Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia.
Viruses. 2017 Oct 20;9(10):305. doi: 10.3390/v9100305.
Programmed cell death or apoptosis is an important component of host defense systems against viral infection. The B-cell lymphoma 2 (Bcl-2) proteins family is the main arbiter of mitochondrially mediated apoptosis, and viruses have evolved sequence and structural mimics of Bcl-2 to subvert premature host cell apoptosis in response to viral infection. The sequencing of the canarypox virus genome identified a putative pro-survival Bcl-2 protein, CNP058. However, a role in apoptosis inhibition for CNP058 has not been identified to date. Here, we report that CNP058 is able to bind several host cell pro-death Bcl-2 proteins, including Bak and Bax, as well as several BH3 only-proteins including Bim, Bid, Bmf, Noxa, Puma, and Hrk with high to moderate affinities. We then defined the structural basis for CNP058 binding to pro-death Bcl-2 proteins by determining the crystal structure of CNP058 bound to Bim BH3. CNP058 adopts the conserved Bcl-2 like fold observed in cellular pro-survival Bcl-2 proteins, and utilizes the canonical ligand binding groove to bind Bim BH3. We then demonstrate that CNP058 is a potent inhibitor of ultraviolet (UV) induced apoptosis in a cell culture model. Our findings suggest that CNP058 is a potent inhibitor of apoptosis that is able to bind to BH3 domain peptides from a broad range of pro-death Bcl-2 proteins, and may play a key role in countering premature host apoptosis.
程序性细胞死亡或细胞凋亡是宿主防御系统对抗病毒感染的重要组成部分。B 细胞淋巴瘤 2（Bcl-2）蛋白家族是线粒体介导的细胞凋亡的主要裁决者，病毒进化出了 Bcl-2 的序列和结构模拟物，以颠覆病毒感染时宿主细胞过早凋亡。金丝雀痘病毒基因组的测序鉴定了一种假定的生存促进 Bcl-2 蛋白，CNP058。然而，迄今为止，尚未确定 CNP058 在凋亡抑制中的作用。在这里，我们报告 CNP058 能够结合几种宿主细胞促凋亡 Bcl-2 蛋白，包括 Bak 和 Bax，以及几种 BH3 仅蛋白，包括 Bim、Bid、Bmf、Noxa、Puma 和 Hrk，具有高到中等亲和力。然后，我们通过确定 CNP058 与 Bim BH3 结合的晶体结构，定义了 CNP058 与促凋亡 Bcl-2 蛋白结合的结构基础。CNP058 采用了在细胞生存促进 Bcl-2 蛋白中观察到的保守 Bcl-2 样折叠，并利用典型的配体结合槽结合 Bim BH3。然后，我们证明 CNP058 是细胞培养模型中紫外线（UV）诱导凋亡的有效抑制剂。我们的研究结果表明，CNP058 是一种有效的凋亡抑制剂，能够结合来自广泛的促凋亡 Bcl-2 蛋白的 BH3 结构域肽，可能在对抗宿主细胞过早凋亡中发挥关键作用。
