Table 1.
LROs and their associated disease models
| Lysosome-Related Organelles |
Cell Types | Description | LRO disease model |
|---|---|---|---|
| LROs-Vertebrate | |||
| Melanosomes | Melanocytes or melanophores in skin, retinal pigment epithelia and other eye pigment cells | Site of melanin synthesis and storage for photoprotection and visual acuity | HPS, CHS, GS |
| Lamellar bodies (mammals) or swimbladder surfactant storage organelles (teleosts) | Alveolar type II (AT2) cells | Organelles for synthesis, storage and secretion of pulmonary surfactant | HPS |
| Lamellar bodies / Lamellar granules | Keratinocytes | Enriched in lipids that are secreted by keratinocytes into extracellular spaces of the epidermis to form a permeability barrier | ARC |
| Cytolytic granules | T cells, Natural killer cells | Store granzymes, perforin and other cytotoxic proteins that induce target cell death upon secretion | FHL, GS type 2, CHS, HPS (AP-3) |
| Weibel-Palade bodies | Endothelial cells | Cigar-shaped secretory granules containing von Willebrand Factor and other proteins that mediate hemostasis and inflammation upon secretion | HPS (BLOC-2 and AP-3), FHL3 |
| Alpha granules | Platelets, Megakaryocytes | Store a variety of protein factors that upon secretion mediate blood clotting, platelet adhesion, hemostasis, inflammation and vascularization | GPS, ARC |
| Dense granules | Platelets, Megakaryocytes (?) | Contain small molecules (e.g. serotonin, calcium, ADP and others) and polyphosphate that upon secretion enhance platelet adhesion and activation | HPS, FHL |
| MHC class II compartments | Activated dendritic cells, B lymphocytes, macrophages, Langerhans cells | Non-terminal late endosomes and lysosomes that are enriched in MHC class II molecules assembling with peptides | CHS |
| Basophilic granules | Mast cells, likely basophils | Store granzymes, heparin, histamine, serotonin, prostaglandin, and leukotrienes for secretion at sites of damage or infection to increase vasodilation | CHS, FHL |
| Azurophilic (primary) granules | Neutrophils, Eosinophils | Store lysosomal enzymes and anti-microbial peptides for release directly into phagosomes | HPS (AP-3), CHS |
| Phagosomes | Macrophages, neutrophils, dendritic cells | Surround phagocytosed microorganisms, apoptotic cells or other large particles; kill and digest the contents and initiate signal transduction cascades | HPS (AP-3), CHS, ARC in insects |
| NOX2+ inhibitory lysosomes | Conventional dendritic cells | Contain the NADPH oxidase NOX2, which negatively regulates proteolysis upon fusion with phagosomes to facilitate cross-presentation | GS2 |
| IRF7 signaling lysosomes | Plasmacytoid dendritic cells | The site of an IRF7 signaling cascade from nucleic acid sensing toll like receptors to initiate production of type I interferon | HPS |
| Acrosomes | Sperm cells | Organelles storing hydrolytic and glycolytic proteins that are secreted by sperm to reach the egg prior to fertilization | GS2 |
| Notochord vacuoles | Notochord inner cells | Organelles required for body axis elongation and spine morphogenesis | HPS |
| LROs-invertebrate | |||
| Pigment granules | Drosophila melanogaster retinal cells | Contain red and brown pigments that are necessary for light insulation in order to prevent the loss or spread of light throughout the eye | HPS |
| Gut granules | Caenorhabditis elegans intestinal cells | Storage compartment putatively containing zinc, anthranilic acid, and lipofuscin | HPS, CHS |
| Zinc storage granules | Drosophila melanogaster Malpighian tubule epithelial cells | Storage compartment that collectively contains the total body pool of chelatable zinc | HPS |
| Post-lysosomes | Dictyostelium discoideum | Deacidified secretory compartments that mature from lysosomes and constitutively secrete undigested material into the extracellular space | CHS |
| Mucocysts | Tetrahymena thermophila | Secretory granules containing peptides that, upon stimulated exocytosis, surround the cell in a thick mucus layer as a method of cellular defense | HPS |
| Riboflavin granules | Bombyx mori Malpighian tubules | Needle-shaped yellow granules that store riboflavin | HPS |
| Integument urate granules | Bombyx mori epidermal cells | Crystal form of the uric acid-containing fat body that make the larval skin opaque for protection from ultraviolet radiation | HPS |
| Putative LROs-vertebrate | |||
| Large dense-core vesicles | Specialized secretory cells (e.g. adrenal chromaffin cells) | Secretion of hormones and neuropeptides | HPS |
| Specific (secondary) granules | Neutrophils | Secretory granules containing cytotoxic proteins involved in the initiation of the inflammatory response | |
| Gelatinase (tertiary) granules | Neutrophils | Secretory granules containing gelatinase, receptors, adhesion molecules and other proteins to mediate cell adhesion to the endothelium | |
| Presynaptic vesicles | Neuron synaptic cleft | Secretory vesicles containing neurotransmitters that are released at the synapse upon stimulation | HPS (AP-3 and BLOC-1) |
| Osteoclast secretory lysosome | Osteoclasts | Secretory lysosomes involved in bone resorption and remodeling | GS2 |
| Fusiform vesicles | Urothelium | Compartment mediating the storage and transport of urothelial plaques for bladder expansion | |
| Putative LROs-invertebrate | |||
| Glue granules | Drosophila melanogaster larval salivary gland epithelial cells | Secretory granules containing highly glycosylated glue proteins required for pupal case adhesion to a solid substrate during metamorphosis | |