细胞内钙信号与平滑肌细胞增殖及去分化

As Calcium sensors on ER membrane, STIM protein will activate calcium channel, Orai1, when ER calcium level is low. The molecular mechanism through which STIM1 couples and activate Orai1 is now a very hot frontier in scientific research. Even though much is known about the structure, function and its coupling with Orai1, little is clear to its homolog, SITM2. Another hot field of research is exploring the physiological roles of STIM. Studies have shown that STIM1 is very important for the proliferation and phenotype switch of smooth muscle cells (SMC). However, the underlying molecular mechanism still remain largely elusive. Our previous work has shown that STIM, while activating Orai1, also can simultaneously inhibit the functionof L-type calcium channel (LTCC). Both LTCC and STIM2 are expressed in SMC, yet their roles in the proliferation and phenotype switch of SMCs are still not very clear. Thus, the current aims of our research are: examine the molecular mechanism by which STIM1, especially STIM2, couple and regulate the function of their target proteins (Orai1, especially LTCC). How STIM proteins and LTCC function during proliferation and phenotype switch of SMCs. Our study will sure improve current understanding on the molecular mechanisms by which STIM1, especially STIM2, couple with their targets and then alter their function. Also, our research will help us understand the mechanisms for the damage-repair of SMCs.

作为内质网膜上的钙感受器，STIM蛋白(包括STIM1及STIM2）会感受内质网内钙水平的降低,结合并激活细胞膜上钙离子通道，Orai1。对STIM1的生理功能以及其耦合并激活Orai1的分子机制的研究一直是个前沿热点领域。但目前对STIM1在平滑肌细胞增殖及表型变化中作用的分子机制还不很清楚,对其同源蛋白STIM2的了解也不多。我们以前的工作表明STIM1在激活Orai1的同时还会耦合抑制L型钙通道。STIM2和L型钙通道在平滑肌内大量存在，他们在上述细胞变化过程中的作用还不清楚。因此本工作的目的是研究1）STIM1，特别是STIM2激活及与它们的靶蛋白（Orai1，特别是LTCC）的相互作用的分子机理；2）STIM和LTCC在平滑肌增殖和表型变化中的作用。我们的研究将提高领域内对内对STIM-Orai1耦合机制的理解，并进一步探索平滑肌损伤修复的机理。

钙池操纵钙内流（SOCE）是一种由STIM蛋白和Orai钙离子通道共同介导的一种钙内流。它在分泌、基因转录、酶活调节、细胞生死等过程中发挥重要的作用，并与众多疾病，特别是心血管病及免疫相关疾病密切相关。为探究STIM介导的钙池操纵钙内流（SOCE）的激活及调控机理，我们利用一组原创的可以在纳米尺度原位实时监测STIM构象变化的荧光探针，阐释了STIM1及STIM2特异性激活的分子机制；鉴定了决定STIM1及STIM2蛋白特异性结合Orai1钙通道，引发SOCE的关键氨基酸位点。还运用一种新型无损原位活体生物素标记技术，结合质谱分析获得了内质网-质膜连接处与STIM1互作的蛋白质组，并进一步鉴定了其中一个候选蛋白STIMATE调控STIM1激活的分子机制。最后我们还制备了一个光遗传学工具，用它实现了对STIM1靶蛋白L型钙通道（LTCC）的可逆光抑制。这些研究进一步阐明了SOCE激活及调控机制，并将为后续研究提供优秀的分子生物学工具或蛋白质组学信息。