Plays a role in vesicle-mediated secretory processes . Required for normal accumulation of secretory vesicles in hippocampus, pituitary and pancreatic islets . Required for the accumulation of normal levels of insulin-containing vesicles and preventing their degradation . Plays a role in insulin secretion in response to glucose stimuli . Required for normal accumulation of the neurotransmitters norepinephrine, dopamine and serotonin in the brain . In females, but not in males, required for normal accumulation and secretion of pituitary hormones, such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH) . Required to maintain normal levels of renin expression and renin release . Seems to lack intrinsic enzyme activity . May regulate catalytic active protein-tyrosine phosphatases such as PTPRA through dimerization