FIGURE 1.

Rab32 and Rab38 coimmunoprecipitate with BLOC-2, AP-3, and AP-1 but not with AP-2. MNT-1 cells were homogenized in the absence of detergents, and the homogenate was centrifuged to yield cytosolic and membrane fractions. The membrane fraction was solubilized in buffer containing 1% Triton X-100, and the same concentration of detergent was added to the cytosol to match the buffer compositions (see “Experimental Procedures”). Both cytosolic and solubilized membrane fractions were divided into aliquots and subjected to immunoprecipitation (IP) using irrelevant IgG, anti-Rab32, or anti-Rab38 rabbit antibodies. The immunoprecipitates, together with an aliquot of the input extracts corresponding to 1% of the material available for immunoprecipitation, were analyzed by immunoblotting (IB) using antibodies to the HPS6, μ3, γ, and-α subunits of BLOC-2, AP-3, AP-1, and AP-2, respectively.