Specificity
Protein tyrosine phosphatases, or PTPs, are type I transmembrane proteins, membrane associated proteins or proteins localized in nuclei. Examples of transmembrane PTPs are LAR, PTPa, PTPb, PTPg, PTPd, PTPe, PTPz, PTPk, PTPm and PTPy. Transmembrane PTPs play diverse roles in a variety of cellular processes during development and in adult tissues. PTPy, also known as PTPRU, FMI, PCP-2, PTP-J, PTPRO, PTP-PI, PTPPSI or GLEPP1, is a receptor-type PTP containing a transmembrane region, two intracellular tandem catalytic domains, and an extracellular region with Ig-like and fibronectin type III-like repeats and a MAM (meprin-A5 antigen-PTPm) domain. PTPy localizes to adheren junctions and is capable of binding and dephosphorylating b-catenin thereby functioning as a negative regulator of b-catenin signaling. In addition, PTPy may function as a tumor suppressor, as its expression is silenced in a variety of tumors via methylation of its promoter.
