AEGiS-11IAC: Activation of the cellular kinase PAK65 by SIV Nef is important for AIDS pathogenesis.

11th International AIDS Conference

Vancouver, British Columbia — July 7-12, 1996

Activation of the cellular kinase PAK65 by SIV Nef is important for AIDS pathogenesis.

Int Conf AIDS 1996 Jul 7-12; 11:217 (abstract no. Th.A.384)
Luciw PA, Cheng-Mayer C, Khan I, Sawai ET; Dept. Med. Path., University of California, Davis, CA. Fax: 916-752-4548. E-mail: PALuciw@UCDavis.edu.

OBJECTIVE: Nef, an accessory gene of HIV and SIV, is dispensable for viral replication in T-lymphocytes in tissue culture; however, this viral gene is important for high virus load and AIDS pathogenesis in the susceptible host. In infected lymphoid cells, Nef interacts with a cellular serine kinase which phosphorylates two cellular proteins, p62 and p72, in an in vitro kinase assay. The objective was to identify the cellular serine kinase associated with Nef and to investigate the signal transduction pathway(s) governed by this interaction.

METHODS: Lymphoid cell lines chronically infected with SIVmac239Nef+ and clones of this virus with site specific mutations in the nef gene were analyzed by immunoprecipitation with monospecific antibodies to Nef and to cellular signaling proteins. These immunoprecipitates were tested in an in vitro kinase assay, and phosphorylated proteins were identified.

RESULTS: The cellular protein p62 associated with Nef was shown to be PAK65, which is a ubiquitous serine kinase that is regulated by interaction with GTP-binding proteins related to the ras proto-oncogene (i.e., rac-1/cdc42hs). Interaction of Nef activates PAK65 as well as p72. Studies with viral mutants in lymphoid cell lines revealed that this interaction is important for enabling Nef to down-regulate CD4 from the cell surface and enhance virion infectivity. To test the biologic significance of these findings, a molecular clone of SIV mac239 containing point mutations in nef abrogating association of Nef with PAK65 was constructed and tested in experimentally inoculated rhesus macaques. Reversion of the mutant virus to prototype nef sequence and function in these animals was correlated with the induction of high virus load and disease progression.

CONCLUSIONS: These studies reveal that the association of Nef with PAK65 is important for pathogenesis, and that effects of Nef on T-cell activation pathways may account for the multifunctional nature of this viral accessory protein. Novel anti-viral therapies could be developed to block the interaction of Nef and PAK65 and thus palliate or prevent AIDS.

Keywords: AEGIS, SIV, Acquired Immunodeficiency Syndrome, Ribosomal Protein S6 Kinases, Genes, nef, Simian Acquired Immunodeficiency Syndrome, Protein-Serine-Threonine Kinases, Macaca mulatta, HIV-2, HIV-1, Antigens, CD4, Virus Replication, Cell Line, HIV, Virion, Proteins, T-Lymphocytes, Animal, In Vitro, genetics, virology, ICA11

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ThA384