id: P51798 gene_symbol: CLCN7 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: CLCN7 encodes ClC-7, a member of the CLC family that functions as an electrogenic 2Cl(-)/1H(+) antiporter (exchanger) rather than a passive chloride channel. It resides in the membranes of late endosomes and lysosomes, and in osteoclasts it localizes to the ruffled border bounding the resorption lacuna. ClC-7 forms an obligate heteromeric complex with the accessory beta-subunit OSTM1, which is required for ClC-7 protein stability and transport activity. By coupling chloride flux to the outwardly directed proton gradient, ClC-7 provides the counter-ion movement that allows the V-ATPase to acidify the lysosomal lumen and the osteoclast resorption space, and it raises luminal chloride concentration. Loss-of-function variants cause osteopetrosis (recessive OPTB4 and dominant Albers-Schonberg OPTA2) together with lysosomal storage and neurodegeneration, whereas certain gain-of-function variants cause a distinct hypopigmentation, organomegaly and delayed-myelination syndrome. alternative_products: - name: '1' id: P51798-1 - name: '2' id: P51798-2 sequence_note: VSP_045698 existing_annotations: - term: id: GO:0005254 label: chloride channel activity evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables review: summary: ClC-7 is an electrogenic 2Cl(-)/1H(+) antiporter, not a passive chloride channel. The "chloride channel activity" term reflects historical CLC family naming but is mechanistically imprecise for ClC-7. action: MODIFY reason: The verified molecular function of ClC-7 is coupled Cl(-)/H(+) exchange, directly demonstrated electrophysiologically with a measured 2Cl(-)/1H(+) stoichiometry. A more accurate term, chloride:proton antiporter activity (GO:0062158), is already present in GOA and should replace the generic channel term. proposed_replacement_terms: - id: GO:0062158 label: chloride:proton antiporter activity supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0005765 label: lysosomal membrane evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: is_active_in review: summary: ClC-7 is active in the lysosomal membrane, where it performs Cl(-)/H(+) exchange. This localization is strongly supported by multiple experimental studies. action: ACCEPT reason: Lysosomal membrane is the core site of ClC-7 action and is corroborated by direct experimental localization and functional studies. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0005770 label: late endosome evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: is_active_in review: summary: ClC-7/OSTM1 resides in the late endosomal/lysosomal system, so late endosome localization is plausible but is a less central site than the lysosome. action: KEEP_AS_NON_CORE reason: Late endosomal localization is consistent with ClC-7 being an endolysosomal transporter, but the dominant and functionally characterized compartment is the lysosome; this phylogenetically inferred late-endosome term is retained as non-core. supported_by: - reference_id: PMID:32851177 supporting_text: CLC-7 functions as an electrogenic antiporter that mainly resides in lysosomes and osteoclast ruffled membranes. reference_section_type: ABSTRACT - term: id: GO:0030321 label: transepithelial chloride transport evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in review: summary: ClC-7 is an intracellular endolysosomal Cl(-)/H(+) antiporter, not a plasma-membrane transporter mediating transepithelial chloride movement. action: REMOVE reason: Transepithelial chloride transport implies vectorial transport across an epithelial cell layer at the plasma membrane. ClC-7 acts on intracellular organelle membranes (lysosome, osteoclast ruffled border); this term is an over-annotation transferred phylogenetically and from a ComplexPortal complex annotation. An OpenScientist run traced the annotation to a ComplexPortal family-level introductory sentence (not specific to ClC-7) that was then propagated by PANTHER IBA to ~1,198 ortholog annotations, and confirmed via sorting-signal analysis that ClC-7 carries N-terminal dileucine and acidic-cluster lysosomal targeting motifs (absent from the plasma-membrane paralogs CLCNKA/CLCNKB) and never participates in transepithelial transport, so the term should be removed rather than merely flagged. supported_by: - reference_id: PMID:32851177 supporting_text: CLC-7 functions as an electrogenic antiporter that mainly resides in lysosomes and osteoclast ruffled membranes. reference_section_type: ABSTRACT - reference_id: file:human/CLCN7/CLCN7-hypotheses/topology-transepithelial-overannotation/openscientist.md supporting_text: a PANTHER IBA (Inferred by Biological Aspect of Ancestor) annotation that propagated this error to CLCN7 orthologs across approximately 1,198 annotations in many species. - reference_id: file:human/CLCN7/CLCN7-hypotheses/topology-transepithelial-overannotation/openscientist.md supporting_text: CLC-7 contains N-terminal dileucine and acidic cluster sorting motifs that actively target it to lysosomes - term: id: GO:0034707 label: chloride channel complex evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: part_of review: summary: ClC-7 is part of an obligate heteromeric complex with the beta-subunit OSTM1. This term captures that real CLCN7-OSTM1 complex (the "channel" label reflects family naming convention). action: ACCEPT reason: The CLCN7-OSTM1 complex is well established structurally and functionally (ComplexPortal CPX-6321), and OSTM1 is required for ClC-7 stability and activity. The term name uses "channel" by family convention, but the complex assignment is correct. supported_by: - reference_id: PMID:21527911 supporting_text: ClC-7 is a slowly voltage-gated 2Cl(-)/1H(+)-exchanger and requires Ostm1 for transport activity. reference_section_type: TITLE - reference_id: PMID:32851177 supporting_text: the highly glycosylated Ostm1 functions like a lid positioned above CLC-7 and interacts extensively with CLC-7 within the membrane. reference_section_type: ABSTRACT - term: id: GO:0062158 label: chloride:proton antiporter activity evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables review: summary: This is the accurate core molecular function of ClC-7, matching the experimentally measured 2Cl(-)/1H(+) exchange. action: ACCEPT reason: Direct electrophysiology established a 2Cl(-)/1H(+)-exchange stoichiometry, and ClC-7 mediates the major lysosomal Cl(-)/H(+) antiport. This term precisely describes the verified activity. supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:1902476 label: chloride transmembrane transport evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in review: summary: ClC-7 mediates transmembrane chloride movement as part of its Cl(-)/H(+) exchange across the lysosomal membrane. action: ACCEPT reason: Chloride transmembrane transport is a correct biological-process description of ClC-7 antiporter activity and is well supported experimentally. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0005254 label: chloride channel activity evidence_type: IEA original_reference_id: GO_REF:0000117 qualifier: enables review: summary: Same imprecise channel term as the IBA annotation, here from an ARBA machine-learning model. ClC-7 is an antiporter. action: MODIFY reason: ClC-7 mediates coupled 2Cl(-)/1H(+) exchange rather than passive channel conduction; chloride:proton antiporter activity (GO:0062158) is the accurate replacement. proposed_replacement_terms: - id: GO:0062158 label: chloride:proton antiporter activity supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - term: id: GO:0005765 label: lysosomal membrane evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: Lysosomal membrane localization, here from UniProt subcellular-location mapping; corroborated by experimental evidence. action: ACCEPT reason: Lysosomal membrane is the core localization of ClC-7 and is independently supported by experimental studies. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0006821 label: chloride transport evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in review: summary: Generic chloride transport, an InterPro2GO transfer. Correct but less specific than chloride transmembrane transport / antiporter activity. action: KEEP_AS_NON_CORE reason: This term is a high-level parent consistent with ClC-7 function but is superseded by the more specific chloride transmembrane transport and chloride:proton antiporter terms already annotated. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0015108 label: chloride transmembrane transporter activity evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: Generic chloride transmembrane transporter activity from InterPro2GO. This is the correct parent of the antiporter activity but does not capture the coupled exchange mechanism. action: KEEP_AS_NON_CORE reason: Correct but generic; the specific chloride:proton antiporter activity (GO:0062158) is the informative molecular-function term. Retained as non-core. supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - term: id: GO:0016020 label: membrane evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: located_in review: summary: Uninformative generic membrane localization from InterPro2GO. action: MARK_AS_OVER_ANNOTATED reason: "\"membrane\" is an uninformatively broad cellular-component term; the\ \ specific lysosomal membrane localization is already captured by experimental\ \ annotations." - term: id: GO:0055085 label: transmembrane transport evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in review: summary: Generic transmembrane transport from InterPro2GO. action: KEEP_AS_NON_CORE reason: A high-level parent of the specific chloride transmembrane transport term; consistent with ClC-7 function but uninformative on its own. Retained as non-core. - term: id: GO:0062158 label: chloride:proton antiporter activity evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: Accurate antiporter molecular function, here from InterPro2GO; matches the experimentally verified activity. action: ACCEPT reason: This is the verified core molecular function and is independently supported by direct electrophysiological measurement of 2Cl(-)/1H(+) exchange. supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - term: id: GO:1902600 label: proton transmembrane transport evidence_type: IEA original_reference_id: GO_REF:0000108 qualifier: involved_in review: summary: Proton transmembrane transport, inferred logically from the antiporter activity. ClC-7 does move protons as part of its coupled exchange. action: ACCEPT reason: Proton movement is an intrinsic half of the 2Cl(-)/1H(+) exchange and is directly supported by the measured stoichiometry and the role in lysosomal acidification. supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32296183 qualifier: enables review: summary: Bare "protein binding" from a high-throughput binary interactome screen; uninformative about ClC-7 function. action: MARK_AS_OVER_ANNOTATED reason: "GO:0005515 protein binding conveys no specific molecular function. The\ \ interactions reported in this large-scale screen are not the functionally defining\ \ OSTM1 partnership and do not warrant a specific term." - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32814053 qualifier: enables review: summary: Bare "protein binding" from a neurodegenerative-disease interactome map; uninformative. action: MARK_AS_OVER_ANNOTATED reason: "GO:0005515 protein binding is uninformative and does not capture a specific\ \ molecular function for ClC-7." - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32851177 qualifier: enables review: summary: This IPI is to OSTM1 (Q86WC4), the functionally essential beta-subunit; however, as bare "protein binding" it is uninformative, and the OSTM1 partnership is better captured by the chloride channel complex term. action: MARK_AS_OVER_ANNOTATED reason: "Although the underlying OSTM1 interaction is biologically central, the\ \ generic GO:0005515 term adds nothing beyond the CLCN7-OSTM1 complex annotation\ \ (GO:0034707). Use the complex term rather than bare protein binding." supported_by: - reference_id: PMID:32851177 supporting_text: the highly glycosylated Ostm1 functions like a lid positioned above CLC-7 and interacts extensively with CLC-7 within the membrane. reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:33961781 qualifier: enables review: summary: Bare "protein binding" (interaction with OSTM1, Q86WC4) from a proteome-scale network study; uninformative as a generic term. action: MARK_AS_OVER_ANNOTATED reason: "The generic GO:0005515 term is uninformative; the OSTM1 partnership it\ \ reflects is already captured by the chloride channel complex annotation." - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:35271311 qualifier: enables review: summary: Bare "protein binding" from the OpenCell endogenous-tagging interactome; uninformative. action: MARK_AS_OVER_ANNOTATED reason: "GO:0005515 protein binding conveys no specific molecular function for\ \ ClC-7." - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:40205054 qualifier: enables review: summary: Bare "protein binding" (OSTM1, Q86WC4) from a multimodal cell-map study; uninformative as a generic term. action: MARK_AS_OVER_ANNOTATED reason: "The generic GO:0005515 term adds nothing beyond the already-annotated\ \ CLCN7-OSTM1 complex term." - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:40355756 qualifier: enables review: summary: Bare "protein binding" from a solute-carrier superfamily interactome; uninformative. action: MARK_AS_OVER_ANNOTATED reason: "GO:0005515 protein binding conveys no specific molecular function and\ \ should not be retained as a core annotation." - term: id: GO:0009268 label: response to pH evidence_type: IEA original_reference_id: GO_REF:0000107 qualifier: involved_in review: summary: Response to pH, transferred electronically from a rat ortholog. There is no direct human experimental support, although ClC-7 does contribute to lysosomal pH regulation. action: KEEP_AS_NON_CORE reason: The term is plausible given ClC-7's role in luminal acidification, but it rests on automated ortholog transfer without direct human evidence and is peripheral to the core transporter function. Retained as non-core. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0005765 label: lysosomal membrane evidence_type: EXP original_reference_id: PMID:18449189 qualifier: located_in review: summary: Direct experimental demonstration that ClC-7 localizes to and functions at the lysosomal membrane. action: ACCEPT reason: This is the strongest, experimentally grounded evidence for ClC-7's core lysosomal membrane localization. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0005765 label: lysosomal membrane evidence_type: IDA original_reference_id: PMID:21527911 qualifier: located_in review: summary: Direct localization of the ClC-7/OSTM1 complex to the lysosomal membrane. action: ACCEPT reason: Experimentally supported core localization; the complex requires OSTM1 for proper expression and trafficking. supported_by: - reference_id: PMID:21527911 supporting_text: ClC-7 is a slowly voltage-gated 2Cl(-)/1H(+)-exchanger and requires Ostm1 for transport activity. reference_section_type: TITLE - term: id: GO:0030321 label: transepithelial chloride transport evidence_type: IDA original_reference_id: PMID:32851177 qualifier: involved_in review: summary: ClC-7 is an intracellular endolysosomal antiporter, not a plasma-membrane mediator of transepithelial chloride flux. This ComplexPortal-derived term mislabels the biological process. action: MARK_AS_OVER_ANNOTATED reason: The cited structural study localizes CLC-7 to lysosomes and osteoclast ruffled membranes, not to polarized epithelial plasma membranes mediating transepithelial transport. The term is an over-annotation. supported_by: - reference_id: PMID:32851177 supporting_text: CLC-7 functions as an electrogenic antiporter that mainly resides in lysosomes and osteoclast ruffled membranes. reference_section_type: ABSTRACT - term: id: GO:0034707 label: chloride channel complex evidence_type: IPI original_reference_id: PMID:32851177 qualifier: part_of review: summary: ClC-7 is part of the obligate CLCN7-OSTM1 heteromeric complex, directly visualized by cryo-EM. action: ACCEPT reason: The cryo-EM structure of the human CLC-7/OSTM1 complex directly establishes this complex membership; OSTM1 forms a glycosylated lid over CLC-7. supported_by: - reference_id: PMID:32851177 supporting_text: the highly glycosylated Ostm1 functions like a lid positioned above CLC-7 and interacts extensively with CLC-7 within the membrane. reference_section_type: ABSTRACT - term: id: GO:0016020 label: membrane evidence_type: HDA original_reference_id: PMID:19946888 qualifier: located_in review: summary: Generic membrane localization from a high-throughput NK-cell membrane proteome; uninformative. action: MARK_AS_OVER_ANNOTATED reason: "\"membrane\" is uninformatively broad; the specific lysosomal membrane\ \ localization is established by direct experimental evidence." - term: id: GO:0005765 label: lysosomal membrane evidence_type: HDA original_reference_id: PMID:17897319 qualifier: located_in review: summary: Lysosomal membrane localization from a lysosomal-proteome mass-spectrometry study, corroborating the core localization. action: ACCEPT reason: Detection in the lysosomal membrane proteome supports the experimentally established core localization of ClC-7. supported_by: - reference_id: PMID:17897319 supporting_text: 'Integral and associated lysosomal membrane proteins.' reference_section_type: TITLE - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-2730959 qualifier: located_in review: summary: Lysosomal membrane localization asserted in the Reactome reaction for CLCN7:OSTM1 Cl-/H+ exchange. action: ACCEPT reason: Consistent with the experimentally established core lysosomal membrane localization and the Cl(-)/H(+) exchange reaction catalyzed there. supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0005254 label: chloride channel activity evidence_type: TAS original_reference_id: PMID:8543009 qualifier: enables review: summary: This 1995 cloning paper named ClC-7 within the CLC "chloride channel family" but reported it could not be expressed as a chloride channel; ClC-7 is now known to be a 2Cl(-)/1H(+) antiporter. action: MODIFY reason: The chloride channel designation reflects family naming, and the cited paper itself found no channel activity in heterologous expression. The verified function is coupled Cl(-)/H(+) exchange (GO:0062158). proposed_replacement_terms: - id: GO:0062158 label: chloride:proton antiporter activity supported_by: - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - term: id: GO:0080025 label: phosphatidylinositol-3,5-bisphosphate binding evidence_type: IDA original_reference_id: PMID:35670560 review: summary: ClC-7 transport is tonically inhibited by the lysosome-specific signaling lipid PI(3,5)P2, which binds a pocket at the transmembrane-cytosolic interface; relief of inhibition activates the antiporter and modulates lysosomal acidification [PMID:35670560]. Gain-of-function HOD variants Y715C and K285T lie in this lipid-binding site and reduce PI(3,5)P2 inhibition [PMID:38838776]. This regulatory molecular function is well established experimentally but is not currently present in GOA. action: NEW supported_by: - reference_id: PMID:35670560 supporting_text: PI(3,5)P2 inhibits ClC-7-mediated currents. - reference_id: PMID:38838776 supporting_text: K285 is located in a suggested binding site for PI(3,5)P2 in the cytoplasmic portion of ClC-7 core_functions: - description: ClC-7 functions as an electrogenic 2Cl(-)/1H(+) antiporter in the lysosomal membrane, exchanging two chloride ions for one proton and thereby providing the counter-ion conductance that supports V-ATPase-driven luminal acidification and raises luminal chloride concentration. molecular_function: id: GO:0062158 label: chloride:proton antiporter activity directly_involved_in: - id: GO:1902476 label: chloride transmembrane transport locations: - id: GO:0005765 label: lysosomal membrane supported_by: - reference_id: PMID:21527911 supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - reference_id: PMID:18449189 supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - description: ClC-7 acts as the alpha-subunit of an obligate heteromeric complex with the beta-subunit OSTM1, which is required for ClC-7 protein stability and transport activity; the assembled CLCN7-OSTM1 complex is the functional transport unit in lysosomes and the osteoclast ruffled border. molecular_function: id: GO:0062158 label: chloride:proton antiporter activity in_complex: id: GO:0034707 label: chloride channel complex locations: - id: GO:0005765 label: lysosomal membrane supported_by: - reference_id: PMID:21527911 supporting_text: ClC-7 is a slowly voltage-gated 2Cl(-)/1H(+)-exchanger and requires Ostm1 for transport activity. reference_section_type: TITLE - reference_id: PMID:32851177 supporting_text: the highly glycosylated Ostm1 functions like a lid positioned above CLC-7 and interacts extensively with CLC-7 within the membrane. reference_section_type: ABSTRACT - description: ClC-7 transport is tonically inhibited by the lysosome-specific signaling lipid PI(3,5)P2, which binds a site at the transmembrane-cytosolic interface; relief of this inhibition (e.g. on PI(3,5)P2 depletion) activates the antiporter and modulates lysosomal acidification. Gain-of-function HOD variants (Y715C, K285T) line this lipid-binding pocket and reduce PI(3,5)P2 inhibition, causing excess transport. This regulatory lipid-binding function is well established but not currently captured in GOA. molecular_function: id: GO:0080025 label: phosphatidylinositol-3,5-bisphosphate binding locations: - id: GO:0005765 label: lysosomal membrane supported_by: - reference_id: PMID:35670560 supporting_text: PI(3,5)P2 inhibits ClC-7-mediated currents. - reference_id: PMID:38838776 supporting_text: K285 is located in a suggested binding site for PI(3,5)P2 in the cytoplasmic portion of ClC-7 - reference_id: file:human/CLCN7/CLCN7-deep-research-falcon.md supporting_text: PI(3,5)P2 directly inhibits ClC-7 by binding at the transmembrane-cytosolic interface and remodeling transporter structure proposed_new_terms: [] suggested_questions: - question: What is the precise contribution of ClC-7-mediated luminal chloride accumulation versus a simple acidification shunt to lysosomal and resorption-lacuna function, given reports of near-normal steady-state lysosomal pH in Clcn7-deficient models? - question: How do gain-of-function variants such as Y715C mechanistically uncouple or alter gating to increase lysosomal acidification, and why does this produce a hypopigmentation/organomegaly phenotype distinct from loss-of-function osteopetrosis? (Partly answered- Y715C/K285T lie in the PI(3,5)P2-binding pocket and reduce tonic lipid inhibition; PMID:38838776, PMID:35670560.) - question: Is the PIKFyve-PI(3,5)P2-ClC-7 axis a physiologically regulated switch that couples lysosomal lipid signaling to chloride/proton antiport in vivo, and does pharmacological PIKFyve modulation alter ClC-7-dependent lysosomal and osteoclast function? suggested_experiments: - description: Reconstitute purified human CLCN7-OSTM1 complex into proteoliposomes and directly measure Cl(-)/H(+) exchange stoichiometry, voltage dependence, and the effect of disease variants on coupling. - description: Use ratiometric luminal pH and chloride sensors in CLCN7-knockout and variant-knock-in lysosomes and osteoclasts to dissect the relative roles of acidification versus luminal chloride loading in cargo degradation and bone resorption. references: - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt findings: [] - id: GO_REF:0000107 title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara findings: [] - id: GO_REF:0000108 title: Automatic assignment of GO terms using logical inference, based on on inter-ontology links findings: [] - id: GO_REF:0000117 title: Electronic Gene Ontology annotations created by ARBA machine learning models findings: [] - id: PMID:17897319 title: Integral and associated lysosomal membrane proteins. findings: - statement: ClC-7 was identified among integral lysosomal membrane proteins by lysosomal membrane proteomics. supporting_text: 'Integral and associated lysosomal membrane proteins.' reference_section_type: TITLE - id: PMID:18449189 title: The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes. findings: - statement: ClC-7 is a Cl-/H+ antiporter that constitutes the major chloride permeability of lysosomes and is important for lysosomal acidification. supporting_text: 'The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes.' reference_section_type: TITLE - id: PMID:19946888 title: Defining the membrane proteome of NK cells. findings: [] - id: PMID:21527911 title: ClC-7 is a slowly voltage-gated 2Cl(-)/1H(+)-exchanger and requires Ostm1 for transport activity. findings: - statement: ClC-7 exchanges chloride for protons with a 2Cl-/1H+ stoichiometry and is slowly voltage-gated. supporting_text: Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. reference_section_type: ABSTRACT - statement: ClC-7 requires the beta-subunit Ostm1 for transport activity. supporting_text: ClC-7 is a slowly voltage-gated 2Cl(-)/1H(+)-exchanger and requires Ostm1 for transport activity. reference_section_type: TITLE - id: PMID:32296183 title: A reference map of the human binary protein interactome. findings: [] - id: PMID:32814053 title: Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains. findings: [] - id: PMID:32851177 title: Molecular insights into the human CLC-7/Ostm1 transporter. findings: - statement: CLC-7 mainly resides in lysosomes and osteoclast ruffled membranes, consistent with an intracellular endolysosomal transporter rather than a transepithelial one. supporting_text: CLC-7 functions as an electrogenic antiporter that mainly resides in lysosomes and osteoclast ruffled membranes. reference_section_type: ABSTRACT - statement: Cryo-EM shows the glycosylated Ostm1 forms a lid over CLC-7 and interacts extensively within the membrane, defining the obligate complex. supporting_text: the highly glycosylated Ostm1 functions like a lid positioned above CLC-7 and interacts extensively with CLC-7 within the membrane. reference_section_type: ABSTRACT - id: PMID:33961781 title: Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. findings: [] - id: PMID:35271311 title: 'OpenCell: Endogenous tagging for the cartography of human cellular organization.' findings: [] - id: PMID:40205054 title: Multimodal cell maps as a foundation for structural and functional genomics. findings: [] - id: PMID:40355756 title: The solute carrier superfamily interactome. findings: [] - id: PMID:8543009 title: ClC-6 and ClC-7 are two novel broadly expressed members of the CLC chloride channel family. findings: - statement: ClC-7 was cloned as a CLC-family member but could not be expressed as a chloride channel in Xenopus oocytes, foreshadowing its later identification as an antiporter. supporting_text: ClC-6 and ClC-7 are two novel broadly expressed members of the CLC chloride channel family. reference_section_type: TITLE - id: Reactome:R-HSA-2730959 title: CLCN7:OSTM1 exchanges Cl- for H+ findings: [] - id: PMID:35670560 title: Tonic inhibition of the chloride/proton antiporter ClC-7 by PI(3,5)P2 is crucial for lysosomal pH maintenance. findings: - statement: The lysosomal lipid PI(3,5)P2 tonically inhibits ClC-7 transport; relieving this inhibition activates the antiporter and modulates V-ATPase-driven lysosomal acidification, establishing PI(3,5)P2 binding as a physiological regulatory function. supporting_text: PI(3,5)P2 inhibits ClC-7-mediated currents. reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed/PMC-verified (PMID:35670560, eLife 2022, Leray et al.). Primary electrophysiology establishing direct PI(3,5)P2 inhibition of ClC-7; basis for the GO:0080025 regulatory molecular function. - id: PMID:38838776 title: Gain-of-function variants in CLCN7 cause hypopigmentation and lysosomal storage disease. findings: - statement: Disease-causing gain-of-function CLCN7 variants (Y715C, K285T) line the PI(3,5)P2-binding pocket and reduce lipid inhibition, increasing transport activity and causing hypopigmentation with lysosomal storage (HOD), distinct from loss-of-function osteopetrosis. supporting_text: K285 is located in a suggested binding site for PI(3,5)P2 in the cytoplasmic portion of ClC-7 reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed/PMC-verified (PMID:38838776, J Biol Chem 2024, Polovitskaya et al.). Links HOD gain-of-function variants to loss of PI(3,5)P2 inhibition, corroborating the regulatory lipid-binding function. - id: file:human/CLCN7/CLCN7-deep-research-falcon.md title: Falcon deep research report for CLCN7 findings: - statement: Falcon deep research corroborates the existing review (2Cl-/1H+ antiporter, obligate OSTM1 complex, lysosome/osteoclast localization, osteopetrosis/HOD spectrum) and surfaces the established PI(3,5)P2 regulatory axis plus pH-independent luminal-chloride roles in cathepsin activation and autophagic/phagolysosomal degradation. supporting_text: PI(3,5)P2 directly inhibits ClC-7 by binding at the transmembrane-cytosolic interface and remodeling transporter structure - id: file:human/CLCN7/CLCN7-hypotheses/topology-transepithelial-overannotation/openscientist.md title: 'OpenScientist hypothesis run: CLCN7 transepithelial chloride transport (GO:0030321) over-annotation' findings: - statement: Localization / sorting-signal analysis concluded that GO:0030321 (transepithelial chloride transport) is over-annotated and should be removed; ClC-7 is an endolysosomal antiporter with N-terminal dileucine and acidic-cluster lysosomal targeting motifs, and the annotation traces to a ComplexPortal family-level intro sentence propagated via PANTHER IBA to ~1,198 ortholog annotations. Recommends adding GO:0007042 (lysosomal lumen acidification). supporting_text: a PANTHER IBA (Inferred by Biological Aspect of Ancestor) annotation that propagated this error to CLCN7 orthologs across approximately 1,198 annotations in many species.