Plays a role in vesicle-mediated secretory processes (PubMed:24843546). Required for normal accumulation of secretory vesicles in hippocampus, pituitary and pancreatic islets (By similarity). Required for the accumulation of normal levels of insulin- containing vesicles and preventing their degradation (PubMed:24843546). Plays a role in insulin secretion in response to glucose stimuli (PubMed:24843546). Required for normal accumulation of the neurotransmitters norepinephrine, dopamine and serotonin in the brain (By similarity). 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) (By similarity). Required to maintain normal levels of renin expression and renin release (By similarity). Seems to lack intrinsic enzyme activity (By similarity). May regulate catalytic active protein-tyrosine phosphatases such as PTPRA through dimerization (By similarity). . [ICA512-transmembrane fragment]: ICA512-TMF regulates dynamics and exocytosis of insulin secretory granules (SGs); binding of ICA512-TMF to SNTB2/beta-2-syntrophin is proposed to restrain SGs mobility and exocytosis by tethering them to the actin cytoskeleton depending on UTRN; the function is inhibited by cytoplasmic ICA512-CFF dimerizing with ICA512-TMF and displacing SNTB2. . [ICA512-cleaved cytosolic fragment]: ICA512-CCF translocated to the nucleus promotes expression of insulin and other granule-related genes; the function implicates binding to and regulating activity of STAT5B probably by preventing its dephosphorylation and potentially by inducing its sumoylation by recruiting PIAS4 (PubMed:15596545, PubMed:16622421, PubMed:18178618). Enhances pancreatic beta-cell proliferation by converging with signaling by STAT5B and STAT3 (PubMed:15596545, PubMed:16622421, PubMed:18178618). ICA512-CCF located in the cytoplasm regulates dynamics and exocytosis of insulin secretory granules (SGs) by dimerizing with ICA512-TMF and displacing SNTB2 thus enhancing SGs mobility and exocytosis (PubMed:18824546, PubMed:20886068). {ECO:0000269|PubMed:15596545, ECO:0000269|PubMed:16622421, ECO:0000269|PubMed:18178618, ECO:0000269|PubMed:18824546, ECO:0000269|PubMed:20886068}. This is the function of PTPRN (protein tyrosine phosphatase receptor type N, Ensembl gene identifier ENSG00000054356).