The cleavage of spike protein НА0→НА1/HA2 by trypsin permits activation of the M2 channel without its proteolytic cleavage in the influenza A virus.

M2 plays numerous regulatory roles in influenza A virus infection confirming the old adage: "a little body often harbors a great sense". The comment here demonstrates that a small viral protein M2, having 14 kD m.w. and situating in the virion at a minor amount of only about 40 molecules per virus particle is resistant to trypsin at concentrations initiating the HA0 cleavage and virus infectivity activation. A mechanism involving a programmed disassembly by cascade-type transmembrane signaling of the HA-M2-M1-RNP cooperation during virus entry into the infected cell is proposed. • We have published data that intravirion cohesion of matrix protein M1 with RNP is regulated by the HA0→HA1+HA2 cleavage. Dr. P. Chlanda has suggested interesting interpretation of our observation (Virology v509,131-132,2017). • Here, we are presenting the Brief Communication resolving this interpretation and supporting our original concept about the up-regulatory role of the Influenza spike protein cleavage НА0→НА1/HA2 for virus ionic channel M2 acidic activation. • The data shed light on influenza virus multiprotein HA-M2-M1-RNP integrity and disclose an important mechanism of its programmed cascade-type disassembly taking place during virus entry into target cell. • The reported up-regulatory role of spike protein proteolytic cleavage for viral transmembrane ionic channels can be a universal mechanism in functioning of many enveloped viruses, such as, coronaviruses, paramyxoviruses, Ebola, HIV, etc. [ABSTRACT FROM AUTHOR]