Enables sphingomyelin phosphodiesterase activator activity. Involved in several processes, including cornified envelope assembly; positive regulation of immune effector process; and positive regulation of protein localization. Located in several cellular components, including basolateral plasma membrane; cytoplasmic vesicle; and lamellipodium. Part of SNARE complex. Is active in glutamatergic synapse and postsynapse. [provided by Alliance of Genome Resources, Apr 2022]