title: ClC-7 is a slowly voltage-gated 2Cl(-)/1H(+)-exchanger and requires Ostm1 for transport activity.
abstract: Mutations in the ClC-7/Ostm1 ion transporter lead to osteopetrosis and lysosomal storage disease. Its lysosomal localization hitherto precluded detailed functional characterization. Using a mutated ClC-7 that reaches the plasma membrane, we now show that both the aminoterminus and transmembrane span of the Ostm1 β-subunit are required for ClC-7 Cl(-)/H(+)-exchange, whereas the Ostm1 transmembrane domain suffices for its ClC-7-dependent trafficking to lysosomes. ClC-7/Ostm1 currents were strongly outwardly rectifying owing to slow gating of ion exchange, which itself displays an intrinsically almost linear voltage dependence. Reversal potentials of tail currents revealed a 2Cl(-)/1H(+)-exchange stoichiometry. Several disease-causing CLCN7 mutations accelerated gating. Such mutations cluster to the second cytosolic cystathionine-β-synthase domain and potential contact sites at the transmembrane segment. Our work suggests that gating underlies the rectification of all endosomal/lysosomal CLCs and extends the concept of voltage gating beyond channels to ion exchangers.
authors.affiliation: Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany.
authors.forename: Lilia
authors.initials: L
authors.lastname: Leisle
authors.forename: Carmen F
authors.initials: CF
authors.lastname: Ludwig
authors.forename: Florian A
authors.initials: FA
authors.lastname: Wagner
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Jentsch
authors.forename: Tobias
authors.initials: T
authors.lastname: Stauber
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D002713:Chlorine / Q000378:metabolism; D004553:Electric Conductivity; D006367:HeLa Cells; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D018408:Patch-Clamp Techniques; D021381:Protein Transport; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D017920:Antiporters; C097540:CLCN7 protein, human; D018118:Chloride Channels; D008565:Membrane Proteins; D050505:Mutant Proteins; C489946:OSTM1 protein, human; D002713:Chlorine; D006859:Hydrogen; D044767:Ubiquitin-Protein Ligases