期刊
JOURNAL OF CELL BIOLOGY
卷 158, 期 1, 页码 103-113出版社
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.200204092
关键词
calreticulin; Ca2+; embryonic stem cells; MEF2C; cardiac myofibrillogenesis
类别
Calreticulin (crt) is an ubiquitously expressed and multifunctional Ca2+-binding protein that regulates diverse vital cell functions including Ca2+ storage in the ER and protein folding. Calreticulin deficiency in mice is lethal in utero due to defects in heart development and function. Herein, we used crt(-/-) embryonic stem (ES) cells differentiated in vitro into cardiac cells to investigate the molecular mechanisms underlying heart failure of knockout embryos. After 8 d of differentiation, beating areas were prominent in ES-derived wild-type (wt) embryoid bodies (EBs), but not in ES-derived crt(-/-) EBs, despite normal expression levels of cardiac transcription factors. Crt(-/-)EBs exhibited a severe decrease in expression and a lack of phosphorylation of ventricular myosin light chain 2 (MLC2v), resulting in an impaired organization of myofibrils. Crt(-/-) phenotype could be recreated in wt cells by chelating extracellular or cytoplasmic Ca2+ with EGTA or BAPTA, or by inhibiting Ca2+/calmodulin-dependent kinases (CaMKs). An imposed ionomycin-triggered cystolic-free Ca2+ concentration ([Ca2+](c)) elevation restored the expression, phosphorylation, and insertion of MLC2v into sarcomeric structures and in turn the myofibrillogenesis. The transcription factor myocyte enhancer factor C2 failed to accumulate into nuclei of crt(-/-) cardiac cells in the absence of ionomycin-triggered [Ca2+], increase. We conclude that the absence of calreticulin interferes with myofibril formation. Most importantly, calreticulin deficiency revealed the importance of a Ca2+-dependent checkpoint critical for early events during cardiac myofibrillogenesis.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据