Model of α-granule movement during platelet spreading. In the resting platelet, α-granules expressing VAMP-3, VAMP-7, and VAMP-8 are dispersed throughout the platelet. During platelet spreading, granules expressing VAMP-3 and VAMP-8 localize to the central granulomere surrounded by a microtubule ring. Granules expressing VAMP-7 move toward the platelet periphery. Exocytosis of granules contributes to expansion of the plasma membrane during spreading.