Premium
NCX3 is a major functional isoform of the sodium–calcium exchanger in osteoblasts
Author(s) -
Sosnoski Donna M.,
Gay Carol V.
Publication year - 2007
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.21483
Subject(s) - gene isoform , sodium calcium exchanger , calcium , chemistry , sodium , microbiology and biotechnology , medicine , biochemistry , biology , gene , organic chemistry
The calcium phosphate‐based skeleton of vertebrates serves as the major reservoir for metabolically available calcium ions. The skeleton is formed by osteoblasts which first secrete a proteinaceous matrix and then provide Ca ++ for the calcification process. The two calcium efflux ports found in most cells are the plasma membrane Ca‐ATPase (PMCA) and the sodium–calcium exchanger (NCX). In osteoblasts, PMCA and NCX are located on opposing sides of the cell with NCX facing the mineralizing bone surface. Two isoforms of NCX have been identified in osteoblasts NCX1, and NCX3. The purpose of this study was to determine the extent to which each of the two NCX isoforms support delivery of Ca ++ into sites of calcification and to discern if one could compensate for the other. SiRNA technology was used to knockdown each isoform separately in MC3T3‐E1 osteoblasts. Osteoblasts in which either NCX1 or NCX3 was impaired were tested for Ca ++ efflux using the Ca ++ specific fluorophore, fluo‐4, in a sodium‐dependent calcium uptake assay adapted for image analysis. NCX3 was found to serve as a major contributor of Ca ++ translocation out of osteoblasts into calcifying bone matrix. NCX1 had little to no involvement. J. Cell. Biochem. 103: 1101–1110, 2008. © 2007 Wiley‐Liss, Inc.