Syntaxin Binding Protein 4 (STXBP4)

The deduced 557-amino acid protein has an N-terminal PDZ domain followed by an EF-hand motif, 2 tandem coiled-coil domains, and a C-terminal WW domain. Northern blot analysis detected Synip predominantly in mouse skeletal muscle and heart. Expression was lower in testis, and lowest in brain, liver, spleen, lung, and kidney. Synip mRNA was also expressed in rat white and brown adipocytes.

During regulated endocytosis, v-SNARE vesicular proteins directly interact with plasma membrane t-SNAREs for vesicle docking and subsequent fusion. Syntaxin-4 (STX4A) is the major plasma membrane SNARE for insulin-stimulated GLUT4 (SLC2A4) translocation in adipocytes.