beneficial for host antiviral activity (Fig. 4) [49].

Disease involvement and therapeutic strategies

Viral infectious diseases

Epidemic encephalitis B is an acute zoonotic central nervous system disease caused by JEV infection [50, 51], whose pathogenic process is associated with the ABHD16A-mediated depalmitoylation. On the one hand, JEV disrupts the S-palmitoylation/depalmitoylation balance of IFITM1 in host cells by inducing ABHD16A expression and concurrently downregulating that of zDHHCs [52]. ABHD16A specifically catalyzes the depalmitoylation of IFITM1, which abrogates the protein’s plasma membrane localization capacity and sequesters it in the cytoplasm [13, 49]. As a result, IFITM1 fails to block the membrane fusion between the JEV envelope and host cell membrane, and consequently loses its core function of inhibiting viral entry and replication. On the other hand, depalmitoylated IFITM1 impairs blood–brain barrier (BBB) integrity, facilitates JEV neuroinvasion, and ultimately elicits the pathological damage of encephalitis [52].

HBV infection remains a major global public health concern, as it can lead to severe liver diseases including liver cirrhosis and hepatocellular carcinoma [53]. A recent study by Wen et al. found that HBV infection markedly upregulates IFITM1 expression and represses that of ABHD16A; this observation has been validated in peripheral blood samples from HBV-positive patients and HepG2.2.15 cell models with stable HBV expression. S-palmitoylation is essential for IFITM1 to inhibit HBV replication. ABHD16A negatively modulates the anti-HBV activity of IFITM1, consequently promoting HBV replication [48].

KC01 serves as a specific inhibitor of ABHD16A with high selectivity, and minimal off-target effects. This compound covalently binds to the catalytic serine residue (Ser355) of ABHD16A, directly abrogating its enzymatic activity [45]. KC01 treatment markedly attenuates the replication of JEV [13]. In addition, it enhances the S-palmitoylation level of IFITM1 and consequently suppresses HBV gene expression and virion production, and no significant cytotoxicity is detected in HepG2.2.15 cells upon KC01 treatment [13, 48]. Given its broad-spectrum antiviral activity, high target selectivity and low cytotoxicity, KC01 holds promise as a potential therapeutic agent for various ABHD16A/IFITM-associated viral infectious diseases.

Current studies have focused on how ABHD16A negatively regulates host antiviral immunity through depalmitoylating IFITM proteins, yet they neglect its pivotal role in alleviating excessive inflammatory responses elicited by viral infections, as viral pathogenesis in the host mainly arises from the inflammatory storm caused by excessive host immunity [54, 55]. Thus, in-depth exploration of ABHD16A’s regulatory mechanisms in the immune system, screening for small-molecule drugs specifically targeting ABHD16A, and identifying additional substrates of this enzyme will provide novel perspectives for treating viral diseases and alleviating inflammation.

Functional characterization of ABHD7 as a Lamin A depalmitoylase and its implications in myoblast differentiation

ABHD7 harbors all the signature motifs necessary for robust epoxide hydrolase activity toward fatty acids [56]. To date, the only characterized function of ABHD7 is to target epoxide-containing lipids, catalyze their conversion into 1,2-diols [57]. However, in the following decade, there were very limited reports on ABHD7 until 2024, when Shen et al. uncovered a pivotal role of ABHD7 as a depalmitoylase in regulating Lamin A S-palmitoylation and subsequent myoblast differentiation [14].

Enzymatic identification

Using co-immunoprecipitation assays, Shen et al. conducted a limited screen targeting ABHD proteins, including ABHD5, ABHD7, ABHD17A, ABHD17C, and ABHD18. They identified that Lamin A, an S-palmitoylated intermediate filament protein, was efficiently co-immunoprecipitated with ABHD7, and further demonstrated that ABHD7 and Lamin A colocalized on the nuclear envelope. Notably, overexpression of ABHD7 significantly removed the palmitate from Lamin A, whereas silencing ABHD7 expression reversed this effect, confirming that ABHD7 functions as the depalmitoylase for Lamin A [14].

Substrate spectrum and molecular mechanisms

Lamin A undergoes S-palmitoylation at cysteine residues C522, C588, and C591. This modification is catalyzed by the palmitoyltransferase zDHHC5, whereas ABHD7 serves as a specific depalmitoylase that erases the palmitoyl group from Lamin A. Shen et al. further performed experiments under metabolic stress conditions, and revealed that lactate treatment upregulated the S-palmitoylation level of Lamin A by weakening the binding affinity between ABHD7 and Lamin A (Fig. 4) [14].

Disease involvement and therapeutic strategies

Laminopathies

Emery–Dreifuss muscular dystrophy (EDMD) is an inherited muscular disorder caused by mutations in the LMNA gene, predominantly manifested as progressive atrophy and functional impairment of skeletal and cardiac muscles [58]. Shen et al. discovered that ABHD7-mediated depalmitoylation of Lamin A facilitates the differentiation of murine myoblasts, and defective myogenic differentiation represents the central pathological event underlying skeletal muscle degeneration in EDMD [14]. Accordingly, dysregulation of ABHD7-governed Lamin A depalmitoylation participates in the pathogenesis of EDMD by impeding myoblast differentiation.

To date, no studies have been reported on targeting ABHD7 for the treatment of laminopathies such as EDMD. Nevertheless, based on the findings of Shen et al. [14], several therapeutic strategies can be explored. First, develop ABHD7-specific small-molecule activators to enhance its depalmitoylase activity, thereby reversing the hype-rpalmitoylation of Lamin A. This would relieve the inhibition of myoblast differentiation and restore normal myocyte maturation and myofiber formation. In addition, a skeletal muscle-targeted ABHD7 overexpression system can be constructed using viral vectors to specifically upregulate ABHD7 expression in skeletal muscle satellite cells or myoblasts, thereby correcting the imbalanced S-palmitoylation of Lamin A. Third, combined intervention in lactate metabolism—by inhibiting lactate production and promoting lactate clearance—could diminish the lactate-mediated disruption of ABHD7-Lamin A interaction, synergistically maintaining a low S-palmitoylation level of Lamin A. In summary, small-molecule drugs and gene therapy strategies centered on ABHD7 hold promise for overcoming the current therapeutic limitations of EDMD and providing a novel, precision intervention pathway for LMNA‑related muscular dystrophy.

ABHD10-dependent depalmitoylation events in mitochondrial homeostasis and disease

Existing studies suggest that ABHD10 exerts its regulatory effects on downstream proteins mainly via S-depalmitoylation, a lipid modification that subsequently impacts mitochondrial performance and bioenergetics. Rather than acting directly on lipid substrates, the enzyme’s connection to lipid metabolism appears to be largely mediated through the activity control of critical metabolic proteins.

Enzymatic identification

S-palmitoylation of resident mitochondrial proteins is involved in multiple essential biological processes of mitochondria [59]. In 2019, Cao et al. utilized a peptide S-deacylase probe to screen serine hydrolases, and demonstrated that only ABHD10 significantly exhibited depalmitoylase activity in mitochondria among eighteen ABHD proteins [12]. To elucidate the specific regulatory functions of the mitochondrial depalmitoylase ABHD10 and identify its specific substrates, Cao et al. focused on peroxiredoxin (PRDX) proteins, key components of the antioxidant defense and redox signaling pathways [60]. ABHD10 overexpression compromised the S-palmitoylation level of PRDX5, whereas PRDX5 S-palmitoylation was elevated in ABHD10-knockdown cells. S-palmitoylation of PRDX5 at Cys100 suppresses its antioxidant function, which is relieved by ABHD10 via depalmitoylation to regulate mitochondrial redox homeostasis (Fig. 4) [12].

Substrate spectrum and molecular mechanisms

Given that PRDX5 serves as a pivotal antioxidant factor in the liver tissue [61], and the pathogenesis of alcoholic liver disease (ALD) is tightly linked to dysregulated hepatic oxidative stress [62]. Li et al. further explored the regulatory role of ABHD10-mediated PRDX5 depalmitoylation in ALD progression [63]. They elucidated that the transcription factor ETS domain-containing protein 3 (ELK-3), a key regulator of TGFβ1-induced hepatic fibrosis [64], bound to the promoter region of ABHD10. This binding process inhibited the transcription of ABHD10, thereby impairing its capacity to mediate PRDX5 depalmitoylation effectively. Accumulation of S-palmitoylated PRDX5 (the antioxidant-inactive form of PRDX5) subsequently induced excessive oxidative stress and hepatic cell dysfunction, ultimately promoting liver injury and fibrosis (Fig. 4) [63].

Zhou et al. recently also revealed the depalmitoylation effect of ABHD10 in the context of sperm mitochondrial sheath biogenesis [65]. ABHD10 directly targets spermatogenesis associated protein 19 (SPATA19), glycerol kinase 2 (GK2), and pyruvate dehydrogenase complex component X (PDHX), thereby mediating their depalmitoylation. Excessive S-palmitoylation can result in the aggregation and decreased stability of SPATA19 and GK2, which are key factors responsible for the formation of sperm mitochondrial sheath [66, 67]. In addition, elevated S-palmitoylation level of PDHX reduces its activity, which in turn leads to mitochondrial oxidative phosphorylation (OXPHOS) dysfunction, and reduced ATP production. These cascading effects ultimately compromise sperm motility and male fertility (Fig. 4) [65].

Disease involvement and therapeutic strategies

Metabolic diseases

Chronic excessive alcohol consumption leads to alcoholic liver disease (ALD), which can progress sequentially to hepatic steatosis, hepatitis, fibrosis, and even cirrhosis. Its core pathological mechanisms are associated with oxidative stress. The mRNA and protein levels of ABHD10 in the liver tissue of ALD patients are significantly downregulated, suggesting that ABHD10 downregulation is a key hallmark of ALD pathological progression. ABHD10 downregulation is accompanied by increased S-palmitoylation levels of PRDX5, which in turn exacerbates oxidative stress in liver tissue, impairs hepatocyte function, and ultimately promotes the progression of ALD to hepatic fibrosis [63].

Li et al. employed recombinant adeno-associated virus (rAAV)-mediated ABHD10 overexpression, which successfully ameliorated hepatic fibrosis and oxidative stress in mice with both early-stage and advanced-stage ALD. Meanwhile, they confirmed that the PPARγ agonist Rosiglitazone can reverse TGFβ1-induced ABHD10 downregulation [63], providing Rosiglitazone as a potential therapeutic agent for the disease.

Reproductive disorders

Asthenospermia is characterized by a marked reduction in sperm motility and abnormalities of the mitochondrial sheath, thereby contributing to male infertility. The sperm mitochondrial sheath serves as the pivotal site for oxidative phosphorylation. A recent study has demonstrated that ABHD10 deficiency induces mitochondrial swelling and inner membrane damage, causes downregulated expression of OXPHOS complex proteins and insufficient ATP production [65].

The exclusive enrichment of ABHD10 in the testicular mitochondrial matrix and its well-defined pathogenic mechanism confer ABHD10 with the potential to serve as a precision diagnostic marker for male infertility. In clinical practice, the detection of ABHD10 mRNA/protein level in semen and testicular tissues can enable the definitive identification of genetic etiologies and provide a robust experimental basis for precision intervention. Furthermore, small-molecule drug development can be directed toward screening agonists of ABHD10 depalmitoylase activity; such agonists may attenuate the aberrant S-palmitoylation of SPATA19, GK2, and PDHX, thereby alleviating the clinical symptoms of male infertility.

In summary, the mitochondria-specific depalmitoylase ABHD10 has increasingly been characterized over the past 5 years to exert multiple regulatory roles in diverse diseases. These findings offer novel perspectives for mechanistic investigation and therapeutic strategies. Moreover, the identified substrates of ABHD10 are predominantly linked to mitochondrial oxidative stress and ATP synthesis. Thus, exploration of the substrate spectrum of ABHD10 is expected to provide a theoretical foundation and novel insights for addressing mitochondria-associated disorders.

Regulatory roles of ABHD8 in S-palmitoylation and NLRP3 inflammasome pathway

Currently, there is very little direct research on ABHD8’s role in modulating lipid metabolism and lipid signaling. The expression and epigenetic modification of ABHD8 have emerged as functional indicators implicated in diverse pathological conditions, including secondary progressive multiple sclerosis [68], postmenopausal osteoporosis [69], breast cancer, and ovarian cancer [70, 71], which position ABHD8 as a promising prognostic biomarker and potential therapeutic candidate.

Enzymatic identification

The activity of pattern recognition receptor NLRP3, which initiates inflammasome assembly and induces pyroptosis, is tightly regulated by multiple post-translational modifications (i.e., S-palmitoylation, phosphorylation and ubiquitination) [72, 73]. Dysregulation of NLRP3 contributes to the pathogenesis of several inflammatory and autoimmune diseases [74]. In 2025, Yang et al. found that ABHD8 specifically interacted with NLRP3, which downregulated NLRP3-induced inflammasome activation by transporting NLRP3 to the lysosome for degradation [15]. Given a previous report indicating that NLRP3 degradation depends on its intrinsic S-palmitoylation [73], Yang et al. hypothesized that ABHD8 may upregulate the S-palmitoylation modification level of NLRP3. As expected, overexpression of ABHD8 promoted the S-palmitoylation modification of NLRP3.

Substrate spectrum and molecular mechanisms

Due to the absence of key acyltransferase motifs in ABHD8, ABHD8 may indirectly regulate NLRP3 post-translational modification. In the following experiments, they further identified that ABHD8 facilitated the S-palmitoylation modification of NLRP3 by recruiting zDHHC12, indicating that ABHD8 played a critical scaffolding role in this process [15].

Emerging evidence establishes ABHD8 as a critical regulator of protein S-palmitoylation. However, unlike other well-characterized ABHD proteins that directly target substrates to catalyze depalmitoylation reactions, ABHD8 lacks acyltransferase motifs and instead enhances substrate S-palmitoylation by recruiting a zDHHC member. zDHHC12 has been implicated to participate in the regulation of progression of HCC and ovarian cancer through S-palmitoylation modification of histone deacetylase 8 (HDAC8) and claudin-3, respectively [75, 76]. Therefore, ABHD8 may also regulate the development of diverse cancers by interacting with zDHHC12. Future studies are warranted to clarify whether ABHD8 can directly mediate the depalmitoylation of its substrates and explore the therapeutic potential of targeting ABHD8 in inflammatory diseases, autoimmune diseases, and cancer progression.

Disease involvement and therapeutic strategies

Viral infectious diseases

Coronavirus disease 2019 (COVID-19) is an acute respiratory disease caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection, and the core mechanism underlying its severe progression is closely associated with tissue damage induced by infection-triggered excessive inflammatory responses [77, 78]. Aberrant activation of NLRP3 inflammasome serves as a key driver of excessive inflammation. It amplifies the inflammatory cascade by inducing the release of pro-inflammatory cytokines and pyroptosis, thereby exacerbating the pathological damage of COVID-19. Yang et al. identified ABHD8 as a critical negative regulator of the NLRP3 inflammasome. ABHD8 promotes NLRP3 S-palmitoylation by recruiting zDHHC12, which reduces the excessive activation of the NLRP3 inflammasome. However, the nucleocapsid (N) protein of SARS-CoV-2 disrupts the interaction between ABHD8 and NLRP3, preventing ABHD8 from mediating NLRP3 S-palmitoylation [15].

Since ABHD8 overexpression has been validated in mouse to significantly attenuate NLRP3 inflammasome activation and alleviate lung tissue injury [15], low-immunogenicity adeno-associated virus (AAV) vectors can be employed in the future to deliver the ABHD8 gene to the lungs, the primary site of injury in COVID-19, for targeted expression. This strategy would enable gene therapy delivery, promote local ABHD8 expression, accelerate NLRP3 degradation, and mitigate pulmonary inflammation.

Divergent structures and conserved catalytic mechanisms of ABHD depalmitoylases

As an increasing number of ABHD proteins have been reported to play crucial regulatory roles in the S-palmitoylation/depalmitoylation (Table 1), a deeper understanding of their structural features is essential to decipher the molecular mechanism underlying their catalytic activity, substrate preference, and functional diversity.

Table 1.

The biological characteristics and associated diseases of ABHD proteins in humans

Member	Subcellular localization	Palmitoylation substrates	Related diseases
ABHD1	Mitochondrion [104]; Membrane [105]	Undetermined	Chanarin–Dorfman syndrome (D)
ABHD2	Flagellum membrane [106]; Cytosol (HPA); Flagellar centriole (HPA)	Undetermined	Male infertility (D); Hypotonia-cystinuria syndrome (D); Chanarin–Dorfman syndrome (D); PHARC syndrome (D)
ABHD3	Nucleoplasm (HPA); Plasma membrane (HPA)	Undetermined	Chanarin–Dorfman syndrome (D)
ABHD4	Nucleoplasm (HPA);	Undetermined	Chanarin–Dorfman syndrome (D); Polyneuropathy (D); Ichthyosis (D)
ABHD5	Lipid droplet [107]; Vesicles (HPA); Cytosol (HPA)	Undetermined	Ichthyosis (D); Lysosomal storage disease (D); Obesity (D); Liver disease (D); Diabetes mellitus (D); Lipodystrophy (D); Ectropion (D)
ABHD6	Vesicles (HPA)	Undetermined	Depressive disorder (D); Polyneuropathy (D)
ABHD7	Nuclear envelope [14] Vesicles (HPA)	Lamin A [14]	Emery–Dreifuss Muscular Dystrophy [14] Ichthyosis (D); Chanarin–Dorfman syndrome (D)
ABHD8	Cytoplasm [15]; Nucleoplasm (HPA)	NLRP3 (indirectly) [15]	Coronavirus disease 2019 [15] Breast cancer (D); Ovarian cancer (D)
ABHD9	Membrane [56]; Nucleoplasm (HPA)	Undetermined	Ichthyosis (D)
ABHD10	Mitochondrion [12, 65]; Cytosol [108]	PRDX5 [12, 63] SPATA19 [65] GK2 [65] PDHX [65]	Alcoholic liver disease [63] Asthenospermia [65] Leucine-sensitive hypoglycemia of infancy (D); Williams–Beuren syndrome (D); Congenital myasthenic syndrome 22 (D); Hypotonia-cystinuria syndrome (D)
ABHD11	Mitochondrion [86]	Undetermined	Williams–Beuren syndrome
ABHD12	Endoplasmic reticulum [109]	Undetermined	PHARC syndrome (D); Polyneuropathy (D); Retinitis pigmentosa (D); Cataract (D); Usher syndrome (D)
ABHD12B	Nucleoplasm (HPA)	Undetermined	Chanarin–Dorfman syndrome (D); Periodontitis (D)
ABHD13	Membrane [110]; Cytosol (HPA)	Undetermined	Ascariasis (D)
ABHD14A	Vesicles (HPA)	Undetermined	Chanarin–Dorfman syndrome (D); Williams–Beuren syndrome (D)
ABHD14B	Cytoplasm [101]; Nucleoplasm (HPA); Nucleoli (HPA)	Undetermined	Methylmalonic acidemia cblB type (D)
ABHD15	Nucleoplasm (HPA); Cytosol (HPA); Membrane [110]	Undetermined	Chanarin–Dorfman syndrome (D)
ABHD16A	Endoplasmic reticulum [83]; Mitochondrion [83]	IFITM1 [13, 33, 48]	Epidemic encephalitis B [13, 49] Chronic hepatitis B [48] PHARC syndrome (D); Polyneuropathy (D)
ABHD16B	Nucleoplasm (HPA)	Undetermined	Chanarin–Dorfman syndrome (D); Eosinophilic variant of chromophobe renal cell carcinoma (D)
ABHD17A	Vesicles (HPA); Plasma membrane [9]; Endosome membrane [9]	N-Ras [9] PSD-95 [9] SCAP [17] Rap2b [18] MAP6 [26] CNAβ1 [27] NLRP3 [28] NOD2 [29] IFITM1 (indirectly) [33] STREX [111] METTL3 [30] H-Ras [112] TEAD1/4 [38]	Hepatocellular carcinoma [17] Colorectal cancer [18] Alzheimer’s disease [25] Schizophrenia [26] Osteoarthritis [30] Crohn’s disease [29] Autoinflammatory diseases [28] Cardiac hypertrophy [27] Neuronal ceroid lipofuscinosis (D)
ABHD17B	Plasma membrane [9]	N-Ras [9] PSD-95 [9] HK1 [19] ASCT2 [20] MAP6 [26] NOD2 [29]	Hepatocellular carcinoma [19] Non-small cell lung cancer [20] Alzheimer’s disease [25] Schizophrenia [26] Crohn’s disease [29] Neuronal ceroid lipofuscinosis (D)
ABHD17C	Plasma membrane [9]	N-Ras [9, 22] PSD-95 [9] ALOX15B [21] MAP6 [26] NOD2 [29] STREX [111]	Hepatocellular carcinoma [22] Pancreatic ductal adenocarcinoma [21] Lung adenocarcinoma [34] Clear cell renal cell carcinoma [35] Alzheimer’s disease [25] Schizophrenia [26] Crohn’s disease [29] Neuronal ceroid lipofuscinosis (D)
ABHD18	Nuclear membrane (HPA); Mitochondrion [95]	Undetermined	Autosomal dominant microcephaly (D); Complex cortical dysplasia with other brain malformations (D); Sebaceous carcinoma (D)

HPA the Human Protein Atlas (https://www.proteinatlas.org), D DISEASES database (https://diseases.jensenlab.org/Search)

The classical α/β hydrolase catalytic triad typically comprises three residues: serine, aspartate, and histidine [79, 80]. As revealed by the sequence alignment, the serine residue serving as the nucleophilic core that attacks the thioester bond between the palmitoyl moiety and substrate cysteine is highly conserved across ABHD depalmitoylases, with epoxide hydrolase ABHD7 being the exception that carries an aspartate at this position [56]. Furthermore, the aspartate residue responsible for stabilizing protonated histidine via hydrogen bonding is also conserved among ABHD7, ABHD10, ABHD16A, and ABHD17A/B/C. The histidine residue, which deprotonates the hydroxyl group of serine to enhance its nucleophilicity, is predominantly located at the C‑terminus of ABHD proteins (Fig. 5).

Fig. 5.

Amino acid sequence alignment of ABHD proteins involved in depalmitoylation regulation. Amino acid sequences were retrieved from UniProt. The sequence alignment was performed using ESPript 3.2. The red box with white characters indicates that the amino acid is strictly conserved (identical) across all sequences in the alignment. The blue frame with red characters indicates that the residues at this column share highly similar physicochemical properties

Beyond the catalytic triad, auxiliary structural modules critically determine enzyme–substrate recognition and membrane association. Based on the crystal structure of mouse ABHD10, it adopts a canonical α/β hydrolase fold with a Ser-His-Asp catalytic triad, whose catalytic serine hydroxyl points directly to the junction of two functionally distinct key pockets (Fig. 6A) [12]. The lipid chain insertion pocket is covered by a characteristic cap domain. Its highly hydrophobic inner surface accommodates the substrate’s palmitoyl lipid chain via hydrophobic interactions. The substrate binding pocket accommodates the substrate peptide backbone and precisely positions the S-palmitoylated cysteine at the catalytic center to ensure the specificity and efficiency of thioester bond hydrolysis. The two pockets act synergistically to mediate substrate recognition and S-depalmitoylation catalysis of ABHD10. By contrast, ABHD17 isoforms lack a cap domain but instead possess an N‑terminal amphipathic helix that undergoes S-palmitoylation, anchoring the enzyme to the plasma membrane. Additionally, a conserved hydrophobic loop (residues 222–233 in ABHD17A) inserts into the lipid bilayer, positioning the catalytic serine optimally for extracting the palmitoyl group from membrane-resident substrates such as N-Ras, PSD-95, and SCAP (Fig. 6a) [81].

Fig. 6.

Structural characteristics of ABHD depalmitoylases. a The structure of mouse ABHD10 (Q6PE15; 44-293 amino acids; PDB: 6NY9), as well as the AlphaFold-predicted structures of human ABHD17A (Q96GS6; 1-310 amino acids; AlphaFold:AF-Q96GS6-F1), human ABHD7 (Q8IUS5; 1-362 amino acids; AlphaFold:AF-Q8IUS5-F1), and human ABHD16A (O95870; 1-558 amino acids; AlphaFold: AF-O95870-F1). b Structure alignments between ABHD10/ABHD17A and their counterparts ABHD16A /ABHD7. Magnified regions represent the conserved catalytic triad between ABHD depalmitoylases. The catalytic triads of ABHD10/ABHD17A and ABHD16A/ABHD7 are highlighted in green and yellow, respectively

Unlike ABHD10 and ABHD17A, the structural properties of ABHD7 and ABHD16A and their functional links to depalmitoylation remain poorly understood. Given the strict conservation of catalytic triad architecture and function across ABHD proteins demonstrated by Ozhelvaci et al. [82], we performed structural overlap analysis to characterize the catalytic triad and structural features of ABHD16A and ABHD7. Protein structure prediction combined with sequence overlap with ABHD10/17A/16A revealed that the catalytic triad of ABHD7 consists of Asp169-Asp307-His336 (Fig. 6b). This unique composition may be attributed to ABHD7’s epoxide hydrolase activity, as enzymes of this class typically employ Asp rather than Ser as the catalytic nucleophile center [56]. Investigations concerning the subcellular localization and structural features of ABHD7 remain remarkably limited. Future research can focus on this gap to explore the enzymatic kinetic differences between the Asp-Asp-His and Ser-Asp-His catalytic triads. Structural overlap of the AlphaFold-predicted crystal structure of ABHD16A with that of ABHD10 and ABHD17A via Matchmaker revealed that Ser355-Asp430-His543 constitutes the catalytic triad of ABHD16A (Fig. 6b). In contrast, ABHD16A lacks the cap structure characteristic of ABHD10; additionally, its N-terminal domain exhibits low homology to that of ABHD17A (Fig. 6b). Such striking discrepancies in three-dimensional protein structural features may account for the predominant localization of ABHD16A on the endoplasmic reticulum rather than the plasma membrane [83]. Future studies could focus on elucidating the mechanistic relationships between the structural properties of ABHD16A and substrate-binding functions.

Another conserved feature among ABHD depalmitoylases is the HXXXXD acyltransferase motif (Fig. 2a). Mutagenesis of this motif in ABHD16A severely impairs its depalmitoylase activity [13], suggesting a role beyond acyltransferase function-possibly in stabilizing the catalytic conformation or facilitating substrate positioning. Consistent with this predictive signature, sequence analysis confirms that ABHD8 lacks the conserved HXXXXD motif (Fig. 2), which likely explains why no study to date has reported direct depalmitoylase activity of ABHD8 toward protein substrates. Notably, classical depalmitoylases APT1/2 and PPT1 lack this motif (Fig. 2b), which may underpin their distinct substrate repertoires and lysosomal/cytosolic localizations.

Collectively, the structure–function relationships of ABHD depalmitoylases can be summarized as follows: a catalytic triad (Ser/Asp–Asp–His) provides the chemical machinery for thioester hydrolysis; auxiliary structural elements (cap domain, palmitoylated helix, hydrophobic loop, or transmembrane segment) dictate subcellular localization and substrate access; and the conserved HXXXXD motif contributes to catalytic integrity. This triad of structural determinants not only explains the functional diversification among known ABHD depalmitoylases but also provides predictive criteria for identifying novel members of this family that may participate in the dynamic S‑palmitoylation cycle.

ABHD proteins that harbor the potential to modulate S-palmitoylation/depalmitoylation

ABHD4

ABHD4 has been reported to participate in signal transduction by hydrolyzing N-acyl phosphatidylethanolamines (NAPEs) [84]. Yokoi et al. investigated the effect of ABHD4 on the depalmitoylation of PSD-95. Although the band intensity corresponding to S-palmitoylated PSD-95 decreased significantly following ABHD4 overexpression, they proposed that this observation may be attributed to ABHD4-mediated downregulation of PSD-95 expression rather than a direct effect on depalmitoylation [24]. Further investigations are warranted to clarify whether ABHD4-mediated downregulation of PSD-95 S-palmitoylation is governed by transcriptional regulation, or arises from direct attenuation of this S-palmitoylation and consequent destabilization of PSD-95.

ABHD5

ABHD5, encoded by comparative gene identification-58 (CGI58), was initially discovered in patients diagnosed with neutral lipid storage disease with ichthyosis [85]. These patients present with symptoms including dry and flaky skin due to lipid metabolism disorders caused by mutations in ABHD5. ABHD5 has been used as a candidate factor for screening regulatory enzymes involved in Lamin A S-palmitoylation. ABHD5, ABHD7, and ABHD17A/C, members of the ABHD family, can interact with Lamin A. Among them, ABHD7 has been verified to have the ability to catalyze the Lamin A depalmitoylation reaction (14). However, the biological functions and significance of the ABHD5-Lamin A interaction, as well as whether this interaction is linked to S-palmitoylation modification, remain to be elucidated through further research.

ABHD11

ABHD11 maintains the catalytic activity of the 2-oxoglutarate (2-OG) dehydrogenase complex (OGDHc), ensuring the normal metabolism of 2-OG within the tricarboxylic acid (TCA) cycle [86]. The recent research further clarifies its regulatory role in immune regulation. ABHD11 is highly expressed in human CD8⁺ T cells, and its specific inhibitor (ML226) downregulates OGDHc catalytic activity by suppressing ABHD11 function, which ultimately modulates T cell differentiation by reducing the secretion of cytotoxic cytokines under hypoxic conditions [87]. By targeting key mitochondrial metabolic nodes and the functional phenotypes of immune cells, ABHD11 has emerged as a core regulatory factor in metabolic-immune crosstalk.

ML226 exerts specific inhibitory effects on ABHD11 by covalent modification of serine at the active site [88, 89]. ML226 is closely related to APT1/2 inhibitor ML211. Although ML211 can strongly inhibit APT1/2, ABHD11 is also its main anti-target. Therefore, as an “anti-probe,” ML226 can effectively eliminate the interference of ABHD11 in the functional study of APT1/2. Combined with the depalmitoylation activity of APT1/2 and the sensitivity of ABHD11 to ML211, it is speculated that ABHD11 may have depalmitoylation potential. Subsequent research can use ML226/ML211 as a starting point to explore the potential of ABHD11 as a depalmitoylation enzyme in cells, providing a theoretical basis for related metabolic and immune diseases.

ABHD12

ABHD12 was initially identified to hydrolyze the endocannabinoid 2-arachidonoylglycerol (2-AG), contributing approximately 9% of total 2-AG hydrolase activity in the brain [90]. ABHD12 is highly expressed in microglia, and plays roles in neuroinflammation regulation by degrading Lysophosphatidylserine [91, 92]. Wang et al. defined ABHD12 as a depalmitoylase [93], based on the finding by Yokoi et al. that ABHD12 can modestly downregulate the S-palmitoylation level of PSD-95 [24]. Notably, ABHD12 is not localized to the spine membrane [24], suggesting that its depalmitoylase function may exert a compensatory role.

ABHD13

ABHD13 was found to reduce the S-palmitoylation level of PSD-95 in a depalmitoylase functional screen, but its catalytic activity toward PSD-95 is markedly lower than that of ABHD17A [24]. Critically, this observation was made in an overexpression-based screening setting. To date, there is no evidence demonstrating that endogenous ABHD13 acts as a physiological regulator of PSD-95 S-palmitoylation under basal conditions. Moreover, ABHD17 isoforms are specifically distributed on dendritic spines, where PSD-95 is highly enriched and executes its synaptic functions, whereas ABHD13 is not localized to dendritic spines [24]. This spatial separation means that under normal physiological conditions, ABHD13 does not have access to the synaptic pool of PSD-95. The proposed compensatory function of ABHD13 only manifests under conditions where ABHD17A function is impaired, rather than representing a constitutive, shared substrate relationship.

In a separate study, Child et al. discovered that ABHD13 shows high homology with Toxoplasma gondii palmitoyl protein thioesterase−1 (TgPpt1). This enzyme regulates T. gondii invasion by mediating the depalmitoylation of target proteins [94]. This finding implies that ABHD13 may retain intrinsic depalmitoylase activity in mammalian cells.

ABHD18

Similar to ABHD10, ABHD18 has also been reported to reside in mitochondria [95]. To date, research on ABHD18 has primarily focused on its catalytic role in the stepwise deacylation of cardiolipin (CL), which converts CL into monolysocardiolipin (MLCL) and dilysocardiolipin (DLCL), ultimately promoting CL degradation [96, 97]. Notably, since ABHD18 is a mitochondria-localized α/β-hydrolase that mediates CL deacylation via its conserved Ser-Asp-His catalytic triad [96], this function does not exclude its potential to exert protein deacylation—specifically depalmitoylation, which is a subset of deacylation targeting acyl-protein linkages [98].

To date, the only study linking ABHD18 to S-palmitoylation post-translational modifications derives from Shen et al.’s work, which explored the regulatory role of the ABHD family in Lamin A S-palmitoylation modification [14]. In this study, Shen et al. observed that exogenously expressed either ABHD18 or ABHD7 can interact with Lamin A, whereas ABHD7 specifically exerted depalmitoylase activity toward Lamin A. However, they did not investigate whether ABHD18 possesses depalmitoylase activity. Further investigation is needed to determine whether the interaction between ABHD18 and Lamin A is functionally linked to depalmitoylation.

ABHD6 and ABHD14B have been identified not to participate in regulating S-palmitoylation modification

ABHD1, ABHD2, ABHD3, ABHD9, ABHD12B, ABHD14A, ABHD15, and ABHD16B have no reported links to S-palmitoylation. In contrast, while studies have investigated the roles of ABHD6 and ABHD14B in S-palmitoylation modification, current experimental evidence does not support a critical regulatory role of ABHD6 and ABHD14B in this PTM.

ABHD6

ABHD6 acts as a core enzyme that catalyzes the hydrolysis of monoacylglycerols (MAGs) and lysophosphatidylglycerol (LPG) [99]. Specifically in the field of S-palmitoylation modification, several groups have treated cells with ABHD6 inhibitor WWL70 and found no significant changes in the localization and S-palmitoylation modification levels of PSD-95 and Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) [9, 29]. Consistently, Won et al. demonstrated that selective inhibition of ABHD6 failed to induce notable alterations in global cellular S-palmitoylation levels [100]. Although selective inhibition of ABHD6 showed no measurable effect on S-palmitoylation incorporation, these results cannot formally exclude the possibility that ABHD6 may act on untested substrates or exert low-level activity in specific native physiological contexts.

ABHD14B

ABHD14B exhibits lysine deacetylase activity, which can transfer an acetyl group from an acetylated lysine to coenzyme A (CoA) to generate acetyl-CoA [101], and is involved in the pathogenesis of type 2 diabetes, cancers, and other pathological processes [102, 103]. It is worth noting that acetyl-CoA and palmitoyl-CoA represent distinct metabolic intermediates. Consistent with this distinction, Rajendran et al. demonstrated that ABHD14B shows strict substrate preference for short-chain acyl substrates and cannot catalyze the hydrolysis of p-nitrophenyl (pNp)-palmitate [101].

ABHD6 and ABHD14B exhibit a closer phylogenetic relationship

Phylogenetic tree construction and analysis based on the maximum likelihood algorithm demonstrated that ABHD6, ABHD14A, and ABHD14B share a closer evolutionary relationship than other ABHD proteins (Fig. 2). An unanswered question persists regarding whether this evolutionary clustering is merely a coincidence, or whether it reflects an intrinsic correlation with their currently characterized lack of depalmitoylase activity. Elucidating the direct mechanistic link between this evolutionary pattern and enzymatic function will establish a robust criterion for the functional classification and annotation of ABHD proteins.

Future perspective

Benefiting from advances in protein structure determination, computational prediction and well-established S-palmitoylation detection methods, the molecular mechanisms by which newly identified ABHD proteins regulate S-palmitoylation have been gradually clarified. However, critical knowledge gaps remain to be addressed for a comprehensive understanding of the regulatory mechanisms of ABHD proteins within the dynamic S-palmitoylation cycle.

ABHD proteins that have been characterized as functional depalmitoylases (e.g., ABHD17A/B/C, ABHD10, ABHD16A, and ABHD7) all contain an HXXXXD motif (Fig. 2). Disruption of this motif in ABHD16A disturbs its depalmitoylation activity [13]. However, the precise role of the HXXXXD motif in the palmitoyl group removal mediated by these ABHD proteins, and whether this motif can serve as a predictive criterion for identifying other ABHD proteins with depalmitoylase activity, require further in-depth investigation.

To date, ABHD depalmitoylases exhibit marked substrate preference (Table 1). This functional specificity may stem from differences in distinct subcellular localization, substrate recognition specificity, and inherent catalytic activity. Spatially, ABHD17A/B/C preferentially localize to the plasma membrane, ABHD10 to mitochondria, ABHD16A to the endoplasmic reticulum, and ABHD7 to the nuclear envelope (Fig. 1; Table 1), restricting each enzyme to substrates within its resident compartment. In addition, structural features such as the unique cap domain of ABHD10 and the N-terminal amphipathic helix plus conserved hydrophobic loop of ABHD17 isoforms define their substrate recognition specificity. Finally, variations in catalytic triad composition-the canonical Ser-Asp-His triad in most ABHD depalmitoylases versus the Asp-Asp-His triad in ABHD7-confer divergent inherent catalytic activity and hydrolytic efficiency. Nevertheless, structural studies on most ABHD proteins remain limited, and the molecular mechanisms underlying their substrate selectivity require further elucidation. Emerging studies have indicated that several ABHD proteins are also involved in the S-palmitoylation of substrates through indirect regulatory manners. ABHD8 upregulates the S-palmitoylation level of the NLRP3 inflammasome by recruiting zDHHC12 [15]. The depalmitoylation process of NLRP3 is directly controlled by ABHD17A [28], while the potential interaction between ABHD8 and ABHD17A has not yet been clarified. Moreover, ABHD16A mediates the specific depalmitoylation of IFITM1 [13]. In contrast, ABHD17A restores IFITM1 S-palmitoylation by downregulating the transcriptional level of ABHD16A [33]. Future investigations are warranted to explore the interactions among ABHD proteins and uncover the regulatory effects of these interactions on substrate S-palmitoylation.

ABHD proteins have been recognized as novel biomarkers linked to the pathogenesis of cancers and infectious diseases [34, 35, 48]. In addition, targeted inhibitors or natural products against ABHD proteins have offered new insights into intervening in the progression of related disorders [21, 23, 48]. However, the targeted delivery of ABHD protein inhibitors or agonists to specific tissues and the precise modulation of ABHD protein activity remain major challenges for clinical translational medicine.

Conclusions

This review systematically summarizes the multifaceted regulatory functions of emerging ABHD proteins in S-palmitoylation, elucidates their conserved and divergent features in primary sequences, structural architectures, and substrate specificities, and further delineates the mechanistic links between dysregulated ABHD-mediated S-palmitoylation modulation and the pathogenesis of associated human disorders. This review provides critical mechanistic insights into the identification of novel S-palmitoylation-regulating enzymes, and establishes a rigorous theoretical foundation for the development of ABHD-targeted diagnostic biomarkers and precision therapeutic interventions for S-palmitoylation-associated diseases.

Abbreviations

ABHD

α/β Hydrolase domain-containing protein

AD

Alzheimer’s disease

AID

Autoinflammatory disease

ALD

Alcoholic liver disease

ALOX15B

Arachidonate 15-lipoxygenase

APT

Acyl-protein thioesterase

BBB

Blood-brain barrier

ccRCC

Clear cell renal cell carcinoma

COVID-19

Coronavirus disease 2019

CRC

Colorectal cancer

EDMD

Emery–Dreifuss muscular dystrophy

ELK-3

ETS domain-containing protein 3

GK2

glycerol kinase 2

HBV

Hepatitis B virus

HCC

Hepatocellular carcinoma

HK1

Hexokinase 1

IFITM

Interferon-inducible transmembrane protein

JEV

Japanese encephalitis virus

LUAD

Lung adenocarcinoma

Lyso-PS

Lysophosphatidylserine

MAP6

Microtubule-associated protein 6

METTL3

Methyltransferase-like 3

MHC III

Major histocompatibility complex class III

NLRP3

NOD-, LRR-, and pyrin domain-containing protein 3

NOD2

Nucleotide-binding oligomerization domain-containing protein 2

NSCLC

Nonsmall cell lung cancer

OGDHc

2-Oxoglutarate (2-OG) dehydrogenase complex

OXPHOS

Oxidative phosphorylation

PAT

Palmitoyl transferase

PDAC

Pancreatic ductal adenocarcinoma

PDHX

Pyruvate dehydrogenase complex component X

PPT

Palmitoyl-protein thioesterase

PRDX5

Peroxiredoxin 5

PSD-95

Postsynaptic density protein 95

PTM

Post-translational modification

RNF5

Ring finger protein 5

SCAP

SREBP cleavage-activating protein

SPATA19

Spermatogenesis associated protein 19

STREX

Stress-axis regulated exon

VSV

Vesicular stomatitis virus

zDHHC

Zinc finger Asp-His–His–Cys domain

Author contributions

X.W. conceived the conceptualization, drafted the original manuscript, and secured the research funding. M.L. designed and compiled all figures and tables. Y.Q. and Y.X. conducted literature retrieval and analysis. J.X. and X.S. reviewed and revised the manuscript, supervised the entire project, and acquired funding support. All authors have read and approved the final published version of the manuscript.

Funding

This work was supported by National Natural Science Foundation of China (32300140 to Xuemeng Shi), Natural Science Foundation of Henan Province (262300422114 to Xin Wen), Key Research and Development Program of Henan Province (251111314700 to Jun Xu), and Key Scientific Research Project Plan of Universities in Henan Province (26A230007 to Xin Wen).

Data availability

No datasets were generated or analyzed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable. This article is a review and does not involve any studies with human participants or animals.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.