Cell Death Regulation by Pro-Apoptotic BOK in Cardiomyocytes

 描述(由申请人提供)：内质网(ER)应激导致的心肌细胞功能障碍和死亡被认为在许多心血管疾病的发展中起着核心作用。因此，了解控制内质网应激触发的细胞程序性死亡的信号网络有望提供有价值的治疗靶点。内质网应激途径始于激活三部分信号转导通路，统称为未折叠蛋白反应(UPR)，试图恢复内环境平衡。然而，如果内质网的损伤太严重，UPR就会通过bcl2家族的细胞死亡调节因子触发线粒体的凋亡。连接内质网应激和bcl2死亡机制的信号网络在很大程度上仍然难以捉摸。针对这一点，我们最近发现，与BCL-2家族的同系物Bax和BAK不同，BOK选择性地调节对内质网应激的细胞凋亡反应，而不是其他刺激。因此，本提案的总体目标是确定BOK传递内质网应激促进细胞凋亡的机制。初步工作支持BOK的非规范功能，该功能主要发生在内质网，在那里它与肌醇-3-磷酸(IP3R)钙转运蛋白结合。我提出了一种多学科的方法，利用遗传学、先进的成像和生物化学来重点研究BOK在心肌细胞中介导ER-线粒体信号的生理作用。特别是，我们将研究(1)BOK功能的精细定位，(2)钙稳态和(3)正常和内质网应激条件下的内质网-线粒体界面。提出的BOK活性的机械解剖将整合内质网的细胞生理学和线粒体bcl2家族对细胞凋亡的调控。了解这一途径可能会产生有价值的药理靶点，以促进细胞在极端内质网应激下的存活，从而缓解或消除心血管疾病中细胞死亡的长期后果。

 DESCRIPTION (provided by applicant): Endoplasmic Reticulum (ER) stress-induced cardiomyocyte dysfunction and death are thought to play a central role in the development of numerous cardiovascular diseases. Therefore, understanding the signaling networks that control programmed cell death triggered by ER stress is expected to provide valuable therapeutic targets. The ER stress pathway begins with activation of a tripartite of signal transduction pathways, collectively known as the Unfolded Protein Response (UPR), in an attempt to restore homeostasis. If the damage at the ER is too severe, however, then the UPR triggers apoptosis at the mitochondria through the BCL-2 family of cell death regulators. The signaling network that connects the ER stress to the BCL-2 death machinery has remained largely elusive. Addressing this point, we recently discovered that BOK, unlike its BCL-2 family homologues BAX and BAK, selectively regulates the apoptotic response to ER stress, but not other stimuli. Thus, the overall goal of this proposal is to define the mechanisms by which BOK transmits ER stress to promote apoptosis. Preliminary work supports a non-canonical function for BOK that largely occurs at the ER where it is bound to the inositol-3-phosphate (IP3R) calcium transporter. I propose a multidisciplinary approach that employs genetics, advanced imaging, and biochemistry to focus on the physiologic role of BOK in mediating ER-mitochondrial signaling in cardiomyocytes. In particular, we will examine (1) the finely resolved localization of BOK function, (2) calcium homeostasis and (3) the ER-mitochondria interface under normal and ER stress conditions. The proposed mechanistic dissection of BOK activity will integrate cellular physiology at the ER with the regulation of apoptosis by the BCL-2 family at the mitochondria. Understanding this pathway will likely yield valuable pharmacologic targets to promote cell survival in the face of extreme ER stress and thereby alleviate or eliminate the long term consequences of cell death in cardiovascular diseases.