The protein tyrosine phosphatase (PTP) family of proteins are signaling molecules that regulate processes such as cell growth, cell differentiation, oncogenic transformation and the mitotic cycle. PCPTP1, also known as PTPRR (Receptor-type tyrosine-protein phosphatase R), ECPTP, PTPBR7 or PTPRQ, is a 657 amino acid protein that functions to sequester inactive mitogen-activated protein kinases (MAPKs) to the cytoplasm. Expressed primarily in the brain with weaker expression in other parts of the body, PCPTP1 is a receptor-like molecule that is able to dephosphorylate MAPKs, thereby rendering them inactive. Three isoforms of PCPTP1 exist and are designated alpha, beta and gamma. The alpha form is localized to the cell membrane, while the beta and gamma forms are localized to the perinuclear areas within the cytoplasm.