Potentially involved in docking of synaptic vesicles at presynaptic active zones. Apical receptor involved in membrane fusion of apical vesicles. Essential for survival of retinal photoreceetors. Functions as a regulator of gene expression. Interacts with REEP6 (By similarity). Interacts with PRPH2 in rod and cone photoreceptors (By similarity). Interacts with ROM1 (By similarity). Interacts with SNAP25 (By similarity). Interacts with VAMP2 (By similarity). Interacts with IPO5. Localized to the inner and outer plexiform layers, the cell body and the inner segments of photoreceptors. Expressed in small intestine, kidney, pancreas, placenta as well as in retina. Weaker expression in lung, liver and heart. Not expressed in brain and skeletal muscle. Expressed only in the retina. Ubiquitously expressed. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the syntaxin family.