PKC-¦Å mediates multiple endothelin-1 actions on systolic Ca²⁺ and contractility in ventricular myocytes

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• 作者：Misuk Kang ; Ka Young Chung
• 关键词：PKC-¦Å ; Endothelin-1 ; Systolic Ca2+ ; Positive inotropy
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2012
• 出版时间：6 July, 2012
• 年：2012
• 卷：423
• 期：3
• 页码：600-605
• 全文大小：711 K

文摘

Endothelin-1 (ET-1) induces positive inotropy (enhanced contractility) in cardiac muscle, but establishing underlying cellular mechanisms has been controversial in part because of a growing number of signaling pathways and end effectors targeted by ET-1. Here we present evidence that ET-1 induces positive inotropism in ventricular tissue by increasing both systolic Ca²⁺ and myofilament Ca²⁺ sensitivity. To examine the roles of PKC-¦Ä and PKC-¦Å in these acute responses to ET-1, kinase inactive dominant negative PKC (dn-PKC) constructs were expressed in adult rat ventricular myocytes. Yellow fluorescent protein (YFP) was fused to dn-PKC constructs to visualize expression and localization of dn-PKC in living myocytes. Due to an alanine to glutamate mutation in the pseudosubstrate site, dn-PKCs constitutively translocated to anchoring sites and were unaffected by agonist or phorbol ester treatment. Dn-PKC-¦Ä-YFP mainly distributed at Z-lines and at intercalated disks in adult myocytes, whereas dn-PKC-¦Å-YFP stained the surface sarcolemma, T-tubules/Z-lines and perinuclear region. Myocytes expressing dn-PKC-¦Ä-YFP showed normal systolic Ca²⁺ and contractile responses to ET-1. In contrast, the entire ensemble of ET-1 responses was blocked in myocytes expressing dn-PKC-¦Å-YFP including increased Ca²⁺ transients, enhanced myofilament Ca²⁺ sensitivity, and positive inotropy. This report provides direct evidence that PKC-¦Å is activated early and robustly following ET-1 stimulation and thus mediates multiple intracellular changes underlying the acute actions of ET-1 on myocardium.