PLC-γ1 Signaling Plays a Subtype-Specific Role in Postbinding Cell Entry of Influenza A Virus

Host signaling pathways and cellular proteins play important roles in the influenza viral life cycle and can serve as antiviral targets. In this study, we report the engagement of host phosphoinositide-specific phospholipase gamma 1 (PLC-gamma 1) in mediating cell entry of influenza virus H1N1 but not H3N2 subtype. Both PLC-gamma 1-specific inhibitor and short hairpin RNA (shRNA) strongly suppress the replication of H1N1 but not H3N2 viruses in cell culture, suggesting that PLC-gamma 1 plays an important subtype-specific role in the influenza viral life cycle. Further analyses demonstrate that PLC-gamma 1 activation is required for viral postbinding cell entry. In addition, H1N1, but not H3N2, infection leads to the phosphorylation of PLC-gamma 1 at Ser 1248 immediately after infection and independent of viral replication. We have further shown that H1N1-induced PLC-gamma 1 activation is downstream of epidermal growth factor receptor (EGFR) signaling. Interestingly, both H1N1 and H3N2 infections activate EGFR, but only H1N1 infection leads to PLC-gamma 1 activation. Taking our findings together, we have identified for the first time the subtype-specific interplay of host PLC-gamma 1 signaling and H1N1 virus that is critical for viral uptake early in the infection. Our study provides novel insights into how virus interacts with the cellular signaling network by demonstrating that viral determinants can regulate how the host signaling pathways function in virally infected cells.