Grab and Rab8a are required for the recruitment of Sec15 to recycling endosomes. (A-B) Representative fluorescence images of GFP-tagged Sec15 and Tfrc in differentiating wild-type, Rab8a knockout (A), and Grab knockout (B) MEL cells. Arrowheads indicate recycling endosomes. Scale bars, 10 μm. (C-D) Analyses of the interaction among the exocyst subunits SEC10, SEC15, and EXO70 in wild-type and GRAB knockout K562 cells by coimmunoprecipitation assays. SEC10 and EXO70 were immunoprecipitated in (C) and (D), respectively. (E) The proposed role of Grab in regulating the exocytosis and recycling of Tfrc in differentiating erythroblasts. IB, immunoblotting; IgG, immunoglobulin G; IP, immunoprecipitation.