Function and regulation of the BCL-2 family

描述(申请人提供)：凋亡通路对癌症生物学的影响是广泛的，因为bcl2蛋白家族调节肿瘤进展的几乎所有步骤，显示出预后价值，并可以预测治疗成功。在临床上，肿瘤细胞在化疗和放射治疗中通过诱导细胞凋亡而死亡，这引发了人们对剖析这一途径如何进行并可能受到药物调控的极大热情。当bcl2蛋白家族促进线粒体外膜通透性(MOMP)，从而触发促凋亡分子从线粒体释放到细胞质中时，细胞凋亡就会发生。两个bcl2家族蛋白BAK和Bax通过在线粒体膜外膜上形成蛋白脂孔直接与MOMP结合。依赖于BAK/BAX的MOMP是细胞凋亡所必需的，并由BCL-2家族的一个亚群启动，即BH3-Only蛋白，例如Bid。我们最近的研究发现，为了BAK/Bax和Bid诱导MOMP，线粒体必须在功能上与鞘磷脂途径相交。新的假设是线粒体鞘脂赋予bcl-2家族功能，这可能解释了BAK/Bax和Bid是如何特异性地针对线粒体的。对上述bcl2家族与线粒体相互作用的好奇心导致了鞘磷脂途径在bcl2家族功能中起着至关重要的作用。我们最近发现，鞘氨醇途径中的两种产物-鞘氨醇-1-PO4和十六烯醛分别直接调节BAK和Bax的激活。目前应用的目标集中在了解鞘氨醇-1-PO4和十六烯醛对bcl2家族功能、MOMP和细胞凋亡的机制贡献。这个项目是经过多年的努力确定MOMP所必需的细胞成分后产生的，我们提出了三个具体的目标：(1)探讨Bid诱导的BAK/Bax激活的鞘磷脂途径的生化要求，(2)阐明BAK/Bax和鞘磷脂途径在细胞命运和肿瘤发生中的功能协作，以及(3)探讨Bax和促进MOMP和细胞凋亡所必需的十六碳肾之间的结构关系。这一提议的科学成果将揭示bcl2家族调控和对细胞凋亡的承诺的新机制。这些数据将阐明BAK/BAX与鞘磷脂之间的功能和结构相互作用(S)，并为未来BAK/BAX药理调节剂的开发奠定基础。 与公共健康相关：当细胞发生变化，将其从正常状态转化为恶性状态时，就会发生癌症。细胞凋亡是一种细胞自杀程序，它消除受损细胞以预防癌症；然而，在化疗和放射治疗后，身体也会启动这一程序，以杀死癌细胞。因此，重要的是要研究控制细胞凋亡的途径，以了解癌症是如何发生和应该被治疗的。

DESCRIPTION (provided by applicant): The impact of the apoptotic pathways on cancer biology is broad because the BCL-2 family of proteins regulates nearly all steps of tumor progression, exhibits prognostic value, and can be predictive of treatment success. In the clinic, tumor cells die in response to chemotherapeutics and radiation treatment by inducing apoptosis, which has generated substantial enthusiasm for dissecting how this pathway proceeds and may be pharmacologically modulated. Apoptosis proceeds when the BCL-2 family of proteins promotes mitochondrial outer membrane permeabilization (MOMP), which triggers the release of pro-apoptotic molecules from mitochondria into the cytoplasm. Two BCL-2 family proteins, BAK and BAX, directly engage MOMP by creating proteolipid pores in the outer mitochondrial membrane. BAK/BAX-dependent MOMP is required for apoptosis, and is initiated by a BCL-2 family subset, the BH3-only proteins, e.g., BID. Our studies recently discovered that in order for BAK/BAX and BID to induce MOMP, mitochondria must functionally intersect with the sphingolipid pathway. The novel hypothesis is that mitochondrial sphingolipids confer function to the BCL-2 family, which may explain how BAK/BAX and BID specifically target mitochondria. Curiosity in the BCL-2 family-mitochondrial interactions mentioned above led to the identification that the sphingolipid pathway plays a crucial role in BCL-2 family function. We recently identified that two products within the sphingolipid pathway, sphingosine-1-PO4 and hexadecenal, directly regulate BAK and BAX activation, respectively. The goals of the current application are focused on understanding the mechanistic contribution of sphingosine-1-PO4 and hexadecenal on BCL-2 family function, MOMP and apoptosis. This project emerged following years of effort to identify cellular components necessary for MOMP, and we propose three specific aims: (1) to explore the biochemical requirements for the sphingolipid pathway on BID-induced BAK/BAX activation, (2) to elucidate the functional cooperation between BAK/BAX and the sphingolipid pathway in the contexts of cellular fate and tumorigenesis, and (3) to probe the structural relationships between BAX and hexadecenal necessary to promote MOMP and apoptosis. The scientific outcome of this proposal will uncover novel mechanisms of BCL-2 family regulation and commitment to apoptosis. These data will elucidate the functional and structural interaction(s) between BAK/BAX and the sphingolipids, and serve as the foundation for the development of BAK/BAX pharmacologic regulators in the future. PUBLIC HEALTH RELEVANCE: Cancer occurs when cells acquire changes that convert them from a normal to malignant state. Apoptosis is a program of cellular suicide that eliminates damaged cells to prevent cancer; yet the body also turns on this program following chemotherapy and radiation treatments in order to kill cancer cells. Therefore, it is important to investigate the pathways that control apoptosis to understand how cancer occurs and should be treated.