TY - JOUR
T1 - Identification and characterization of a sodium/calcium exchanger, NCX-1, in osteoclasts and its role in bone resorption
AU - Moonga, Baljit S.
AU - Davidson, Robert
AU - Sun, Li
AU - Adebanjo, Olugbenga A.
AU - Moser, James
AU - Abedin, Mohammad
AU - Zaidi, Neeha
AU - Huang, Christopher L.H.
AU - Zaidi, Mone
N1 - Funding Information:
This study was supported by grants to M.Z. from the National Institutes of Health (RO1-AG14917-05) and the Department of Veterans Affairs (Merit Review Award and GRECC). C.L.-H.H. thanks the Leverhulme Trust for support and the Medical Research Council of the UK for support for the Calcium Homeostasis Co-operative Group and for project grant funding. N.Z. was a summer student at the Philadelphia VA/Medical College of Pennsylvania where initial experiments were performed.
PY - 2001
Y1 - 2001
N2 - We provide the first demonstration for a Na+/Ca2+ exchanger, NCX-1, in the osteoclast. We speculate that by using Na+ exchange, NCX-1 couples H+ extrusion with Ca2+ fluxes during bone resorption. Microspectrofluorimetry of fura-2-loaded osteoclasts revealed a rapid and sustained, but reversible, cytosolic Ca2+ elevation upon Na+ withdrawal. This elevation was abolished by the cytosolic introduction (by gentle permeabilization) of a highly specific Na+/Ca2+ exchange inhibitor peptide, XIP, but not its inactive analogue, sXIP. Confocal microscopy revealed intense plasma membrane immunofluorescence with an isoform-specific monoclonal anti-NCX-1 antibody applied to gently permeabilized osteoclasts. Electrophysiological studies using excised outside-in membrane patches showed a low-conductance, Na+-selective, dichlorobenzamil-sensitive, amiloride-insensitive channel that we tentatively assigned as being an NCX. Finally, to examine for physiological relevance, an osteoclast resorption (pit) assay was performed. There was a dramatic reduction of bone resorption following NCX-1 inhibition by dichloroben- zamil and XIP (but not with S-XIP). Together, the results suggest that a functional NCX, likely NCX-1, is involved in the regulation of osteoclast cytosolic Ca2+ and bone resorption.
AB - We provide the first demonstration for a Na+/Ca2+ exchanger, NCX-1, in the osteoclast. We speculate that by using Na+ exchange, NCX-1 couples H+ extrusion with Ca2+ fluxes during bone resorption. Microspectrofluorimetry of fura-2-loaded osteoclasts revealed a rapid and sustained, but reversible, cytosolic Ca2+ elevation upon Na+ withdrawal. This elevation was abolished by the cytosolic introduction (by gentle permeabilization) of a highly specific Na+/Ca2+ exchange inhibitor peptide, XIP, but not its inactive analogue, sXIP. Confocal microscopy revealed intense plasma membrane immunofluorescence with an isoform-specific monoclonal anti-NCX-1 antibody applied to gently permeabilized osteoclasts. Electrophysiological studies using excised outside-in membrane patches showed a low-conductance, Na+-selective, dichlorobenzamil-sensitive, amiloride-insensitive channel that we tentatively assigned as being an NCX. Finally, to examine for physiological relevance, an osteoclast resorption (pit) assay was performed. There was a dramatic reduction of bone resorption following NCX-1 inhibition by dichloroben- zamil and XIP (but not with S-XIP). Together, the results suggest that a functional NCX, likely NCX-1, is involved in the regulation of osteoclast cytosolic Ca2+ and bone resorption.
KW - Bone resorption
KW - Na/Ca exchange
KW - Osteoclasts
KW - Osteoporosis
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U2 - 10.1006/bbrc.2001.4870
DO - 10.1006/bbrc.2001.4870
M3 - Article
C2 - 11350050
AN - SCOPUS:0034817370
SN - 0006-291X
VL - 283
SP - 770
EP - 775
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
IS - 4
ER -