Activation of phosphatidylinositol 3-kinase signaling by the nonstructural NS1 protein is not conserved among type A and B influenza viruses.

Recently it has been shown by several laboratories that the influenza A virus nonstructural protein 1 (A/NS1) binds and activates phosphatidylinositol 3-kinase (PI3K). This function of the protein is likely to prevent premature apoptosis induction during viral propagation. Here we show that the B/NS1 protein completely lacks the capacity to induce PI3K signaling. Thus, PI3K activation is another unique function of A/NS1 that is different from the action of its influenza B virus counterpart.