Nef interferes with cellular signal transduction pathways in a number of ways. Nef is associated with lipid rafts through its amino-terminal myristoylation and a proline-rich SH3-binding domain. These cholesterol-rich membrane microdomains appear to concentrate potent signaling mediators. Nef was found to complex with and activate serine/threonine protein kinase PAK-2, which may contribute to activation of infected cells. In vitro, HIV-infected T cells produce enhanced levels of interleukin-2 during activation. When expressed in macrophages, Nef intersects the CD40L signaling pathway inducing secretion of chemokines and other factors that attract resting T cells and promote their infection by HIV.