Cardiac expression of the Na1/Ca21 exchanger NCX1 is GATA factor dependent

Nicholas, Susanne B., and Kenneth D. Philipson. Cardiac expression of the Na1/Ca21 exchanger NCX1 is GATA factor dependent. Am. J. Physiol. 277 (Heart Circ. Physiol. 46): H324–H330, 1999.—The cardiac sarcolemmal Na1/Ca21 exchanger plays a primary role in Ca21 efflux and is important in regulating intracellular Ca21 and beat-to-beat contractility. Of the three Na1/Ca21 exchanger genes cloned (NCX1, NCX2, and NCX3), only NCX1 is expressed in cardiac myocytes. NCX1 has alternative promoters for heart, kidney, and brain tissue-specific transcripts. Analysis of the cardiac NCX1 promoter (at 2336 bp) identified a cardiac-specific minimum promoter (at 2137) and two GATA sites (at 275 and 2145). In this study, gel shift and supershift analyses identified GATA-4 in primary neonatal cardiac myocytes. Site-directed mutagenesis of the GATA-4 site at 275 abolishes binding and reduces activity of the minimum and full-length promoters by .90 and ,60%, respectively. Mutation of the GATA site at 2145 reduces activity of the full-length promoter by ,30%. Mutation of an E-box at 2175 does not alter promoter activity.