Effects of phospholemman downregulation on contractility and [Ca2+]i transients in adult rat cardiac myocytes
Effects of phospholemman downregulation on contractility and [Ca2+]i transients in adult rat cardiac myocytes
复制标题
DOI：
10.1152/ajpheart.00997.2003
复制
发表时间：
2004-04-01
影响因子：
4.8
通讯作者：
Cheung, JY
中科院分区：
文献类型：
--
作者：
Mirza, MA;Zhang, XQ;Cheung, JY
心肌梗死（MI）后大鼠心肌中磷脂蛋白（PLM）表达升高。在正常成年大鼠心肌细胞中，PLM的过度表达改变了收缩功能和胞浆Ca2+浓度（[Ca2+](i)）的稳态，其方式与心肌梗死后心肌细胞中观察到的相似。在这项研究中，我们测试了正常成年大鼠肌细胞中的PLM下调是否会导致收缩性和[Ca2+](i)与心肌梗死后肌细胞中观察到的相反的短暂变化。与单独表达绿色荧光蛋白（GFP）的腺病毒（Adv）感染的对照肌细胞相比，同时表达GFP和大鼠反义PLM （rASPLM）的Adv感染的肌细胞在第3天PLM蛋白含量减少23% (P < 0.012)，但在肌浆网（SR） Ca2+-ATPase、Na+/Ca2+交换器（NCX1）、Na+-K+-ATPase和钙sequestrin水平上没有差异。rASPLM处理不影响SR Ca2+摄取和全细胞电容。在rASPLM肌细胞中，咖啡因诱导的挛缩弛豫更快，NCX1电流振幅更高，表明PLM下调增强了NCX1活性。在天然大鼠心肌细胞中，共免疫沉淀实验表明PLM与NCX1相关。在0.6 mM [Ca2+](o)时，rASPLM肌细胞的收缩和[Ca2+](i)瞬态振幅明显低于对照GFP肌细胞（P < 0.003）。在5 mM [Ca2+](o)时，rASPLM肌细胞的收缩和[Ca2+](i)瞬态振幅均较高。这种收缩模式和[Ca2+](i)短暂行为在rASPLM肌细胞中与心肌梗死后大鼠肌细胞中观察到的相反。我们得出结论，正常大鼠心肌细胞中PLM的下调增强了NCX1功能，并影响了[Ca2+](i)瞬态和收缩幅度。我们认为，PLM下调为改善心肌细胞收缩异常提供了一种潜在的治疗策略。
Phospholemman (PLM) expression was increased in rat hearts after myocardial infarction (MI). Overexpression of PLM in normal adult rat cardiac myocytes altered contractile function and cytosolic Ca2+ concentration ([Ca2+](i)) homeostasis in a manner similar to that observed in post-MI myocytes. In this study, we tested whether PLM downregulation in normal adult rat myocytes resulted in contractility and [Ca2+](i) transient changes opposite to those observed in post-MI myocytes. Compared with control myocytes infected with adenovirus (Adv) expressing green fluorescent protein (GFP) alone, myocytes infected with Adv expressing both GFP and rat antisense PLM (rASPLM) had 23% less PLM protein ( P < 0.012) at 3 days, but no differences were found in sarcoplasmic reticulum (SR) Ca2+-ATPase, Na+/Ca2+ exchanger (NCX1), Na+-K+-ATPase, and calsequestrin levels. SR Ca2+ uptake and whole cell capacitance were not affected by rASPLM treatment. Relaxation from caffeine-induced contracture was faster, and NCX1 current amplitudes were higher in rASPLM myocytes, indicating that PLM downregulation enhanced NCX1 activity. In native rat cardiac myocytes, coimmunoprecipitation experiments indicated an association of PLM with NCX1. At 0.6 mM [Ca2+](o), rASPLM myocytes had significantly (P < 0.003) lower contraction and [Ca2+](i) transient amplitudes than control GFP myocytes. At 5 mM [Ca2+](o), both contraction and [Ca2+](i) transient amplitudes were higher in rASPLM myocytes. This pattern of contractile and [Ca2+](i) transient behavior in rASPLM myocytes was opposite to that observed in post-MI rat myocytes. We conclude that downregulation of PLM in normal rat cardiac myocytes enhanced NCX1 function and affected [Ca2+](i) transient and contraction amplitudes. We suggest that PLM downregulation offers a potential therapeutic strategy for ameliorating contractile abnormalities in MI myocytes.