HIV-1-associated brain pathology exhibits regional variability and we therefore studied the genetic differences in the V1-V5 domains of the HIV env gene in up to four regions of brain (frontal lobe, basal ganglia, medial temporal lobe, and nonmedial temporal lobe) from three patients. We found that in each separate brain region HIV-1 forms different quasispecies and that there is little gene flow among these regions. In further support of brain region-specific evolution of HIV-1, we analyzed amino acid signatures in these clones. In addition to known amino acid signatures associated with macrophage tropism and the lack of syncytium formation, we found 15 majority amino acid signature patterns from the V1-V5 env sequences associated with the neuroanatomical regions analyzed from the three individuals. Furthermore, on average, intrabrain genetic distances for the HIV-1 env were estimated to be much smaller than genetic distances between brain regions. Specific strains of HIV-1 may be neurotropic or neuroinvasive (replication preference in brain tissue) and may contribute to pathology, cognitive loss, and neuropsychiatric disease.

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The retroviral Gag-like protein p58 gag expressed in a highly metastatic ascites rat mammary adenocarcinoma has been implicated in cell surface changes contributing to xenotransplantability. p58 gag is present in the cells in a plasma membrane-and micro®lament-associated signal transduction particle containing Src and is phosphorylated on tyrosine. Overlay analyses and a nity chromatography with glutathione S-transferase (GST) fusion proteins of Src homology-3 (SH3) domains showed direct binding of the Src but not the Crk SH3 domain to p58 gag . This association was con®rmed by coimmunoprecipitation of partially puri®ed p58 gag from ascites cell lysates with platelet Src. Further, a GSTp58 gag fusion protein bound full length c-Src from either platelets or c-Src-expressing insect cells. The GST-p58 gag fusion protein, but not GST, was phosphorylated by platelet or insect cell-expressed c-Src, but not by a kinase negative c-Src variant. The binding of GST-p58 gag to c-Src was almost completely abolished by a 50-fold excess of the GST-SH3 domain of Src, and a parallel decrease in tyrosine phosphorylation of p58 gag was observed. These results demonstrate that p58 gag is tyrosine-phosphorylated as a consequence of its speci®c association with c-Src via its SH3 domain. These observations suggest a mechanism by which Gag proteins may contribute to retroviral maturation or pathogenesis through binding and relocalization of SH3 domaincontaining proteins such as Src-like tyrosine kinases to sites of association of micro®laments with the plasma membrane.

No abstract