A Representative images of HEK293T cells transfected with mCherry2-Syx1 or EGFP-Munc18-1. Lipophilic dye DiD (1,1-Dioctadecyl-3,3,3,3-tetramethylindodicarbocyanine) was used as the plasma membrane marker. B Representative images of HEK293T cells co-transfected with mCherry2-Syx1 and EGFP labeled WT or mutants of Munc18-1. 