Localization of syntaxin-3, serotonin, and c-kit in resting and stimulated WT and VAMP-8–deficient BMMCs. Colocalization of SG marker syntaxin-3 and serotonin was analyzed in nonstimulated (NS) and PMA/ionomycin (3 minutes)–stimulated (S) WT (A) and VAMP-8–deficient (B) BMMCs. Cells were stained with rabbit anti–syntaxin-3 and mouse antiserotonin. For comparison, relative localization to the plasma membrane marker c-kit (rat mAb) is shown. Cells were analyzed by confocal microscopy. Representative single optical sections as well as 2-color (2C) and 3-color (3C) overlay images are shown. Compartments showing overlap for 2 colors and 3 colors appear as yellow and white, respectively. Bars represent 5 μm.