Description
Non-infectious influenza A virus possessing uncleaved HA0 is activated by trypsin via the HA0→HA1/2 cleavage. The cleaved HA1/2 provides virus entry into target cell where the intravirion acidification through the M2 channel plays important role. We have suggested that HA0 plugs the M2 channel and its cleavage into HA1+HA2 by trypsin is responsible for a functional priming of M2 channel [Zhirnov et al. Virology, 492:187-196; (2016)]. After this publication, Dr. Petr Chlanda has proposed an alternative and interesting idea that trypsin can cleave and activate both the HA0 and the M2 in parallel [P.Chlanda, Virology, 509: 131-132 (2017)]. Moreover, the M2 molecule is known to have two Arg residues in the N-terminal exomembrane domain, as potential trypsin targets. To test this idea experimentally, we treated noninfectious HA0 virus with increasing concentrations of trypsin and monitored changes in virus infectivity and in electrophoretic patterns of M2, HA0, and HA1/2 by western-blot analysis. Virus activation was revealed to arise to maximum levels already at low and mild trypsin concentrations (0,5-10 µg/ml) in parallel with the HA0→HA1/2 cleavage. In contrast to the HA0 cleavability, the M2 was found to be noncleavable and resistant to trypsin even at concentrations as high as 25 µg/ml and more. This clear link between the HA0→HA1/2 cleavage and virus activation at the intact uncleaved M2 protein compromises the Chlanda’s idea of the M2 independent proteolytic activation. By the other side, these data support our concept that (i) uncleaved HA0 plays down-regulatory role for the M2 ion channel in virus particle and (ii) the HA0 proteolytic transition to HA1/2 is a prerequisite for the M2 channel functional priming prior to its activation by low pH that is critically important for virus uncoating process.
| Choose secondary Session | Viral Replication |
|---|---|
| Choose primary session | Virus host cell interaction |
