L-type calcium channel C terminus autoregulates transcription.
L-type calcium channel C terminus autoregulates transcription.
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DOI：
10.1161/circresaha.108.191387
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发表时间：
2009-06-19
影响因子：
20.1
通讯作者：
Satin J
中科院分区：
文献类型：
--
作者：
Schroder E;Byse M;Satin J
钙（Ca）稳态对心肌细胞功能至关重要，必须严格调节。本研究的指导性假设是心脏L型钙通道（CaV1.2）的羧基末端裂解产物自动调节表达。首先，我们证实了钙通道C-末端（CCt）在小鼠心肌细胞从成熟和发育心室切割。过表达全长CCt导致CaV1.2启动子活性降低34±8%，截短CCt导致CaV1.2启动子活性降低80±3%（n= 12）。CCt全长分布于胞浆和细胞核中。缺失突变体的CCt有一个更大的相对亲和力的细胞核比全长的CCt，这是一致的增加阻遏CaV1.2启动子活性截短的CCt。染色质免疫沉淀（ChIP）分析显示，CCt相互作用与CaV1.2启动子在成人心室心肌细胞的启动子模块包含Nkx2.5/Mef 2，C/EBp，顺式调节模块。下一个检验的假设是CCt促进与细胞肥大相关的转录信号传导。本研究探讨了血清对胎儿心肌细胞CaV1.2的调控作用。我们测试了ANF启动子活性作为阳性对照，并测量了胎鼠心室肌细胞CaV1.2启动子、蛋白和L型电流（伊卡，L）的血清反应。血清增加ANF启动子活性和细胞大小的预期。血清戒断增加CaV1.2启动子活性、mRNA和伊卡，L。此外，血清戒断降低了CCt的相对核定位。启动子缺失突变体分析的组合，以及启动子突变体对血清戒断的响应支持CCt，CaV1.2的蛋白水解片段，自动调节心肌细胞中CaV1.2表达的结论。这些数据支持的新机制，一个移动的部分CaV1.2链接钙处理核信号。
Calcium (Ca) homeostasis is critical for cardiac myocyte function and must be tightly regulated. The guiding hypothesis of this study is that a carboxyl-terminal cleavage product of the cardiac L-type calcium channel (CaV1.2) auto-regulates expression. First, we confirmed that the Ca channel C-terminus (CCt) is cleaved in murine cardiac myocytes from mature and developing ventricle. Over-expression of full-length CCt caused a 34±8% decrease of CaV1.2 promoter activity, and truncated CCt caused an 80±3% decrease of CaV1.2 promoter (n= 12). The full-length CCt distributes into cytosol and nucleus. A deletion mutant of CCt has a greater relative affinity for the nucleus than full-length CCt, and this is consistent with increased repression of CaV1.2 promoter activity by truncated CCt. Chromatin immunoprecipitation (ChIP) analysis revealed that CCt interacts with the CaV1.2 promoter in adult ventricular cardiac myocytes at promoter modules containing Nkx2.5/Mef2, C/EBp, and a cis regulatory module. The next hypothesis tested was that CCt contributes to transcriptional signaling associated with cellular hypertrophy. We explored whether fetal cardiac myocyte CaV1.2 was regulated by serum in vitro. We tested ANF promoter activity as a positive control, and measured the serum-response of CaV1.2 promoter, protein, and L-type current (ICa,L) from fetal mouse ventricular myocytes. Serum increased ANF promoter activity and cell size as expected. Serum withdrawal increased CaV1.2 promoter activity, mRNA, and ICa,L. Moreover, serum withdrawal decreased the relative nuclear localization of CCt. A combination of promoter deletion mutant analyses, and the response of promoter mutants to serum withdrawal support the conclusion that CCt, a proteolytic fragment of CaV1.2, auto-regulates CaV1.2 expression in cardiac myocytes. These data support the novel mechanism that a mobile segment of CaV1.2 links Ca handling to nuclear signaling.