Characterization of acid flux in osteoclasts from patients harboring a G215R mutation in ClC-7

The chloride-proton antiporter ClC-7 has been speculated to be involved in acidification of the lysosomes and the resorption lacunae in osteoclasts; however, neither direct measurements of chloride transport nor acidification have been performed. Human osteoclasts harboring a dominant negative mutat...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 2009-01, Vol.378 (4), p.804-809
Main Authors: Henriksen, Kim, Gram, Jeppe, Neutzsky-Wulff, Anita Vibsig, Jensen, Vicki Kaiser, Dziegiel, Morten H., Bollerslev, Jens, Karsdal, Morten A.
Format: Article
Language:English
Subjects:
60 APPLIED LIFE SCIENCES
ACIDIFICATION
Acids - metabolism
ACTIN
ADOII
Arginine - genetics
Bone Resorption - genetics
Bone Resorption - metabolism
CALCIUM
Calcium - metabolism
Chloride Channels - antagonists & inhibitors
Chloride Channels - genetics
Chloride Channels - physiology
CHLORIDES
CHLORINE IONS
ClC-7
ClCN7
Genes, Dominant
Glycine - genetics
HUMAN POPULATIONS
Humans
Hydrogen-Ion Concentration
Influx
LYSOSOMES
Lysosomes - metabolism
MEMBRANES
MICROTUBULES
Mutation
MUTATIONS
Osteoclasts
Osteoclasts - metabolism
Osteoclasts - ultrastructure
PROTONS
SEX
SKELETON
Vacuolar Proton-Translocating ATPases - antagonists & inhibitors
Vacuolar Proton-Translocating ATPases - metabolism
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Summary:The chloride-proton antiporter ClC-7 has been speculated to be involved in acidification of the lysosomes and the resorption lacunae in osteoclasts; however, neither direct measurements of chloride transport nor acidification have been performed. Human osteoclasts harboring a dominant negative mutation in ClC-7 (G215R) were isolated, and used these to investigate bone resorption measured by CTX-I, calcium release and pit scoring. The actin cytoskeleton of the osteoclasts was also investigated. ClC-7 enriched membranes from the osteoclasts were isolated, and used to test acidification rates in the presence of a V-ATPase and a chloride channel inhibitor, using a H + and Cl − driven approach. Finally, acidification rates in ClC-7 enriched membranes from ADOII osteoclasts and their corresponding controls were compared. Resorption by the G215R osteoclasts was reduced by 60% when measured by both CTX-I, calcium release, and pit area when comparing to age and sex matched controls. In addition, the ADOII osteoclasts showed no differences in actin ring formation. Finally, V-ATPase and chloride channel inhibitors completely abrogated the H + and Cl − driven acidification. Finally, the acid influx was reduced by maximally 50% in the ClC-7 deficient membrane fractions when comparing to controls. These data demonstrate that ClC-7 is essential for bone resorption, via its role in acidification of the lysosomes and resorption lacunae in osteoclasts.
ISSN:0006-291X
1090-2104
DOI:10.1016/j.bbrc.2008.11.145