Defining the role of membrane contact sites during Kaposi’s Sarcoma-Associated Herpesvirus infection

Abstract

Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic gammaherpesvirus and remains one of the leading causes of cancer among immunocompromised individuals world-wide. Like all herpesviruses, KSHV maintains a biphasic life cycle, consisting of a life-long latency sporadically broken by active lytic replication. Like all viruses, KSHV infection induces the remodeling of multiple organellar compartments to either maintain viral latency or promote lytic replication.However, how KSHV drives these remodeling events and how they promote virus-induced tumor progression remain poorly understood. Recently, our group has uncovered that organelle remodeling during herpesvirus infection is directly linked to virus-induced alterations in membrane contact sites (MCS), protein-to-protein or protein-to-membrane connections that form dynamic organelle-organelle communication networks. Here, we use super resolution confocal microscopy to characterize dynamic KSHV-induced remodeling events of mitochondria, peroxisomes, and endosome populations throughout KSHV infection. Then, using siRNA-based knockdown approaches, we demonstrate that MCS proteins that form contacts between the ER and each of these compartments have a significant impact on KSHV lytic gene expression, virion production, and cell survival during lytic replication. Lastly, we find that knockdown of these MCS proteins can not only partially reverse KSHV induced alterations of mitochondria and peroxisomes but also significantly impact the abundance of multiple oncogenic and antiviral cell signaling receptors. Collectively, these findings demonstrate that membrane contacts play a critical role both in driving organelle remodeling events during both phases of KSHV infection that may promote both oncogenic cell signaling and successful lytic replication. Findings from this study have significantly improved our understanding of how KSHV infection alters subcellular compartments to promote diverse replication states and how these changes may drive viral oncogenesis.