α-Granule protein trafficking through endosomal compartments. Some α-granule proteins are endocytosed into early endosomes where sorting occurs. STX12 is required for membrane fusion to deliver that cargo. The VPS16B/VPS33B complex initially binds STX12 and then may be handed off to the CCC complex. CCC facilitates retrieval of these proteins from the endosomal system and directs them to α-granules.