Mitochondrial DRM targeting by HHV-8 viral interferon regulatory factor-1

描述(申请人提供)：人类疱疹病毒8型(HHV-8)编码非结构蛋白，通过多种抑制相互作用调节宿主细胞的抗病毒机制。我们发现，病毒干扰素调节因子-1(vIRF-1)通过核隔离(Bim)抑制包括Bim和Bid在内的BH3-Only蛋白(BOP)的促凋亡活性，或直接抑制它们诱导线粒体释放细胞色素c。此外，我们还发现vIRF-1可以独立于其与BOPS的相互作用而定位于线粒体，并特异性地靶向线粒体抗洗涤剂膜组分(MitoDRms)，这是一种脂筏。近来，MitoDRM已被确定为线粒体的一个重要的功能微域，并成为治疗各种退行性疾病和癌症的一个有吸引力的靶点。尽管mitoDRM的重要性与日俱增，但对mitoDRM在病毒感染中的作用知之甚少。据我们所知，vIRF-1是已知的第一个靶向mitoDRM的病毒蛋白。此外，我们的初步数据表明，vIRF-1的N末端富含脯氨酸的结构域(PD，1-75个残基)对于mitoDRM靶向和保护细胞免受线粒体损伤是必不可少的。此外，vIRF-1与线粒体以类似于有丝分裂期间发生的聚集体的方式共同定位，表明vIRF-1在线粒体质量控制和相关细胞生存中可能发挥作用。为了确定vIRF-1通过mitoDRM靶向和细胞保护在HHV-8复制中的作用，本建议重点研究：1)vIRF-1 PD靶向mitoDRM的新结构决定因素；2)vIRF-1 mitoDRM锚定和细胞保护的分子机制；3)mitoDRM定位的vIRF-1在有丝分裂和HHV-8复制中的功能意义。因此，这一建议将检验病毒-宿主相互作用的新范例，并可能为基于已确定的相互作用和机制的新型抗病毒药物的未来开发提供基础。

DESCRIPTION (provided by applicant): Human herpesvirus 8 (HHV-8) encodes non-structural proteins that regulate host cell antiviral mechanisms via multiple inhibitory interactions. We have found that viral interferon regulatory factor-1 (vIRF-1) inhibits the pro-apoptotic activity of BH3-only proteins (BOPs) including Bim and Bid by nuclear sequestration (Bim) or directly suppressing their induction of cytochrome c release from mitochondria. In addition, we have found that vIRF-1 can localize to mitochondria independently of its interaction with BOPs and specifically targets mitochondrial detergent-resistant membrane fractions (mitoDRMs), a type of lipid raft. MitoDRMs have been recently identified as a functionally important microdomain of mitochondria and emerged as an attractive target for the treatment of a variety of degenerative diseases and cancer. Despite the increasing significance of mitoDRMs, little is known about the role of mitoDRMs in virus infection. To our knowledge, vIRF-1 is the first viral protein known to target to mitoDRMs. Furthermore, our preliminary data have shown that the N-terminal proline-rich domain (PD, 1-75 residues) of vIRF-1 is essential for mitoDRM targeting and protects cells from mitochondrial damage. Also, vIRF-1 co-localizes with mitochondria in an aggregate resembling those occurring during mitophagy, indicating a possible role of vIRF-1 in mitochondria quality control and associated cell survival. To determine the contribution of vIRF-1 through mitoDRM targeting and cell protection to HHV-8 replication, this proposal focuses on examining: 1) the novel structural determinants of mitoDRM targeting by vIRF-1 PD; 2) the molecular mechanisms of vIRF-1 mitoDRM anchoring and cell protection; 3) the functional significance of mitoDRM-localized vIRF-1 in mitophagy and HHV-8 replication. This proposal will thus examine a novel paradigm of virus-host interaction, and potentially provide a basis for future development of novel antiviral agents based on the identified interactions and mechanisms.