PTPRR(protein tyrosine phosphatase, receptor type, R) is also named as PCPTP1, PTP-SL, PTPBR7 and belongs to the protein-tyrosine phosphatase family. It sequesters mitogen-activated protein kinases (MAPKs) such as MAPK1, MAPK3 and MAPK14 in the cytoplasm in an inactive form. It has four isoforms that they have molecular weights of 72, 60, 42 and 37 kDa, respectively, and differ in the length of their N-terminal part which result in distinct subcellular localizations. All PTPRR isoforms are found to be short-lived proteins, with half-lives of around 3-5 hours, and are constitutively phosphorylated on one or two of the previously identified protein kinase A and MAP kinase target sites.