Viruses customize autophagy protein for efficient viral entry.

While the cell imposes multiple barriers to virus entry, enveloped viruses are remarkably still able to gain entry to their cellular hosts by hitchhiking and remodeling the endomembrane system to traffic within, and eventually escape from, endosomal organelles for their genome release. Elucidating viral entry mechanisms and their interaction with the host trafficking network is necessary for antiviral therapy. Here, we focus on the use of host autophagy molecular factors during the entry of prototypic negative-stranded RNA viruses, and highlight recent progress in our understanding of the role of one such factor, UVRAG, in both viral and cellular endocytic membrane trafficking and fusion events.

UVRAG is required for virus entry through combinatorial interaction with the class C-Vps complex and SNAREs.

Enveloped viruses exploit the endomembrane system to enter host cells. Through a cascade of membrane-trafficking events, virus-bearing vesicles fuse with acidic endosomes and/or lysosomes mediated by SNAREs triggering viral fusion. However, the molecular mechanisms underlying this process remain elusive. Here, we found that UV-radiation resistance-associated gene (UVRAG), an autophagic tumor suppressor, is required for the entry of the prototypic negative-strand RNA virus, including influenza A virus and vesicular stomatitis virus, by a mechanism independent of IFN and autophagy. UVRAG mediates viral endocytic transport and membrane penetration through interactions with the class C vacuolar protein sorting (C-Vps) tethering complex and endosomal glutamine-containing SNAREs [syntaxin 7 (STX7), STX8, and vesicle transport through t-SNARE homolog 1B (Vti1b)], leading to the assembly of a fusogenic trans-SNARE complex involving vesicle-associated membrane protein (VAMP8), but not VAMP7. Indeed, UVRAG stimulates VAMP8 translocation to virus-bearing endosomes. Inhibition of VAMP8, but not VAMP7, significantly reduces viral entry. Our data indicate that UVRAG, in concert with C-Vps, regulates viral entry by assembling a specific fusogenic SNARE complex. Thus, UVRAG governs downstream viral entry, highlighting an important pathway capable of potential antiviral therapeutics.