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Johnson DR, O'Connor JC, Dantzer R, Freund GG. Inhibition of vagally mediated immune-to-brain signaling by vanadyl sulfate speeds recovery from sickness. Proc Natl Acad Sci U S A 2005; 102:15184-9. [PMID: 16217019 PMCID: PMC1257721 DOI: 10.1073/pnas.0507191102] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Indexed: 01/04/2023] Open
Abstract
To the ill patient with diabetes, the behavioral symptoms of sickness such as fatigue and apathy are debilitating and can prevent recuperation. Here we report that peripherally administered insulin-like growth factor 1 (IGF-1) attenuates LPS-dependent depression of social exploration (sickness) in nondiabetic (db/+) but not in diabetic (db/db) mice. We show that the insulin/IGF-1 mimetic vanadyl sulfate (VS) is effective at augmenting recovery from sickness in both db/+ and db/db mice. Specifically, peak illness was reached at 2 h for both VS and control animals injected with LPS, and VS mice recovered 50% faster than non-VS-treated animals. Examination of the mechanism of VS action in db/+ mice showed that VS paradoxically augmented peritoneal macrophage responsivity to LPS, increasing both peritoneal and ex vivo macrophage production of IL-1beta and IL-6 but not TNF-alpha. The effects of VS in promoting recovery from sickness were not restricted to LPS, because they were also observed after direct administration of IL-1beta. To explore the possibility that VS impairs immune-to-brain communication via vagal afferents, the vagally mediated satiety-inducing effects of cholecystokinin 8 were tested in db/+ mice. Cholecystokinin decreased food intake in saline-injected mice but not in VS-treated mice. VS also inhibited LPS-dependent up-regulation of IL-1beta and IL-6 mRNA in the brain, while increasing by 50% the cerebral expression of transcripts of the specific antagonist of IL-1 receptors IL-1RA and IL-1R2. Taken together, these data indicate that VS improves recovery from LPS-induced sickness by blocking vagally mediated immune-to-brain signaling and by up-regulating brain expression of IL-1beta antagonists.
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Affiliation(s)
- Daniel R Johnson
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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52
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Haj FG, Zabolotny JM, Kim YB, Kahn BB, Neel BG. Liver-specific Protein-tyrosine Phosphatase 1B (PTP1B) Re-expression Alters Glucose Homeostasis of PTP1B–/–Mice. J Biol Chem 2005; 280:15038-46. [PMID: 15699041 DOI: 10.1074/jbc.m413240200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Protein-tyrosine phosphatase 1B (PTP1B) is an important negative regulator of insulin and leptin signaling in vivo. Mice lacking PTP1B (PTP1B-/- mice) are hyper-responsive to insulin and leptin and resistant to diet-induced obesity. The tissue(s) that mediate these effects of global PTP1B deficiency remain controversial. We exploited the high degree of hepatotropism of adenoviruses to assess the role of PTP1B in the liver. Liver-specific re-expression of PTP1B in PTP1B-/- mice led to marked attenuation of their enhanced insulin sensitivity. This correlated with, and was probably caused by, decreased insulin-stimulated tyrosyl phosphorylation of the insulin receptor (IR) and IR substrate 2-associated phosphatidylinositide 3-kinase activity. Analysis using phospho-specific antibodies for the IR revealed preferential dephosphorylation of Tyr-1162/1163 compared with Tyr-972 by PTP1B in vivo. Our findings show that the liver is a major site of the peripheral action of PTP1B in regulating glucose homeostasis.
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Affiliation(s)
- Fawaz G Haj
- Cancer Biology Program, Division of Hematology-Oncology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, 02215, USA
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53
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Wiesmann C, Barr KJ, Kung J, Zhu J, Erlanson DA, Shen W, Fahr BJ, Zhong M, Taylor L, Randal M, McDowell RS, Hansen SK. Allosteric inhibition of protein tyrosine phosphatase 1B. Nat Struct Mol Biol 2004; 11:730-7. [PMID: 15258570 DOI: 10.1038/nsmb803] [Citation(s) in RCA: 385] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 05/04/2004] [Indexed: 12/19/2022]
Abstract
Obesity and type II diabetes are closely linked metabolic syndromes that afflict >100 million people worldwide. Although protein tyrosine phosphatase 1B (PTP1B) has emerged as a promising target for the treatment of both syndromes, the discovery of pharmaceutically acceptable inhibitors that bind at the active site remains a substantial challenge. Here we describe the discovery of an allosteric site in PTP1B. Crystal structures of PTP1B in complex with allosteric inhibitors reveal a novel site located approximately 20 A from the catalytic site. We show that allosteric inhibitors prevent formation of the active form of the enzyme by blocking mobility of the catalytic loop, thereby exploiting a general mechanism used by tyrosine phosphatases. Notably, these inhibitors exhibit selectivity for PTP1B and enhance insulin signaling in cells. Allosteric inhibition is a promising strategy for targeting PTP1B and constitutes a mechanism that may be applicable to other tyrosine phosphatases.
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Affiliation(s)
- Christian Wiesmann
- Sunesis Pharmaceuticals, 341 Oyster Point Boulevard, South San Francisco, California 94080, USA
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54
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Le HT, Ponniah S, Pallen CJ. Insulin signaling and glucose homeostasis in mice lacking protein tyrosine phosphatase α. Biochem Biophys Res Commun 2004; 314:321-9. [PMID: 14733908 DOI: 10.1016/j.bbrc.2003.12.087] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Studies in cultured cells have implicated protein tyrosine phosphatase alpha (PTPalpha) as a potential regulator of insulin signaling. The physiological role of PTPalpha in insulin action was investigated using gene-targeted mice deficient in PTPalpha. PTPalpha-null animals had normal body weights and circulating levels of glucose and insulin in random fed and fasted states. In glucose and insulin tolerance tests, their efficiency of blood glucose clearance was comparable to wild-type mice. Kinetics and extents of insulin-stimulated insulin receptor and IRS-1 tyrosine phosphorylation were similar in wild-type and PTPalpha(-/-) liver, muscle, and adipose tissue. However, the association of IRS-1 and PI 3-K was altered in PTPalpha(-/-) liver, with increased insulin-independent and reduced insulin-stimulated association compared to wild-type samples. This did not affect activation of the downstream signaling effector Akt. Our data indicate that PTPalpha is not a negative regulator of insulin signaling and does not perform an essential role in mediating the physiological action of insulin.
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Affiliation(s)
- Hoa T Le
- Department of Pathology and Laboratory Medicine, British Columbia Research Institute for Children's and Women's Health, University of British Columbia, V5Z 4H4 Vancouver, BC, Canada
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55
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Xie L, Lee SY, Andersen JN, Waters S, Shen K, Guo XL, Moller NPH, Olefsky JM, Lawrence DS, Zhang ZY. Cellular effects of small molecule PTP1B inhibitors on insulin signaling. Biochemistry 2004; 42:12792-804. [PMID: 14596593 DOI: 10.1021/bi035238p] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein tyrosine phosphatase 1B (PTP1B) is implicated as a negative regulator of insulin receptor (IR) signaling and a potential drug target for the treatment of type 2 diabetes and other associated metabolic syndromes. To further define the role of PTP1B in insulin signaling and to test the hypothesis that blocking the activity of PTP1B would augment the action of insulin, we prepared several cell permeable, potent and selective, small molecule PTP1B inhibitors, and evaluated their biological effects in several insulin sensitive cell lines. Our data indicate that PTP1B inhibitors bind to and colocalize with PTP1B on the surface of the endoplasmic reticulum and PTP1B exerts its negative effect on insulin signaling upstream of phosphatidylinositol 3-kinase and MEK1. Treatment of cells with PTP1B inhibitors, both in the presence and in the absence of insulin, markedly enhances IRbeta and IRS-1 phosphorylation, Akt and ERK1/2 activation, Glut4 translocation, glucose uptake, and Elk1 transcriptional activation and cell proliferation. These results indicate that small molecule inhibitors targeted to PTP1B can act as both insulin mimetics and insulin sensitizers. Taken together, our findings combined with results from PTP1B knockout, antisense, and biochemical studies provide strong evidence that PTP1B negatively regulates insulin signaling and that small molecule PTP1B inhibitors have the ability to potentiate and augment the action of insulin.
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Affiliation(s)
- Laiping Xie
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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56
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Kushner JA, Haj FG, Klaman LD, Dow MA, Kahn BB, Neel BG, White MF. Islet-sparing effects of protein tyrosine phosphatase-1b deficiency delays onset of diabetes in IRS2 knockout mice. Diabetes 2004; 53:61-6. [PMID: 14693698 DOI: 10.2337/diabetes.53.1.61] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Protein tyrosine phosphatase-1b (Ptp1b) inhibits insulin and leptin signaling by dephosphorylating specific tyrosine residues in their activated receptor complexes. Insulin signals are mediated by tyrosine phosphorylation of the insulin receptor and its downstream targets, such as Irs1 and Irs2. Irs2 plays an especially important role in glucose homeostasis because it mediates some peripheral actions of insulin and promotes pancreatic beta-cell function. To determine whether the deletion of Ptp1b compensates for the absence of Irs2, we analyzed mice deficient in both Ptp1b and Irs2. Pancreatic beta-cell area decreased in Ptp1b(-/-) mice, consistent with decreased insulin requirements owing to increased peripheral insulin sensitivity. By contrast, peripheral insulin sensitivity and beta-cell area increased in Irs2(-/-)::Ptp1b(-/-) mice, which improved glucose tolerance in Irs2(-/-)::Ptp1b(-/-) mice and delayed diabetes until 3 months of age. However, beta-cell function eventually failed to compensate for absence of Irs2. Our studies demonstrate a novel role for Ptp1b in regulating beta-cell homeostasis and indicate that Ptp1b deficiency can partially compensate for lack of Irs2.
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Affiliation(s)
- Jake A Kushner
- Howard Hughes Medical Institute, Joslin Diabetes Center, and Division of Endocrinology, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA
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57
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Dadke S, Chernoff J. Protein-tyrosine phosphatase 1B mediates the effects of insulin on the actin cytoskeleton in immortalized fibroblasts. J Biol Chem 2003; 278:40607-11. [PMID: 12902327 DOI: 10.1074/jbc.m306772200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin regulates diverse cellular responses including actin reorganization. The mechanism by which insulin induces formation of lamellipodia in cultured cells is not known but is likely to involve activation of Src family protein-tyrosine kinases. Here we show that protein-tyrosine phosphatase 1B (PTPIB) activates Src, thereby initiating the activation of a Rac-dependent pathway leading to cytoskeletal remodeling. Conversely, expression of a proline to alanine (P309,310A) PTP1B mutant, which cannot activate Src, fails to activate Rho GTPases or cause changes in actin organization. Rat fibroblasts lacking PTP1B expression do not activate Src or Rac in response to insulin and cannot reorganize actin. These results show that PTP1B, best known as a negative regulator of the metabolic effects of insulin, is required for the effects of insulin on actin organization in immortalized fibroblasts.
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58
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Ragab A, Bodin S, Viala C, Chap H, Payrastre B, Ragab-Thomas J. The tyrosine phosphatase 1B regulates linker for activation of T-cell phosphorylation and platelet aggregation upon FcgammaRIIa cross-linking. J Biol Chem 2003; 278:40923-32. [PMID: 12857726 DOI: 10.1074/jbc.m303602200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Human platelets express the receptor for immunoglobulin G, FcgammaRIIa, that triggers cell aggregation upon interaction with immune complexes. Here, we report that the rapid tyrosine phosphorylation of the Linker for Activation of T-cell (LAT) in human platelets stimulated by FcgammaRIIa cross-linking was followed by its complete dephosphorylation in an alphaIIb/beta3 integrin-dependent manner. Concomitant to LAT dephosphorylation, the protein tyrosine phosphatase 1B (PTP1B) was activated through a mechanism involving its proteolysis by calpains downstream of integrins. Both PTP1B and LAT were associated with the actin cytoskeleton complex formed during platelet aggregation. Moreover, phospho-LAT appeared as a good substrate of activated PTP1B in vitro and these two proteins interacted upon platelet activation by FcgammaRIIa cross-linking. The permeant substrate-trapping PTP1B (TAT-PTP1B D181A) partly inhibited LAT dephosphorylation in human platelets, strongly suggesting that this tyrosine phosphatase was involved in this regulatory pathway. Using a pharmacological inhibitor, we provide evidence that PTP1B activation and LAT dephosphorylation processes were required for irreversible platelet aggregation. Altogether, our results demonstrate that PTP1B plays an important role in the integrin-mediated dephosphorylation of LAT in human platelets and is involved in the control of irreversible aggregation upon FcgammaRIIa stimulation.
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Affiliation(s)
- Ashraf Ragab
- INSERM U563, Centre de Physiopathologie de Toulouse-Purpan, Institut Fédératif de Recherche 30, Universite Paul Sabatier, Hôpital Purpan, 31059 Toulouse Cedex, France
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59
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Lefebvre DC, Felberg J, Cross JL, Johnson P. The noncatalytic domains of Lck regulate its dephosphorylation by CD45. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1650:40-9. [PMID: 12922168 DOI: 10.1016/s1570-9639(03)00190-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Src-family tyrosine kinase, Lck, contains two key regulatory phosphotyrosine residues, tyrosine 394 (Tyr-394) and tyrosine 505 (Tyr-505), both of which can be dephosphorylated by CD45. Here, the interaction of CD45 with its substrate, Lck, was determined to be complex, involving multiple interactions with both the catalytic and noncatalytic regions of Lck. CD45 preferentially dephosphorylated Tyr-394 over Tyr-505 in Lck. This was not due to sequence specificity surrounding the phosphotyrosine, but was due to the noncatalytic domains of Lck. The interactions with the noncatalytic domains of Lck and CD45 enhanced the dephosphorylation of Tyr-394 whereas intramolecular interactions within Lck reduced, but did not abolish, the dephosphorylation of Tyr-505. This demonstrates that the noncatalytic domains of Lck regulate the dephosphorylation of both Tyr-394 and Tyr-505 by CD45.
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Affiliation(s)
- Dennis C Lefebvre
- Department of Microbiology and Immunology, University of British Columbia, #300-6174 University Boulevard, Vancouver, BC, Canada V6T 1Z3
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60
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Abstract
Tyrosine dephosphorylation, serine phosphorylation, and proteasomal degradation of insulin receptor substrates (IRSs) are implicated in the negative regulation of insulin action. Here we show that simultaneous inhibition of IRS-1 tyrosine dephosphorylation and proteasomal degradation synergistically augments insulin-responsive glucose uptake. L6 skeletal muscle cells (L6 cells) were treated with inhibitors of protein-tyrosine phosphatases, proteasomal degradation, and mammalian target of rapamycin (mTOR), and the effects of insulin on glucose uptake, IRS-1 tyrosine phosphorylation, phosphatidylinositol (PI) 3-kinase activity, and IRS-1 mass were examined. Pretreatment of L6 cells with sodium orthovanadate (Na(3)VO(4)) plus the mTOR inhibitor rapamycin caused a 5-fold increase in insulin-responsive glucose uptake at 2 hours when compared to insulin alone. Evaluation of IRS-1 associated PI 3-kinase activity, IRS-1-associated p85 mass, and IRS-1 tyrosine phosphorylation showed that 2 hours after insulin addition they were reduced by 70% from maximal activity. Likewise, IRS-1 mass was reduced by 50%. When L6 cells were pretreated with Na(3)VO(4) plus the proteasome inhibitor MG-132 or the mTOR inhibitor rapamycin prior to insulin addition, IRS-1 mass loss as well as IRS-1/PI-3 kinase complex decay was blocked at 2 hours and PI 3-kinase activity was increased 2.5-fold and 4-fold, respectively, over insulin alone. Finally, treatment of L6 cells with subtherapeutic amounts of vanadyl sulfate and rapamycin induced a synergistic 3-fold increase in insulin-induced glucose uptake at 2 hours. These findings indicate that vanadium and rapamycin synergize to enhance glucose uptake by preventing IRS-1 mass loss and IRS-1/PI 3-kinase complex decay and may offer a new approach to enhance glucose transport in diabetes.
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Affiliation(s)
- Jason C O'Connor
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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61
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Espanel X, Wälchli S, Rückle T, Harrenga A, Huguenin-Reggiani M, Hooft van Huijsduijnen R. Mapping of synergistic components of weakly interacting protein-protein motifs using arrays of paired peptides. J Biol Chem 2003; 278:15162-7. [PMID: 12551909 DOI: 10.1074/jbc.m211887200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein-protein recognition usually involves multiple interactions among different motifs that are scattered over protein surfaces. To identify such weak interactions, we have developed a novel double peptide synthesis (DS) method. This method allows us to map protein-protein interactions that involve two linear dis- continuous components from a polypeptide by the use of spatially addressable synergistic pairs of synthetic peptides. The DS procedure is based on the "SPOT" membrane-bound peptide synthesis technique, but to synthesize a mixture of two peptides, it uses both Fmoc (N-(9-fluorenyl)methoxycarbonyl))-alanine and Alloc-alanine at the first cycle. This allows their selective deprotection by either piperidine or tributyltin/palladium treatment, respectively. Using SPOT DS, we confirmed as a proof of principle that Elk-1 Ser(383) phosphorylation by ERK-2 kinase is stimulated by the presence of the Elk-1-docking domain. SPOT DS can also be used to dissect protein-protein motifs that define phosphatase substrate affinity. Using this technique, we identified three new regions in the insulin receptor that stimulate the dephosphorylation of the receptor by protein-tyrosine phosphatase (PTP) 1B and presumably increase the selectivity of PTP for this substrate. These data demonstrate that the SPOT DS technique allows the identification of non-linear weakly interacting protein motifs, which are an important determinant of protein kinase and phosphatase substrate specificity and of protein-protein interactions in general.
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Affiliation(s)
- Xavier Espanel
- Serono Pharmaceutical Research Institute, Geneva 1228, Switzerland
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62
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Asante-Appiah E, Kennedy BP. Protein tyrosine phosphatases: the quest for negative regulators of insulin action. Am J Physiol Endocrinol Metab 2003; 284:E663-70. [PMID: 12626322 DOI: 10.1152/ajpendo.00462.2002] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Type 2 diabetes is increasing at an alarming rate worldwide, and there has been a considerable effort in several laboratories to identify suitable targets for the design of drugs against the disease. To this end, the protein tyrosine phosphatases that attenuate insulin signaling by dephosphorylating the insulin receptor (IR) have been actively pursued. This is because inhibiting the phosphatases would be expected to prolong insulin signaling and thereby facilitate glucose uptake and, presumably, result in a lowering of blood glucose. Targeting the IR protein tyrosine phosphatase, therefore, has the potential to be a significant disease-modifying strategy. Several protein tyrosine phosphatases (PTPs) have been implicated in the dephosphorylation of the IR. These phosphatases include PTPalpha, LAR, CD45, PTPepsilon, SHP2, and PTP1B. In most cases, there is evidence for and against the involvement of the phosphatases in insulin signaling. The most convincing data, however, support a critical role for PTP1B in insulin action. PTP1B knockout mice are not only insulin sensitive but also maintain euglycemia (in the fed state), with one-half the level of insulin observed in wild-type littermates. Interestingly, these mice are also resistant to diet-induced obesity when fed a high-fat diet. The insulin-sensitive phenotype of the PTP1B knockout mouse is reproduced when the phosphatase is also knocked down with an antisense oligonucleotide in obese mice. Thus PTP1B appears to be a very attractive candidate for the design of drugs for type 2 diabetes and obesity.
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Affiliation(s)
- Ernest Asante-Appiah
- Department of Biochemistry and Molecular Biology, Merck Frosst Center for Therapeutic Research, Pointe-Claire - Dorval, Quebec, Canada H9R 4P8
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63
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Markova B, Herrlich P, Rönnstrand L, Böhmer FD. Identification of protein tyrosine phosphatases associating with the PDGF receptor. Biochemistry 2003; 42:2691-9. [PMID: 12614164 DOI: 10.1021/bi0265574] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein tyrosine phosphatase (PTP) in-gel assays were used to explore association of PTPs with the platelet-derived growth factor beta-receptor (PDGFbetaR). Five PTP activity bands of approximately 120, approximately 70, approximately 60, approximately 53, and approximately 45 kDa could be detected in PDGFbetaR immunoprecipitates and were identified by immunodepletion experiments as PTP-PEST, SHP-2, an active fragment of SHP-2, PTP-1B, and T-cell PTP, respectively. The PTP pattern that was obtained was similar in PDGFbetaR immunoprecipitates from HEK 293 cells overexpressing the human PDGFbetaR and from murine fibroblasts. Association of PTP-1B with the PDGFbetaR was stabilized by pretreatment of the cells with hydrogen peroxide. The epidermal growth factor receptor (EGFR) immunoprecipitated from fibroblasts, and c-Kit isolated from CHRF myeloid cells, were associated with partially overlapping but quantitatively different patterns of PTPs. PTP-PEST was the predominant PTP in EGFR immunoprecipitates, and SHP-1 appeared in c-Kit immunoprecipitates. We propose that the differential association of PTPs with different RTKs is related to their respective contributions to regulation of RTK signaling.
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Affiliation(s)
- Boyka Markova
- Research Unit Molecular Cell Biology, Medical Faculty, Friedrich Schiller University, Drackendorfer Strasse 1, D-07747 Jena, Germany
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64
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Haj FG, Markova B, Klaman LD, Bohmer FD, Neel BG. Regulation of receptor tyrosine kinase signaling by protein tyrosine phosphatase-1B. J Biol Chem 2003; 278:739-44. [PMID: 12424235 DOI: 10.1074/jbc.m210194200] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Receptor tyrosine kinases (RTKs) are key regulators of cellular homeostasis. Based on in vitro and ex vivo studies, protein tyrosine phosphatase-1B (PTP1B) was implicated in the regulation of several RTKs, yet mice lacking PTP1B show defects mainly in insulin and leptin receptor signaling. To address this apparent paradox, we studied RTK signaling in primary and immortalized fibroblasts from PTP1B(-/-) mice. After growth factor treatment, cells lacking PTP1B exhibit increased and sustained phosphorylation of the epidermal growth factor receptor (EGFR) and the platelet-derived growth factor receptor (PDGFR). However, Erk activation is enhanced only slightly, and there is no increase in Akt activation in PTP1B-deficient cells. Our results show that PTP1B does play a role in regulating EGFR and PDGFR phosphorylation but that other signaling mechanisms can largely compensate for PTP1B deficiency. In-gel phosphatase experiments suggest that other PTPs may help to regulate the EGFR and PDGFR in PTP1B(-/-) fibroblasts. This and other compensatory mechanisms prevent widespread, uncontrolled activation of RTKs in the absence of PTP1B and probably explain the relatively mild effects of PTP1B deletion in mice.
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Affiliation(s)
- Fawaz G Haj
- Cancer Biology Program, Division of Hematology Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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65
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Suryawan A, Davis TA. Protein-tyrosine-phosphatase 1B activation is regulated developmentally in muscle of neonatal pigs. Am J Physiol Endocrinol Metab 2003; 284:E47-54. [PMID: 12388170 DOI: 10.1152/ajpendo.00210.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The high activity of the insulin-signaling pathway contributes to the enhanced feeding-induced stimulation of translation initiation in skeletal muscle of neonatal pigs. Protein-tyrosine-phosphatase 1B (PTP1B) is a negative regulator of the tyrosine phosphorylation of the insulin receptor (IR) and insulin receptor substrate 1 (IRS-1). The activity of PTP1B is determined mainly by its association with IR and Grb2. We examined the level of PTP1B activity, PTP1B protein abundance, PTP1B tyrosine phosphorylation, and the association of PTP1B with IR and Grb2 in skeletal muscle and liver of fasted and fed 7- and 26-day-old pigs. PTP1B activity in skeletal muscle was lower (P < 0.05) in 7- compared with 26-day-old pigs but in liver was similar in the two age groups. PTP1B abundances were similar in muscle but lower (P < 0.05) in liver of 7- compared with 26-day-old pigs. PTP1B tyrosine phosphorylation in muscle was lower (P < 0.05) in 7- than in 26-day-old pigs. The associations of PTP1B with IR and with Grb2 were lower (P < 0.05) at 7 than at 26 days of age in muscle, but there were no age effects in liver. Finally, in both age groups, fasting did not have any effect on these parameters. These results indicate that basal PTP1B activation is developmentally regulated in skeletal muscle of neonatal pigs, consistent with the developmental changes in the activation of the insulin-signaling pathway reported previously. Reduced PTP1B activation in neonatal muscle likely contributes to the enhanced insulin sensitivity of skeletal muscle in neonatal pigs.
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Affiliation(s)
- Agus Suryawan
- United States Department of Agriculture/Agriculture Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA
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66
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Espanel X, Huguenin-Reggiani M, Hooft van Huijsduijnen R. The SPOT technique as a tool for studying protein tyrosine phosphatase substrate specificities. Protein Sci 2002; 11:2326-34. [PMID: 12237455 PMCID: PMC2373693 DOI: 10.1110/ps.0213402] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The activity of protein tyrosine phosphatases (PTPs) is restricted by their substrate specificities. The analysis of PTP specificity was greatly helped by the discovery that "substrate-trapping" PTP mutants, such as PTP-1B D181A, stably and specifically bind their substrates. We have set up a PTP substrate specificity assay based on the SPOT technique, which involves the microsynthesis of (phospho)peptides on membranes. To validate this approach, substrate trapping PTP-1B was tested on its cognate ligand, the autophosphorylated insulin receptor (IR). On SPOT membranes, IR peptides with phosphotyrosine 1163 were efficiently bound by PTP1B D181A, and dephosphorylated by PTP-1B. Phosphotyrosine 1163 was preferred over the neighboring 1158 and 1162 phosphotyrosines. PTP-1B also recognized IR-like motifs in Trk autophosphorylation domains, and STAT 5 phosphopeptides. Using a gridded 20-by-20 SPOT library, we show that peptides with the YZM motif (Z: phosphotyrosine) are the strongest ligands for PTP-1B D181A, but not the optimal substrates for dephosphorylation by wild-type PTP1B. In addition we show that PTP-1B and PTP-beta dephosphorylation efficiency is strongly modulated by the introduction of phospho-serine or phospho-threonine in their cognate phospho-tyrosine substrates. Altogether our data illustrate that the SPOT technique is a highly efficient tool for the study of PTP substrate specificity.
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Affiliation(s)
- Xavier Espanel
- Serono Pharmaceutical Research Institute, 14, chemin des Aulx, 1228 Plan-Les-Ouates, Geneva, Switzerland
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Sreejayan N, Lin Y, Hassid A. NO attenuates insulin signaling and motility in aortic smooth muscle cells via protein tyrosine phosphatase 1B-mediated mechanism. Arterioscler Thromb Vasc Biol 2002; 22:1086-92. [PMID: 12117721 DOI: 10.1161/01.atv.0000020550.65963.e9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Hyperinsulinemia is a significant risk factor for the pathogenesis of vascular disease. Protein tyrosine phosphatase 1B (PTP1B) has been recognized as a modulator of insulin signaling in nonvascular cells, and we have recently reported that NO increases the activity of PTP1B in rat vascular smooth muscle cells. In the present study, we tested the hypothesis that NO attenuates insulin-stimulated cell motility via a PTP1B-mediated mechanism involving downregulation of insulin signal transduction. METHODS AND RESULTS Treatment of primary aortic smooth muscle cells from newborn rats with the NO donor S-nitroso-N-acetylpenicillamine reduced cell motility, tyrosine phosphorylation levels of insulin receptor beta subunit and insulin receptor substrate-1, and extracellular signal-regulated kinase activity. Overexpression of wild-type PTP1B via an adenoviral vector blocked the capacity of insulin to stimulate cell motility and insulin receptor phosphorylation, whereas expression of a dominant-negative mutant of PTP1B attenuated the capacity of NO to decrease cell motility. CONCLUSIONS Our findings indicate that activation of PTP1B is necessary and sufficient to account for the capacity of NO to decrease insulin-stimulated signal transduction and cell motility in cultured aortic smooth muscle cells. The results could explain the capacity of NO to oppose neointima formation in states of hyperinsulinemia.
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MESH Headings
- Animals
- Animals, Newborn
- Aorta, Thoracic/cytology
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/enzymology
- Butadienes/pharmacology
- Cell Communication/drug effects
- Cell Communication/physiology
- Cell Movement/drug effects
- Cell Movement/genetics
- Cell Movement/physiology
- Cells, Cultured
- Diabetes Mellitus, Type 2/enzymology
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Drug Synergism
- Enzyme Inhibitors/pharmacology
- Female
- Insulin/metabolism
- Insulin/physiology
- Mitogen-Activated Protein Kinase 1/antagonists & inhibitors
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 1/physiology
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Mitogen-Activated Protein Kinases/metabolism
- Mitogen-Activated Protein Kinases/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Mutation
- Nitric Oxide/antagonists & inhibitors
- Nitric Oxide/pharmacology
- Nitric Oxide Donors/pharmacology
- Nitriles/pharmacology
- Penicillamine/analogs & derivatives
- Penicillamine/pharmacology
- Phosphotyrosine/metabolism
- Protein Serine-Threonine Kinases/antagonists & inhibitors
- Protein Serine-Threonine Kinases/physiology
- Protein Tyrosine Phosphatase, Non-Receptor Type 1
- Protein Tyrosine Phosphatase, Non-Receptor Type 12
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Protein Tyrosine Phosphatases/deficiency
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/physiology
- Rats
- Rats, Sprague-Dawley
- Receptor, Insulin/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- src Homology Domains/drug effects
- src Homology Domains/physiology
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Affiliation(s)
- Nair Sreejayan
- Department of Physiology and Vascular Biology Center, University of Tennessee Health Science Center, Memphis 38163, USA
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68
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Dadke S, Chernoff J. Interaction of protein tyrosine phosphatase (PTP) 1B with its substrates is influenced by two distinct binding domains. Biochem J 2002; 364:377-83. [PMID: 12023880 PMCID: PMC1222582 DOI: 10.1042/bj20011372] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have shown previously that protein tyrosine phosphatase (PTP) 1B interacts with insulin receptor and negatively regulates insulin signalling by an N-terminal binding domain [Dadke, Kusari and Chernoff (2000) J. Biol. Chem. 275, 23642-23647] and it also negatively regulates integrin signalling through a proline-rich region present in the C-terminus [Liu, Hill and Chernoff (1996) J. Biol. Chem. 271, 31290-31295; Liu, Sells and Chernoff (1998) Curr. Biol. 8, 173-176]. Here we show that PTP1B mutants that are defective in Src homology 3 domain binding fully retain the ability to inhibit insulin signalling, whereas mutants defective in insulin-receptor binding fully retain the ability to inhibit integrin signalling. In contrast, both the C-terminal proline-rich region and the tandem tyrosine residues present in the N-terminal region are required for the activation of Src family kinases. These data show that PTP1B can independently regulate insulin and integrin signals, and that Src might represent a convergence point for regulating signal transduction by this phosphatase.
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Affiliation(s)
- Shrikrishna Dadke
- Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA
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69
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Abstract
Immortalized brown adipocyte cell lines have been generated from fetuses of mice deficient in the insulin-like growth factor I receptor gene (IGF-IR(-/-)), as well as from fetuses of wild-type mice (IGF-IR(+/+)). These cell lines maintained the expression of adipogenic- and thermogenic-differentiation markers and show a multilocular fat droplets phenotype. IGF-IR(-/-) brown adipocytes lacked IGF-IR protein expression; insulin receptor (IR) expression remained unchanged as compared with wild-type cells. Insulin-induced tyrosine autophosphorylation of the IR beta-chain was augmented in IGF-IR--deficient cells. Upon insulin stimulation, tyrosine phosphorylation of (insulin receptor substrate-1) IRS-1 was much higher in IGF-IR(-/-) brown adipocytes, although IRS-1 protein content was reduced. In contrast, tyrosine phosphorylation of IRS-2 decreased in IGF-IR--deficient cells; its protein content was unchanged as compared with wild-type cells. Downstream, the association IRS-1/growth factor receptor binding protein-2 (Grb-2) was augmented in the IGF-IR(-/-) brown adipocyte cell line. However, SHC expression and SHC tyrosine phosphorylation and its association with Grb-2 were unaltered in response to insulin in IGF-IR--deficient brown adipocytes. These cells also showed an enhanced activation of mitogen-activated protein kinase (MAPK) kinase (MEK1/2) and p42/p44 mitogen-activated protein kinase (MAPK) upon insulin stimulation. In addition, the lack of IGF-IR in brown adipocytes resulted in a higher mitogenic response (DNA synthesis, cell number, and proliferating cell nuclear antigen expression) to insulin than wild-type cells. Finally, cells lacking IGF-IR showed a much lower association between IR or IRS-1 and phosphotyrosine phosphatase 1B (PTP1B) and also a decreased PTP1B activity upon insulin stimulation. However, PTP1B/Grb-2 association remained unchanged in both cell types, regardless of insulin stimulation. Data presented here provide strong evidence that IGF-IR--deficient brown adipocytes show an increased insulin sensitivity via IRS-1/Grb-2/MAPK, resulting in an increased mitogenesis in response to insulin.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport
- Adipose Tissue, Brown/drug effects
- Adipose Tissue, Brown/embryology
- Animals
- Cell Division/drug effects
- Cell Line, Transformed
- Enzyme Activation
- GRB2 Adaptor Protein
- Gene Expression
- Insulin/pharmacology
- Insulin Receptor Substrate Proteins
- Insulin-Like Growth Factor I/pharmacology
- Intracellular Signaling Peptides and Proteins
- MAP Kinase Kinase 1
- MAP Kinase Kinase 2
- Mice
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinase Kinases/metabolism
- Mitogen-Activated Protein Kinases/metabolism
- Phosphoproteins/metabolism
- Phosphorylation
- Phosphotyrosine/metabolism
- Protein Serine-Threonine Kinases/metabolism
- Protein Tyrosine Phosphatase, Non-Receptor Type 1
- Protein Tyrosine Phosphatases/metabolism
- Protein-Tyrosine Kinases/metabolism
- Proteins/metabolism
- Receptor, IGF Type 1/deficiency
- Receptor, IGF Type 1/genetics
- Receptor, IGF Type 1/physiology
- Shc Signaling Adaptor Proteins
- Src Homology 2 Domain-Containing, Transforming Protein 1
- fas Receptor/genetics
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Affiliation(s)
- Cecilia Mur
- Departamento de Bioquímica y Biología Molecular, Centro Mixto CSIC/UCM, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
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70
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Béréziat V, Kasus-Jacobi A, Perdereau D, Cariou B, Girard J, Burnol AF. Inhibition of insulin receptor catalytic activity by the molecular adapter Grb14. J Biol Chem 2002; 277:4845-52. [PMID: 11726652 DOI: 10.1074/jbc.m106574200] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Grb14 belongs to the Grb7 family of adapters and was recently identified as a partner of the insulin receptor (IR). Here we show that Grb14 inhibits in vitro IR substrate phosphorylation. Grb14 does not alter the K(m) for ATP and behaves as an uncompetitive inhibitor for the IR substrate. Similar experiments performed with other members of the Grb7 family, Grb7 and Grb10, and with IGF-1 receptor argue in favor of a specific inhibition of the IR catalytic activity by Grb14. The IR-interacting domain of Grb14, the PIR, is sufficient for the inhibitory effect of Grb14, whereas the SH2 domain has no effect on IR catalytic activity. In Chinese hamster ovary (CHO) cells overexpressing both IR and Grb14, Grb14 binds to the IR as early as 1 min after insulin stimulation, and the two proteins remain associated. When interacting with Grb14, the IR is protected against tyrosine phosphatases action and therefore maintained under a phosphorylated state. However, the binding of Grb14 to the IR induces an early delay in the activation of Akt and ERK1/2 in CHO-IR cells, and ERK1/2 are less efficiently phosphorylated. These findings show that Grb14 is a direct inhibitor of the IR catalytic activity and could be considered as a modulator of insulin signaling.
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Affiliation(s)
- Veronique Béréziat
- Endocrinologie et Métabolisme, CNRS UPR 1524 Institut Cochin de Genetique Moleculaire, 24 rue du Faubourg Saint-Jacques, 75674 Paris Cedex 14, France
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71
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Cheng A, Dubé N, Gu F, Tremblay ML. Coordinated action of protein tyrosine phosphatases in insulin signal transduction. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:1050-9. [PMID: 11856336 DOI: 10.1046/j.0014-2956.2002.02756.x] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Insulin is the principal regulatory hormone involved in the tight regulation of fuel metabolism. In response to blood glucose levels, it is secreted by the beta cells of the pancreas and exerts its effects by binding to cell surface receptors that are present on virtually all cell types and tissues. In humans, perturbations in insulin function and/or secretion lead to diabetes mellitus, a severe disorder primarily characterized by an inability to maintain blood glucose homeostasis. Furthermore, it is estimated that 90-95% of diabetic patients exhibit resistance to insulin action. Thus an understanding of insulin signal transduction and insulin resistance at the molecular level is crucial to the understanding of the pathogenesis of this disease. The insulin receptor (IR) is a transmembrane tyrosine kinase that becomes activated upon ligand binding. Consequently, the receptor and its downstream substrates become tyrosine phosphorylated. This activates a series of intracellular signaling cascades which coordinately initiate the appropriate biological response. One important mechanism by which insulin signaling is regulated involves the protein tyrosine phosphatases (PTPs), which may either act on the IR itself and/or its substrates. Two well characterized examples include leuckocyte antigen related (LAR) and protein tyrosine phosphatase-1B (PTP-1B). The present review will discuss the current knowledge of these two and other potential PTPs involved in the insulin signaling pathway.
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Affiliation(s)
- Alan Cheng
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
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72
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Wang J, Cheung AT, Kolls JK, Starks WW, Martinez-Hernandez A, Dietzen D, Bryer-Ash M. Effects of adenovirus-mediated liver-selective overexpression of protein tyrosine phosphatase-1b on insulin sensitivity in vivo. Diabetes Obes Metab 2001; 3:367-80. [PMID: 11703427 DOI: 10.1046/j.1463-1326.2001.00173.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM Protein tyrosine phosphatase-1B (PTP-1B) is an intracellular PTP known to dephosphorylate and inactivate upstream tyrosine phosphoproteins in the insulin signalling cascade. We and others reported increased abundance of catalytically impaired PTP-1B in tissue lysates from obese human subjects with and without type 2 diabetes, while genetic knockout of PTP-1B improves insulin sensitivity and prevents nutritionally mediated insulin resistance and obesity. The aim of the present work was to further elucidate the role of PTP-1B in glucose metabolism in vivo. METHODS We used adenoviral constructs incorporating cDNAs for either wild-type (W/T) or a catalytically inactive C(215)S (C/S) mutant PTP-1B to achieve liver-selective PTP-1B overexpression in young Sprague-Dawley rats using tail vein injection, based on the high degree of hepatotropism of adenovirus 5 (Ad5). An Ad5-lacZ construct encoding beta-galactosidase was used as a control for viral effects alone. A hyperinsulinaemic euglycaemic clamp was used to study whole body glucose disposal and endogenous glucose production rates. RESULTS Control studies in HIRcB cells confirmed catalytic activity and inactivity of W/T and C/S respectively. Mean PTP-1B abundance was 2.24 +/- 0.02- and 2.33 +/- 0.04-fold of saline-treated control in liver lysates of W/T and C/S rats respectively. Liver selective overexpression was confirmed by analysis of tissue lysates from liver, fat and muscle tissues. Ad5 treatment did not result in a statistically or clinically significant liver injury, as determined by serum alanine aminotransferase and histological examination. Seven days post injection, no significant difference in rate of weight gain, fasting blood glucose or insulin levels were seen in any group. Similarly, under steady-state glucose clamp conditions, glucose disposal rate (R(d)), endogenous glucose production rate (EGP) and serum insulin levels were similar in all groups. CONCLUSION We conclude that moderate medium-term overabundance, to a degree resembling that seen in insulin-resistant states, of PTP-1B in liver tissue does not alter insulin action on glucose metabolism and that the major site of action of PTP-1B is presumably at insulin-responsive target tissue or tissues other than the liver.
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Affiliation(s)
- J Wang
- University of Tennessee, Memphis, TN, USA
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73
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Dadke S, Kusari A, Kusari J. Phosphorylation and activation of protein tyrosine phosphatase (PTP) 1B by insulin receptor. Mol Cell Biochem 2001; 221:147-54. [PMID: 11506178 DOI: 10.1023/a:1010909031310] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have previously reported a direct in vivo interaction between the activated insulin receptor and protein-tyrosine phosphatase-1B (PTP1B), which leads to an increase in PTP1B tyrosine phosphorylation. In order to determine if PTP1B is a substrate for the insulin receptor tyrosine kinase, the phosphorylation of the Cys 215 Ser, catalytically inactive mutant PTP1B (CS-PTP1B) was measured in the presence of partially purified and activated insulin receptor. In vitro, the insulin receptor tyrosine kinase catalyzed the tyrosine phosphorylation of PTP1B. 53% of the total cellular PTP1B became tyrosine phosphorylated in response to insulin in vivo. Tyrosine phosphorylation of PTP1B by the insulin receptor was absolutely dependent upon insulin-stimulated receptor autophosphorylation and required an intact kinase domain, containing insulin receptor tyrosines 1146, 1150 and 1151. Tyrosine phosphorylation of wild type PTP1B by the insulin receptor kinase increased phosphatase activity of the protein. Intermolecular transdephosphorylation was demonstrated both in vitro and in vivo, by dephosphorylation of phosphorylated CS-PTP1B by the active wild type enzyme either in a cell-free system or via expression of the wild type PTP1B into Hirc-M cell line, which constitutively overexpress the human insulin receptor and CS-PTP1B. These results suggest that PTP1B is a target protein for the insulin receptor tyrosine kinase and PTP1B can regulate its own phosphatase activity by maintaining the balance between its phosphorylated (the active form) and dephosphorylated (the inactive form) state.
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Affiliation(s)
- S Dadke
- Department of Physiology, Tulane University School of Medicine, New Orleans, LA, USA
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74
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Dadke SS, Li HC, Kusari AB, Begum N, Kusari J. Elevated expression and activity of protein-tyrosine phosphatase 1B in skeletal muscle of insulin-resistant type II diabetic Goto-Kakizaki rats. Biochem Biophys Res Commun 2000; 274:583-9. [PMID: 10924321 DOI: 10.1006/bbrc.2000.3188] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the cellular mechanism(s) of insulin resistance associated with non-insulin dependent diabetes mellitus (NIDDM) using skeletal muscles isolated from non-obese, insulin resistant type II diabetic Goto-Kakizaki (GK) rats, a well known genetic rat model for type II diabetic humans. Relative to non-diabetic control rats (WKY), insulin-stimulated insulin receptor (IR) autophosphorylation and insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation were significantly inhibited in GK skeletal muscles. This may be due to increased dephosphorylation by a protein tyrosine phosphatase (PTPase). Therefore, we measured skeletal muscle total PTPase and PTPase 1B activities in the skeletal muscles isolated from control rats (WKY) and diabetic Goto-Kakizaki (GK) rats. PTPase activity was measured using a synthetic phosphopeptide, TRDIY(P)ETDY(P)Y(P)RK, as the substrate. Basal PTPase activity was 2-fold higher (P < 0.001) in skeletal muscle of GK rats when compared to WKY. Insulin infusion inhibited skeletal muscle PTPase activity in both control (26.20% of basal, P < 0.001) and GK (25.35% of basal, P < 0.001) rats. However, PTPase activity in skeletal muscle of insulin-stimulated GK rats was 200% higher than hormone-treated WKY controls (P < 0.001). Immunoprecipitation of PTPase 1B from skeletal muscle lysates and analysis of the enzyme activity in immunoprecipitates indicated that both basal and insulin-stimulated PTPase 1B activities were significantly higher (twofold, P < 0.001) in skeletal muscle of diabetic GK rats when compared to WKY controls. The increase in PTPase 1B activity in diabetic GK rats was associated with an increased expression of the PTPase 1B protein. We concluded that insulin resistance of GK rats is accompanied atleast by an abnormal regulation of PTPase 1B. Elevated PTPase 1B activity through enhanced tyrosine dephosphorylation of the insulin receptor and its substrates, may lead to impaired glucose tolerance and insulin resistance in GK rats.
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Affiliation(s)
- S S Dadke
- Department of Physiology, Tulane University School of Medicine, New Orleans, Louisianna, USA
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