Influenza A virus NS1 protein binds p85β and activates phosphatidylinositol-3-kinase signaling

doi:10.1073/pnas.0606109103

Influenza A virus NS1 protein binds p85β and activates phosphatidylinositol-3-kinase signaling

*Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Fife KY16 9ST, United Kingdom; and
^†Howard Hughes Medical Institute and Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208-3500

Contributed by Robert A. Lamb, July 25, 2006

Abstract

Influenza A virus NS1 is a multifunctional protein, and in virus-infected cells NS1 modulates a number of host-cell processes by interacting with cellular factors. Here, we report that NS1 binds directly to p85β, a regulatory subunit of phosphatidylinositol-3-kinase (PI3K), but not to the related p85α subunit. Activation of PI3K in influenza virus-infected cells depended on genome replication, and showed kinetics that correlated with NS1 expression. Additionally, it was found that expression of NS1 alone was sufficient to constitutively activate PI3K, causing the phosphorylation of a downstream mediator of PI3K signal transduction, Akt. Mutational analysis of a potential SH2-binding motif within NS1 indicated that the highly conserved tyrosine at residue 89 is important for both the interaction with p85β, and the activation of PI3K. A mutant influenza virus (A/Udorn/72) expressing NS1 with the Y89F amino acid substitution exhibited a small-plaque phenotype, and grew more slowly in tissue culture than WT virus. These data suggest that activation of PI3K signaling in influenza A virus-infected cells is important for efficient virus replication.

Footnotes

^‡To whom correspondence may be addressed. E-mail: rer{at}st-andrews.ac.uk or ralamb{at}northwestern.edu
Author contributions: B.G.H., D.J., R.A.L., and R.E.R. designed research; B.G.H. and D.J. performed research; Y.-H.C. contributed new reagents/analytic tools; B.G.H., D.J., R.A.L., and R.E.R. analyzed data; and B.G.H., R.A.L., and R.E.R. wrote the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations:

PKR,

protein kinase R;

PR8,

influenza virus A/Puerto Rico/8/34;

PI3K,

phosphatidylinositol-3-kinase;

SeV,

Sendai virus;

p.i.,

postinfection;

MDCK,

Madin–Darby canine kidney.