(A) Reimmunoprecipitation of PAK and PIX from Nef IPs of infected CEMx174 cells. Cell lysates from ∼7 × 106 cells were split into two portions (2.5 × 106 and 4.5 × 106 cells) and subjected to Nef immunoprecipitation and IVKA. One portion was reserved as the IVKA control for SF2 Δnef (Nef−) (lane 1), SF2 wild type (SF2) (lane 2) and SF2 Nef P73A (P73) (lane 3). The larger portion was subjected to reimmunoprecipitation with anti-PAK (P) (lanes 4, 7, and 11), anti-PIX (X) (lanes 5, 8, and 12), anti-Vav (V) (lanes 6, 9, and 13), or anti-Hck (H) (lane 10) antibodies as described in Materials and Methods. Western analysis with either anti-PAK (P) (lane 14), anti-PIX (X) (lane 15), or anti-Vav (V) (lane 16) antibody was performed on CEMx174 cell lysates. The band at 49.4 kDa is the immunoglobulin heavy chain. (B) Reimmunoprecipitation of PAK and PIX from infected primary macrophages was performed as described above except that ∼1 × 106 cells were used. Results of IVKAs performed as controls for SF162 Δnef-infected (Nef−), SF162 wild-type (SF162), and R25 wild-type (R25) cells are shown in lanes 1, 2, and 3, respectively. Reimmunoprecipitation was performed with anti-PAK (lanes 4, 7, and 10), anti-PIX (lanes 5, 8, and 11), or anti-Vav (lanes 6, 9, and 12) antibodies. Western analysis with anti-PIX, anti-PAK, or anti-Vav antibody was performed on macrophage cell lysates, and results are shown in lanes 13, 14, and 15, respectively.