The Role of GATA, CArG, E-box, and a Novel Element in the Regulation of Cardiac Expression of the Na+-Ca2+ Exchanger Gene

The cardiac Na+-Ca2+ exchanger (NCX1) is the principal Ca2+ efflux mechanism in cardiocytes. The exchanger is up-regulated in both cardiac hypertrophy and failure. In this report, we identify the cis-acting elements that control cardiac expression and α-adrenergic up-regulation of the exchanger gene. Deletion analysis revealed that a minimal cardiac promoter fragment from −184 to +172 is sufficient for cardiac expression and α-adrenergic stimulation. Mutational analysis revealed that both the CArG element at −80 and the GATA element at −50 were required for cardiac expression. Gel mobility shift assay supershift analysis demonstrated that the serum response factor binds to the CArG element and GATA-4 binds to the GATA element. Point mutations in the −172 E-box demonstrated that it was required for α-adrenergic induction. In addition, deletion analysis revealed one or more enhancer elements in the first intron (+103 to +134) that are essential for phenylephrine up-regulation but bear no homology to any known transcription element. Therefore, this work demonstrates that SRF and GATA-4 are critical for NCX1 expression in neonatal cardiomyocytes and that the −172 E-box in addition to a novel enhancer element(s) are required for phenylephrine up-regulation of NCX1 and may mediate its hypertrophic up-regulation. The cardiac Na+-Ca2+ exchanger (NCX1) is the principal Ca2+ efflux mechanism in cardiocytes. The exchanger is up-regulated in both cardiac hypertrophy and failure. In this report, we identify the cis-acting elements that control cardiac expression and α-adrenergic up-regulation of the exchanger gene. Deletion analysis revealed that a minimal cardiac promoter fragment from −184 to +172 is sufficient for cardiac expression and α-adrenergic stimulation. Mutational analysis revealed that both the CArG element at −80 and the GATA element at −50 were required for cardiac expression. Gel mobility shift assay supershift analysis demonstrated that the serum response factor binds to the CArG element and GATA-4 binds to the GATA element. Point mutations in the −172 E-box demonstrated that it was required for α-adrenergic induction. In addition, deletion analysis revealed one or more enhancer elements in the first intron (+103 to +134) that are essential for phenylephrine up-regulation but bear no homology to any known transcription element. Therefore, this work demonstrates that SRF and GATA-4 are critical for NCX1 expression in neonatal cardiomyocytes and that the −172 E-box in addition to a novel enhancer element(s) are required for phenylephrine up-regulation of NCX1 and may mediate its hypertrophic up-regulation. The Na+-Ca2+ exchanger (NCX1) 1The abbreviations used are: NCX, sodium calcium exchanger; MEM, Eagle's minimum essential medium; SRF, serum response factor; bp, base pair(s); USF, upstream stimulatory factorcatalyzes the electrogenic exchange of one intracellular calcium ion for three extracellular sodium ions across the plasma membrane in many mammalian cells. Transport is reversible and can facilitate calcium entry, which in the heart is capable of triggering calcium release from the sarcoplasmic reticulum (1Kimura J. Noma A. Irisawa H. Nature. 1986; 319: 596-597Crossref PubMed Scopus (278) Google Scholar). The exchanger is most abundant in the heart, where it regulates Ca2+ fluxes across the sarcolemma and serves a critical role in the maintenance of the cellular calcium balance for excitation-contraction coupling. Na+-Ca2+ exchanger activity in cardiomyocytes is regulated by several factors. It is activated by cytosolic Ca2+ and MgATP (2Hilgemann D.W. Nature. 1990; 344: 242-245Crossref PubMed Scopus (249) Google Scholar) and inhibited by cytosolic sodium (3Hilgemann D.W. Matsuoka S. Nagel G.A. Collins A. J. Gen. Physiol. 1992; 100: 905-932Crossref PubMed Scopus (240) Google Scholar) and ATP depletion (4Condrescu M. Gardner J.P. Chernaya G. Aceto J.F. Kroupis C. Reeves J.P. J. Biol. Chem. 1995; 270: 9137-9146Crossref PubMed Scopus (90) Google Scholar). A high affinity Ca2+-binding domain has been identified in the large cytoplasmic loop (residues 371–508) that is believed to be responsible for calcium regulation (5Levitsky D.O. Nicoll D.A. Philipson K.D. J. Biol. Chem. 1994; 269: 22847-22852Abstract Full Text PDF PubMed Google Scholar). It is also inhibited by the exchanger inhibitory peptide, which corresponds to a 20-amino acid segment at the N terminus of the large cytoplasmic loop (6Li Z. Nicoll D.A. Collins A. Hilgemann D.W. Filoteo A.G. Penniston J.T. Weiss J.N. Tomich J.M. Philipson K.D. J. Biol. Chem. 1991; 266: 1014-1020Abstract Full Text PDF PubMed Google Scholar). A recent study has demonstrated that the exchanger is phosphorylated via a protein kinase C-dependent pathway and that NCX1 phosphorylation appears to coincide with up-regulation of exchanger activity (7Iwamoto T. Pan Y. Wakabayashi S. Imagawa T. Yamanaka H.I. Shigekawa M. J. Biol. Chem. 1996; 271: 13609-13615Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar). In addition, the exchanger is regulated at the transcriptional level in cardiac hypertrophy, ischemia, and failure. In the feline model of acute right ventricular hypertrophy, NCX1 message levels are rapidly up-regulated following pressure overload (8Kent R.L. Rozich J.D. McCollam P.L. McDermott D.E. Thacker U.F. Menick D.R. McDermott P.J. Cooper G. Am. J. Physiol. 1993; 265: H1024-H1029Crossref PubMed Google Scholar, 9Menick D.R. Barnes K.V. Thacker U.F. Dawson M.M. McDermott D.E. Rozich J.D. Kent R.L. Cooper G.T. Ann. N. Y. Acad. Sci. 1996; 779: 489-501Crossref PubMed Scopus (27) Google Scholar). An increase in NCX1 mRNA expression is also observed in cultured cardiac myocytes following α-adrenergic stimulation by phenylephrine or exposure to veratridine. Importantly, the exchanger is also up-regulated at both the message and protein levels in end-stage heart failure (10Studer R. Reinecke H. Bilger J. Eschenhagen T. Bohm M. Hasenfuss G. Just H. Holtz J. Drexler H. Circ. Res. 1994; 75: 443-453Crossref PubMed Scopus (518) Google Scholar). Very little is known about the genetic elements and transcription factors that regulate NCX1 expression. Identification of the factors involved in NCX1 up-regulation is important to unraveling the sequence of molecular events that initiates hypertrophic growth. Furthermore, it may provide insight into the basis of the development of decompensated heart failure. The feline (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar), human (12Kraev A. Chumakov I. Carafoli E. Genomics. 1996; 37: 105-112Crossref PubMed Scopus (44) Google Scholar, 13Scheller T. Kraev A. Skinner S. Carafoli E. J. Biol. Chem. 1998; 273: 7643-7649Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar), and rat (13Scheller T. Kraev A. Skinner S. Carafoli E. J. Biol. Chem. 1998; 273: 7643-7649Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar, 14Nicholas S.B. Yang W. Lee S.L. Zhu H. Philipson K.D. Lytton J. Am. J. Physiol. 1998; 274: H217-H232PubMed Google Scholar) NCX1 genes have recently been cloned. The NCX1 gene is unusual in that it contains three promoters and multiple 5′-untranslated region exons upstream of the coding region. As a result of alternative promoter usage and the resulting alternative splicing, there are multiple tissue-specific variants of the Na+-Ca2+ exchanger (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar,15Lee S.L. Yu A.S. Lytton J. J. Biol. Chem. 1994; 269: 14849-14852Abstract Full Text PDF PubMed Google Scholar, 16Kofuji P. Lederer W.J. Schulze D.H. Am. J. Physiol. 1993; 265: F598-F603PubMed Google Scholar, 17Quednau B.D. Nicoll D.A. Philipson K.D. Am. J. Physiol. 1997; 272: C1250-C1261Crossref PubMed Google Scholar). The feline cardiac minimal promoter (−184 to +172) is responsive to α-adrenergic stimulation and sufficient to drive expression of a reporter gene in neonatal cardiomyocytes but not mouse L cells (18Cheng G. Hagen T.P. Dawson M.L. Menick D.R. Circulation. 1998; 98: I609Google Scholar). Analysis of the DNA sequence of the feline cardiac basal NCX1 promoter revealed a number of elements that may be involved in regulation and are conserved in the rat promoter (14Nicholas S.B. Yang W. Lee S.L. Zhu H. Philipson K.D. Lytton J. Am. J. Physiol. 1998; 274: H217-H232PubMed Google Scholar). There are two CANNTG motifs (E-boxes) at positions −172 and −153 that are potential target sites for the basic helix-loop-helix family of transcription factors. E-box-binding proteins have been demonstrated to mediate the cardiac expression of several genes including the ventricular myosin light chain 2 (19Navankasattusas S. Sawadogo M. van Bilsen M. Dang C.V. Chien K.R. Mol. Cell. Biol. 1994; 14: 7331-7339Crossref PubMed Scopus (67) Google Scholar), cardiac α-actin (20French B.A. Chow K.L. Olson E.N. Schwartz R.J. Mol. Cell. Biol. 1991; 11: 2439-2450Crossref PubMed Google Scholar), and α- and β-myosin heavy chain (21Molkentin J.D. Brogan R.S. Jobe S.M. Markham B.E. J. Biol. Chem. 1993; 268: 2602-2609Abstract Full Text PDF PubMed Google Scholar). This region also contains consensus sequence for two GATA boxes at positions −125 and −50. Several cardiac specific genes such as myosin light chain IA, myosin light chain IV, and β-myosin heavy chain (22Rindt H. Gulick J. Knotts S. Neumann J. Robbins J. J. Biol. Chem. 1993; 268: 5332-5338Abstract Full Text PDF PubMed Google Scholar, 23Kurabayashi M. Komuro I. Shibasaki Y. Tsuchimochi H. Takaku F. Yazaki Y. J. Biol. Chem. 1990; 265: 19271-19278Abstract Full Text PDF PubMed Google Scholar) contain conserved GATA binding motifs. The GATA elements in the atrial natriuretic peptide (24Grepin C. Dagnino L. Robitaille L. Haberstroh L. Antakly T. Nemer M. Mol. Cell. Biol. 1994; 14: 3115-3129Crossref PubMed Scopus (249) Google Scholar) and α-myosin heavy chain (25Molkentin J.D. Kalvakolanu D.V. Markham B.E. Mol. Cell. Biol. 1994; 14: 4947-4957Crossref PubMed Google Scholar) gene have been shown to be critical for cardiac expression. This region also contains a single MEF-2 element at position −166. A MEF-2-like motif appears to be required for cardiac-specific expression of the rat cardiac troponin T gene. There are six Nkx-2.5 binding sites in the first 1831 bases of the NCX promoter including one in the first 250 bases. The factor Nkx-2.5 has been shown to be in cardiac and important role in cardiac A single CArG element is at position A CArG element is also in the region of the cardiac α-myosin heavy cardiac myosin light chain and troponin T genes (25Molkentin J.D. Kalvakolanu D.V. Markham B.E. Mol. Cell. Biol. 1994; 14: 4947-4957Crossref PubMed Google Scholar, L. Mol. Cell. Biol. PubMed Scopus Google Scholar, J.D. J. Biol. Chem. 1993; 268: Full Text PDF PubMed Google Scholar, N. Mol. Cell. Biol. 1993; PubMed Scopus Google Scholar, J.D. Circ. Res. 1996; PubMed Scopus Google Scholar). The CArG elements of and cardiac α-actin are to the serum response element and as a binding for the serum response factor In the we a analysis of the NCX1 promoter elements important for neonatal expression and α-adrenergic induction. three expression of NCX1 in neonatal cardiomyocytes both the CArG element at −80 to and the GATA element at −50 to mobility shift analysis revealed specific for both of SRF is one of the factors binding to the CArG and GATA-4 binds to the GATA element. and deletion analysis revealed a at position and enhancer element or elements in the first (+103 to which are essential for α-adrenergic of the This region no homology to any of the known transcription and were from or and reporter were from Eagle's minimum essential and serum were from for supershift were from The was from were of the and were from or A of the NCX promoter was into the as (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar). were and were to contain the by of NCX were used to the mutations into the by chain the The promoter region of was the to that the were from neonatal and cultured by the McDermott P.J. J.D. Am. J. Physiol. 1990; PubMed Google Scholar). ventricular was from neonatal and with and in and The was for at with the cells were into serum and at 250 The were in The and was more were by to for to with E. R.S. S.M. Chien K.R. J. Biol. Chem. 1991; 266: Full Text PDF PubMed Google Scholar). were in at in of Eagle's with and and essential and serum for the were and in Eagle's including the were in serum to The were by the calcium DNA C. H. Mol. Cell. Biol. PubMed Scopus Google Scholar). The of was and of Na+-Ca2+ was with of expression and in of the was and where phenylephrine was and the cells were in for cells were with to any were in of and for in reporter The were and at and activity were as (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar). were from neonatal rat as R.J. P. S.L. 1991; 11: Google Scholar). from neonatal were 2 in of 2 and 2 was to the which was and two of was to the to a of more with a the was at for at were with of and as The was in of by with a The was at for at to the large and at at The was for to at for proteins the was at −80 was in the of in binding of at the were and in at of at The were and to or supershift or were to the and for to the addition of the a of the used in A to to to for contain a for in a for contain a for The were by analysis and was as by the In of the NCX1 cardiac promoter (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar), we demonstrated that a the first 250 of the the and of the first intron is sufficient for expression and α-adrenergic stimulation of the reporter gene. have shown that a bases of the region has the activity as the (18Cheng G. Hagen T.P. Dawson M.L. Menick D.R. Circulation. 1998; 98: I609Google Scholar). This is also in with has been for the rat NCX1 minimal promoter (14Nicholas S.B. Yang W. Lee S.L. Zhu H. Philipson K.D. Lytton J. Am. J. Physiol. 1998; 274: H217-H232PubMed Google Scholar). There are consensus for a number of potential factors in the NCX1 cardiac minimal promoter There are two potential binding sites for the GATA family of transcription factors and two CANNTG motifs (E-boxes) that are potential target sites for the basic helix-loop-helix family of transcription factors. This region also contains a single MEF-2 a CArG and a binding for the factor It is of to that sequence of both GATA the CArG and the −153 E-box are conserved in both the feline and rat NCX1 promoters (14Nicholas S.B. Yang W. Lee S.L. Zhu H. Philipson K.D. Lytton J. Am. J. Physiol. 1998; 274: H217-H232PubMed Google Scholar). the we mutations into of and the activity of of the was with the to its to cardiac specific expression NCX1 promoter was in in at three neonatal Point mutations the MEF-2 and Nkx-2.5 elements in reporter activity of of the elements any role in the transcription of the NCX1 gene to a Point mutations the −172 −153 and −125 GATA elements reporter to of promoter Therefore, elements to to NCX1 Importantly, mutations the −80 CArG element or the −50 GATA element in activity of of the control the CArG element at −80 and the GATA element at −50 are critical to NCX1 expression in neonatal cardiocytes. the potential of the NCX1 cardiac elements we mobility shift with from neonatal rat heart were for the E-box to CArG to and the GATA to element of the −172 E-box reporter gene expression to of control levels in of neonatal this E-box may a role in NCX1 expression. of from neonatal heart with a E-box in the of a specific was by its with a of E-box but not by a GATA This E-box element is to a MEF-2 element which is as of the sequence in the used for the mobility shift that the MEF-2 element not to be important for NCX1 expression in neonatal cardiomyocytes this element a role in NCX1 one it to to the of factors binding to the E-box with a of MEF-2 element no the This demonstrates that the MEF-2 element not a role in the observed with the E-box element it is to a role in NCX1 expression in neonatal An E-box element in the α-myosin heavy chain gene I. J. Biol. Chem. 1995; 270: PubMed Scopus Google Scholar) has been demonstrated to be responsible for the up-regulation of the gene in response to this E-box has been shown to a protein to upstream stimulatory factor I. J. Biol. Chem. 1995; 270: PubMed Scopus Google Scholar). Gel were to is a of the NCX1 −172 E-box binding of the protein with 2 of not result in a supershift In addition, the of this was not by with of the basic helix-loop-helix factors or Therefore, the NCX1 −172 E-box protein not of or of from neonatal rat with for the NCX1 −80 CArG element in the of two specific with a of the or a the NCX1 CArG sequence both of with a of CArG sequence not the binding of the to of In addition, with DNA E-box not for binding to The SRF, which a CArG element in the cardiac α-actin promoter J. M. S. T. Schwartz R.J. 1996; PubMed Scopus Google Scholar), may be involved in the cardiac specific transcription of SRF binds to the NCX1 CArG a supershift assay was with of the protein with 2 of SRF a that at one of the is SRF or is to SRF of from neonatal cardiomyocytes with GATA to revealed a single with of GATA sequence or DNA not the with a of GATA the GATA-4 and are in the GATA-4 was in the NCX1 −50 GATA GATA-4 and were with the and by shift The GATA-4 the −50 GATA supershift was with the not that GATA-4 but not with this In to identify elements α-adrenergic mutations in the elements in the minimal promoter were into neonatal rat with increase in activity that of (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar) or cardiomyocytes with the NCX1 demonstrates that mutations in the −153 and −125 GATA elements not α-adrenergic stimulation. a of expression with with mutations in the −80 CArG and −50 GATA which are required for transcriptional activity in the neonatal have not α-adrenergic expression. In are to a the NCX1 This may be in to the transcription level of −50 GATA and −80 CArG NCX1 with the −172 E-box sequence a increase in activity with phenylephrine This is is in the NCX1 Therefore, the NCX1 −172 element appears to be required for α-adrenergic up-regulation. This is to the promoter in which E-box element was demonstrated to be responsible for up-regulation in response to activity I. J. Biol. Chem. 1995; 270: PubMed Scopus Google Scholar). of the the first and bases of the first in which was at position of the of control not any up-regulation in response to phenylephrine not Therefore, in addition to the −172 one or more elements the or the first bases of intron to be required for α-adrenergic stimulation of the NCX1 gene. A of were to identify the region responsible for α-adrenergic stimulation. Deletion of the bases of the first and the first bases of intron sequence also in a with activity and to that the elements responsible for α-adrenergic stimulation are in this region Analysis of the first intron sequence revealed a single GATA element at GATA-4 has been recently demonstrated to important role in the hypertrophic of both and promoters Jobe S.M. H. J.D. S. Markham B.E. Acad. Sci. S. A. 1997; PubMed Scopus Google Scholar, Lee Jobe S.M. Markham B.E. Circulation. 1997; PubMed Scopus Google Scholar), mutations were into the consensus GATA element reporter gene expression that the GATA element was not required for α-adrenergic up-regulation. A deletion from to activity and was to but the deletion from to was responsive to stimulation. In to this element or α-adrenergic up-regulation was with a mutations positions and The of this region was sufficient to activity more α-adrenergic stimulation. In this of deletion and have a region from to that the two bases of the and the first bases of intron This region contains one or more elements that are for α-adrenergic stimulation of NCX1 and at one of is in and analysis revealed no consensus sequence for known transcriptional α-adrenergic stimulation of Na+-Ca2+ exchanger expression is via the −172 E-box and a novel element or elements in the first In to this region and elements in this region mobility shift were neonatal heart with a to the NCX1 cardiac novel element region were observed binding to the cardiac novel element region a of the DNA were used to of the with cardiac novel element region but the with the cardiac novel element region the mutations positions and not or but the was with the the and but of Therefore, the and to be specific for the region. In addition, the the element by that a of it positions and have used gene to identify the elements cardiac expression and α-adrenergic up-regulation of the NCX1 gene. we that NCX1 expression in neonatal rat ventricular myocytes at two DNA sequence CArG and The CArG element at −80 from the CArG sequence is required for cardiac expression of the NCX1 gene. In addition, we have demonstrated that the SRF is a of the binding to the NCX1 CArG that SRF is required for basal NCX1 expression. CArG boxes are in the promoters of many genes and have been shown to be involved in as as cardiac regulation T. L. Mol. Cell. Biol. PubMed Scopus Google Scholar, S.L. J.N. Mol. Cell. Biol. 1993; PubMed Scopus Google Scholar, F. R. P. A. W. M. Mol. Cell. Biol. 1995; PubMed Scopus Google Scholar). the NCX1 CArG element is required for basal it not to mediate α-adrenergic expression. This is to has been identified in the human cardiac α-actin promoter and mouse α-actin promoter L. 1990; PubMed Scopus Google Scholar). recently has it been the SRF which transcriptional of regulate SRF and factors to provide by which SRF provide tissue-specific transcriptional and have been demonstrated to the transcriptional activity of SRF the promoter D.A. M. Mol. Cell. Biol. 1995; PubMed Scopus Google Scholar). and Schwartz Schwartz R.J. Mol. Cell. Biol. 1996; PubMed Google Scholar) have shown that the with SRF to the cardiac α-actin This is serum response element and not the Nkx-2.5 element. of SRF with Nkx-2.5 may also be important in the cardiac regulation of the NCX1 we that the Nkx-2.5 element not to be required for NCX1 expression in neonatal rat and this element is not in the rat NCX1 promoter (14Nicholas S.B. Yang W. Lee S.L. Zhu H. Philipson K.D. Lytton J. Am. J. Physiol. 1998; 274: H217-H232PubMed Google Scholar). This in the NCX1 be via the CArG and not the Nkx-2.5 to was for the cardiac α-actin gene. Importantly, Nkx-2.5 and SRF have recently been shown to regulate the cardiac α-actin promoter with GATA-4 N. Nemer M. Schwartz R.J. Mol. Cell. Biol. 1998; PubMed Scopus Google Scholar). have not transcription factor in addition to SRF, cardiac expression of NCX1 is also regulated by a GATA-4 are the of SRF, and the GATA-4 factors in the of the NCX1 GATA elements have important role in the transcriptional regulation of several cardiac specific genes including α-myosin heavy chain (25Molkentin J.D. Kalvakolanu D.V. Markham B.E. Mol. Cell. Biol. 1994; 14: 4947-4957Crossref PubMed Google Scholar), cardiac troponin M. Z. J.M. Mol. Cell. Biol. 1994; 14: PubMed Scopus Google Scholar), myosin light chain N. N. Mol. Cell. Biol. 1996; PubMed Scopus Google Scholar), and the natriuretic peptide (24Grepin C. Dagnino L. Robitaille L. Haberstroh L. Antakly T. Nemer M. Mol. Cell. Biol. 1994; 14: 3115-3129Crossref PubMed Scopus (249) Google Scholar). GATA elements not a role in the basal cardiac expression of the β-myosin heavy chain or a GATA binding is for the of genes in in pressure overload Jobe S.M. H. J.D. S. Markham B.E. Acad. Sci. S. A. 1997; PubMed Scopus Google Scholar, Lee Jobe S.M. Markham B.E. Circulation. 1997; PubMed Scopus Google Scholar). GATA-4 a critical role in the cardiac expression of NCX1 but is not required for α-adrenergic up-regulation. the of the −172 of the consensus in the minimal promoter to mediate the α-adrenergic stimulation. A of deletion that a region the first (+103 to +134) contains one or more elements for α-adrenergic up-regulation. this region contains no consensus binding motifs for known transcription factors. of the rat (14Nicholas S.B. Yang W. Lee S.L. Zhu H. Philipson K.D. Lytton J. Am. J. Physiol. 1998; 274: H217-H232PubMed Google Scholar), human (13Scheller T. Kraev A. Skinner S. Carafoli E. J. Biol. Chem. 1998; 273: 7643-7649Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar), and feline (11Barnes K.V. Cheng G. Dawson M.M. Menick D.R. J. Biol. Chem. 1997; 272: 11510-11517Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar) gene sequence in this region revealed homology bases to and that of the bases in the region from to are the of this work by no the of α-adrenergic responsive elements in the NCX1 that the −172 and the region to are both for α-adrenergic stimulation in the of the α-adrenergic stimulation has been demonstrated to that result in cardiac this study demonstrates that this region α-adrenergic it to be it also up-regulation in response to It is important to that were in neonatal cardiocytes. In of neonatal is to identify and to the role of that mediate in expression. the of the elements identified and mediate basal cardiac expression hypertrophic up-regulation to be in cardiomyocytes in with the NCX1 promoter to the and role of the and the novel element in the expression of NCX1 development and in the and hypertrophic are to and for and and for the for