期刊
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
卷 288, 期 2, 页码 H650-H659出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00268.2004
关键词
GDP dissociation inhibitor; TAT-mediated protein transduction; K+ channel; ventricular; cardiomyocyte
资金
- NHLBI NIH HHS [R01 HL-64356, R01 HL-72897, R01 HL-61476] Funding Source: Medline
- NIGMS NIH HHS [GM-54169] Funding Source: Medline
Regulation of ionic channels plays a pivotal role in controlling cardiac function. Here we show that the Rho family of small G proteins regulates L-type Ca2+ currents in ventricular cardiomyocytes. Ventricular myocytes isolated from transgenic (TG) mice that overexpress the specific GDP dissociation inhibitor Rho GDI-alpha exhibited significantly decreased basal L-type Ca2+ current density ( similar to 40%) compared with myocytes from nontransgenic (NTG) mice. The Ca2+ channel agonist BAY K 8644 and the beta-adrenergic agonist isoproterenol increased Ca2+ currents in both NTG and TG myocytes to a similar maximal level, and no changes in mRNA or protein levels were observed in the Ca2+ channel alpha(1)-subunits. These results suggest that the channel activity but not the expression level was altered in TG myocytes. In addition, the densities of inward rectifier and transient outward K+ currents were unchanged in TG myocytes. The amplitudes and rates of basal twitches and Ca2+ transients were also similar between the two groups. When the protein was delivered directly into adult ventricular myocytes via TAT-mediated protein transduction, Rho GDI-alpha significantly decreased Ca2+ current density, which supports the idea that the defective Ca2+ channel activity in TG myocytes was a primary effect of the transgene. In addition, expression of a dominant-negative RhoA but not a dominant-negative Rac-1 or Cdc42 also significantly decreased Ca2+ current density, which indicates that inhibition of Ca2+ channel activity by overexpression of Rho GDI-alpha is mediated by inhibition of RhoA. This study points to the L-type Ca2+ channel activity as a novel downstream target of the RhoA signaling pathway.
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