α2δ-1–Linked NMDA and AMPA Receptors in Neuropathic Pain and Gabapentinoid Action

Abstract

Chronic neuropathic pain is a debilitating condition that presents a significant therapeutic challenge. Unlike nociceptive pain, neuropathic pain is predominantly driven by glutamate NMDA receptors (NMDARs) and/or Ca²⁺-permeable AMPA receptors (CP-AMPARs) at synapses between primary afferent nerves and excitatory neurons in the spinal dorsal horn. The α2δ-1 protein, encoded by Cacna2d1 and historically recognized as a subunit of voltage-activated Ca²⁺ channels, is the primary target of gabapentinoids, such as gabapentin and pregabalin, which are widely prescribed for neuropathic pain and epilepsy. However, gabapentinoids have minimal effects on Ca²⁺ channel activity. Recent studies reveal that α2δ-1 plays a pivotal role in amplifying nociceptive input to the spinal cord in neuropathic pain. This action is mediated through its dynamic physical interactions with phosphorylated NMDARs and GluA1/GluA2 subunits via its intrinsically disordered C-terminal region. α2δ-1 not only promotes synaptic trafficking of NMDARs but also disrupts heteromeric assembly of GluA1/GluA2 subunits in the spinal dorsal horn. The central function of α2δ-1 is to elevate intracellular Ca²⁺ concentrations at both presynaptic and postsynaptic sites, augmenting nociceptive transmission. Consequently, α2δ-1 serves as a dual regulator coordinating synaptic expression of NMDARs and GluA1 homomeric CP-AMPARs, a function that underlies the therapeutic actions of gabapentinoids. By inhibiting α2δ-1, gabapentinoids reduce the hyperactivity of synaptic α2δ-1–bound NMDARs and CP-AMPARs, thereby dampening the excessive excitatory synaptic transmission characteristic of neuropathic pain. These newly identified roles of α2δ-1 in orchestrating glutamatergic synaptic plasticity suggest that gabapentinoids could be repurposed for treating other neurological disorders involving dysregulated synaptic NMDARs and CP-AMPARs.

Graphical Abstract

Schematic shows the role of α2δ-1 in nerve injury–induced synaptic NMDAR hyperactivity in the spinal dorsal horn.

Under normal conditions, NMDARs exhibit minimal phosphorylation due to constitutive calcineurin activity, and they are not significantly associated with α2δ-1 proteins or expressed at presynaptic or postsynaptic sites. However, traumatic nerve injury reduces calcineurin activity and/or enhances the activity of protein kinases such as PKC and CK2, leading to increased NMDAR phosphorylation at primary afferent central terminals and excitatory neurons in the spinal dorsal horn. Phosphorylated NMDARs interact with upregulated α2δ-1, promoting their trafficking to presynaptic and postsynaptic sites. This process results in synaptic NMDAR hyperactivity and heightened excitatory glutamatergic input within the spinal cord.

1. Introduction

Clinically significant pain conditions involving the somatic structure can be broadly categorized into two major types: nociceptive pain and neuropathic pain. Nociceptive pain, the most common type, represents the body’s physiological response to harmful stimuli detected by nociceptors. It typically results from damage or injury to peripheral tissues. Examples include postoperative pain, musculoskeletal pain, and arthritic pain. These conditions are driven by tissue-derived inflammatory mediators and are predominantly detected by transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) channels present in primary sensory neurons (Caterina et al. 2000; Davis et al. 2000; Obata et al. 2005). The nociceptive signals are then transmitted via TRPV1/TRPA1 and voltage-activated Ca²⁺ channels (VACCs) expressed on primary afferent central terminals in the spinal cord. Consequently, nociceptive pain generally responds well to conventional analgesics. Nonsteroidal anti-inflammatory drugs work by inhibiting the production of inflammatory mediators that activate TRPV1/TRPA1 channels, whereas opioids suppress VACC activity via inhibitory G proteins (Huang et al. 2019; Kohno et al. 1999; Sun et al. 2019; Wu et al. 2004; Zamponi & Snutch 1998). However, persistent inflammatory pain is not maintained by glutamate N-methyl-D-aspartate receptors (NMDARs) and is not linked to altered NMDAR activity in the spinal dorsa horn (Cheng et al. 2008; Huang et al. 2019). Additionally, gabapentinoids, including gabapentin and pregabalin, are generally ineffective in managing nociceptive pain caused by tissue inflammation and surgery (Verret et al. 2020; Bensen et al. 2023).

Neuropathic pain, in contrast, is a debilitating condition characterized by chronic pain resulting from diseases or injuries that directly impact the somatic nervous system. Common examples include postherpetic neuralgia, diabetic neuropathy, chemotherapy-induced neuropathy, and spinal cord injury. It often manifests as shooting or burning sensations and poses a significant therapeutic challenge due to its complex mechanisms and limited treatment options. Current treatments for neuropathic pain primarily include antidepressants and gabapentinoids. However, opioids have little effect on NMDAR-mediated nociceptive hypersensitivity and can even paradoxically enhance presynaptic NMDAR activity in the spinal cord (Deng et al. 2019b; Yaksh 1989; Zhou et al. 2010; Zhou et al. 2011). Neuropathic pain predominantly stems from the abnormal amplification of nociceptive signals transmitted from primary sensory nerves to the spinal dorsal horn (Campbell & Meyer 2006; Woolf & Salter 2000; Waxman & Zamponi 2014). A central mechanism underlying its pathophysiology is synaptic plasticity within the spinal cord. Specifically, enhanced synaptic transmission mediated by two major ionotropic glutamate receptor types—NMDARs and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs)—plays a pivotal role in amplifying nociceptive input from primary sensory nerves to the spinal dorsal horn (Figure 1). Persistent activation of synaptic NMDARs and Ca²⁺-permeable AMPARs (CP-AMPARs) increases Ca²⁺ influx into spinal dorsal horn synapses, triggering presynaptic transmitter release and postsynaptic potentiation, which amplify nociceptive input (Deng et al. 2019b; Xie et al. 2022; Huang et al. 2022; Chaplan et al. 1997; Chen et al. 2014b; Chen et al. 2013). Furthermore, postsynaptic NMDAR stimulation disrupts normal synaptic inhibition mediated by γ-aminobutyric acid (GABA) and glycine through proteolysis of the potassium chloride cotransporter 2 (KCC2) (Zhou et al. 2012; Li et al. 2016). This disruption further enhances nociceptive glutamatergic input to excitatory neurons in the spinal dorsal horn (Huang et al. 2024a). In addition, postsynaptic AMPARs are responsible for fast excitatory neurotransmission and play a critical role in initiating postsynaptic membrane depolarization. Their subunit composition, synaptic trafficking, and functional properties are dynamically regulated in response to neuronal activity, enabling rapid adjustments in synaptic strength in chronic pain states (Huang et al. 2024b; Chen et al. 2019a; Li et al. 2021; Chen et al. 2013).

Figure 1. Schematic representation highlights the major differences in synaptic transmission from primary sensory nerves to spinal dorsal horn neurons between nociceptive pain and neuropathic pain.

Nociceptive pain arises from tissue injury, which activates primary sensory neurons expressing nociceptive sensors (nociceptors), such as transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) channels. These nociceptive signals are transmitted through TRPA1/TRPV1 channels and voltage-activated Ca²⁺ channels (VACCs) located on the central terminals of primary afferent neurons in the spinal cord. In contrast, neuropathic pain stems from diseases or injuries directly to sensory nerves, leading to the generation of ongoing ectopic nerve discharges. These signals are amplified by increased synaptic activity involving NMDA receptors (NMDARs) and Ca²⁺-permeable AMPA receptors (CP-AMPARs) in the spinal dorsal horn.

Although NMDARs have a well-established role in the development of neuropathic pain (Salter & Pitcher 2012; Zhou et al. 2011), clinically used NMDAR antagonists are largely ineffective for treating chronic neuropathic pain in humans. This is likely due to the severe adverse effects associated with non-selective NMDAR blockade, especially at high doses. In contrast, the clinical efficacy of gabapentinoids has been recognized for nearly 40 years, with the α2δ-1 protein (encoded by the Cacna2d1 gene) validated as their primary target. Because α2δ-1 is commonly known as a subunit of VACCs and a binding target of gabapentinoids, it has long been assumed that the therapeutic effects of gabapentinoids are linked to VACC inhibition. However, numerous studies have demonstrated that gabapentinoids have minimal effects on VACC activity or VACC-mediated synaptic transmission (Rock et al. 1993; Schumacher et al. 1998; Brown & Randall 2005; Li et al. 2011; Zhou et al. 2025; Chen et al. 2018). Until recently, the precise mechanism of their therapeutic action remained unclear. This review highlights current insights into α2δ-1–mediated synaptic plasticity in neuropathic pain and discuss the mechanisms underlying therapeutically relevant effects of gabapentinoids.

2. Gabapentinoid efficacy in neuropathic pain and their binding targets

Gabapentin and pregabalin, the two widely prescribed gabapentinoid drugs, are first-line pharmacological treatments for neuropathic pain resulting from traumatic nerve injury, diabetic neuropathy, cancer chemotherapy, spinal cord injury, and postherpetic neuralgia (Dworkin et al. 2003; Rowbotham et al. 1998; Sisignano et al. 2014; Tesfaye et al. 2022; Siddall et al. 2006; Tai et al. 2002). Compared to clinically used NMDAR antagonists, such as ketamine and memantine, gabapentinoids generally have minimal effects on cognitive and psychomotor performance (Freynhagen et al. 2005; Hindmarch et al. 2005). It is important to note that many patients with cancer, major surgeries, diabetic neuropathy, and chronic low back pain experience mixed nociceptive and neuropathic pain, resulting from a combination of tissue and nerve injuries. Furthermore, neuropathic pain is not a single disease entity but rather encompasses diverse etiologies and distinct cellular and molecular mechanisms. For instance, in the animal model of diabetic neuropathy, spinal dorsal horn neurons exhibit increased synaptic CP-AMPARs without a corresponding increase in synaptic NMDAR activity (Chen et al. 2019a). In contrast, NMDARs in primary sensory neurons and their terminals play a critical role in chemotherapy-induced pain hypersensitivity, whereas postsynaptic NMDARs in spinal excitatory neurons primarily amplify nociceptive signals in neuropathic pain caused by traumatic nerve injury (Huang et al. 2023). These complexities likely contribute to limited efficacy of gabapentinoids in some patient populations with chronic neuropathic pain.

Although originally designed as GABA mimetics, gabapentin and pregabalin exert little influence on GABA levels or GABA receptors (Taylor & Harris 2020). The α2δ protein was initially identified as the [³H]gabapentin-binding target in pig cerebral cortex membranes (Gee et al. 1996). In recombinant expression systems, α2δ-1 displays higher gabapentin affinity (KD ~50 nM) compared to α2δ-2 (KD ~150 nM) (Marais et al. 2001). The C terminus of the α2δ-1 protein is essential for the proper assembly of the [³H]gabapentin binding pocket (Brown & Gee 1998). Gabapentin binding is largely diminished in the brain tissues from Cacna2d1 knockout mice (Fuller-Bicer et al. 2009). Similarly, pregabalin binds to α2δ-1 and α2δ-2 in native and recombinant human and porcine systems (Li et al. 2011). A newer gabapentinoid, mirogabalin, exhibits stronger binding affinity and slower dissociation from α2δ-1 (Kitano et al. 2019). Importantly, the analgesic effects of gabapentin and pregabalin on neuropathic pain are abolished in Cacna2d1 knockout mice (Patel et al. 2013; Huang et al. 2020), providing compelling evidence for the essential role of α2δ-1 in the therapeutic effects of gabapentinoids.

The gabapentin and pregabalin binding sites are located on the N terminus of the α2 protein (Field et al. 2006). A single amino acid substitution, R217A, diminishes [³H]gabapentin binding both in vitro (Wang et al. 1999) and in genetically modified mice expressing the R217A mutant (Field et al. 2006). Gabapentin displaces an endogenous ligand, L-leucine, which acts as a positive modulator of α2δ-1 (Felix et al. 2013), and inhibits post-Golgi forward trafficking of α2δ-1 (Bauer et al. 2010). Computational structure-based studies of human α2δ-1 have identified R217 as a critical residue for drug binding, with D428 and D467 serving as additional anchoring points for amino acid-derived drugs (Kotev et al. 2018). Recent cryo-electron microscopy data indicate that gabapentin binds within a pocket located in the dCache1 domain of α2δ-1 and α2δ-2 (Chen et al. 2023).

3. α2δ-1 protein structure and distribution in the nervous system

The α2δ protein family comprises four subtypes: α2δ-1, α2δ-2, α2δ-3, and α2δ-4. These proteins were originally identified as subunits of VACCs and are composed of a 140 kDa α2 protein and a 32 kDa δ protein, first discovered in the skeletal muscle (Borsotto et al. 1985; Leung et al. 1987). Electrophoresis under reduced conditions indicates that the α2 and δ subunits of α2δ-1 are connected by disulfide bonds (Gong et al. 2001). The α2 protein exhibits binding affinity for wheat germ agglutinin and concanavalin A, with its structure consisting of a large glycosylated extracellular domain and a small transmembrane domain (Campbell et al. 1988; Jay et al. 1991). However, it lacks phosphorylation sites and binding sites for dihydropyridine or phenylalkylamine Ca²⁺ channel blockers (Campbell et al. 1988). The δ subunit is not a distinct translation product but is instead a carboxyl-terminal peptide resulting from proteolytic processing of the α2 protein (Jay et al. 1991). While most α2δ proteins are proteolytically cleaved in native tissues, uncleaved α2δ-1 has been detected in dorsal root ganglion (DRG) neurons (Kadurin et al. 2016).

The α2δ-1 protein is a type I transmembrane protein with multiple domains, including an N terminus, one von Willebrand type A (VWA) domain, four tandem cache domains organized into two double-cache domains, a metal ion coordinated by the MIDAS motif in the VWA domain, and a hydrophobic transmembrane C terminus (Brown & Gee 1998; Wu et al. 2016). Cryo-electron microscopy has revealed four disulfide bonds between the α2 and δ subunits and two additional bonds within the δ subunit. Moreover, 15 out of 16 predicted glycosylation sites are located on the surface of the α2δ complex (Wu et al. 2016). The C terminus of α2δ-1 likely functions as an intrinsically disordered protein region (Chen et al. 2018; Li et al. 2021), akin to the C termini of NMDARs and AMPARs. This characteristic explains why the α2δ-1 C terminus remains unresolved in cryo-electron microscopy analyses. While it has been suggested that α2δ proteins are membrane-anchored via a glycosylphosphatidylinositol (GPI) anchor—based on a single experiment showing that phosphatidylinositol-specific phospholipase C (PI-PLC) treatment reduces calcium current density (Davies et al. 2010)—this proposition lacks strong supporting evidence and has yet to be independently validated.

In the nervous system, α2δ-1 is predominantly expressed in neurons within the DRG, the spinal dorsal horn, and various brain regions (Cole et al. 2005; Taylor & Garrido 2008). Its localization is primarily at synaptic terminals rather than neuronal cell bodies (Taylor & Garrido 2008). α2δ-1 mRNA expression has been observed in brain regions associated with cortical processing, learning and memory, defensive behaviors, neuroendocrine secretion, autonomic control, general arousal, and primary sensory transmission (Cole et al. 2005). Additionally, α2δ-1 mRNA is preferentially colocalized with glutamatergic excitatory neurons (Koga et al. 2023; Taylor & Garrido 2008). Consistently, α2δ-1 mRNA is predominantly found in vesicular glutamate transporter-2 (VGluT2)-expressing neurons in the spinal dorsal horn (Koga et al. 2023). In contrast, α2δ-2 mRNA seems to be present mainly in GABAergic inhibitory neurons (Cole et al. 2005).

4. Expression changes and functional significance of α2δ-1 in neuropathic pain

Traumatic nerve injury induces a sustained upregulation of α2δ-1 in the rat DRG (Luo et al. 2001). α2δ-1 mRNA is expressed in 73%, 40%, and 19% of small, medium, and large DRG neurons, respectively, with hybridization signal increasing by 2.8-, 2.5-, and 3.7-fold after nerve injury (Newton et al. 2001). Nerve injury also enhances α2δ-1 trafficking to both central and peripheral terminals of DRG neurons (Bauer et al. 2009). Chemotherapy drugs affect α2δ-1 expression variably. Paclitaxel increases α2δ-1 levels in rat DRG neurons (Kawakami et al. 2012) and the spinal dorsal horn (Chen et al. 2019b). Similarly, oxaliplatin upregulate α2δ-1 mRNA and protein in the rat spinal dorsal horn (Yamamoto et al. 2016). However, treatment with vincristine has no significant effect on α2δ-1 expression levels in the DRG or spinal cord (Luo et al. 2002). In resiniferatoxin-induced small-fiber neuropathy, a non-viral model of postherpetic neuralgia, α2δ-1 is upregulated in small, medium, and large DRG neurons labeled with calcitonin gene-related peptide, isolectin B4, NF200, and tyrosine hydroxylase (Zhang et al. 2021). Additionally, streptozotocin-induced diabetic neuropathy increases α2δ-1 protein levels in the rat DRG and spinal cord (Luo et al. 2002).

The transcriptional and epigenetic mechanisms underlying α2δ-1 upregulation in neuropathic pain remain poorly understood. Overexpression of a transcription factor, specificity protein 1 (Sp1), enhances the Cacna2d1 promoter activity, whereas siRNA-mediated Sp1 silencing significantly reduces α2δ-1 protein expression in cell lines (Martinez-Hernandez et al. 2013). Spinal nerve ligation increases Sp1 and α2δ-1 expression in the DRG, whereas the Sp1 inhibitor mithramycin A suppresses their expression (Gomez et al. 2019). Egr1, another transcription factor, also regulates α2δ-1 expression in cell lines (Gonzalez-Ramirez et al. 2018), but its role in neuropathic pain conditions remains unclear.

Genome-wide analyses indicate that nerve injury has minimal impact on the DNA methylation status of Cacna2d1 in the DRG (Garriga et al. 2018). However, nerve injury increases histone acetylation at the Cacna2d1 promoter, diminishing the enrichment of histone deacetylase-2 (HDAC2) despite elevated HDAC2 protein levels in DRG tissues (Zhang et al. 2022; Laumet et al. 2015). Remarkably, HDAC2 knockdown or conditional knockout in DRG neurons induces persistent mechanical pain hypersensitivity, which is attenuated in Cacna2d1 knockout mice (Zhang et al. 2022). These findings suggest that HDAC2 normally restrains α2δ-1 expression and the development of chronic pain. Following nerve injury, HDAC2 dissociates from the Cacna2d1 promoter, resulting in increased α2δ-1 expression in DRG neurons. Additionally, nerve injury enhances the activity of casein kinase II (CK2), which phosphorylates HDAC2, reducing its binding to the Cacna2d1 promoter and thereby promoting Cacna2d1 transcription in the DRG (Ghosh et al. 2024).

The role of α2δ-1 in chronic neuropathic pain has been demonstrated through gain- and loss-of-function studies. Mice with constitutive Cacna2d1 overexpression exhibit hyperalgesia, tactile allodynia, and increased spinal dorsal horn neuronal responses to painful stimuli (Li et al. 2006). Similarly, intrathecal administration of Cacna2d1-expressing viral vectors in naïve rats induces pain hypersensitivity, which is reversed by NMDAR antagonists (Chen et al. 2018). Conversely, intrathecal treatment with α2δ-1 antisense oligonucleotides reverses tactile allodynia induced by peripheral nerve or spinal cord injury in rats (Li et al. 2004; Boroujerdi et al. 2011). Cacna2d1 knockout mice display delayed mechanical hypersensitivity after partial sciatic nerve injury (Patel et al. 2013). In addition, nociceptive hyperactivity associated with peripheral neuropathic induced by treatment with paclitaxel or resiniferatoxin is largely attenuated in Cacna2d1 knockout mice (Chen et al. 2019b; Zhang et al. 2021).

5. α2δ-1 as a master regulator of glutamatergic synaptic plasticity in neuropathic pain

The role of α2δ-1 in neuropathic pain is well-documented, but recent research has shed light on the precise mechanisms through which this protein contributes to chronic neuropathic pain. Below, we summarize recent findings on the critical function of α2δ-1 in regulating aberrant glutamatergic synaptic transmission in the spinal cord during neuropathic pain.

5.1. α2δ-1 dynamically interacts with and promotes NMDAR synaptic trafficking

Neuropathic pain conditions are often associated with excessive NMDAR activity, which amplifies nociceptive signaling from primary sensory neurons to secondary spinal dorsal horn neurons (Chen et al. 2014b; Xie et al. 2016; Zhang et al. 2021; Chen et al. 2014a). This heightened NMDAR activity also impairs normal synaptic inhibition by GABA and glycine in spinal dorsal horn neurons by inducing KCC2 proteolysis (Zhou et al. 2012; Li et al. 2016; Huang et al. 2023; Huang et al. 2024a). Under normal conditions, NMDARs are expressed inside DRG neurons and their central terminals in the spinal cord (Liu et al. 1994; McRoberts et al. 2011). These presynaptic NMDARs are inactive, and conditional knockout of GluN1, the obligatory subunit of NMDARs, in DRG neurons does not affect baseline nociception (Chen et al. 2022; Huang et al. 2020; McRoberts et al. 2011). Additionally, most NMDARs in spinal dorsal horn neurons are not located at postsynaptic sites, and postsynaptic NMDARs are minimally open at negative membrane potentials due to Mg²⁺ block under normal conditions. Therefore, NMDARs at the spinal cord level are not actively involved in physiological nociceptive transmission, which explains why intrathecal injection of NMDAR antagonists has no effect on nociceptive thresholds in naïve animals (Yamamoto & Yaksh 1992; Chen et al. 2014a; Zhou et al. 2012; Xie et al. 2016).

Both spinal NMDAR hyperactivity and α2δ-1 upregulation occur in various neuropathic pain conditions, and both NMDAR antagonists and gabapentinoids are effective in alleviating neuropathic pain in animal models and patients. In our initial study exploring the potential relationship between α2δ-1 and NMDARs in nerve injury–induced neuropathic pain, we found that treatment with gabapentin fully reverses nerve injury–induced hyperactivity of both presynaptic and postsynaptic NMDARs in spinal dorsal horn neurons (Chen et al. 2018). Interestingly, overexpression of α2δ-1 in naïve rats enhances NMDAR activity at both presynaptic and postsynaptic sites in spinal dorsal horn neurons, and α2δ-1 overexpression–induced pain hypersensitivity is reversed by NMDAR antagonists. Conversely, siRNA-mediated knockdown or genetic deletion of Cacna2d1 reduces nerve injury-induced presynaptic and postsynaptic NMDAR hyperactivity (Chen et al. 2018). Coimmunoprecipitation assays revealed that α2δ-1, but not α2δ-2 or α2δ-3, physically interacts with GluN2A- and GluN2B-containing NMDARs in a heterologous expression system and in spinal cord tissues from both rats and humans. Additionally, live cell luminescence resonance energy transfer (LRET) assays indicate that α2δ-1 is in close proximity to NMDARs (Figure 2) (Chen et al. 2018). Using gene truncation and chimera approaches, we discovered that α2δ-1 interacts with GluN2A- and GluN2B-containing NMDARs via its C terminus. In contrast, the N terminus and VWA domain of α2δ-1, which mediate the gabapentinoid binding and interaction with the VACC α1 subunit, respectively, are not involved in the α2δ-1–NMDAR interaction. Importantly, a peptide mimicking the C-terminal domain of α2δ-1 competitively disrupts the α2δ-1–NMDAR protein complexes, reducing cell surface and synaptic trafficking of NMDARs both in vitro and in vivo (Chen et al. 2018; Luo et al. 2018; Chen et al. 2019b; Zhou et al. 2018). These findings provide compelling evidence that α2δ-1 interacts with NMDARs primarily through the C terminus, promoting their synaptic targeting and surface trafficking in neuropathic pain conditions.

Figure 2. LRET nano-positioning system-based model of α2δ-1–NMDAR interaction.

The LRET-determined distances to the acceptor fluorophore [59 X for site 30 on GluN2A (cyan) and 57 X for site 20 on GluN1 (magenta)] were used to generate the spheres: blue for GluN2A and green for GluN1. The extracellular domains of the α2δ-1 (orange) and NMDAR structures were moved to place the YFP fluorophore (yellow *) tagged to α2δ-1 at the plane of intersection of the LRET radii spheres with the additional constraint of having Cys1071 of the extracellular domain of α2δ-1 (red) near the membrane. There is currently no structural information for the transmembrane C-terminus (residues beyond 1071) of α2δ-1. Reproduced from (Chen et al. 2018).

Intriguingly, α2δ-1 reduces Mg²⁺ block of the GluN1/Glu2A channel, but not the GluN1/GluN2B channel (Chen et al., 2018). We also discovered that α2δ-1 interacts exclusively with functional heteromeric NMDARs (GluN1/GluN2A and GluN1/GluN2B) but not individual NMDAR subunits (Chen et al. 2018). Moreover, α2δ-1 functions primarily as a phospho-binding protein and preferentially interacts with phosphorylated GluN1/GluN2A and GluN1/GluN2B receptors in vitro and in vivo (Zhou et al. 2021b). This insight clarifies why previous proteomic studies using brain tissues did not detect interactions between α2δ-1 and NMDARs. These findings indicate that the dynamic interaction between α2δ-1 and NMDARs is critically dependent on the phosphorylation status of NMDARs. The dynamic interaction between α2δ-1 and NMDARs is critically dependent on the phosphorylation status of GluN2A- and GluN2B-containing NMDARs. Consistent with this, gabapentinoids block protein kinase C (PKC) activator-induced glutamate release (Maneuf & McKnight 2001) and reduce substance P and calcitonin gene-related peptide release only under conditions of inflammation-induced PKC activation in the spinal cord (Fehrenbacher et al. 2003). Nerve injury or chemotherapy increases the activity of protein kinases, such as CK2 and PKC, and reduces calcineurin phosphatase activity in the spinal cord (Miletic et al. 2015; Miletic et al. 2013; Chen et al. 2014b; Xie et al. 2016; Xie et al. 2017a; Xie et al. 2017b), which likely plays a major role in potentiated NMDAR phosphorylation and the dynamic α2δ-1–NMDAR interaction in neuropathic pain conditions.

A series of studies utilizing gabapentinoids, Cacna2d1 knockout, and the α2δ-1 C-terminus peptide has demonstrated the pivotal role of α2δ-1–bound NMDARs in the development of chronic pain caused by nerve injury, paclitaxel-induced neuropathy, resiniferatoxin-induced small-fiber neuropathy, and calcineurin inhibitors (Chen et al. 2018; Chen et al. 2019b; Huang et al. 2023; Huang et al. 2020; Zhang et al. 2021). Notably, brief theta-burst stimulation (TBS) of primary afferent nerves, mimicking nerve injury–induced ectopic bursting discharges, induces NMDAR-mediated long-term potentiation (LTP) in spinal dorsal horn neurons, resulting in long-lasting pain hypersensitivity. This effect is abolished by treatment with α2δ-1 C-terminus peptide or in Cacna2d1 knockout mice, suggesting that primary afferent bursting firing activity can rapidly enhance the α2δ-1–NMDAR interaction in the spinal cord (Huang et al. 2022). TBS or nerve injury promotes the α2δ-1–NMDAR interaction and their synaptic trafficking primarily in VGluT2-expressing excitatory dorsal horn neurons, rather than VGAT-expressing inhibitory neurons (Huang et al. 2023; Huang et al. 2022). Within the spinal dorsal horn, α2δ-1 is predominantly upregulated at primary afferent–excitatory neuron synapses after nerve injury (Yamanaka et al. 2021), explaining the cell type–specific increases in synaptic NMDARs in neuropathic pain conditions. These findings clearly indicate that α2δ-1–bound NMDARs at primary afferent–excitatory neuron synapses play a crucial role in driving nociceptive input to the spinal dorsal horn in chronic neuropathic pain (Figure 3).

Figure 3. Schematic shows the role of α2δ-1 in nerve injury–induced synaptic NMDAR hyperactivity in the spinal dorsal horn.

Under normal conditions, NMDARs exhibit minimal phosphorylation due to constitutive calcineurin activity, and they are not significantly associated with α2δ-1 proteins or expressed at presynaptic or postsynaptic sites. However, traumatic nerve injury reduces calcineurin activity and/or enhances the activity of protein kinases such as PKC and CK2, leading to increased NMDAR phosphorylation at primary afferent central terminals and excitatory neurons in the spinal dorsal horn. Phosphorylated NMDARs interact with upregulated α2δ-1, promoting their trafficking to presynaptic and postsynaptic sites. This process results in synaptic NMDAR hyperactivity and heightened excitatory glutamatergic input within the spinal cord.

5.2. α2δ-1 interacts with and controls synaptic AMPAR phenotypes

Unlike NMDARs, which are obligatory GluN1-containing heteromeric receptors, functional AMPARs are tetrameric ion channels composed of homomeric or heteromeric combinations of GluA1, GluA2, GluA3, and GluA4 subunits. At excitatory synapses, AMPARs predominantly consist of GluA1/GluA2 heteromers, and in some cases, GluA3/GluA2 subunits (Derkach et al. 2007; Traynelis et al. 2010). The GluA2 subunit is crucial in shaping AMPAR biophysics. AMPARs containing the glutamine/arginine (Q/R) edited GluA2 subunit are Ca²⁺-impermeable and exhibit a linear current-voltage (I-V) relationship, whereas those lacking the Q/R edited GluA2 are CP-AMPARs and display an inwardly rectifying I-V relationship (Bowie & Mayer 1995). Nerve injury or diabetic neuropathy increases the prevalence of GluA2-lacking, CP-AMPARs in the spinal dorsal horn, contributing to pain hypersensitivity (Chen et al. 2013; Chen et al. 2019a). However, the molecular mechanisms driving the increased synaptic prevalence of CP-AMPARs in neuropathic pain remain poorly understood until recently.

In our study examining α2δ-1–NMDAR interactions (Chen et al. 2018), we attempted using anti-GluA1 and anti-GluA2 antibodies as negative controls in coimmunoprecipitation experiments. Unexpectedly, we found that α2δ-1 also interacts with both GluA1 and GluA2 subunits in cell lines and spinal cord tissues (Li et al. 2021). This intriguing finding prompted further investigation into the role of α2δ-1 in regulating synaptic AMPARs during neuropathic pain. GluA1 and GluA2 subunits typically form GluA1/GluA2 heterotetramers in the endoplasmic reticulum (ER), which are rapidly transported to synaptic sites (Mansour et al. 2001; Greger et al. 2002). However, coexpression of α2δ-1 alters the I-V relationship from linear to inwardly rectifying in cell lines expressing both GluA1 and GluA2. Furthermore, α2δ-1 overexpression in the spinal cord of naïve rats enhances CP-AMPAR activity in the spinal dorsal horn, while Cacna2d1 knockout reduces nerve injury–induced postsynaptic CP-AMPARs in the spinal cord (Li et al. 2021). LRET assays revealed that α2δ-1 directly interacts with GluA1 and GluA2 subunits (Figure 4). Strikingly, coimmunoprecipitation and Proximity ligation assays demonstrated that α2δ-1 physically disrupts thee GluA1/GluA2 heteromeric assembly both in vitro and in vivo.

Figure 4. LRET nano-positioning model of YFP-α2δ-1 and GluA2 homomeric AMPARs.

The extracellular domains of the α2δ-1 (orange) and AMPAR structure (cyan, magenta, yellow, and green are the tetrameric GluA2 subunits) were moved to place the YFP fluorophore (site shown in green) tagged to α2δ-1 at the LRET-based distance of 54 Å with respect to the acceptor site (site 23 shown in magenta) on the AMPAR, along with the additional constraint of having Cys-1071 (red sphere) of the extracellular domain of α2δ-1 (red) near the membrane segments of the AMPAR. There is currently no structural information for the transmembrane C-terminus (residues beyond Cys-1071) of α2δ-1. Reproduced from (Li et al. 2021).

Notably, using gene truncation and chimera approaches, we found that α2δ-1 interacts with both GluA1 and GluA2 primarily via its C terminus, but not its N terminus or VWA domain. A C-terminal peptide of α2δ-1 disrupts these interactions, effectively restoring GluA1/GluA2 heteromeric assembly and surface expression (Li et al. 2021; Zhou et al. 2022a; Huang et al. 2024b). In addition, the N-terminal signal peptide of GluA1 and GluA2 is critical for their diagonal heteromeric assembly (He et al. 2016). Gabapentinoids, which bind to α2δ-1 near its N terminus (Wang et al. 1999), may inhibit α2δ-1’s interference with GluA1/GluA2 assembly (Li et al. 2021). Thus, by physically interacting with GluA1 and GluA2 and disrupting their heteromeric assembly, α2δ-1 promotes the synaptic expression of GluA1 homotetramer–containing CP-AMPARs in the spinal cord (Figure 5). This process amplifies excitatory glutamatergic input to spinal dorsal horn neurons, contributing to chronic neuropathic pain.

Figure 5. Graphical representation illustrates the role of α2δ-1 in nerve injury–induced postsynaptic Ca²⁺-permeable AMPARs within the spina cord.

Under normal conditions, GluA1 and GluA2 subunits preferentially assemble into GluA1/GluA2 heterotetramers, ensuring that synaptic transmission from primary afferent central terminals to spinal dorsal horn neurons is mediated by postsynaptic GluA2-containing, Ca²⁺-impermeable AMPA receptors (AMPARs). However, in neuropathic pain conditions, the upregulated expression of α2δ-1 directly interacts with GluA1 and GluA2, disrupting their heteromeric assembly in the endoplasmic reticulum (ER). Consequently, this leads to the synaptic incorporation of GluA1 homotetramers, which are Ca²⁺-permeable AMPARs, in spinal dorsal horn neurons.

6. Other proteins interacting with α2δ-1 and their relevance to gabapentinoids

α2δ-1 was originally identified as part of the VACC complexes and is widely regarded as a VACC subunit. α2δ proteins interact with the α1 subunits of VACCs through a predicted VWA domain on the α2 protein (Cantí et al. 2005). α2δ-1 may facilitate VACC activation by increasing the voltage sensitivity of voltage-sensing domains I–III, allowing Ca²⁺ influx within physiological membrane potentials (Savalli et al. 2016). However, quantitative proteomic analysis indicates that α2δ-1 has only a weak interaction with VACC α1 subunits in the brain (Muller et al. 2010). Moreover, coexpression of α2δ-1 in cell lines has minimal impact on the current density of reconstituted VACCs (Wu et al. 2009). Similarly, α2δ-1 ablation does not affect VACC currents in brain neurons (Felsted et al. 2017) or significantly alter the distribution pattern of the VACC α1 subunit in the brain (Held et al. 2020). In addition, gabapentin and pregabalin have no clear effect on VACC activity in neurons or transfected cell lines or VACC-mediated neurotransmitter release at presynaptic terminals (Rock et al. 1993; Schumacher et al. 1998; Brown & Randall 2005; Li et al. 2011; Zhou et al. 2025; Chen et al. 2018). Even prolonged gabapentin treatment (e.g., for one week) does not significantly affect VACC activity in cultured neurons (Hoppa et al. 2012).

Despite the critical role of VACCs in normal nociceptive transmission, neither Cacna2d1 knockout mice nor gabapentinoids affect normal nociception (Chen et al. 2019b; Huang et al. 2022; Chen et al. 2018; Li et al. 2021). Correspondingly, Cacna2d1 knockout and gabapentinoids do not alter the amplitude of AMPAR- and NMDAR-mediated excitatory postsynaptic currents (EPSCs) of spinal dorsal horn neurons evoked from the dorsal root in control animals (Chen et al. 2019b; Huang et al. 2022; Chen et al. 2018; Li et al. 2021). These findings suggest that VACCs are not therapeutically relevant targets of gabapentinoids in neuropathic pain.

α2δ-1 interacts with thrombospondins (TSPs) via its VWA domain, promoting new synaptogenesis but not affecting established synaptic connections in the brain (Eroglu et al. 2009). α2δ-1 may mediate excitatory synaptogenesis following spinal cord injury, contributing to abnormal sympathetic reflexes involved in dysautonomia (Brennan et al. 2021). Additionally, the interaction between TSP4 and α2δ-1 has been implicated in increased glutamatergic input to spinal dorsal horn neurons in nerve injury–induced neuropathic pain (Park et al. 2016). However, co-transfection of α2δ-1 with TSP4 reduces gabapentin’s binding affinity to α2δ-1 on cell membrane (Lana et al. 2016). Furthermore, the TSP-α2δ-1 interaction is not inhibited by gabapentin in vitro (El-Awaad et al. 2019), suggesting that gabapentin may not directly target this interaction to alleviate neuropathic pain. Mice with a global Cacna2d1 knockout exhibit only minor impairments in learning and memory (Zhou et al. 2018), challenging the proposed role of α2δ-1 in synaptogenesis during brain development. It should be noted that blocking NMDARs rapidly reverses nerve injury–induced increases in the frequency of miniature excitatory postsynaptic currents (mEPSCs) in spinal dorsal horn neurons, suggesting that potentiated synaptic NMDAR activity, rather than increased synaptogenesis, drives augmented synaptic glutamate release in neuropathic pain (Huang et al. 2023; Chen et al. 2018; Xie et al. 2016; Zhang et al. 2021). Additionally, gabapentinoids’ inability to affect already developed synaptogenesis cannot account for their rapid onset in alleviating neuropathic pain.

α2δ-1 also directly interacts with large-conductance voltage- and Ca²⁺-activated K⁺ (BK) channels via its N terminus, competing with VACC α1 subunits for α2δ-1 binding (Zhang et al., 2018). Notably, gabapentin does not affect the regulation of VACCs by BK channels (Zhang et al., 2018). To date, there is no evidence linking α2δ-1–BK channel complexes to the therapeutic effects of gabapentinoids in neuropathic pain. Furthermore, α2δ-1 may interact with low-density lipoprotein receptor-related protein 1 (LRP1), potentially influencing VACC trafficking (Kadurin et al. 2017). However, no evidence has linked α2δ-1–LRP1 complexes to neuropathic pain or the therapeutic effects of gabapentinoids.

7. α2δ-1–linked NMDARs and AMPARs: therapeutically relevant targets of gabapentinoids in neuropathic pain and other disorders

Understanding the dynamic interactions between α2δ-1 and NMDARs/AMPARs in regulating synaptic plasticity is essential for elucidating therapeutically relevant actions of gabapentinoids in neuropathic pain treatment. Gabapentinoids inhibit NMDAR synaptic trafficking and activity in the spinal cord, thereby reducing pain hypersensitivity in animal models of neuropathic pain induced by traumatic nerve injury, paclitaxel treatment, resiniferatoxin-induced small-fiber sensory neuropathy, and calcineurin inhibitor treatment (Chen et al. 2018; Chen et al. 2019b; Huang et al. 2020; Zhang et al. 2021). Furthermore, gabapentinoids suppress synaptic CP-AMPARs in the spinal cord by preventing α2δ-1 from disrupting the heteromeric assembly of GluA1/GluA2. This effect has been demonstrated in neuropathic pain models caused by traumatic nerve injury, streptozotocin-induced diabetic neuropathy, and calcineurin inhibitor treatment (Huang et al. 2024b; Li et al. 2021). Importantly, when the gabapentin binding site near the N terminus of α2δ-1 is mutated (R217A), the α2δ-1 mutant retains its ability to promote NMDAR synaptic trafficking and disrupt GluA1/GluA2 heteromeric assembly. However, gabapentin fails to affect the activity of NMDARs and CP-AMPARs potentiated by the α2δ-1 mutant (Chen et al. 2018; Li et al. 2021).

Because α2δ-1 interacts with multiple proteins, it has historically been challenging to identify which of the interactions are relevant to therapeutic actions of gabapentinoids. Recent studies, however, have clarified this issue. The VWA domain near the N terminus of the α2 protein enables α2δ-1 to interact with VACCs, TSPs, BK channels, and LRP1, whereas its C-terminal region facilitates interactions with NMDARs and AMPARs. Two crucial lines of evidence indicate that α2δ-1 interactions with NMDARs and AMPARs are predominantly responsible for the therapeutic effects of gabapentinoids in neuropathic pain. First, both intrathecal and systemic administration of an α2δ-1 C-terminus peptide, which disrupts α2δ-1 interactions with NMDARs and AMPARs, effectively attenuates neuropathic pain in animal models (Chen et al. 2018; Chen et al. 2019b; Huang et al. 2020; Zhang et al. 2021). Second, studies using Cacna2d1 knockout mice reveal that re-expression of wild-type α2δ-1 at the spinal cord level induces pain hypersensitivity. However, re-expression of a chimeric α2δ-1 protein, in which the C-terminal region is replaced by that of α2δ-3, fails to do so (Li et al. 2021; Chen et al. 2018).

The identification of α2δ-1–bound NMDARs and AMPARs in glutamatergic synaptic plasticity has significant therapeutic implications beyond neuropathic pain. For instance, disrupting α2δ-1–NMDARs in the paraventricular nucleus of the hypothalamus can reverse persistent hypertension caused by chronic stress (Zhou et al. 2021a), angiotensin II (Ma et al. 2018a), and calcineurin inhibitors (Zhou et al. 2022b; Zhou et al. 2023), as well as in spontaneously hypertensive rats (Ma et al. 2018b). Also, α2δ-1 augments synaptic CP-AMPARs by inhibiting GluA1/GluA2 heteromeric assembly in the hypothalamus, contributing to hypertension caused by calcineurin inhibitors and observed in spontaneously hypertensive rats (Zhou et al. 2022a; Zhou et al. 2024). Moreover, α2δ-1–NMDARs play a significant role in neuronal NMDAR hyperactivity and subsequent brain damage caused by brain ischemia (Luo et al. 2018; Wu et al. 2023). In the context of opioid-induced addiction behavior, α2δ-1 mediates synaptic NMDAR hyperactivity in the nucleus accumbens caused by repeated opioid exposure (Jin et al. 2023). Therefore, gabapentinoids hold significant potential for repurposing as treatments for ischemic stroke, neurogenic hypertension, and opioid use disorder.

α2δ-1 is uniquely involved in amplifying nociceptive transmission via its interactions with NMDARs and AMPARs in chronic neuropathic pain but does not play a significant role in acute physiological nociception, which is predominantly mediated by VACCs (Figure 1). Thus, gabapentinoids alone have minimal analgesic effect in patients with acute postoperative pain (Verret et al. 2020). Brief and repeated stimulation of μ-opioid receptors can potentiate nociceptive primary afferent input to spinal dorsal horn neurons via presynaptic α2δ-1–bound NMDARs, thereby contributing to opioid-induced hyperalgesia and reduced analgesic efficacy (Deng et al. 2019a; Chen et al. 2022; Zhou et al. 2010; Zhao et al. 2012). Consistent with these findings, clinical studies indicate that gabapentinoids enhance the analgesic effect of opioids and reduce opioid consumption in patients with acute postoperative pain (Dierking et al. 2004; Dirks et al. 2002; Eckhardt et al. 2000; Yücel et al. 2011). Thus, gabapentinoids can enhance the analgesic effect of opioids on acute pain and reduce opioid-induced hyperalgesia and tolerance.

8. Molecular mechanisms underlying other α2δ-1– and α2δ-2–mediated effects of gabapentinoids

The α2δ-1–NMDAR interaction is of high physiological relevance, playing a critical role in corticostriatal long-term potentiation (LTP) and LTP-associated learning and memory (Zhou et al. 2018). α2δ-1–bound NMDARs are present in the striatum of both mice and humans, and both gabapentin and α2δ-1 C-terminus peptide can block the coincident presynaptic and postsynaptic NMDAR activity of medium spiny neurons potentiated by TBS (Zhou et al. 2018). These effects may underlie certain adverse effects of gabapentinoids, such as delusions and drowsiness. Notably, CP-AMPARs of motor neurons associated with amyotrophic lateral sclerosis (ALS) primarily result from impaired RNA editing at the Q/R site of GluA2 (Aizawa et al. 2016; Hosaka et al. 2021), rather than reduced GluA1/GluA2 assembly. This distinction may explain why gabapentin is ineffective for treating patients with ALS (Miller et al. 2001).

Gabapentinoids cause gait abnormalities and ataxia, particularly in the elderly (Çağlar Okur et al. 2019; Rissardo & Caprara 2020; Kanao-Kanda et al. 2016; Rentsch et al. 2020). Because Cacna2d1 knockout mice do not exhibit gait disorders, these adverse effects are unlikely caused by α2δ-1 inhibition. Recent findings also reveal a physical interaction between α2δ-2 proteins and unedited GluK1(Q)/GluK2(Q), Ca²⁺-permeable kainate receptor subunits, in the cerebellum, where α2δ-2 enhances postsynaptic GluK1-containing kainate receptor activity in Purkinje cells, thereby regulating motor coordination (Zhou et al. 2025). Interestingly, α2δ-2 promotes surface expression of GluK1 receptors via its C terminus, and cerebellar injection of a peptide derived from the α2δ-2 C terminus impairs motor function (Zhou et al. 2025). These findings suggest that gabapentinoids may contribute to gait disorders and ataxia by inhibiting the activity of α2δ-2–bound GluK1 receptors in the cerebellum. Notably, gabapentinoids can paradoxically exacerbate certain seizure types, particularly absence and myoclonic seizures (Di Rocco et al. 2013; Perucca et al. 1998; Striano et al. 2007). Whether these unexpected effects are linked to α2δ-2–bound kainate receptors in inhibitory neurons of the brain remains to be determined. In addition, α2δ-2 has been identified as a developmental switch that restricts axon growth and regeneration. Pharmacological inhibition of α2δ-2 with gabapentin or pregabalin has been shown to enhance axon regeneration in mice following spinal cord injury (Sun et al. 2020; Tedeschi et al. 2016). It is important to investigate whether this regenerative effect of gabapentinoids involves the inhibition of α2δ-2–bound GluK1-containing receptors in the spinal cord.

9. Conclusions and perspectives

Recent studies highlight the pivotal role of α2δ-1 and α2δ-2 proteins in regulating synaptic ionotropic glutamate receptors independently of VACC function. Notably, α2δ-1 primarily modulates NMDARs and AMPARs in excitatory neurons, while α2δ-2 regulates kainate receptors in inhibitory neurons. Several γ proteins, including the γ2 (stargazin), γ7, and γ8, initially identified as VACC subunits, have now been recognized as transmembrane AMPAR regulatory proteins (Chen et al. 2000; Kato et al. 2007; Rouach et al. 2005). Collectively, these γ proteins, along with α2δ-1 and α2δ-2, could be reclassified as glutamate receptor regulatory proteins.

The dynamic interaction between α2δ-1 and NMDARs/AMPARs is particularly significant due to its critical involvement in synaptic trafficking and the subunit assembly of these receptors. In the context of neuropathic pain, α2δ-1 serves dual functions: it enhances intracellular Ca²⁺ levels at glutamatergic synapses, thereby strengthening excitatory synaptic transmission by promoting the synaptic expression of NMDARs and CP-AMPARs in the spinal dorsal horn. These processes highlight the critical role of α2δ-1 in amplifying nociceptive transmission and maintaining central sensitization in chronic neuropathic pain. Gabapentinoids achieve their therapeutic effects primarily by inhibiting α2δ-1–linked NMDARs and CP-AMPARs at primary afferent–spinal excitatory synapses under neuropathic pain conditions. These mechanisms of action explain why gabapentinoids are particularly effective in treating neuropathic pain but not nociceptive pain. Notably, gabapentinoids and the α2δ-1 C-terminal peptide selectively target α2δ-1–NMDAR complexes without affecting physiological NMDARs that are not bound to α2δ-1. This selectivity minimizes adverse effects compared to clinically used NMDAR antagonists.

Although substantial progress has been made in elucidating the critical role of α2δ-1 in orchestrating synaptic plasticity under neuropathic pain conditions, many questions remain unanswered. For example, while α2δ-1 directly interacts with and promotes synaptic trafficking of GluN2A- and GluN2B-containing NMDARs (Chen et al. 2018), its potential regulation of GluN2C- and GluN2D-containing NMDARs remains unknown. Also, it is unclear how the gabapentinoid binding to the N terminus of α2δ-1 influences its C-terminal interactions with NMDARs and AMPARs. The allosteric communication between the two sites of α2δ-1 is not known. Molecular modeling (Figures 2 and 4) suggests that the membrane-spanning C terminus of α2δ-1 physically interacts with the transmembrane domain of NMDARs and AMPARs (Chen et al. 2018; Li et al. 2021). However, the specific regions of NMDARs and AMPARs involved in these interactions remain to be identified. Furthermore, both gabapentin and pregabalin rapidly inhibit ectopic bursting activity in injured primary afferent nerves (Chen et al. 2001; Pan et al. 1999). Yet, it is uncertain whether α2δ-1–bound NMDARs contribute to nerve injury–induced ectopic activity in peripheral nerves. Considering the comparable expression levels of GluA1 and GluA3 in glutamatergic synapses, further studies are warranted to elucidate whether and how α2δ-1 influences GluA3-containing AMPARs in neuropathic pain. It is also unknown whether the interaction between α2δ-1 and AMPAR subunits is phosphorylation-dependent and regulated by specific kinases or phosphatases. Additionally, although gabapentinoids effectively treat fibromyalgia and generalized anxiety disorder, it remains unclear whether α2δ-1–bound NMDARs and/or AMPARs contribute to these conditions. Similarly, while gabapentinoids are used as adjunctive therapy for partial seizures in epilepsy (Chadwick et al. 1998; Zaccara et al. 2014), the role of α2δ-1 interactions with NMDARs or AMPARs in the pathogenesis of different epilepsy types remains unexplored. Addressing these knowledge gaps will advance our understanding of α2δ-1–mediated synaptic plasticity and guide the rational use of gabapentinoids in treating various neurological disorders.

List of Abbreviations:

AMPAR

α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor

CP-AMPAR

Ca²⁺-permeable AMPA receptor

DRG

dorsal root ganglion

ER

endoplasmic reticulum

HDAC2

histone deacetylase-2

GABA

γ-aminobutyric acid

KCC2

potassium chloride cotransporter 2

LRET

luminescence resonance energy transfer

LTP

long-term potentiation

NMDAR

N-methyl-D-aspartate receptor

TBS

theta-burst stimulation

TSP

thrombospondin

TRPA1

transient receptor potential ankyrin 1

TRPV1

transient receptor potential vanilloid 1

VACC

voltage-activated Ca²⁺ channel

VWA

von Willebrand type A