Screening The Inhibitors Of Protein Tyrosine Phosphatases

Protein tyrosine phosphatases (PTPs) and protein tyrosine kinases that are coordinately implicated in cell signaling transduction are closely associated with numerous physiologic and pathologic phenomenon such as tumors, cardiac and vascular diseases, immune disorders, contagion, nervous and metabolic diseases.Protein tyrosine phosphatase 1B (PTP1B) is one of the protein tyrosine phosphatase (PTPs) family and the first separated PTP. Recent years, it has been proved that PTP1B is a potential target of treatment typeⅡdiabetes and obesity by knock-out mice model. PTP1B blocks the insulin signal pathways by dephosphorylating insulin receptor (IR) and insulin receptor substrates (IRS).TCPTP(T cell-protein tyrosine phosphatase), has become an important member of the PTPs family in two aspects. Firstly, TCPTP has been reported to act on downstream signaling events initiated by the epidermal growth receptor, suggesting that it may act as an important modulator of receptor tyrosine kinases and mitogenic signaling. Secondly, the finding of immune deficiency and lethality observed in TCPTP null mice emphasizes the importance of this small PTP in the hematopoietic system. A role for TCPTP in oncogenesis is currently emerging. TCPTP seems to play a negative role in tumorigenesis and play a positive regulator of cell proliferation. Further analysis of TCPTP expression in human cancer cells and tissues will help to elucidate and define the role of this enzyme in oncogenesis.The protein tyrosine phosphatase SHP1 is a well-known inhibitor of activation-promoting signaling cascades in hematopoietic cells. Recently findings showed a novel role for SHP1 in the regulation of glucose homeostasis through modulation of insulin signaling in liver and muscle as well as hepatic insulin clearance as a result of enhanced insulin receptor signaling to IRS-PI3K-Akt in liver and muscle.SHP2, encoded by the ptpn11 gene, belongs to the protein tyrosine phosphatase family. The presence of two NH2-terminal Src homology 2 (SH2) domains suggested that this phosphatase may be involved in signaling mediated through receptor tyrosine kinases. SHP2 regulates multiple signal pathways by interacting directly with many kinds of growth factor receptors, such as RAS-RAF-MAPK,JAK-STAT,Erk,PI3K. In addition to regulating cell proliferation and differentiation, the mutation of SHP2 has been detected in various clinical diseases. Expression of SHP2 in cells leads to a negative regulation of insulin signaling and downstream functional responses, such as GS. In addition to IR, the IRSs have also been suggested as targets through which SHP2 may modulate insulin signaling.The HePTP (haematopoietic protein tyrosine phosphatase) is a 38 kDa MAP kinase-specific enzyme expressed throughout thymic development and in all T-cell lineages, as well as in other leucocytes. Expression of HePTP in T-cells results in a reduction in Erk2 and p38 kinase activation, but there are no effects on the upstream kinase MEK (MAP kinase/ERK kinase), on JNK or on overall tyrosine phosphorylation. Excess HePTP may correlate with reduced proliferation and loss of HePTP with increased cell proliferation and/or survival. Amplification and overexpression of HePTP has also been reported in a case of myelogenous leukemia. A connection with lymphoid proliferation is also supported by the finding that the HePTP gene is transcriptionally activated in T cells treated with interleukin-2.In synthesis, gene mutation and abnormal expression of PTPs cause many human diseases, such as cancers,diabetes and leukemia. Therefore, as a new therapeutic target, screened the PTPs inhibitor in vitro has provided the theory basis to the new medicine development and the application. In our study, the catalytic domain of the PTP1B,TCPTP,SHP1,SHP2 and fusion protein GST-HePTP have been employed in order to obtain potent and selective inhibitors. Using ion exchange chromatography and affinity chromatography, we obtained high-purity△PTP1B,△TCPTP,△SHP1,△SHP2, as well as GST-HePTP fusion protein. More than 200 kinds of traditional Chinese medicine herbs and a few kinds of teas were examined by enzymatic reaction kinetics experiment in vitro. 27 kinds of herbs and 7 kinds of teas show effective inhibition on all of the 5 kinds of PTPs, the inhibition ratio of which achieve above 90% . 4 kinds of herbs and 4 kinds of teas have specific inhibition on△SHP1. There are another 4 kinds of herbs can inhibit bothΔSHP1 andΔSHP2 conspicuously, simultaneously, another 4 kinds of teas can inhibitΔPTP1B,ΔSHP1 andΔSHP2 conspicuously.Recently researches indicate that PTP1B, SHP1 and SHP2 negatively modulate glucose homeostasis through the insulin signal pathway. Inhibiting their activity may help recover the control of blood glucose in diabetic. Some of the traditional Chinese medicine herbs we used have obviously effects on reducing the blood glucose, but whether their therapeutical effect through inhibiting PTP1B,SHP1 or SHP2 still need more evidences to be proved. The tea polyphenols have pivotal pharmacological action. In this research, several kinds of teas show conspicuous and selective inhibition onΔPTP1B,ΔSHP1 andΔSHP2.We get several traditional Chinese medicine herbs and teas which has conspicuous and selective inhibition onΔPTP1B,ΔSHP1 andΔSHP2. It may provide theory basis for the development of novel drugs which treat PTPs related diseases and lead to the secondary development of traditianal Chinese medicine herbs.