Mechanisms by which Bok binds to IP3Rs and regulates mitochondrial dynamics

项目总结 Bcl-2蛋白家族是一组在内源性细胞凋亡和细胞周期调控中发挥重要作用的蛋白。 包括蛋白质BOK。虽然许多Bcl-2蛋白家族的成员已经完全 研究发现，BOK是一种知之甚少的蛋白质，具有促凋亡、抗凋亡和非凋亡的特性。 我们的实验室以前已经证明，BOK与肌醇1，4，5-三磷酸受体是结构性结合的 (IP3Rs)，这是发现在内质网(ER)膜上的四聚体钙通道。 哺乳动物细胞。而其他的Bcl2蛋白家族成员也被报道与IP3Rs相互作用。 BOK-IP3R的交互效率要高得多，基本上所有BOK都绑定到IP3R。我们已经展示了 BOK与所有组织中的IP3Rs相互作用，包括大脑皮层和海马体。此外，我们 已经发现BOK保护IP3R不被蛋白质水解性切割，在没有IP3R的情况下，BOK 是泛素化的，并被蛋白酶体迅速降解。最近的数据显示，博克促进了 线粒体融合，与BOK基因敲除的小鼠胚胎成纤维细胞有更多的碎片化 线粒体与对照细胞的比较。由于BOK在海马神经元中高表达，并且 线粒体功能障碍经常会导致神经退行性疾病，BOK可能扮演着 在神经退行性疾病的发展中的作用。因此，本研究目前的目标是1) 确定内质网结合的BOK如何促进线粒体融合活性和2)定义确切的 BOK-IP3R绑定接口的性质。这些目标的结果将填补我们目前在知识方面的空白 关于BOK在细胞中的作用和BOK-IP3R的相互作用，并可以为我们的整体 了解Bcl2蛋白家族的各种功能。

PROJECT SUMMARY The Bcl-2 protein family is a group of proteins that plays an important role in intrinsic apoptosis and includes the protein Bok. While many members of the Bcl-2 protein family have been thoroughly studied, Bok is a very poorly understood protein, with pro-, anti-, and non-apoptotic properties reported. Our lab has shown previously that Bok is constitutively bound to inositol 1,4,5-trisphosphate receptors (IP3Rs), which are tetrameric calcium channels found in the endoplasmic reticulum (ER) membrane of mammalian cells. While other Bcl-2 protein family members have been reported to interact with IP3Rs, the Bok-IP3R interaction is much more efficient, with essentially all Bok bound to IP3Rs. We have shown that Bok interacts with IP3Rs in all tissues, including cerebral cortex and hippocampus. Additionally, we have discovered that Bok protects IP3Rs from proteolytic cleavage, and in the absence of IP3Rs, Bok is ubiquitinated and rapidly degraded by the proteasome. Recent data has shown that Bok promotes mitochondrial fusion, and Bok knock-out mouse embryonic fibroblast cells have more fragmented mitochondria compared to control cells. Since Bok is expressed highly in hippocampal neurons, and mitochondrial dysfunction can often lead to neurodegenerative disease, it is possible that Bok plays a role in the development of neurodegenerative disease. Therefore, the current aims of this study are 1) to determine how ER-bound Bok promotes mitochondrial fusion activity and 2) to define the exact nature of the Bok-IP3R binding interface. Results from these aims will fill our current gaps in knowledge regarding Bok’s role in the cell and the Bok-IP3R interaction, and can contribute to our overall knowledge of the various functions of the Bcl-2 protein family.