Rem-GTPase regulates cardiac myocyte L-type calcium current
Rem-GTPase regulates cardiac myocyte L-type calcium current
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DOI：
10.4161/chan.20192
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发表时间：
2012-05-01
期刊：
影响因子：
3.3
通讯作者：
Satin, Jonathan
中科院分区：
文献类型：
--
作者：
Magyar, Janos;Kiper, Carmen E.;Satin, Jonathan
理论基础：L型钙通道(LTCC)是维持钙稳态的关键。在异源表达研究中，RGK类RAS相关G蛋白调节LTCC功能；然而，RGK-LTCC相互作用的生理学相关性尚未得到检验。目的：本研究验证了RGK蛋白Rem通过LTCC调节小鼠心肌细胞天然钙电流(I-Ca，I-L)的假说。方法与结果：构建REM基因敲除小鼠(Rem(-/-))，并评估其对I-Ca、I-L和钙的处理特性。REM(-/-)心肌细胞表现为I-Ca、I-L密度增高。与野生型I-Ca、I-L相比，I-Ca、I-L的激活在电压轴上正向移动，而β-肾上腺素能刺激使这种移动正常化。电流动力学、稳态失活和易化不受Rem(-/-)的影响。细胞缩短无显著差异。在没有明显表型差异的情况下，I-Ca、I-L密度的增加促使我们探索可能的补偿机制。尽管I-Ca、I-L密度较大，但与野生型相比，Rem(-/-)型心肌细胞Ca~(2+)抽动的瞬时幅度明显减小。计算机模拟和免疫印迹分析表明，Rem(-/-)LTCC的相对去磷酸化可以解释钙瞬变的矛盾减少。结论：这是首次在活体心肌细胞中证明RGK蛋白的缺失影响I-Ca，I-L。
Rationale: The L-type calcium channels (LTCC) are critical for maintaining Ca2+-homeostasis. In heterologous expression studies, the RGK-class of Ras-related G-proteins regulates LTCC function; however, the physiological relevance of RGK-LTCC interactions is untested.Objective: In this report we test the hypothesis that the RGK protein, Rem, modulates native Ca2+ current (I-Ca,I-L) via LTCC in murine cardiomyocytes.Methods and Results: Rem knockout mice (Rem(-/-)) were engineered, and I-Ca,I-L and Ca2+-handling properties were assessed. Rem(-/-) ventricular cardiomyocytes displayed increased I-Ca,I-L density. I-Ca,I-L activation was shifted positive on the voltage axis, and beta-adrenergic stimulation normalized this shift compared with wild-type I-Ca,I-L. Current kinetics, steady-state inactivation and facilitation was unaffected by Rem(-/-). Cell shortening was not significantly different. Increased I-Ca,I-L density in the absence of frank phenotypic differences motivated us to explore putative compensatory mechanisms. Despite the larger I-Ca,I-L density, Rem(-/-) cardiomyocyte Ca2+ twitch transient amplitude was significantly less than that compared with wild type. Computer simulations and immunoblot analysis suggests that relative dephosphorylation of Rem(-/-) LTCC can account for the paradoxical decrease of Ca2+ transients.Conclusions: This is the first demonstration that loss of an RGK protein influences I-Ca,I-L in vivo in cardiac myocytes.