{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nMCOLN3 is a Ca²⁺‐permeable, inwardly rectifying cation channel whose pore properties are highly dynamic and subject to complex regulation. The channel is activated after pre‐exposure to sodium‐free conditions and subsequently modulated by extracytosolic H⁺, with specific residues in its large luminal loop (e.g., a string of histidines) controlling its gating. Mutations such as A419P disrupt this regulatory mechanism, locking the channel in a constitutively open state and expanding the pore, which alters ionic permeability and contributes to pathophysiological conditions. In addition, systematic mutagenesis indicates that extracellular negative charges are important for sodium‐mediated block, and recent cryo‐EM studies have shed light on its distinctive pore architecture that underpins these regulatory processes."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "5"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn addition to its intrinsic biophysical properties, MCOLN3 exhibits a dynamic subcellular distribution and forms both homo‐ and heteromultimeric complexes with other TRPML family members as well as with channels from related subfamilies (e.g., TRPV5). Predominantly localized to early and late endosomes and trafficked to autophagosomes under stress conditions, MCOLN3 plays a crucial role in endocytosis and membrane trafficking. Its intermixing with TRPML1, TRPML2, and even heteromerization with TRPV5 appears to dictate not only its subcellular targeting but also functional diversity, ultimately impacting the degradation of cargos such as the epidermal growth factor receptor as well as the maturation of autophagosomes. Furthermore, interactions with autophagy‐related proteins (e.g., GATE16) underscore its role in facilitating autophagosome fusion events."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "6", "end_ref": "12"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nMCOLN3’s function is further modulated by post‐translational modifications such as palmitoylation, which governs its trafficking between subcellular compartments and is essential for its role in autophagosome formation. In sensory hair cells, for instance, the aberrant gain‐of‐function mutations in MCOLN3 lead to sustained Ca²⁺ influx that, while initially tolerated due to compensatory mechanisms (including plasma membrane Ca²⁺ ATPases), eventually contribute to cellular degeneration and hearing loss. Thus, MCOLN3 integrates complex gating, localization, and modification mechanisms to regulate calcium dynamics and membrane trafficking processes central to both normal physiology and disease pathogenesis."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "13", "end_ref": "15"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Hyun Jin Kim, Qin Li, Sandra Tjon-Kon-Sang, et al. 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