Potentially involved in docking of synaptic vesicles at presynaptic active zones. Apical receptor involved in membrane fusion of apical vesicles. . [Isoform B]: Essential for survival of retinal photoreceetors. . [Isoform 3]: Functions as a regulator of gene expression. . This is the function of STX3 (syntaxin 3, Ensembl gene identifier ENSG00000166900).