Role of caveolae in signal-transducing function of cardiac Na+/K+-ATPase
Role of caveolae in signal-transducing function of cardiac Na+/K+-ATPase
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DOI：
10.1152/ajpcell.00555.2002
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发表时间：
2003-06-01
影响因子：
5.5
通讯作者：
Askari, A
中科院分区：
文献类型：
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作者：
Liu, LJ;Mohammadi, K;Askari, A
哇巴因与 Na+/K+-ATP 酶结合可激活 Src/表皮生长因子受体 (EGFR)，从而启动调节生长的多个信号通路。在心肌细胞和完整的心脏中，早期哇巴因诱导的导致 ERK1/2 快速激活的途径也调节细胞内 Ca2+ 浓度 ([Ca2+](i)) 和收缩性。本研究的目的是探讨小窝在这些早期信号事件中的作用。通过已建立的无去污剂程序从心肌细胞、心室、肾细胞系和肾外髓质中分离出的小窝中，通过免疫印迹分析检测Na+/K+-ATP酶亚基。分离的大鼠心脏小窝含有 Src、EGFR、ERK1/2 和 20-30% 的 Na+/K+-ATPase α(1)- 和 α(2)-亚型细胞内容物，以及几乎所有细胞小窝蛋白-3。成人心肌细胞的免疫荧光显微镜显示外周肌膜和 T 小管中存在 Caveolin-3 和 α-亚型，并表明它们部分共定位。将收缩的离体大鼠心脏暴露于正性肌力剂量的哇巴因并对离体心脏小窝进行分析表明，哇巴因导致：1）总小窝 ERK1/2 没有变化，但小窝磷酸化/活化 ERK1/2 增加了两到三倍； 2) Caveolar α(1)-亚型和 Caveolin-3 没有变化； 3) 小凹 Src 和 α(2)-亚型增加 50-60%。这些发现与之前的观察结果相结合，表明将 Na+/K+-ATPase 连接到 ERK1/2 和 [Ca2+](i) 的途径组件在心脏小窝微域内组织。他们还表明，哇巴因诱导的 Src 和 α(2)-异构体向小凹的募集参与了哇巴因正性肌力作用的表现。
Ouabain binding to Na+/K+-ATPase activates Src/epidermal growth factor receptor (EGFR) to initiate multiple signal pathways that regulate growth. In cardiac myocytes and the intact heart, the early ouabain-induced pathways that cause rapid activations of ERK1/2 also regulate intracellular Ca2+ concentration ([Ca2+](i)) and contractility. The goal of this study was to explore the role of caveolae in these early signaling events. Subunits of Na+/K+-ATPase were detected by immunoblot analysis in caveolae isolated from cardiac myocytes, cardiac ventricles, kidney cell lines, and kidney outer medulla by established detergent-free procedures. Isolated rat cardiac caveolae contained Src, EGFR, ERK1/2, and 20-30% of cellular contents of alpha(1)- and alpha(2)-isoforms of Na+/K+-ATPase, along with nearly all of cellular caveolin-3. Immunofluorescence microscopy of adult cardiac myocytes showed the presence of caveolin-3 and alpha-isoforms in peripheral sarcolemma and T tubules and suggested their partial colocalization. Exposure of contracting isolated rat hearts to a positive inotropic dose of ouabain and analysis of isolated cardiac caveolae showed that ouabain caused 1) no change in total caveolar ERK1/2, but a two-to threefold increase in caveolar phosphorylated/activated ERK1/2; 2) no change in caveolar alpha(1)-isoform and caveolin-3; and 3) 50-60% increases in caveolar Src and alpha(2)-isoform. These findings, in conjunction with previous observations, show that components of the pathways that link Na+/K+-ATPase to ERK1/2 and [Ca2+](i) are organized within cardiac caveolae microdomains. They also suggest that ouabain-induced recruitments of Src and alpha(2)-isoform to caveolae are involved in the manifestation of the positive inotropic effect of ouabain.