Mono-ubiquitylated ORF45 Mediates Association of KSHV Particles with Internal Lipid Rafts for Viral Assembly and Egress

PLoS Pathogens

Fanxiu Zhu¹  Yan Wang¹  Nannan Zhu²  Xin Wang³  Wenwei Li³  Yan Yuan³ 

[1] Department of Biological Sciences, Florida State University, Tallahassee, Florida, United States of America;Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania, United States of America;Institute of Human Virology and Ministry of Education Key Laboratory of Tropical Disease Control, Zhongshan School of Medicine, Sun Yat-Sen University, Guangdong, China

关键词: Virions;    Cell membranes;    Tegument proteins;    Vesicles;    Kaposi's sarcoma-associated herpesvirus;    Lipids;    Viral packaging;    Immunoprecipitation;   

DOI  :  10.1371/journal.ppat.1005332

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Herpesviruses acquire their envelope by budding into the lumen of cytoplasmic membrane vesicles. This process is initiated by component(s) on viral particles, which recognize the budding site where the viral glycoproteins are present and recruit cellular cargo transport and sorting machinery to the site to complete the budding process. Proteins in the tegument layer, connecting capsid and envelope, are candidates for the recognition of budding sites on vesicle membrane and induction of budding and final envelopment. We examined several outer and matrix tegument proteins of Kaposi’s sarcoma-associated herpesvirus (KSHV) and found that ORF45 associates with lipid rafts (LRs) of cellular membrane. LRs are membrane micro-domains, which have been implicated as relay stations in intracellular signaling and transport including viral entry and virion assembly. The ability of ORF45 to target LR is dependent on the mono-ubiquitylation of ORF45 at Lys297 as the mutation at Lys297 (K297R) abolished LR-association of ORF45. The K297R mutation also impairs ORF45 and viral particle co-localization with trans-Golgi network and endosomes, but facilitates ORF45 and viral particles co-localizing with lysosomes. More importantly, the recombinant KSHV carrying ORF45 K297R mutant (BAC-K297R) was found severely defective in producing mature and infectious virion particles in comparison to wild type KSHV (BAC16). Taken together, our results reveal a new function of KSHV tegument protein ORF45 in targeting LR of host cell membrane, promoting viral particles co-localization with trans-Golgi and endosome vesicles and facilitating the maturation and release of virion particles, suggesting that ORF45 plays a role in bringing KSHV particles to the budding site on cytoplasmic vesicle membrane and triggering the viral budding process for final envelopment and virion maturation.

【 授权许可】

CC BY