STXBP5 (syntaxin binding protein 5) is a SNARE regulatory protein that plays dual, tissue-specific roles in exocytosis. In endothelial cells, STXBP5 inhibits exocytosis by interacting with syntaxin-4 and suppressing von Willebrand factor (vWF) and P-selectin release 1. Conversely, in platelets, STXBP5 promotes secretion by interacting with core machinery complexes including syntaxin-11/SNAP23 heterodimers and the cytoskeleton, facilitating granule cargo packaging and multi-granule type secretion 2. This functional antagonism explains why STXBP5-deficient mice show elevated plasma vWF but impaired platelet hemostasis 1. Genetic variations in STXBP5 associate with multiple cardiovascular phenotypes: SNPs correlate with circulating tPA levels and vWF level variation in type 1 von Willebrand disease 34, while a functional SNP (rs1039084) linked to decreased thrombosis recapitulates human phenotypes in engineered mice 5. Beyond hemostasis, STXBP5-AS1 (an antisense lncRNA regulating STXBP5 expression) associates with adult and childhood ADHD symptoms 6, and both STXBP5 and STXBP5-AS1 function as tumor suppressors in glioma, with epigenetic silencing correlating with tumorigenesis 7.