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. Regulates catecholamine loading of DCVs. May specifically mediate the Ca(2+)-dependent exocytosis of large dense-core vesicles (DCVs) and other dense-core vesicles by acting as a PtdIns(4,5)P2-binding protein that acts at prefusion step following ATP-dependent priming and participates in DCVs-membrane fusion. However, it may also participate in small clear synaptic vesicles (SVs) exocytosis and it is unclear whether its function is related to Ca(2+) triggering. Interacts with the dopamine receptor DRD2 (By similarity). Interacts with RASL10B (By similarity). Homodimer. Membrane-associated to vesicles. Strongly enriched in synaptic fractions. Preferentially binds to dense core vesicles but not to synaptic vesicles. Binds phosphoinosides, with a strong selectivity for PtdIns(4,5)P2 over PtdIns(3,4,5)P3. Probably localizes to different vesicles compared to CADPS2. Specifically expressed in neural and endocrine secretory tissues. Expressed in brain, pancreas, hypothalamus, pituitary and adrenal but not in heart, placenta, lung, liver, skeletal muscle or kidney. In brain, it is absent from the cell body layers of the hippocampus and dentate gyrus but abundant in the synaptic neuropil, except for the stratum lucidum and stratum lacunosum moleculare where it is not detected. In the cerebellum, it is mainly detected in the glomeruli of the granule cell layer where it colocalized with synaptophysin. In the olfactory bulb, it is detected mainly in the glomeruli. In the adult adrenal gland, where it is restricted to the medulla (at protein level). The PH domain is essential for regulated exocytosis and binds phospholipids and plasma membrane. It however does not mediate binding to DCVs.