Protein-tyrosine-phosphatase SHPTP2 is a required positive effector for insulin downstream signaling.

Abstract

SHPTP2 is a ubiquitously expressed tyrosine-specific protein phosphatase that contains two aminoterminal Src homology 2 (SH2) domains responsible for its association with tyrosine-phosphorylated proteins. In this study, expression ofdominant interfering mutants of SHPTP2 was found to inhibit insulin stimulation of c-fos reporter gene expression and activation of the 42-kDa (Erk2) and 44-kDa (Erkl) mitogen-activated protein kinases. Cotransfection of dominant interfering SHPTP2 mutants with v-Ras or Grb2 indicated that SHPTP2 regulated insulin signaling either upstream of or in parallel to Ras function. Furthermore, phosphotyrosine blotting and immunoprecipitation identified the 125-kDa focal adhesion kinase (pp125FAK) as a substrate for insulin-dependent tyrosine dephosphorylation. These data demonstrate that SHPTP2 functions as a positive regulator of insulin action and that insulin signaling results in the dephosphorylation of tyrosine-phosphorylated ppl25FAK.The insulin receptor is a ligand-stimulated transmembrane protein-tyrosine kinase that phosphorylates itself as well as intracellular substrates on specific tyrosine residues (1, 2). One proximal intracellular target for the kinase-activated insulin receptor has been identified as a 185-kDa protein, termed insulin receptor substrate 1 (IRS1) (3,4). This molecule contains several insulin receptor-specific tyrosine phosphorylation sites that provide recognition signals for the binding of specific Src homology 2 (SH2) domain-containing proteins (5, 6). The interaction of IRS1 with signaling proteins containing multiple SH2 domains provides a mechanism by which insulin can modulate the function of several distinct pathways. For example, activation of phosphatidylinositol (PI) 3-kinase activity occurs upon the association of the p85 subunit of the PI 3-kinase with tyrosine-phosphorylated IRS1 (7-9). It has been suggested that the insulin activation of Ras function results from the interaction and/or appropriate targeting of the guanine nucleotide exchange factor Sos with IRS1 (6, 10). This is thought to occur via the constitutive association of the Src homology 3 (SH3) domains of the adapter protein Grb2 with the C-terminal domain of Sos (Grb2/Sos complex) and subsequent binding of the Grb2 SH2 domain to tyrosinephosphorylated IRS1 (10, 11).Recently, several groups have identified a ubiquitously expressed 68-kDa tyrosine-specific protein phosphatase, SHPTP2 (also termed Syp, PTP1D, SHPTP3, PTP2C, or PTPL1), that contains two N-terminal SH2 domains and a C-terminal catalytic domain (12-17). The SH2 domains of this phosphatase mediate the binding of SHPTP2 to tyrosinephosphorylated epidermal growth factor receptor, plateletderived growth factor receptor, and IRS1, resulting in the activation of protein-tyrosine-phosphatase activity (18)(19)(20)(21). Although protein tyrosine phosphatase activity is generally thought to function as the inactivating arm of receptor kinase signaling pathways, in the case of T-cell receptor signaling, the CD45 protein-tyrosi...

SHP-2 binds to Tyr763 and Tyr1009 in the PDGF β-receptor and mediates PDGF-induced activation of the Ras/MAP kinase pathway and chemotaxis

“…Similarly, Yamauchi et al (1995) found that a dominant negative form of SHP-2 blocked insulin stimulation of Erk1 and Erk2 activation, suggesting an involvement of SHP-2 in stimulation of the MAP kinase cascade.…”

Selective impairment of insulin signalling in the hypothalamus of obese Zucker rats

“…The insulin receptor is a protein tyrosine kinase which, when activated by insulin binding, undergoes rapid autophosphorylation and phosphorylates intracellular protein substrates, including insulin receptor substrates (IRSs-IRS-1 and IRS-2 are the most important) [9,10,11] and Shc [12]. Following tyrosine phosphorylation, the IRSs act as docking proteins for several Src homology 2 domaincontaining proteins, including phosphatidylinositol 3-kinase (PI3-kinase), Grb2, SHP2, Nck and Fyn [13,14,15,16,17]. Downstream to PI 3-kinase there is activation of a serine/threonine kinase, Akt [18].…”

Lysophosphatidic acid-induced association of SHP-2 with SHPS-1: roles of RHO, FAK, and a SRC family kinase

“…These results suggest that SRC or some other SRC family kinase may contribute to LPA-induced tyrosine phosphorylation of SHPS-1 and its association with SHP-2. Milarski and Saltiel, 1994;Xiao et al, 1994;Yamauchi et al, 1995) or EGF (Bennett et al, 1996), indicating that SHP-2 may mediate this response. To investigate the physiological consequences of SHPS-1-SHP-2 complex formation in response to LPA, we examined the e ects of overexpression of a catalytically inactive SHP-2 or of SHPS-1 on LPA-induced MAP kinase activation in CHO cells.…”

“…Furthermore, in response to insulin, SHP-2 binds via its SH2 domains to IRS-1, a major substrate for the insulin receptor tyrosine kinase (Sun et al, 1991) and is thereby activated (Kuhne et al, 1993;Matozaki et al, 1995;Pluskey et al, 1995). The expression of a catalytically inactive SHP-2 inhibits insulin-induced activation of RAS and mitogen-activated protein (MAP) kinase (Noguchi et al, 1994;Milarski and Saltiel, 1994;Xiao et al, 1994;Yamauchi et al, 1995) as well as EGF-induced MAP kinase activation (Bennett et al, 1996) and thereby blocks DNA synthesis and cell proliferation. Moreover, microinjection of RNAs encoding catalytically inactive SHP-2 into Xenopus oocytes induces marked posterior truncation and inhibits ®broblast growth factor-and activin-mediated mesoderm induction (Tang et al, 1995).…”