Functions in endosome to Golgi retrograde transport. In response to calcium influx, may interact with SNARE fusion receptors and membrane phospholipids to mediate endosome fusion with the trans-Golgi network. By promoting the recycling of secretory vesicle transmembrane proteins, it indirectly controls dense-core secretory vesicle biogenesis, maturation and their ability to mediate the constitutive and regulated secretion of neurotransmitters and hormones. May regulate behavior and food intake by controlling calcium-stimulated exocytosis of neurotransmitters including NPY and serotonin and hormones like insulin (By similarity). Proposed to play a role in hypothalamic neuronal firing by modulating gamma-aminobutyric acid (GABA)ergic inhibitory neurotransmission (Probable). Binds 3 Ca(2+) ions per C2 domain. Interacts with ADGRB1, this interaction is direct. Interacts with endosomal SNARE proteins VAMP3, VAMP4, STX6 and STX16; this interaction is increased in the presence of calcium. Rapidly recruited to the plasma membrane and to Golgi structures in response to increased intracellular calcium concentration. Prominently expressed in brain structures including hypothalamus, amygdala, stria terminalis and periaqueductal gray (at protein level). Expressed in nonneuronal tissues, including placenta, lung, pancreas, spleen, and testes. Within placenta, expression is restricted to the syncytiotrophoblasts. Mutant mice are viable, fertile and have overall normal development. Behavioral phenotyping show increased susceptibility to pentylenetetrazole-induced seizures, increased anxiety in females, and benzodiazepine tolerance in males. Belongs to the unc-13 family. Extended N-terminus.