A surface groove essential for viral Bcl-2 function during chronic infection in vivo.
A surface groove essential for viral Bcl-2 function during chronic infection in vivo.
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DOI：
10.1371/journal.ppat.0010010
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发表时间：
2005-09
期刊：
影响因子：
6.7
通讯作者：
Virgin HW 4th
中科院分区：
文献类型：
--
作者：
Loh J;Huang Q;Petros AM;Nettesheim D;van Dyk LF;Labrada L;Speck SH;Levine B;Olejniczak ET;Virgin HW 4th
抗凋亡Bcl-2家族蛋白通过蛋白质表面上的疏水BH 3结合沟结合促凋亡Bcl-2家族成员的BH 3结构域来抑制培养细胞中的凋亡。我们通过分析病毒Bcl-2家族蛋白，研究了哺乳动物体内抗凋亡Bcl-2蛋白的BH 3结合沟的生理重要性。我们发现γ-疱疹病毒68（γ HV 68）Bcl-2家族蛋白（γ HV 68 v-Bcl-2），这是已知的抑制培养细胞中的凋亡，抑制原代淋巴细胞中的凋亡和酵母中的Bax毒性。γ HV 68 v-Bcl-2结构的核磁共振测定揭示了BH 3结合沟，其通过与宿主Bcl-2家族蛋白共有的分子机制结合来自促凋亡Bcl-2家族成员Bax和巴克的BH 3结构域肽，涉及BH 3肽结合沟中的保守精氨酸。在BH 3结合沟内，这种保守的精氨酸和两个相邻氨基酸突变为丙氨酸（SGR突变为AAA）导致正确折叠的蛋白质缺乏野生型γ HV 68 v-Bcl-2结合Bax BH 3肽和阻断Bax毒性的能力。我们测试了在病毒感染过程中的v-Bcl-2结构域的生理重要性，通过工程病毒突变体编码的v-Bcl-2含有的SGR AAA突变。该突变导致病毒在γ HV 68从潜伏期的有效再激活和有效持续γ HV 68复制方面都有缺陷。这些研究表明，在慢性感染期间，病毒Bcl-2家族成员的BH 3肽结合沟中的氨基酸具有重要的功能作用。病毒可以通过表达在结构和功能上类似于宿主细胞蛋白的蛋白质来操纵它们的宿主。由病毒操纵的一个重要的细胞过程是细胞凋亡，这是一种由Bcl-2样促凋亡和抗凋亡蛋白家族调节的细胞死亡程序。γ疱疹病毒编码Bcl-2家族蛋白（v-Bcl-2），可能有助于其引起肿瘤的能力，并持续其宿主的一生。作者解析了鼠γ疱疹病毒68（γ HV 68）v-Bcl-2的结构，发现它与细胞抗凋亡蛋白相似，并且v-Bcl-2使用与细胞Bcl-2相同的机制与促凋亡Bcl-2家族蛋白的肽结合。此外，他们发现，表达突变形式的v-Bcl-2的γ HV 68病毒不能与促凋亡Bcl-2家族蛋白的肽结合，其在小鼠中引起慢性病毒感染的能力有缺陷。因此，与宿主抗凋亡Bcl-2蛋白共享的v-Bcl-2的特定结构特征和分子机制对于该蛋白在病毒感染期间的功能是重要的。这些发现增强了我们对慢性γ-疱疹病毒感染的分子机制的理解，并表明靶向v-Bcl-2蛋白的功能可能具有治疗益处。
Antiapoptotic Bcl-2 family proteins inhibit apoptosis in cultured cells by binding BH3 domains of proapoptotic Bcl-2 family members via a hydrophobic BH3 binding groove on the protein surface. We investigated the physiological importance of the BH3 binding groove of an antiapoptotic Bcl-2 protein in mammals in vivo by analyzing a viral Bcl-2 family protein. We show that the γ-herpesvirus 68 (γHV68) Bcl-2 family protein (γHV68 v-Bcl-2), which is known to inhibit apoptosis in cultured cells, inhibits both apoptosis in primary lymphocytes and Bax toxicity in yeast. Nuclear magnetic resonance determination of the γHV68 v-Bcl-2 structure revealed a BH3 binding groove that binds BH3 domain peptides from proapoptotic Bcl-2 family members Bax and Bak via a molecular mechanism shared with host Bcl-2 family proteins, involving a conserved arginine in the BH3 peptide binding groove. Mutations of this conserved arginine and two adjacent amino acids to alanine (SGR to AAA) within the BH3 binding groove resulted in a properly folded protein that lacked the capacity of the wild-type γHV68 v-Bcl-2 to bind Bax BH3 peptide and to block Bax toxicity in yeast. We tested the physiological importance of this v-Bcl-2 domain during viral infection by engineering viral mutants encoding a v-Bcl-2 containing the SGR to AAA mutation. This mutation resulted in a virus defective for both efficient reactivation of γHV68 from latency and efficient persistent γHV68 replication. These studies demonstrate an essential functional role for amino acids in the BH3 peptide binding groove of a viral Bcl-2 family member during chronic infection. Viruses can manipulate their hosts by expressing proteins that structurally and functionally resemble host cellular proteins. One important cellular process manipulated by viruses is apoptosis, a cell death program that is regulated by a family of Bcl-2-like proapoptotic and antiapoptotic proteins. Gammaherpesviruses encode Bcl-2 family proteins (v-Bcl-2) that may contribute to their ability to cause tumors and persist for the lifetime of their hosts. The authors solved the structure of the murine γ-herpesvirus 68 (γHV68) v-Bcl-2 and found that it is similar to cellular antiapoptotic proteins and that v-Bcl-2 uses the same mechanism as cellular Bcl-2 to bind to peptides from proapoptotic Bcl-2 family proteins. Furthermore, they found that a γHV68 virus expressing a mutated form of v-Bcl-2 that cannot bind to peptides from proapoptotic Bcl-2 family proteins is defective in its ability to cause chronic viral infection in mice. Thus, a specific structural feature and molecular mechanism of the v-Bcl-2 that is shared with host antiapoptotic Bcl-2 proteins is important for the function of this protein during viral infection. These findings enhance our understanding of the molecular mechanisms of chronic γ-herpesvirus infection, and suggest that targeting the functions of the v-Bcl-2 protein might have therapeutic benefit.