Syntaxin-4, a member of the Qa sensitive factor attachment protein receptor (SNARE) syntaxin family has been implicated in fusion events at the plasma membrane in a number of cells in the immune system. This protein enables sphingomyelin phosphodiesterase activator activity, and is active in glutamatergic synapse and postsynapse. Study demonstrates that syntaxin-4 plays a critical role in the secretion of IgE from plasma cells and sheds some light on the mechanisms by which these cells constitutively traffic vesicles to the surface for secretion. Together with STXB3 and VAMP2, it may also play a role in docking/fusion of intracellular GLUT4-containing vesicles with the cell surface in adipocytes and in docking of synaptic vesicles at presynaptic active zones (By similarity).