Calcium-binding protein involved in exocytosis of vesicles filled with neurotransmitters and neuropeptides. Probably acts upstream of fusion in the biogenesis or maintenance of mature secretory vesicles. May specifically mediate the Ca(2+)-dependent exocytosis of large dense-core vesicles (DCVs) and other dense-core vesicles (By similarity). Specifically required to activate the neuronal G-alpha pathway. Functions with G-alpha proteins from the same motor neurons to regulate locomotion (PubMed:16272411). Involved in regulating entry into quiescence triggered by satiety (PubMed:18316030). Probably by regulating neuronal transmission downstream of lin-3 and receptor lin-23 and phospholipase plc-3 and upstream of innexin unc-7 and egl-4/PKG in ALA neurons, involved in the decrease in pharyngeal pumping during the quiescent state that precedes each larval molt (PubMed:17891142). Plays a role in octopamine signaling and specifically, the octopamine inhibition of aversion responses in olfactory sensory neurons (PubMed:22124329). Probably by controlling the secretion of FLP neuropeptides, regulates the turning step of male mating behavior (PubMed:17611271). Membrane-associated to vesicles (By similarity). Strongly enriched in synaptic fractions. Often concentrated at or near active zones of motor neuron synapses. Within the ventral, dorsal and sublateral nerve cords, it is concentrated in cholinergic synapses. Within the ventral and dorsal nerve cords, it is not concentrated at most non-cholinergic synapses in the nerve cords, such as the GABAergic, glutamatergic, and catecholaminergic synapses. However, within the nerve ring, which contains a large number of interneuronal synapses in the head, it is clearly concentrated in regions containing large numbers of non-cholinergic synapses. The PH domain is essential for regulated exocytosis and binds phospholipids. Worms display increased adult life span and constitutive dauer formation (PubMed:10377425). RNAi-mediated knockdown in ADL sensory neurons results in reduced octopamine inhibition of the aversive response when animals are exposed to 100% 1-octanol (PubMed:22124329).