The Nef protein of the primate lentiviruses, including human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV), is a myristylated protein associated with increased viral replication and enhanced pathogenicity. Both the potentiation of T-lymphocyte activation and the enhanced serine-phosphorylation of HIV-1 capsid by Nef correlate with increased viral replication. We report the functional interactions of the Nef proteins with Src kinases. The Nef proteins from HIV-1 and SIV bind to Lck as well as Hck, Lyn, and Fyn. The SH3 and SH2 domains of Lck are sufficient for coprecipitation with non-tyrosine-phosphorylated Nef proteins. The conserved core region of HIV-1 Nef is essential for the interaction with Lck and is also important for enhanced HIV-1 replication in T-lymphocytes. In addition, we show that SIV and HIV-1 Nef proteins are differentially tyrosine-phosphorylated. The kinase-active Lck tyrosine-phosphorylates SIVmac239 Nef but does not phosphorylate HIV-1 Nef. These data suggest that the association of Nef and Lck is central to the enhanced viral replication of HIV-1 and SIV in T-lymphocytes.
Copyright 1999 Academic Press.