集钙蛋白1型对心肌钙信号调节及其在糖尿病心肌病中的作用及机制研究

Calsequestrin, an important Ca2+ storage protein in muscle sarcoplasmic reticulum, has 2 subtypes, skeletal muscle calsequestrin (CSQ-1) and cardiac calsequestrin (CSQ-2). Many studies have shown that CSQ is an important protein in Ca2+ stores for Ca2+ storage as well as Ca2+ release regulation. Our previous studies have found that CSQ-1 could interact with stromal interaction molecule (STIM-1), which further downregulates STIM-1 interacting with Ca2+ release-activated Ca2+ modulator (Oria-1) and the following activation of store-operated Ca2+ entry (SOCE). Additionally, we also found that CSQ-1 expression is reduced in diabetic platelets from rats and patients human and is involved in the hyperactivity of diabetic platelets. Moreover, in addition to CSQ-2, myocardium also expresses CSQ-1 subtype. Interestingly, CSQ-1 but not CSQ-2 expression was deceased in the heart of type 2 diabetes rats, in which obvious cardiac dysfunction and manifestations of diabetic cardiomyopathy appeared. As far as we know, it is still not clear whether functional CSQ-1 is expressed in the heart, and whether its abundant change is involved in the pathological changes in diabetes cardiomyopathy. Therefore, in this project, using molecular biological, physiological and pharmacological techniques we are going to investigate that CSQ-1 is involved in the regulation of Ca2+ signaling in normal heart under physiological conditions. In addition, we also identify whether the signal pathway of CSQ-1–STIM-1 interaction exists in myocardium and accounts, at least partly, for its regulatory role in Ca2+ signaling and myocardium contraction in the heart. Furthermore, we identify whether its change in the expression level or the signal pathway participates in the generation of disordered cardiac contraction in diabetes cardiomyopathy. Therefore, through all these investigations, this study may provide a novel signal transduction pathway for the regulation of cardiac Ca2+ signaling/contractility by CSQ-1 in the heart under physiological condition and also a new possible mechanism underlying the malfunction of cardiac contractility in diabetic cardiomyopathy.

集钙蛋白有骨骼肌型(CSQ-1)和心肌型(CSQ-2)二个亚型, 是细胞内钙库重要的贮钙和调节钙释放蛋白。前期研究发现1）CSQ-1与内质网膜基质作用分子-1(STIM-1)相互作用，从而抑制了STIM-1与释放激活钙通道调节分子-1的相互作用及其介导的钙库耗竭性钙内流（store operated Ca2+ entry)；2）糖尿病血小板CSQ-1表达减少并致血小板的高反应性和高聚集性；3）重要是在大鼠糖尿病心肌病中CSQ-1表达也下调，而CSQ-2表达不变。由于心肌是否表达功能性CSQ-1，并参与糖尿病心肌病理病变过程未知。本项目将通过分子生物学，生理和药理学技术，系统地研究CSQ-1对心肌细胞钙信号及其收缩功能的生理性调节作用及其机制，并进一步研究CSQ-1水平下调与糖尿病心肌病的关系，从而为心肌钙信号的调控和糖尿病心肌收缩功能失调提供新的理论基础。

背景：在非电兴奋性细胞和病理性心肌细胞，外钙内流由内钙耗竭致钙通道开放(SOCE）介导。集钙蛋白有骨骼肌型(CSQ-1)和心肌型(CSQ-2)二个亚型, 是细胞内钙库重要的贮钙和调节肌浆网钙释放蛋白。研究发现遗传性儿茶酚胺多形性室性心律失常(CPVT)和恶性高热病(MH)分别与CSQ-2和CSQ-1基因变异、表达减少或缺失有关。前期研究发现1）糖尿病血小板的CSQ-1表达减少并致血小板的高反应性和高聚集性；2）糖尿病心肌病中CSQ-1表达也下调，而CSQ-2表达不变。由于心肌是否表达功能性CSQ-1，并参与糖尿病心肌病理病变过程未知。本项目主要系统地研究CSQ-1对心肌细胞钙信号及其收缩功能的生理性调节作用及其机制，并进一步研究CSQ表达改变与糖尿病心肌病的关系，从而为心肌钙信号的调控和糖尿病心肌收缩功能失调提供新的理论基础。.重要结果：1）心脏表达功能性的CSQ1，且CSQ1与兰尼定受体通道结合和相互作用，调节肌浆网钙释放。CSQ1基因敲减使动物窦性心律加快，且麻药或高温通过增加心肌细胞早后去极化（EAD）诱导室性心律失常，其机制与CSQ1功能的改变减弱对兰尼定受体的抑制有关。2）糖尿病心脏CSQ2的表达显著上调，并介导了SOCE重要的激活蛋白STIM-1的高表达，后者通过激活SOCE通道Orai1，使SOCE内流增加介导了糖尿病的心肌肥大和心衰。3）协助前一项国自然完成缝隙连接蛋白Cx43调节心肌细胞生存并完成诱导和参与心肌缺血再灌损伤中心肌细胞凋亡的机制研究。.意义：本研究首次揭示了功能性的CSQ1在心脏表达并诱导MH心律失常发生的机制；首次揭示了CSQ2在调节SOCE的机制，尤其在糖尿病心肌病中的重要作用；同时发现丝氨酸282位点磷酸化是Cx43维系心肌细胞生存的关键位点，该磷酸化下调参与缺血再灌注心肌凋亡。目前共发表SCI论文8篇（IF>8一篇，>6一篇），专利1项，另2篇论文在审稿和撰写中，培养研究生8人和青年教师2人。

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