Cdk5 regulation of calcium dynamics

我们实验室的一般兴趣是了解蛋白激酶如何调节特殊的细胞功能。我们主要关注细胞周期蛋白依赖性激酶（Cdks），特别是Cdk5。Cdk5是一种丝氨酸/苏氨酸激酶，与哺乳动物的发育密切相关，因此，我们的长期目标是揭示Cdk5调节和功能的基本分子和细胞机制。在我们超过二十年的Cdk5研究中，我们已经证明Cdk5活性受特定蛋白质激活剂的调节，并且Cdk5相互作用有助于增强或抑制多种细胞功能。我们的研究突破明确了Cdk5在基因表达、细胞分化和分泌等方面的基本作用和意义。我们最近的研究指出Cdk5作为钙（Ca2+）动力学和细胞增殖的调节剂。通过利用Cdk5-/-敲除和小鼠胚胎成纤维细胞（MEF）模型系统，我们发现Cdk5-/- MEF的增殖速度比wt更快。我们进一步发现，atp诱导的ip3r介导的Ca2+从Cdk5-/- MEF的内质网（ER）释放更多。由于我们发现Cdk5与IP3R相互作用，而IP3R1型有两个潜在的Cdk5磷酸化位点，我们的前提是Cdk5控制IP3R1介导的内质网Ca2+释放，可能是通过IP3R1磷酸化。我们的数据表明，Cdk5对ER Ca2+释放的控制限制了Ca2+流入线粒体。由于线粒体Ca2+摄取与瞬时mPTP开放和ROS的产生有关，从而促进细胞增殖，我们的观点是Cdk5控制er -线粒体Ca2+串扰，调节线粒体Ca2+浓度（[Ca2+]m），瞬时mPTP开放和ROS水平，并随后调节细胞增殖。事实上，Ca2+是导致不同细胞活动的信号转导途径的关键，cdk5调节的Ca2+动力学可能解释了cdk5调节的细胞增殖。因此，根据我们的一般假设，Cdk5是一个复杂的蛋白质-蛋白质相互作用和磷酸化事件系统的关键，这些系统调节特定的细胞过程，我们的短期目标是了解Cdk5控制的Ca2+动力学和Cdk5调节的细胞增殖之间的联系，我们的具体目标是：(i)研究Cdk5对ip3r介导的Ca2+信号通路的调节，以及（ii）研究Cdk5参与Ca2+调节的线粒体介导的功能。我们提出的研究将(i)产生关于Cdk5及其在控制Ca2+动力学和细胞增殖中的基本作用的新的重要知识，这将（ii）为我们旨在阐明Cdk5在哺乳动物发育中的重要性的计划的下一步奠定基础，以及（iii）提升两位HQP的地位，他们将把100%的时间奉献给我们的研究计划，这将成为他们培训和发展的渠道。

The general interest of our laboratory is to understand how protein kinases regulate specialized cell functions. We focus on cyclin-dependent kinases (Cdks) in general and Cdk5 in particular. Cdk5 is a serine/threonine kinase that has been strongly implicated in mammalian development, and thus, our long-term objective is to uncover the fundamental molecular and cellular mechanisms of Cdk5 regulation and function. Throughout our over two decades of Cdk5 studies, we have demonstrated that Cdk5 activity is regulated by specific protein activators and that Cdk5 interactions serve to enhance or inhibit diverse cellular functions. Our research breakthroughs define the basic roles and significance of Cdk5 in gene expression, cell differentiation and secretion among others. Our recent studies point to Cdk5 as a regulator of calcium (Ca2+) dynamics and cell proliferation. By taking advantage of the Cdk5-/- knockout and mouse embryonic fibroblast (MEF) model systems, we found that Cdk5-/- MEFs proliferate at a faster rate compared to wt. We further found greater ATP-induced IP3R-mediated Ca2+ release from the endoplasmic reticulum (ER) in Cdk5-/- MEFs. Since we found that Cdk5 interacts with IP3R, and IP3R type 1 has two potential Cdk5 phosphorylation sites, our premise is that Cdk5 controls IP3R1-mediated Ca2+ release from the ER, possibly through IP3R1 phosphorylation. Our data suggest that Cdk5 control of ER Ca2+ release limits Ca2+ influx into mitochondria. Because mitochondrial Ca2+ uptake is associated with transient mPTP opening and production of ROS, which promotes cell proliferation, our view is that Cdk5 controls ER-mitochondria Ca2+ crosstalk, regulating mitochondrial Ca2+ concentration ([Ca2+]m), transient mPTP opening and ROS level, and subsequently, cell proliferation. Indeed, Ca2+ is key to signal transduction pathways leading to different cellular activities, and it is possible that Cdk5-regulated Ca2+ dynamics accounts for Cdk5-regulated cell proliferation. Thus, in line with our general hypothesis that Cdk5 is key to an elaborate system of protein-protein interactions and phosphorylation events that modulate specific cellular processes, and our short-term goal of understanding the connections between Cdk5-controlled Ca2+dynamics and Cdk5-regulated cell proliferation, our specific aims are: (i) to examine Cdk5 regulation of the IP3R-mediated Ca2+ signaling pathway, and (ii) to investigate Cdk5 involvement in Ca2+-regulated, mitochondria-mediated functions. Our proposed research will (i) generate new and significant knowledge on Cdk5 and its fundamental role in controlling Ca2+ dynamics and cell proliferation, which will (ii) serve as foundation for our next steps in our program that aims to elucidate the importance of Cdk5 in mammalian development, and (iii) elevate the status of two HQP, who will dedicate 100% of their time on our research program, which will serve as their channels for training and development.