Clustering of Rab11 vesicles in influenza A virus infected cells creates hotspots containing the 8 viral ribonucleoproteins

Abstract

Influenza A virus is an important human pathogen causative of yearly epidemics and occasional pandemics. The ability to replicate within the host cell is a determinant of virulence, amplifying viral numbers for host-to-host transmission. This process requires multiple rounds of entering permissive cells, replication, and virion assembly at the plasma membrane, the site of viral budding and release. The assembly of influenza A virus involves packaging of several viral (and host) proteins and of a segmented genome, composed of 8 distinct RNAs in the form of viral ribonucleoproteins (vRNPs). The selective assembly of the 8-segment core remains one of the most interesting unresolved problems in virology. The recycling endosome regulatory GTPase Rab11 was shown to contribute to the process, by transporting vRNPs to the periphery, giving rise to enlarged cytosolic puncta rich in Rab11 and the 8 vRNPs. We recently reported that vRNP hotspots were formed of clustered vesicles harbouring protruding electron-dense structures that resembled vRNPs. Mechanistically, vRNP hotspots were formed as vRNPs outcompeted the cognate effectors of Rab11, the Rab11-Family-Interacting-Proteins (FIPs) for binding, and as a consequence impair recycling sorting at an unknown step. Here, we speculate on the impact that such impairment might have in host immunity, membrane architecture and viral assembly.

Keywords: Rab11 GTPase; Rab11 family interacting proteins (FIPs); correlative light and electron microscopy; influenza A virus assembly; recycling endosome; segmented genome; viral ribonucleoproteins (vRNPs).

Figure 1.

Proposed model for assembly of 8-vRNPs on route to the plasma membrane using a Rab11-dependent pathway.

Figure 2.

Rab11 cycle in vesicular transport (steps in Rab11 cycle are numbered from 1 to 6). Figure adapted from ref. .

Figure 3.

Proposed model for Rab11 vesicular impairment during IAV infection.