title: ATP depletion inhibits the endocytosis of ClC-2.
abstract: The chloride channel, ClC-2 is expressed ubiquitously and participates in multiple physiological processes. In particular, ClC-2 has been implicated in the regulation of neuronal chloride ion homeostasis and mutations in ClC-2 are associated with idiopathic generalized epilepsy. Despite the physiological and pathophysiological significance of this channel, its regulation remains incompletely understood. The functional expression of ClC-2 at the cell surface has been shown to be enhanced by depletion of cellular ATP, implicating its possible role in cellular energy sensing. In the present study, biochemical assays of cell surface expression suggest that this gain of function reflects, in part, an increase in channel number due to the reduction in ClC-2 internalization by endocytosis. Cell surface expression of the disease-causing mutant: G715E, thought to lack wild-type nucleotide binding affinity, is similarly affected, suggesting that ATP-depletion modifies the function of proteins in the endocytic pathway rather than ClC-2 directly. Using a combination of immunofluorescence and biochemical studies, we confirmed that ClC-2 is internalized via dynamin-dependent endocytosis and that the change in surface expression evoked by ATP depletion is partially mimicked by inhibition of dynamin function using a dynamin dominant-negative mutant (DynK44A). Furthermore, trafficking via the early endosomal compartment occurs in part through rab5-associated vesicles and recycling of ClC-2 to the cell surface occurs through a rab11 dependent pathway. In summary, we have determined that the internalization of ClC-2 by endocytosis is inhibited by metabolic stress, highlighting the importance for understanding the molecular mechanisms mediating the endosomal trafficking of this channel.
authors.affiliation: Programme in Molecular Structure and Function, Research Institute in the Hospital for Sick Children, Toronto, Canada.
authors.forename: Sonja U
authors.initials: SU
authors.lastname: Dhani
authors.forename: Patrick
authors.initials: P
authors.lastname: Kim Chiaw
authors.forename: Ling-Jun
authors.initials: LJ
authors.lastname: Huan
authors.forename: Christine E
authors.initials: CE
authors.lastname: Bear
mesh_terms: D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000963:Antimetabolites / Q000494:pharmacology; D019921:Biotinylation; D000090007:CLC-2 Chloride Channels; D019556:COS Cells; D002232:Carbocyanines; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D018076:DNA, Complementary; D003847:Deoxyglucose / Q000494:pharmacology; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D009154:Mutation; D011506:Proteins / Q000378:metabolism; D051381:Rats; D012402:Rotenone / Q000494:pharmacology; D014162:Transfection; D014475:Uncoupling Agents / Q000494:pharmacology; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D000199:Actins; D000255:Adenosine Triphosphate; D000911:Antibodies, Monoclonal; D000963:Antimetabolites; D000090007:CLC-2 Chloride Channels; D002232:Carbocyanines; D018118:Chloride Channels; D018076:DNA, Complementary; D003847:Deoxyglucose; D034281:Dynamins; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D011506:Proteins; D012402:Rotenone; D014475:Uncoupling Agents; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C089187:cyanine dye 3; C085321:cyanine dye 5