title: c-Src control of chloride channel support for osteoclast HCl transport and bone resorption.
abstract: Bone degradation by osteoclasts depends upon active transport of hydrogen ions to solubilize bone mineral. This transport is supported by the parallel actions of a proton ATPase and a chloride channel located in the osteoclast ruffled membrane. We have previously identified a novel chloride channel, p62, which appears to be the avian counterpart to CLIC-5b and is expressed coincident with the appearance of acid secretion as avian osteoclasts differentiate in culture. In this article, we show that suppression of CLIC-5b in differentiating avian osteoclasts results in decreased acidification by vesicles derived from these cells and decreased ability of the cells to resorb bone. Acidification is rescued by the presence of valinomycin, consistent with a selective loss of chloride channel but not proton pump activity. Osteoclast bone resorption is known to be dependent on the expression of the tyrosine kinase, c-Src. We show that CLIC-5b from osteoclasts has affinity for both Src SH2 and SH3 domains. We find that suppression of expression of Src in developing osteoclasts results in decreased vesicular acidification, which is rescued by valinomycin, consistent with the loss of chloride conductance in the proton pump-containing vesicles. Suppression of c-Src causes no change in the steady state level of CLIC-5b expression, but does result in failure of proton pump and CLIC-5b to colocalize in cultured osteoclast precursors. We conclude that suppression of c-Src interferes with osteoclast bone resorption by disrupting functional co-localization of proton pump and CLIC-5b.
authors.affiliation: UNC Kidney Center and the Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill, 27599, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Edwards
authors.forename: Christopher
authors.initials: C
authors.lastname: Cohen
authors.forename: Weibing
authors.initials: W
authors.lastname: Xu
authors.forename: Paul H
authors.initials: PH
authors.lastname: Schlesinger
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D001862:Bone Resorption / Q000209:etiology*; D000081247:CSK Tyrosine-Protein Kinase; D002454:Cell Differentiation; D002478:Cells, Cultured; D002645:Chickens; D018118:Chloride Channels / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D005260:Female; D006851:Hydrochloric Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D008840:Microfilament Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D008969:Molecular Sequence Data; D010010:Osteoclasts / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D017494:Proton Pumps / Q000502:physiology; D018909:src Homology Domains; D019061:src-Family Kinases
chemical_list: C411466:CLIC5 protein, human; D018118:Chloride Channels; D002712:Chlorides; C490803:Clcn7 protein, mouse; D008840:Microfilament Proteins; D017494:Proton Pumps; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D006851:Hydrochloric Acid