TY - JOUR
T1 - Myosin heavy chain gene expression in neonatal rat heart cells
T2 - Effects of [Ca2+]i and contractile activity
AU - Ming, Q. I.
AU - Puglisi, José L.
AU - Byron, Kenneth L.
AU - Ojamaa, Kaie
AU - Klein, Irwin
AU - Bers, Donald M
AU - Samarel, Allen M.
PY - 1997
Y1 - 1997
N2 - To determine if mechanical signals or alterations in intracellular Ca2+ concentration ([Ca2+]i) affect myosin heavy chain (MHC) gene expression in spontaneously beating, neonatal rat ventricular myocytes, contractile activity was inhibited with verapamil, KCl, or 2,3-butanedione monoxime (BDM), and their acute and chronic effects on myocyte shortening, [Ca2+]i, and MHC gene expression were examined. Despite their differing effects on [Ca2+]i; verapamil, KC1, and BDM all inhibited contractile activity and markedly downregulated ß-MHC mRNA levels to 24 5, 21 7, and 6 2% of contracting cells, respectively. In contrast, these inhibitors of contraction upregulated a-MHC mRNA levels to 163 19, 156 7, and 198 20% of contracting cells, respectively. Transient transfection with a rat ß-MHC promoter-luciferase expression plasmid demonstrated that all inhibitors of contraction significantly decreased ß-MHC promoter activity. Paradoxically, contractile arrest also inhibited α-MHC promoter activity, suggesting that increased α-MHC mRNA levels resulted from posttranscriptional mechanisms. Actinomycin D rnRNA stability assays indicated that α-MHC mRNA half-life was prolonged in noncontracting cells (33 h) compared with contracting myocytes (14 h). Contraction-dependent alterations in MHC gene expression were not dependent on release of angiotensin or other growth factors into the culture medium. Thus intrinsic mechanical signals rather than alterations in [Ca2+]j regulate α-MHC and ß-MHC gene expression by both transcriptional and posttranscriptional mechanisms.
AB - To determine if mechanical signals or alterations in intracellular Ca2+ concentration ([Ca2+]i) affect myosin heavy chain (MHC) gene expression in spontaneously beating, neonatal rat ventricular myocytes, contractile activity was inhibited with verapamil, KCl, or 2,3-butanedione monoxime (BDM), and their acute and chronic effects on myocyte shortening, [Ca2+]i, and MHC gene expression were examined. Despite their differing effects on [Ca2+]i; verapamil, KC1, and BDM all inhibited contractile activity and markedly downregulated ß-MHC mRNA levels to 24 5, 21 7, and 6 2% of contracting cells, respectively. In contrast, these inhibitors of contraction upregulated a-MHC mRNA levels to 163 19, 156 7, and 198 20% of contracting cells, respectively. Transient transfection with a rat ß-MHC promoter-luciferase expression plasmid demonstrated that all inhibitors of contraction significantly decreased ß-MHC promoter activity. Paradoxically, contractile arrest also inhibited α-MHC promoter activity, suggesting that increased α-MHC mRNA levels resulted from posttranscriptional mechanisms. Actinomycin D rnRNA stability assays indicated that α-MHC mRNA half-life was prolonged in noncontracting cells (33 h) compared with contracting myocytes (14 h). Contraction-dependent alterations in MHC gene expression were not dependent on release of angiotensin or other growth factors into the culture medium. Thus intrinsic mechanical signals rather than alterations in [Ca2+]j regulate α-MHC and ß-MHC gene expression by both transcriptional and posttranscriptional mechanisms.
KW - Angiotensin II
KW - Calcium
KW - Indo 1
KW - Intracellular calcium concentration
KW - Signal transduction
KW - Transcription
KW - Verapamil
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M3 - Article
C2 - 9277337
AN - SCOPUS:33745394490
VL - 273
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 2 PART 1
ER -