Influenza virus matrix-2 protein (M2)

The Influenza virus matrix-2 (M2) protein is a homotetrameric integral membrane protein that functions as a pH-gated, proton-selective ion channel essential for viral replication (Pinto et al., 1992, PubMed: 1374445). During the early stages of infection, the M2 channel facilitates the acidification of the viral interior within the endosome, leading to the dissociation of the viral ribonucleoprotein (vRNP) from the matrix protein M1, a process known as uncoating (Helenius, 1992, PubMed: 1314155). In the later stages, M2 helps maintain the pH of the trans-Golgi network to prevent the premature activation of the hemagglutinin (HA) protein during its transport to the cell surface (Ciampor et al., 1992, PubMed: 1531944). The extracellular domain of the protein, known as M2e, is highly conserved across different influenza A subtypes, making it a primary target for the development of universal influenza vaccines and therapeutic monoclonal antibodies (Neirynck et al., 1999, PubMed: 10523637). While adamantane-based drugs like amantadine and rimantadine were once standard treatments that functioned by blocking the M2 channel pore, their clinical utility has been severely compromised by the global spread of resistant mutations, such as S31N (Bright et al., 2005, PubMed: 16174826). Consequently, modern therapeutic strategies are shifting toward targeting the M2e domain to induce broad-spectrum immunity through mechanisms like antibody-dependent cellular cytotoxicity (ADCC) (Fiers et al., 2004, PubMed: 15542471). This target remains a focal point for pandemic preparedness due to its structural conservation across various avian and human influenza strains.

Other names

Matrix protein 2M2 viroporinM2e ectodomainAM2BM2Proton-coupled ion channel M2

Inhibition of the M2 ion channel prevents the influx of protons into the viral interior, thereby blocking the dissociation of the viral ribonucleoprotein complex from the matrix protein and halting viral uncoating. Monoclonal antibodies targeting the M2e ectodomain act via antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) to eliminate infected cells.