Exo70 promotes herpesvirus secretory vesicle tethering and virion release in an exocyst complex-dependent manner
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The exocyst complex, a multisubunit protein complex, mediates secretory vesicles fusion with the plasma membrane (PM) to deliver materials to the cell surface or to release cargoes to the extracellular space, but whether it is related to viral secretory vesicles tethering and virion release is unknown. Here, we identified that the exocyst complex subunit Exo70 promotes the trafficking of herpesvirus secretory vesicles and the release of mature virions in an exocyst complex-dependent manner. Mechanistically, mutation of Exo70 Lys632 and Lys635 diminishes viral secretory vesicles anchoring to PM. Moreover, the small GTPase Rab11a is necessary for the transport of viral secretory vesicles, and the Snapin-Exo70-SNAP23 axis is involved in fusion of viral secretory vesicles to the PM and release of virions. Most significantly, we discovered that Endosidin2 (ES2), an inhibitor of exocytosis via the exocyst complex, provides protection against herpesvirus infection in cells and mice. Overall, these findings unveil a previously uncharacterized role and mechanism of the exocyst complex in viral replication, highlighting its potential as an effective strategy against herpesvirus infection.
Author summary
Herpesviruses, such as herpes simplex virus 1 (HSV-1) and bovine herpes virus type 1 (BoHV-1), are highly prevalent pathogens that establish lifelong infections and cause various diseases in humans and animals. While the mechanisms underlying the transport of herpesvirus secretory vesicles from the Golgi to the PM and the subsequent viral release are still poorly understood. In our study, we have discovered that Exo70 promotes the trafficking of HSV-1 and BoHV-1 secretory vesicles and facilitates the release of mature virions in an exocyst complex-dependent manner. Mechanistically, both knockdown of Exo70 and a phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2)-binding-deficient mutant of Exo70 caused virions to be trapped in the cytoplasm and unable to tether to PM, indicating that the binding of Exo70 to PI(4,5)P2 is critical for the docking virus secretory vesicles with PM. Additionally, the Snapin-Exo70-SNAP23 axis plays a pivotal role in the fusion between viral secretory vesicles and the PM, ultimately facilitating the release of virions. We found that Rab11a is necessary for viral secretory vesicle trafficking mediated by Exo70. Most importantly, we discovered that ES2, a transport inhibitor that combines with Exo70 to terminate the final stage of exocytosis via the exocyst complex, can protect cells and mice from α-herpesvirus infection.
