IA-2/PTPRN is a member of the protein tyrosine phosphatase (PTP) family,which contains a transmembrane region,an intracellular PTP-like domain and an extracellular N-terminus. Experiments found that IA-2/PTPRN localizes to secretory granules and is exclusively expressed in neuroendocrine cells (including pancreatic islets cell). IA-2/PTPRNwas found to be a major autoantigen in insulin-dependent diabetes mellitus and the detection of autoantibodies against IA-2/PTPRN is commonly used as a diabetes diagnosis marker.