Protein-Tyrosine Phosphatase 1B Complexes with the Insulin Receptor in Vivo and Is Tyrosine-phosphorylated in the Presence of Insulin

Abstract

In response to insulin, protein-tyrosine phosphatase 1B (PTPase 1B) dephosphorylates 95-and 160 -180-kDa tyrosine phosphorylated (PY) proteins (Kenner, K. A., Anyanwu, E., Olefsky, J. M., and Kusari, J. (1996) J. Biol. Chem. 271, 19810 -19816 Studies using mutant IRs demonstrated that IR autophosphorylation is necessary for the PTPase 1B-IR interaction. These results suggest that PTPase 1B complexes with the autophosphorylated insulin receptor in intact cells, either directly or within a complex involving additional proteins. The interaction requires multiple tyrosine phosphorylation sites within both the receptor and PTPase 1B.Insulin is a potent metabolic and growth-promoting hormone that has pleiotropic effects at the level of the cell and within the intact organism. Insulin acts on cells to stimulate glucose, protein, and lipid metabolism, as well as RNA and DNA synthesis, by modifying the activity of a variety of enzymes and transport processes (1). As a first step in initiating these responses, insulin binds to its plasma membrane receptor. The insulin receptor is a heterotetrameric protein consisting of two ␣ and two ␤ subunits linked by disulfide bonds to form a ␤-␣-␣-␤ structure. After insulin binding, the insulin receptor undergoes autophosphorylation on tyrosine residues. Autophosphorylation increases the tyrosine kinase activity of the insulin receptor, which in turn phosphorylates one or more cellular substrates, leading to a cascade of secondary phosphorylation and dephosphorylation reactions (2).As the molecular mechanism of insulin action is defined with increasing clarity, so too is our appreciation of the central role played by protein tyrosine phosphorylation. Regulated tyrosine phosphorylation represents a balance of protein-tyrosine kinase (PTKase) 1 and protein-tyrosine phosphatase (PTPase) activities. To date, most attempts to assess the role of proteintyrosine phosphorylation in insulin signal transduction have focused on the action of kinases and thus furnish an incomplete picture of this dynamic process. PTPases can be used as probes to test the role of protein tyrosine phosphorylation, complementing studies performed on the PTKases.Extensive progress in the identification and characterization of PTPases has been made in recent years (3), partially as a result of our appreciation of the PTKases (4). PTPase 1B was the first PTPase to be isolated in homogeneous form and sequenced (5, 6). PTPase 1B possesses a catalytic domain characterized by the 11-amino acid sequence motif, (I/V)HCX-AGXXR(S/T)G. This motif contains cysteine (Cys 215 ) and arginine (Arg 221 ) residues critical for the catalytic activity of the enzyme (7-9). The cDNA sequences for human (10, 11) and rat (8) PTPase 1B predict a protein of 50 kDa with 435 and 432 amino acids, respectively. The conserved phosphatase domain of PTPase 1B is contained within the domain spanning residues 30 to 278. The COOH-terminal noncatalytic extension of the protein serves a regulatory function. The COOH-terminal 35 residues target the ...

The genetic component of human longevity: New insights from the analysis of pathway‐based SNP‐SNP interactions

“…The link between the IGF1R‐PTPN1 proteins is known: literature data indicate a crucial role of PTPN1 as a tumour suppressor, able to negatively regulate multiple pathways of cell growth directly through IGF1R and IR , or indirectly through leptin receptor GHR (Neel & Tonks, 2016). Experimental data report that the protein interaction IGF1R‐PTPN1 is regulated by insulin levels (Bandyopadhyay et al., 1997). Furthermore, in experimental organisms, PTPN1 is involved in inflammatory mechanisms and insulin resistance associated with diabetes and obesity during aging (González‐Rodríguez et al., 2012).…”

Turn‐off, drop‐out: Functional state switching of cadherins

“…Elimination of the ER localization signal does not alter the interaction of PTP1B with N-cadherin, indicating that targeting of PTP1B to the N-cadherin complex does not depend on prior targeting to the ER. Furthermore, targeting to specific plasma membrane locations does not appear to depend on cleavage of the ER targeting sequence, as the PTP1B associated with focal adhesion complexes and the insulin receptor (Bandyopadhyay et al, 1997) has an apparent molecular mass of ϳ50 kD, that of the intact protein. Interaction with focal adhesion complexes is most likely through interaction with p130 cas and is mediated by a proline rich, SH3-binding domain in PTP1B (Liu et al, 1996).…”

Protein-tyrosine-phosphatase 1B activation is regulated developmentally in muscle of neonatal pigs

“…Even though there is an abundance of experimental evidence indicating that PTP1B acts as a negative regulator of insulin signaling, direct interaction of PTP1B with the IR, which is crucial for dephosphorylation of the activated IR, has been documented only in cultured cell systems or in vitro studies (5,12,21,35,36,43). For example, with use of brown adipocyte culture, the direct interaction between wild-type PTP1B and the IR was demonstrated in insulin-stimulated cells (35).…”

“…Mechanistic studies of PTP1B's action suggest that interaction between PTP1B and the IR is important for catalyzing IR dephosphorylation (5,11,12,23,36,43). Receptor tyrosine kinases appear to undergo internalization and form complexes with PTP1B, thereby removing phosphate groups from tyrosine residues (23).…”

“…Receptor tyrosine kinases appear to undergo internalization and form complexes with PTP1B, thereby removing phosphate groups from tyrosine residues (23). Studies further suggest that the phosphorylated and activated IR transiently binds and phosphorylates tyrosine residues of PTP1B, thereby increasing its catalytic activity (5,12). Catalytically active PTP1B can then interact with and dephosphorylate the IR, thus attenuating insulin action.…”