A Novel Membrane Glycoprotein, SHPS-1, That Binds the SH2-Domain-Containing Protein Tyrosine Phosphatase SHP-2 in Response to Mitogens and Cell Adhesion

Abstract

Protein tyrosine phosphatases (PTPases), such as SHP-1 and SHP-2, that contain Src homology 2 (SH2) domains play important roles in growth factor and cytokine signal transduction pathways. A protein of ϳ115 to 120 kDa that interacts with SHP-1 and SHP-2 was purified from v-src-transformed rat fibroblasts (SR-3Y1 cells), and the corresponding cDNA was cloned. The predicted amino acid sequence of the encoded protein, termed SHPS-1 (SHP substrate 1), suggests that it is a glycosylated receptor-like protein with three immunoglobulin-like domains in its extracellular region and four YXX(L/V/I) motifs, potential tyrosine phosphorylation and SH2-domain binding sites, in its cytoplasmic region. Various mitogens, including serum, insulin, and lysophosphatidic acid, or cell adhesion induced tyrosine phosphorylation of SHPS-1 and its subsequent association with SHP-2 in cultured cells. Thus, SHPS-1 may be a direct substrate for both tyrosine kinases, such as the insulin receptor kinase or Src, and a specific docking protein for SH2-domain-containing PTPases. In addition, we suggest that SHPS-1 may be a potential substrate for SHP-2 and may function in both growth factor-and cell adhesion-induced cell signaling.

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

“…One possible explanation is that the two SH2 domains of SHP-2 have di erent binding speci®city. When comparing the sequences surrounding naturally occuring association sites for SHP-2, Tyr763 is quite similar to the association sites found in a number of other molecules (Table 1) (Case et al, 1994;Fujioka et al, 1996;Jackson et al, 1997;Ohnishi et al, 1996;Ottinger et al, 1998;Sugimoto et al, 1994). Many of these molecules have an alanine residue in position +1, an acidic residue in position +2, followed by either leucine or isoleucine in position +3.…”

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

“…Furthermore, the interaction of FAK with SRC results in increases in the catalytic activities of both tyrosine kinases, leading to formation of a FAK-GRB2-SOS complex that mediates MAP kinase activation (Schlaepfer et al, 1994;Schlaepfer and Hunter, 1996). Because SHPS-1 is a substrate for v-SRC kinase Fujioka et al, 1996), we next examined whether SRC kinase is important in LPAinduced tyrosine phosphorylation of SHPS-1. For this purpose, we generated CHO cells (CSK-WT) that overexpress rat CSK, a SRC-like kinase that inhibits the activity of SRC family kinases by phosphorylating a COOH-terminal tyrosine residue Okada et al, 1991).…”

“…Indeed, LPA-induced tyrosine phosphorylation of SHPS-1 is also reduced in SRC-de®cient cells derived from Src knockout mice (Takeda, Matozaki, Imamoto, Soriano and Kasuga, unpublished observation). SHPS-1 serves as a good substrate for v-SRC kinase in vivo Fujioka et al, 1996). Because LPA induces activation of SRC kinase (Ilic et al, 1995), this enzyme may catalyze the tyrosine phosphorylation of SHPS-1 in response to LPA.…”

“…CHO cells overexpressing human insulin receptors (CHO-IR cells) were maintained in Ham's F-12 medium supplemented with 10% fetal bovine serum (FBS). CHO-IR cells that overexpress either a catalytically inactive SHP-2 (CHO-SHP-2-C/S) or wild-type SHPS-1 (CHO-SHPS-1-WT) were generated as previously described (Noguchi et al, 1994;Fujioka et al, 1996).…”

“…Insulin, EGF, serum and cell adhesion each rapidly stimulates tyrosine phosphorylation of SHPS-1 and its association with SHP-2 Kharitonenkov et al, 1997). In vitro binding studies with a phosphotyrosyl peptide library have suggested that the SH2 domains of SHP-2 bind to phosphopeptides that contain the sequence motif pYXX(L/V/I) (Songyang et al, 1993;Fujioka et al, 1996), where pY represents phosphorylated tyrosine. Thus, the SH2 domains of SHP-2 may bind to one or more phosphorylated tyrosine residues in the cytoplasmic domain of SHPS-1.…”