FUNCTIONAL PROTEIN TYROSINE PHOSPHATASES IN PLATELETS

Abstract

Platelets are small anucleate cells in blood that are derived from megakaryocytes and their primary function is to prevent bleeding. Upon vascular injury, the sub-endothelial collagen gets exposed to which platelets bind and aggregate eventually forming a platelet plug. There are several receptors on platelet surface that can be divided into two broad categories; the immune-receptor tyrosine-based activation motif (ITAM) and the G protein-coupled receptors (GPCRs). The role of several protein tyrosine kinases (PTKs) downstream of ITAM and GPCRs has been extensively studied. However, the role of protein tyrosine phosphatases (PTPs) have been under-investigated in platelets. PTPs are important for dephosphorylating and activating or inactivating the protein. Proteomics studies show presence of 10 receptor like and 10 cytoplasmic phosphatases in platelets. To date, only five non-transmembrane PTPs (NTPTPs), PTP-1B, Shp1, Shp2, LMW-PTP, MEG2-PTP and a one receptor- like PTP (RPTP), CD148,