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Birajdar SV, Mazahir F, Alam MI, Kumar A, Yadav AK. Repurposing and clinical attributes of antidiabetic drugs for the treatment of neurodegenerative disorders. Eur J Pharmacol 2023; 961:176117. [PMID: 37907134 DOI: 10.1016/j.ejphar.2023.176117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 10/03/2023] [Accepted: 10/12/2023] [Indexed: 11/02/2023]
Abstract
The risk of neurodegeneration was found to be increased among people with type 2 diabetes mellitus (T2DM). Brain disorders like Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic lateral sclerosis, and others are considered neurodegenerative diseases and can be characterized by progressive loss of neurons. The deficiency of insulin, impaired signaling, and its resistance lead to alteration in the neuronal functioning of the brain. Insulin degrading enzyme (IDE) plays a significant role in the amyloid β metabolism, aggregation, and deposition of misfolded proteins in the brain's hippocampal and cortical neuronal regions. The insulin signaling via IP3 activation upregulates the IDE and could be a promising approach to regulate neurodegeneration. The repurposing of existing antidiabetic drugs such as Metformin, DPP-4 inhibitors, thiazolidinediones, glucagon-like peptides (GLP-1), sodium-glucose co-transport-2 (SGCT-2) inhibitors, and insulin could be an alternative and effective strategy to treat neurodegeneration via modulating insulin signaling, insulin resistance, IDE activity, oxidative stress, mitochondrial dysfunction, serum lipid profile and neuroinflammation in the brain. Antidiabetic medications reduce the risk of neuroinflammation, oxidative stress, and Aβ deposition by enhancing their clearance rate. The downregulation of IDE alters the degradation of Aβ monomers in the Tg2576 APP mice. Also, the treatment with metformin activated the AMPK pathway and suppressed mTOR and BACE-1 protein expression in the APP/PS1-induced mice model. Thus, the primary intention of this review is to explore the link between T2DM and neurodegenerative disorders, and the possible role of various antidiabetic drugs in the management of neurodegenerative disorders.
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Affiliation(s)
- Swapnali Vasant Birajdar
- Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER) Raebareli, Lucknow, 226002, Uttar Pradesh, India
| | - Farhan Mazahir
- Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER) Raebareli, Lucknow, 226002, Uttar Pradesh, India
| | - Md Imtiyaz Alam
- Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER) Raebareli, Lucknow, 226002, Uttar Pradesh, India
| | - Amit Kumar
- Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER) Raebareli, Lucknow, 226002, Uttar Pradesh, India
| | - Awesh K Yadav
- Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER) Raebareli, Lucknow, 226002, Uttar Pradesh, India.
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2
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Amaral LMPF, Moniz T, Silva AMN, Rangel M. Vanadium Compounds with Antidiabetic Potential. Int J Mol Sci 2023; 24:15675. [PMID: 37958659 PMCID: PMC10650557 DOI: 10.3390/ijms242115675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/19/2023] [Accepted: 10/24/2023] [Indexed: 11/15/2023] Open
Abstract
Over the last four decades, vanadium compounds have been extensively studied as potential antidiabetic drugs. With the present review, we aim at presenting a general overview of the most promising compounds and the main results obtained with in vivo studies, reported from 1899-2023. The chemistry of vanadium is explored, discussing the importance of the structure and biochemistry of vanadate and the impact of its similarity with phosphate on the antidiabetic effect. The spectroscopic characterization of vanadium compounds is discussed, particularly magnetic resonance methodologies, emphasizing its relevance for understanding species activity, speciation, and interaction with biological membranes. Finally, the most relevant studies regarding the use of vanadium compounds to treat diabetes are summarized, considering both animal models and human clinical trials. An overview of the main hypotheses explaining the biological activity of these compounds is presented, particularly the most accepted pathway involving vanadium interaction with phosphatase and kinase enzymes involved in the insulin signaling cascade. From our point of view, the major discoveries regarding the pharmacological action of this family of compounds are not yet fully understood. Thus, we still believe that vanadium presents the potential to help in metabolic control and the clinical management of diabetes, either as an insulin-like drug or as an insulin adjuvant. We look forward to the next forty years of research in this field, aiming to discover a vanadium compound with the desired therapeutic properties.
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Affiliation(s)
- Luísa M. P. F. Amaral
- LAQV, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, s/n, 40169-007 Porto, Portugal; (L.M.P.F.A.); (T.M.)
| | - Tânia Moniz
- LAQV, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, s/n, 40169-007 Porto, Portugal; (L.M.P.F.A.); (T.M.)
- LAQV, REQUIMTE, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - André M. N. Silva
- LAQV, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, s/n, 40169-007 Porto, Portugal; (L.M.P.F.A.); (T.M.)
- LAQV, REQUIMTE, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Maria Rangel
- LAQV, REQUIMTE, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
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3
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Therapeutic Properties of Vanadium Complexes. INORGANICS 2022. [DOI: 10.3390/inorganics10120244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Vanadium is a hard, silver-grey transition metal found in at least 60 minerals and fossil fuel deposits. Its oxide and other vanadium salts are toxic to humans, but the toxic effects depend on the vanadium form, dose, exposure duration, and route of intoxication. Vanadium is used by some life forms as an active center in enzymes, such as the vanadium bromoperoxidase of ocean algae and nitrogenases of bacteria. The structure and biochemistry of vanadate resemble those of phosphate, hence vanadate can be regarded as a phosphate competitor in a variety of biochemical enzymes such as kinases and phosphatases. In this review, we describe the biochemical pathways regulated by vanadium compounds and their potential therapeutic benefits for a range of disorders including type 2 diabetes, cancer, cardiovascular disease, and microbial pathology.
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Increased O-GlcNAcylation promotes IGF-1 receptor/PhosphatidyI Inositol-3 kinase/Akt pathway in cervical cancer cells. Sci Rep 2022; 12:4464. [PMID: 35296731 PMCID: PMC8927345 DOI: 10.1038/s41598-022-08445-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 03/04/2022] [Indexed: 12/28/2022] Open
Abstract
O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) is a reversible post-translational modification on serine and threonine residues of cytosolic, nuclear and mitochondrial proteins. O-GlcNAcylation level is regulated by OGT (O-GlcNAc transferase), which adds GlcNAc on proteins, and OGA (O-GlcNAcase), which removes it. Abnormal level of protein O-GlcNAcylation has been observed in numerous cancer cell types, including cervical cancer cells. In the present study, we have evaluated the effect of increasing protein O-GlcNAcylation on cervical cancer-derived CaSki cells. We observed that pharmacological enhancement of protein O-GlcNAcylation by Thiamet G (an inhibitor of OGA) and glucosamine (which provides UDP-GlcNAc substrate to OGT) increases CaSki cells proliferation, migration and survival. Moreover, we showed that increased O-GlcNAcylation promotes IGF-1 receptor (IGF1R) autophosphorylation, possibly through inhibition of protein tyrosine-phosphatase 1B activity. This was associated with increased IGF-1-induced phosphatidyl-Inositol 3-phosphate production at the plasma membrane and increased Akt activation in CaSki cells. Finally, we showed that protein O-GlcNAcylation and Akt phosphorylation levels were higher in human cervical cancer samples compared to healthy cervix tissues, and a highly positive correlation was observed between O-GlcNAcylation level and Akt phosphorylation in theses tissues. Together, our results indicate that increased O-GlcNAcylation, by activating IGF1R/ Phosphatidyl inositol 3-Kinase (PI-3K)/Akt signaling, may participate in cervical cancer cell growth and proliferation.
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Sampath H, Ntambi JM. The role of stearoyl-CoA desaturase in obesity, insulin resistance, and inflammation. Ann N Y Acad Sci 2012; 1243:47-53. [PMID: 22211892 DOI: 10.1111/j.1749-6632.2011.06303.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Stearoyl-CoA desaturase 1 (SCD1) is an essential lipogenic enzyme that has been shown to play an intrinsic role in the development of obesity and related conditions, such as insulin resistance. Through the generation of various mouse models of SCD1 deficiency, we have come to understand that SCD1 plays a role, directly or indirectly, in diverse metabolic processes, including lipogenesis, fatty acid oxidation, insulin signaling, thermogenesis, and inflammation. This review will address recent advances in our understanding of this key regulator of cellular metabolic processes, including the role of SCD1 in maintaining skin barrier integrity and the role of skin SCD1 in the metabolic phenotype elicited by global SCD1 deficiency.
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Affiliation(s)
- Harini Sampath
- Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, Oregon, USA
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6
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Mitra A, Kalayarasan S, Gupta V, Radha V. TC-PTP dephosphorylates the guanine nucleotide exchange factor C3G (RapGEF1) and negatively regulates differentiation of human neuroblastoma cells. PLoS One 2011; 6:e23681. [PMID: 21876762 PMCID: PMC3158094 DOI: 10.1371/journal.pone.0023681] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 07/24/2011] [Indexed: 11/29/2022] Open
Abstract
The guanine nucleotide exchange factor, C3G (RapGEF1), functions in multiple signaling pathways involved in cell adhesion, proliferation, apoptosis and actin reorganization. C3G is regulated by tyrosine phosphorylation on Y504, known to be mediated by c-Abl and Src family kinases. In the present study we explored the possibility of cellular phospho-C3G (pC3G) being a substrate of the intracellular T-cell protein tyrosine phosphatase TC-PTP (PTPN2) using the human neuroblastoma cell line, IMR-32. In vivo and in vitro binding assays demonstrated interaction between C3G and TC-PTP. Interaction is mediated through the Crk-binding region of C3G and C-terminal noncatalytic residues of TC-PTP. C3G interacted better with a substrate trap mutant of TC48 and this complex formation was inhibited by vanadate. Endogenous pC3G colocalized with catalytically inactive mutant TC48 in the Golgi. Expression of TC48 abrogated pervanadate and c-Src induced phosphorylation of C3G without affecting total cellular phospho-tyrosine. Insulin-like growth factor treatment of c-Src expressing cells resulted in dephosphorylation of C3G dependent on the activity of endogenous TC48. TC48 expression inhibited forskolin induced tyrosine phosphorylation of C3G and neurite outgrowth in IMR-32 cells. Our results identify a novel Golgi localized substrate of TC48 and delineate a role for TC48 in dephosphorylation of substrates required during differentiation of human neuroblastoma cells.
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Affiliation(s)
- Aninda Mitra
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, Andhra Pradesh, India
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7
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Abstract
The phosphoinositide (PI) cycle, discovered over 50 years ago by Mabel and Lowell Hokin, describes a series of biochemical reactions that occur on the inner leaflet of the plasma membrane of cells in response to receptor activation by extracellular stimuli. Studies from our laboratory have shown that the retina and rod outer segments (ROSs) have active PI metabolism. Biochemical studies revealed that the ROSs contain the enzymes necessary for phosphorylation of phosphoinositides. We showed that light stimulates various components of the PI cycle in the vertebrate ROS, including diacylglycerol kinase, PI synthetase, phosphatidylinositol phosphate kinase, phospholipase C, and phosphoinositide 3-kinase (PI3K). This article describes recent studies on the PI3K-generated PI lipid second messengers in the control and regulation of PI-binding proteins in the vertebrate retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology and Cell Biology, and Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. r
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Rajala RVS, Tanito M, Neel BG, Rajala A. Enhanced retinal insulin receptor-activated neuroprotective survival signal in mice lacking the protein-tyrosine phosphatase-1B gene. J Biol Chem 2010; 285:8894-904. [PMID: 20061388 DOI: 10.1074/jbc.m109.070854] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein-tyrosine phosphatase 1B (PTP1B) has been implicated in the negative regulation of insulin signaling. We previously demonstrated that light-induced tyrosine phosphorylation of the retinal insulin receptor (IR) results in the activation of phosphoinositide 3-kinase/Akt survival pathway in rod photoreceptor cells. The molecular mechanism behind light-induced activation of IR is not known. We investigated the in vivo mechanism of IR activation and found that PTP1B activity in dark-adapted retinas was significantly higher than in light-adapted retinas. We made a novel finding in this study that the light-dependent regulation of PTP1B activity is signaled through photobleaching of rhodopsin. Conditional deletion of PTP1B in rod photoreceptors by the Cre-loxP system resulted in enhanced IR signaling. Further PTP1B activity negatively regulated the neuroprotective survival signaling in the retina. One of the challenging questions in the retina research is how mutations in human rhodopsin gene slowly disable and eventually disrupt photoreceptor functions. Our studies suggest that a defect in the photobleaching of rhodopsin and mutation in rhodopsin gene enhances the activity of PTP1B, and this activated activity could down-regulate the IR survival signaling. Our studies suggest that PTP1B antagonists could be potential therapeutic agents to treat stress-induced photoreceptor degenerations and provide further evidence that rhodopsin photoexcitation may trigger signaling events alternative to the classic phototransduction.
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Affiliation(s)
- Raju V S Rajala
- Department of Ophthalmology, Dean A McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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9
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Aga-Mizrachi S, Brutman-Barazani T, Jacob AI, Bak A, Elson A, Sampson SR. Cytosolic protein tyrosine phosphatase-epsilon is a negative regulator of insulin signaling in skeletal muscle. Endocrinology 2008; 149:605-14. [PMID: 18006633 DOI: 10.1210/en.2007-0908] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Whereas positive regulatory events triggered by insulin binding to insulin receptor (IR) have been well documented, the mechanism by which the activated IR is returned to the basal status is not completely understood. Recently studies focused on the involvement of protein tyrosine phosphatases (PTPs) and how they might influence IR signaling. In this study, we examined the possibility that cytosolic PTPepsilon (cytPTPepsilon) is involved in IR signaling. Studies were performed on L6 skeletal muscle cells. cytPTPepsilon was overexpressed by using pBABE retroviral expression vectors. In addition, we inhibited cytPTPepsilon by RNA silencing. We found that insulin induced rapid association of cytPTPepsilon with IR. Interestingly, this association appeared to occur in the plasma membrane and on stimulation with insulin the two proteins internalized together. Moreover, it appeared that almost all internalized IR was associated with cytPTPepsilon. We found that knockdown of cytPTPepsilon by RNA silencing increased insulin-induced tyrosine phosphorylation of IR and IR substrate (IRS)-1 as well as phosphorylation of protein kinase B and glycogen synthase kinase-3 and insulin-induced stimulation of glucose uptake. Moreover, overexpression of wild-type cytPTPepsilon reduced insulin-induced tyrosine phosphorylation of IR, IRS-1, and phosphorylation of protein kinase B and glycogen synthase kinase-3 and insulin-induced stimulation of glucose uptake. Finally, insulin-induced tyrosine phosphorylation of IR and IRS-1 was greater in skeletal muscle from mice lacking the cytPTPepsilon gene than that from wild-type control animals. We conclude that cytPTPepsilon serves as another major candidate negative regulator of IR signaling in skeletal muscle.
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Affiliation(s)
- Shlomit Aga-Mizrachi
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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10
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Grünblatt E, Salkovic-Petrisic M, Osmanovic J, Riederer P, Hoyer S. Brain insulin system dysfunction in streptozotocin intracerebroventricularly treated rats generates hyperphosphorylated tau protein. J Neurochem 2007; 101:757-70. [PMID: 17448147 DOI: 10.1111/j.1471-4159.2006.04368.x] [Citation(s) in RCA: 274] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The intracerebroventricular (icv) application of streptozotocin (STZ) in low dosage was used in 3-month-old rats to explore brain insulin system dysfunction. Three months following STZ icv treatment, the expression of insulin-1 and -2 mRNA was significantly reduced to 11% in hippocampus and to 28% in frontoparietal cerebral cortex, respectively. Insulin receptor (IR) mRNA expression decreased significantly in frontoparietal cerebral cortex and hippocampus (16% and 33% of control). At the protein/activity level, different abnormalities of protein tyrosine kinase activity (increase in hippocampus), total IR beta-subunit (decrease in hypothalamus) and phosphorylated IR tyrosine residues (increase) became apparent. The STZ-induced disturbance in learning and memory capacities was not abolished by icv application of glucose transport inhibitors known to prevent STZ-induced diabetes mellitus. The discrepancy between reduced IR gene expression and increase in both phosphorylated IR tyrosine residues/protein tyrosine kinase activity may indicate imbalance between phosphorylation/dephosphorylation of the IR beta-subunit causing its dysfunction. These abnormalities may point to a complex brain insulin system dysfunction after STZ icv application, which may lead to an increase in hyperphosphorylated tau-protein concentration. Brain insulin system dysfunction is discussed as possible pathological core in the generation of hyperphosphorylated tau protein as a morphological marker of sporadic Alzheimer's disease.
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Affiliation(s)
- Edna Grünblatt
- Clinical Neurochemistry and National Parkinson Foundation Centre of Excellence Laboratory, Clinic for Psychiatry and Psychotherapy, Bayrische Julius-Maximilian University of Würzburg, Würzburg, Germany.
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11
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Inada S, Ikeda Y, Suehiro T, Takata H, Osaki F, Arii K, Kumon Y, Hashimoto K. Glucose enhances protein tyrosine phosphatase 1B gene transcription in hepatocytes. Mol Cell Endocrinol 2007; 271:64-70. [PMID: 17509747 DOI: 10.1016/j.mce.2007.04.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 04/15/2007] [Accepted: 04/19/2007] [Indexed: 01/11/2023]
Abstract
Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of the insulin receptor signal transduction pathway. We investigated the effects of glucose on PTP1B transcription in the human hepatocyte cell line Huh7. Using a reporter gene assay, we found that D-glucose dose-dependently enhanced the PTP1B promoter activity. Real-time PCR demonstrated that D-glucose also increased PTP1B mRNA expression. Protein kinase C (PKC) inhibitors partially but significantly inhibited the transactivation by D-glucose. Mithramycin, a Sp1 inhibitor, completely abrogated this transactivation. The deletion of three possible Sp1 sites in the promoter region of PTP1B significantly reduced the basal promoter activity and transactivation by D-glucose. Sp1 activation by PKC is one of the key mechanisms in the regulation of several gene expressions. Our data suggested that glucose enhanced PTP1B transcription through Sp1 activation by PKC. Increased hepatic PTP1B expression may partly explain glucose toxicity in diabetes.
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Affiliation(s)
- Shojiro Inada
- Department of Endocrinology, Metabolism and Nephrology, Kochi Medical School, Kochi University, Kohasu, Nankoku, Kochi 783-8505, Japan
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12
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Salkovic-Petrisic M, Hoyer S. Central insulin resistance as a trigger for sporadic Alzheimer-like pathology: an experimental approach. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2007:217-33. [PMID: 17982898 DOI: 10.1007/978-3-211-73574-9_28] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
A growing body of evidence implicates impairments in brain insulin signaling in early sporadic Alzheimer disease (sAD) pathology. However, the most widely accepted hypothesis for AD aetiology stipulates that pathological aggregations of the amyloid beta (Abeta) peptide are the cause of all forms of Alzheimer's disease. Streptozotocin-intracerebroventricularly (STZ-icv) treated rats are proposed as a probable experimental model of sAD. The current work reviews evidence obtained from this model indicating that central STZ administration induces brain pathology and behavioural alterations resembling those in sAD patients. Recently, alterations of the brain insulin system resembling those in sAD have been found in the STZ-icv rat model and are associated with tau protein hyperphosphorylation and Abeta-like aggregations in meningeal vessels. In line with these findings the hypothesis has been proposed that insulin resistance in the brain might be the primary event which precedes the Abeta pathology in sAD.
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Affiliation(s)
- M Salkovic-Petrisic
- Department of Pharmacology and Croatian Institute for Brain Research, Medical School, University of Zagreb, Zagreb, Croatia.
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Morrison CD, White CL, Wang Z, Lee SY, Lawrence DS, Cefalu WT, Zhang ZY, Gettys TW. Increased hypothalamic protein tyrosine phosphatase 1B contributes to leptin resistance with age. Endocrinology 2007; 148:433-40. [PMID: 17038557 PMCID: PMC2596872 DOI: 10.1210/en.2006-0672] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Animals at advanced ages exhibit a reduction in central leptin sensitivity. However, changes in growth, metabolism, and obesity risk occur much earlier in life, particularly during the transition from youth to middle age. To determine when initial decreases in central leptin sensitivity occur, leptin-dependent suppression of food intake was tested in 8-, 12-, and 20-wk-old male, chow-fed Sprague Dawley rats. Intracerebroventricular leptin injection (3 microg) suppressed 24-h food intake in 8- and 12-wk-old rats (P < 0.05) but not 20-wk-old rats. To identify potential cellular mediators of this resistance, we focused on protein tyrosine phosphatase 1B (PTP1B), a recently described inhibitor of leptin signaling. PTP1B protein levels, as determined by Western blot, were significantly higher in mediobasal hypothalamic punches collected from 20-wk-old rats, compared with 8-wk-old rats (P < 0.05). When 20-wk-old rats were fasted for 24 h, levels of hypothalamic PTP1B decreased (P < 0.05), coincident with a restoration of leptin sensitivity. To directly test whether inhibition of PTP1B restores leptin sensitivity, 20-wk-old chow-fed rats were pretreated with a pharmacological PTP1B inhibitor 1 h before leptin, and 24-h food intake was recorded. As expected, leptin alone produced a small but nonsignificant reduction in food intake. However, pretreatment with the PTP1B inhibitor resulted in a marked improvement in leptin-dependent suppression of food intake (P < 0.05). These data are consistent with the hypothesis that increases in PTP1B contribute to hypothalamic leptin resistance as rats transition into middle age.
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Affiliation(s)
- Christopher D Morrison
- Neurosignaling Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, USA.
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14
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Abstract
Type 2 diabetes and obesity are characterised by insulin and leptin resistance. Studies suggest that these may be due to defects in the insulin and leptin signalling pathways. Over the last decade, a considerable body of evidence has been amassed indicating that protein tyrosine phosphatase 1B (PTP1B) is involved in the downregulation of insulin and leptin signalling. Consequently, compounds that inhibit PTP1B have potential as therapeutics for treating Type 2 diabetes and obesity. This review covers recent advances in PTP1B inhibitors with an emphasis on recent attempts to create potent, selective and cell-permeable small-molecule inhibitors.
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Affiliation(s)
- Scott D Taylor
- Department of Chemistry, University of Waterloo, Ontario, Canada.
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15
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Gouni-Berthold I, Giannakidou E, Müller-Wieland D, Faust M, Kotzka J, Berthold HK, Krone W. The Pro387Leu variant of protein tyrosine phosphatase-1B is not associated with diabetes mellitus type 2 in a German population. J Intern Med 2005; 257:272-80. [PMID: 15715684 DOI: 10.1111/j.1365-2796.2004.01446.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVES Diabetes mellitus type 2 (DM-2) is a complex disorder with a strong genetic background. Protein tyrosine phosphatase-1B (PTP-1B) dephosphorylates various receptor protein kinases in vitro, including the beta subunit of the insulin receptor, therefore representing a potential candidate to be involved in the polygenic pathogenesis of DM-2. Recently a Pro387Leu variant of the PTP-1B gene has been associated with an increased risk of DM-2 in a Danish population. Reports from China and Finland failed to confirm this association. DESIGN, SETTING AND SUBJECTS The purpose of the present study was to examine the possible association between the presence of DM-2 and the Pro387Leu polymorphism in a German Caucasian population. A total of 836 subjects (age 20-92 years) participated in the study. The presence of the Pro387Leu variant of the PTP-1B gene was investigated using polymerase chain reaction (PCR) restriction fragment-length polymorphism in 402 subjects with DM-2 (231 men, 171 women, age 63.1 +/- 10.8 years, BMI 28.7 +/- 5.1 kg m(-2)) and in 434 normoglycemic age- and sex-matched control subjects (248 men, 186 women, age 64.4 +/- 6.5 years, BMI 26.5 +/- 3.7 kg m(-2)). RESULTS Nine subjects in the control group and nine in the diabetic group (allelic frequency 0.99% in both groups) carried the Pro387Leu polymorphism. A meta-analysis on published data of >3000 subjects including our own data did not find an association between the polymorphism and DM-2. In addition, the polymorphism had no significant influence on the presence of atherosclerotic disease, whilst the influence of other known cardiovascular risk factors was confirmed. Furthermore, the impact of the mutation on metabolic and anthropometric parameters in both groups was examined. Amongst the controls there were no significant differences in BMI, HDL and LDL cholesterol or blood pressure between the two groups with or without the Pro387Leu polymorphism. The same was true for the diabetic group. Interestingly, in both diabetics and controls, Pro387Leu carriers had significantly higher triglycerides. In a logistic regression model only BMI and family history but not polymorphism were predictors of DM-2. CONCLUSIONS In conclusion, the present data suggest that in a German Caucasian population the Pro387Leu polymorphism of the PTP-1B gene is not associated with DM-2 but may play a role in other metabolic phenotypes.
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Affiliation(s)
- I Gouni-Berthold
- Department of Internal Medicine II, University of Cologne and Center of Molecular Medicine Cologne (CMMC), Cologne, Germany.
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16
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Evans JL, Jallal B. Protein tyrosine phosphatases: their role in insulin action and potential as drug targets. Expert Opin Investig Drugs 2005; 8:139-60. [PMID: 15992069 DOI: 10.1517/13543784.8.2.139] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Protein tyrosine phosphatases (PTPases) are the enzymes responsible for the selective dephosphorylation of tyrosine residues. PTPases function to regulate a wide array of biological responses mediated by growth factors and other stimuli by balancing the cellular level of phosphotyrosine in concert with their counterparts, protein tyrosine kinases. The important roles which PTPases play in regulating intracellular signalling and, ultimately, biological function along with the recent availability of information regarding their structural features has highlighted them as potential targets for pharmacological modulation. This is demonstrated by the increased level of activity directed towards the identification of novel small-molecule PTPase inhibitors. The rationale and potential utility of this drug discovery approach is discussed here, with particular emphasis on its application for the treatment of insulin resistance and Type 2 diabetes.
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Affiliation(s)
- J L Evans
- Diabetes Program, SUGEN, Inc., 230 East Grand Avenue, San Francisco, CA 94080, USA.
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Wei Y, Chen YJ, Li D, Gu R, Wang WH. Dual effect of insulin-like growth factor on the apical 70-pS K channel in the thick ascending limb of rat kidney. Am J Physiol Cell Physiol 2004; 286:C1258-63. [PMID: 15151916 DOI: 10.1152/ajpcell.00441.2003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used the patch-clamp technique to study the effect of insulin-like growth factor I (IGF-I) on the apical 70-pS K channel in the isolated thick ascending limb (TAL) of the rat kidney. The isolated TAL was cut open to gain access to the apical membrane. Addition of 25 nM IGF-I stimulates the apical 70-pS K channel and increases channel activity, defined by the product of channel open probability and channel number, from 0.31 to 1.21. The stimulatory effect of IGF-I is not mediated by nitric oxide- or protein tyrosine phosphatase-dependent mechanisms, because inhibition of nitric oxide synthase or blocking protein tyrosine phosphatase did not abolish the stimulatory effect of IGF-I on the 70-pS K channel. In contrast, inhibition of mitogen-activated protein (MAP) kinase with PD-98059 or U0126 abolished the stimulatory effect of IGF-I. This suggests that MAP kinase is responsible for mediating the effect of IGF-I on the apical K channels. Moreover, the effect of IGF-I on the apical 70-pS K channel is biphasic because high concentrations (>200 nM) inhibit apical 70-pS K channels. Application of 400 nM IGF-I decreased channel activity from 1.45 to 0.2. The inhibitory effect of IGF-I is not blocked by calphostin C (an inhibitor of PKC), but inhibition of protein tyrosine kinase with herbimycin A abolished the IGF-induced inhibition. We conclude that IGF-I has a dual effect on the apical 70-pS K channel in the TAL: low concentrations of IGF-I stimulate, whereas high concentrations inhibit the channel activity. The stimulatory effect of IGF-I is mediated by a MAP kinase-dependent pathway, whereas the inhibitory effect is the result of stimulation of protein tyrosine kinase.
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Affiliation(s)
- Yuan Wei
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA
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18
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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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Weng J, Yan J, Huang Z, Sui Y, Xiu L. Missense mutation of Pro387Leu in protein tyrosine phosphatase-1B (PTP-1B) is not associated with type 2 diabetes in a Chinese Han population. Diabetes Care 2003; 26:2957. [PMID: 14514610 DOI: 10.2337/diacare.26.10.2957] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Rahman SM, Dobrzyn A, Dobrzyn P, Lee SH, Miyazaki M, Ntambi JM. Stearoyl-CoA desaturase 1 deficiency elevates insulin-signaling components and down-regulates protein-tyrosine phosphatase 1B in muscle. Proc Natl Acad Sci U S A 2003; 100:11110-5. [PMID: 12960377 PMCID: PMC196935 DOI: 10.1073/pnas.1934571100] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2003] [Indexed: 11/18/2022] Open
Abstract
We have shown previously that mice with a targeted disruption in the stearoyl-CoA desaturase 1 gene (SCD1-/-) have increased insulin sensitivity compared with control mice. Here we show that the SCD1-/- mice have increased insulin signaling in muscle. The basal tyrosine phosphorylation of the insulin receptor and insulin receptor substrates 1 and 2 are elevated. The tyrosine phosphorylation of insulin-like growth factor-1 receptor was similar between SCD1+/+ and SCD1-/- mice. The association of insulin receptor substrates 1 and 2 with alphap85 subunit of phosphatidylinositol 3-kinase as well as the phosphorylation of Akt-Ser-473 and Akt-Thr-308 are also elevated in the SCD1-/- mice. Interestingly, the mRNA levels, protein mass, and activity of the protein-tyrosine phosphatase-1B implicated in the attenuation of the insulin signal are reduced in the SCD1-/- mice, whereas the levels of the leukocyte antigen-related protein phosphatase are similar between two groups of mice. The content of glucose transporter 4 in the plasma membrane and basal as well as insulin-mediated glucose uptake are increased in the SCD1-/- mice. In addition, the muscle glycogen content and the activities of glycogen synthase and phosphorylase are increased in the SCD1-/- mice. We hypothesize that loss of SCD1 function induces increased insulin signaling at least in part by a reduction in the expression of protein-tyrosine phosphatase 1B. SCD1 could be a therapeutic target in the treatment of diabetes.
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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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22
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Katz J, Stavropoulos F, Cohen D, Robledo J, Stewart C, Heft M. IGF-1 and insulin receptor expression in the minor salivary gland tissues of Sjögren's syndrome and mucoceles--immunohistochemical study. Oral Dis 2003; 9:7-13. [PMID: 12617251 DOI: 10.1034/j.1601-0825.2003.02898.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To investigate the expression of IGF-1 receptors and insulin receptors on the minor salivary gland (MSG) tissues of patients diagnosed with Sjögren's syndrome (SS) and normal salivary gland tissue surrounding mucoceles. SUBJECTS AND METHODS Five MSG tissue sections from SS and seven from mucocele patients were stained immunohistochemically using antibody to IGF-1 receptor and insulin receptor in a horse radish peroxidase and DAB system. RESULTS The expression of the insulin receptor was increased in the SS sections compared with controls, while the insulin-like growth factor-1 receptor was more intensely expressed in the controls. CONCLUSION The presence of differential expression of receptors for IGF and insulin might suggest a possible role of these growth factors in the pathogenesis of SS.
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Affiliation(s)
- J Katz
- Department of Oral and Maxillofacial Surgery and Diagnostic Sciences, College of Dentistry, University of Florida, Gainesville, FL 32610-0416, USA.
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Hiroki A, Hatakeyama H, Kawakami M, Watanabe T, Takei I, Umezawa K. Antidiabetic effect of a nitrosamine-free dephostatin analogue, methoxime-3,4-dephostatin, in db/db mice. Biomed Pharmacother 2002; 56:179-85. [PMID: 12109810 DOI: 10.1016/s0753-3322(02)00176-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Et-3,4-dephostatin, a protein-tyrosine phosphatase (PTPase) inhibitor, potentiates insulin-dependent signal transduction and shows an antidiabetic effect in mice. However, it contains a nitrosamine moiety that is often mutagenic and carcinogenic. Therefore, we previously designed and synthesized methoxime-3,4-dephostatin as a nitrosamine-free analogue of dephostatin. In the present paper, we studied in situ and in vivo antidiabetic effects of this PTPase inhibitor. Methoxime-3,4-dephostatin induced 2-deoxyglucose transport by mouse 3T3-L1 adipocytes and rat L6 myocytes without insulin. It also inhibited glucagon-induced glucose release from primary culture rat hepatocytes. When hepatocytes were prepared from starved rats, methoxime-3,4-dephostatin did not inhibit the release of glucose, indicating that the chemical may act on glycogenolysis. Oral administration of methoxime-3,4-dephostatin for 3-7 days inhibited the increase in the blood glucose level in type-2 diabetes model db/db mice. It also decreased food and water intakes of mice, but showed no liver or blood toxicity.
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Affiliation(s)
- A Hiroki
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Yokohama, Japan
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24
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Czech MP, Van Renterghem B, Sleeman MW. Insulin Receptor Tyrosine Kinase. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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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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26
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Suzuki T, Hiroki A, Watanabe T, Yamashita T, Takei I, Umezawa K. Potentiation of insulin-related signal transduction by a novel protein-tyrosine phosphatase inhibitor, Et-3,4-dephostatin, on cultured 3T3-L1 adipocytes. J Biol Chem 2001; 276:27511-8. [PMID: 11342532 DOI: 10.1074/jbc.m011726200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously isolated dephostatin from Streptomyces as a novel inhibitor of CD45-associated protein-tyrosine phosphatase. We prepared Et-3,4-dephostatin as a stable analogue and found it to inhibit PTP-1B and SHPTP-1 protein-tyrosine phosphatases selectively but not to inhibit CD45 and leukocyte common antigen-related phosphatase ones effectively. Et-3,4-dephostatin increased the tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 with or without insulin in differentiated 3T3-L1 mouse adipocytes. The increase of tyrosine phosphorylation by Et-3,4-dephostatin was more prominent in 6-h than in 30-min incubation. It also increased phosphorylation and activation of Akt with or without insulin. Et-3,4-dephostatin also enhanced translocation of glucose transporter 4 from the cytoplasm to the membrane and 2-deoxy-glucose transport. Et-3,4-dephostatin-induced glucose uptake was inhibited by SB203580, a p38 inhibitor, but not by PD98059, a MEK inhibitor, or by cycloheximide as insulin-induced uptake. Interestingly, although LY294002, a phosphatidylinositol 3-kinase inhibitor, inhibited the insulin-induced glucose uptake completely, it only partially inhibited the Et-3,4-dephostatin-induced uptake. It also blocked insulin-induced glucose transporter 4 translocation but not the Et-3,4-dephostatin-induced one. The increase in c-Cbl tyrosine phosphorylation caused by Et-3,4-dephostatin was stronger than that in insulin receptor phosphorylation. These observations indicate that a phosphatidylinositol 3-kinase-independent pathway involving c-Cbl is more important in Et-3,4-dephostatin-induced glucose uptake than in insulin-induced uptake. Et-3,4-dephostatin showed an in vivo antidiabetic effect in terms of reducing the high blood glucose level in KK-A(y) mice after oral administration. Thus, Et-3,4-dephostatin potentiated insulin-related signal transductions in cultured mouse adipocytes and showed an antidiabetic effect in mice.
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Affiliation(s)
- T Suzuki
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-0061, Japan
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27
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Fukada T, Tonks NK. The reciprocal role of Egr-1 and Sp family proteins in regulation of the PTP1B promoter in response to the p210 Bcr-Abl oncoprotein-tyrosine kinase. J Biol Chem 2001; 276:25512-9. [PMID: 11316810 DOI: 10.1074/jbc.m101354200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein-tyrosine phosphatase 1B (PTP1B) is an important regulator of protein-tyrosine kinase-dependent signaling pathways. Changes in expression and activity of PTP1B have been associated with various human diseases; however, the mechanisms by which PTP1B expression is regulated have yet to be characterized. Previously, we have shown that the expression of PTP1B is enhanced by p210 Bcr-Abl and that PTP1B is a specific antagonist of transformation induced by this oncoprotein protein-tyrosine kinase. Here we have characterized the PTP1B promoter and demonstrate that a motif with features of a stress-response element acts as a p210 Bcr-Abl-responsive sequence, termed PRS. We have shown that three C(2)H(2) zinc finger proteins, namely Sp1, Sp3, and Egr-1, bind to PRS. Whereas binding of either Sp1 or Sp3 induced promoter function, Egr-1 repressed Sp3-mediated PTP1B promoter activation. The binding of Egr-1 to PRS is suppressed by p210 Bcr-Abl due to the inhibition of Egr-1 expression, resulting in the enhancement of PTP1B promoter activity. Our data indicate that Egr-1 and Sp family proteins play a reciprocal role in the control of expression from the PTP1B promoter.
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Affiliation(s)
- T Fukada
- Cold Spring Harbor Laboratory, Demerec Bldg., 1 Bungtown Rd., Cold Spring Harbor, NY 11724-2208, USA
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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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Klaman LD, Boss O, Peroni OD, Kim JK, Martino JL, Zabolotny JM, Moghal N, Lubkin M, Kim YB, Sharpe AH, Stricker-Krongrad A, Shulman GI, Neel BG, Kahn BB. Increased energy expenditure, decreased adiposity, and tissue-specific insulin sensitivity in protein-tyrosine phosphatase 1B-deficient mice. Mol Cell Biol 2000; 20:5479-89. [PMID: 10891488 PMCID: PMC85999 DOI: 10.1128/mcb.20.15.5479-5489.2000] [Citation(s) in RCA: 969] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2000] [Accepted: 04/24/2000] [Indexed: 12/16/2022] Open
Abstract
Protein-tyrosine phosphatase 1B (PTP-1B) is a major protein-tyrosine phosphatase that has been implicated in the regulation of insulin action, as well as in other signal transduction pathways. To investigate the role of PTP-1B in vivo, we generated homozygotic PTP-1B-null mice by targeted gene disruption. PTP-1B-deficient mice have remarkably low adiposity and are protected from diet-induced obesity. Decreased adiposity is due to a marked reduction in fat cell mass without a decrease in adipocyte number. Leanness in PTP-1B-deficient mice is accompanied by increased basal metabolic rate and total energy expenditure, without marked alteration of uncoupling protein mRNA expression. In addition, insulin-stimulated whole-body glucose disposal is enhanced significantly in PTP-1B-deficient animals, as shown by hyperinsulinemic-euglycemic clamp studies. Remarkably, increased insulin sensitivity in PTP-1B-deficient mice is tissue specific, as insulin-stimulated glucose uptake is elevated in skeletal muscle, whereas adipose tissue is unaffected. Our results identify PTP-1B as a major regulator of energy balance, insulin sensitivity, and body fat stores in vivo.
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Affiliation(s)
- L D Klaman
- Cancer Biology Program, Division of Hematology-Oncology, Boston, Massachusetts 02215, USA
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30
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Melis A, Watts SW, Florian J, Klarr S, Webb RC. Insulin-like growth factor inhibits vascular contraction to 5-hydroxytryptamine: involvement of tyrosine phosphatase. GENERAL PHARMACOLOGY 2000; 34:137-45. [PMID: 10974421 DOI: 10.1016/s0306-3623(00)00055-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This study tests the hypothesis that insulin-like growth factor 1 (IGF-1)-induced vasodilation is due to the stimulation of tyrosine phosphatase. Rat aortic segments (endothelium intact) were placed in muscle baths for force measurement. Segments were contracted to serotonin [5-hydroxytyptamine (5-HT), 10(-7)-10(-5) M] before and after incubation with IGF-1 (10-100 nM; 90 min). IGF-1 caused a 20% inhibition of 5-HT-induced contractions. This inhibition was reversed by the tyrosine phosphatase inhibitors sodium orthovanadate and molybdate. Orthovanadate did not alter inhibitory properties of the calcium channel antagonist verapamil, suggesting that the phosphatase inhibitors were relatively specific. IGF-1-induced inhibition was not altered by blockade of nitric oxide synthase. Western blot analysis confirmed that the 5-HT-induced stimulation of tyrosine phosphorylation of the 42-kDa extracellular signal-regulated mitogen-activated protein kinase protein was reduced by IGF-1 (52% inhibition), an inhibition that was attenuated by orthovanadate. These data are consistent with the hypothesis that the vasodilator activity of IGF-1 is mediated by the activation of a tyrosine phosphatase.
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MESH Headings
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/enzymology
- Aorta, Thoracic/physiology
- Drug Synergism
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiology
- Enzyme Inhibitors/pharmacology
- In Vitro Techniques
- Insulin-Like Growth Factor I/pharmacology
- Male
- Mitogen-Activated Protein Kinases/metabolism
- Molybdenum/pharmacology
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/physiology
- Nitric Oxide/physiology
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitroarginine/pharmacology
- Phosphorylation/drug effects
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Protein Tyrosine Phosphatases/metabolism
- Rats
- Rats, Sprague-Dawley
- Serotonin/pharmacology
- Serotonin Antagonists/pharmacology
- Vanadates/pharmacology
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
- Vasodilator Agents/pharmacology
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Affiliation(s)
- A Melis
- Department of Physiology, University of Michigan Medical School, Ann Arbor, MI 48109-0622, USA
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Ren J, Samson WK, Sowers JR. Insulin-like growth factor I as a cardiac hormone: physiological and pathophysiological implications in heart disease. J Mol Cell Cardiol 1999; 31:2049-61. [PMID: 10591031 DOI: 10.1006/jmcc.1999.1036] [Citation(s) in RCA: 219] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Accumulating evidence has indicated that insulin-like growth factor-1 (IGF-1) plays a specific role in the intricate cascade of events of cardiovascular function, in addition to its well established growth-promoting and metabolic effects. IGF-1 is believed to mediate many effects of growth hormone (GH), IGF-1 promotes cardiac growth, improves cardiac contractility, cardiac output, stroke volume, and ejection fraction. In humans, IGF-1 improves cardiac function after myocardial infarction by stimulating contractility and promoting tissue remodeling. Furthermore, IGF-1 facilitates glucose metabolism, lowers insulin levels, increases insulin sensitivity, and improves the lipid profile. These data suggest an attractive therapeutic potential of IGF-1. Both clinically observed and experimentally induced impairments of cardiac function are also found to be associated with abnormal IGF-1 levels. IGF-1 and its binding proteins have been considered as markers for the presence of certain cardiac abnormalities, indicating that IGF-1 may be a risk factor for certain cardiac disorders. The present review will emphasize the role of IGF-1 in the regulation of cardiac growth and function, and the potential pathophysiological role of IGF-1 in cardiac function.
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Affiliation(s)
- J Ren
- Department of Physiology, University of North Dakota School of Medicine and Health Sciences, Grand Forks 58203, USA
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32
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Cheung A, Kusari J, Jansen D, Bandyopadhyay D, Kusari A, Bryer-Ash M. Marked impairment of protein tyrosine phosphatase 1B activity in adipose tissue of obese subjects with and without type 2 diabetes mellitus. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1999; 134:115-23. [PMID: 10444024 DOI: 10.1016/s0022-2143(99)90115-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Protein tyrosine phosphatases (PTPs) are required for the dephosphorylation of the insulin receptor (IR) and its initial cellular substrates, and it has recently been reported that PTP-1B may play a role in the pathogenesis of insulin resistance in obesity and type 2 diabetes mellitus (DM). We therefore determined the amount and activity of PTP-1B in abdominal adipose tissue obtained from lean nondiabetic subjects (lean control (LC)), obese nondiabetic subjects (obese control (OC)), and subjects with both type 2 DM (DM2) and obesity (obese diabetic (OD)). PTP-1B protein levels were 3-fold higher in OC than in LC (1444 +/- 195 U vs 500 +/- 146 U (mean +/- SEM), P < .015), while OD exhibited a 5.5-fold increase (2728 +/- 286 U, P < .01). PTP activity was assayed by measuring the dephosphorylating activity toward a phosphorus 32-labeled synthetic dodecapeptide. In contrast to the increased PTP-1B protein levels, PTP-1B activity per unit of PTP-1B protein was markedly reduced, by 71% and 88% in OC and OD, respectively. Non-PTP-1B tyrosine phosphatase activity was comparable in all three groups. Similar results were obtained when PTP-1B activity was measured against intact human IR. A significant correlation was found between body mass index (BMI) and PTP-1B level (r = 0.672, P < .02), whereas BMI and PTP-1B activity per unit of PTP-1B showed a strong inverse correlation (r = -0.801, P < .002). These data suggest that the insulin resistance of obesity and DM2 is characterized by the increased expression of a catalytically impaired PTP-1B in adipose tissue and that impaired PTP-1B activity may be pathogenic for insulin resistance in these conditions.
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Affiliation(s)
- A Cheung
- Department of Medicine, University of Tennessee College of Medicine, Memphis, USA
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Abstract
Recent evidence suggests that the p53 molecule appears in two different forms: the mutant p53 that stimulates tumor progression, and wild type p53 that inhibits tumor progression. In addition, it has been established that tumor necrosis factor-alpha (TNF-alpha) can activate the expression of wild type p53 in concert with the nuclear transcription factor, NF-kappa B. Both TNF-alpha and NF-kappa B are also involved in the stimulation of the pathway that leads to the expression of major histocompatibility complex (MHC) class I molecules and, hence, antigen presentation to the T cells. In this paper we shall advance the hypothesis that: (i) TNF-alpha indirectly controls immune surveillance; and (ii) TNF-alpha controls DNA repair and tumor suppression through the regulation of wild type p53. Thus, it is hypothesized that elevated TNF-alpha is primarily responsible for promoting tumor progression.
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Affiliation(s)
- R J Holden
- Medical Research Unit, University of Wollongong, New South Wales, Australia
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Holden RJ, Pakula IS, Mooney PA. Tumor necrosis factor-alpha: a continuum of liability between insulin-dependent diabetes mellitus, non-insulin-dependent diabetes mellitus and carcinoma (review). Med Hypotheses 1999; 52:319-23. [PMID: 10465670 DOI: 10.1054/mehy.1997.0008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In this review, tumor necrosis factor-alpha (TNF-alpha) is identified as the uniting principle linking the pathogenesis of insulin-dependent diabetes mellitus (IDDM), non-insulin dependent diabetes mellitus (NIDDM) and carcinoma. Elevated TNF-alpha initially increases, and then inhibits, the activity of a number of key enzymes involved in energy metabolism and major histocompatibility (MHC) class I molecule expression. These enzymes include: protein-tyrosine kinase (PTKase) and protein-tyrosine phosphatase (PTPase--enzymes involved in energy metabolism, cell proliferation and stimulation of the MHC class I molecule pathway. Of primary importance is the inhibiting effect of TNF-alpha on PTKase, since this induces insulin resistance in NIDDM and carcinoma, and PTPase, which inhibits MHC class I molecule expression. Studies have shown that IDDM is associated with an increase in PTPase activity which leads to overexpression of MHC class I molecules and a concomitant destruction of pancreatic beta cells. Conversely, carcinoma is associated with an inhibition of PTPase activity, which reduces the expression of MHC class I antigen expression on the cell surface thereby allowing malignant cells to escape immune surveillance. It will be argued that there is continuum of liability between these three conditions, initiated by the effect of TNF-alpha on these key enzymes.
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Affiliation(s)
- R J Holden
- Medical Research Unit, University of Wollongong, NSW, Australia
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35
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Holden RJ, Pakula IS, Mooney PA. An immunological model connecting the pathogenesis of stress, depression and carcinoma. Med Hypotheses 1998; 51:309-14. [PMID: 9824837 DOI: 10.1016/s0306-9877(98)90054-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recently there has been considerable conjecture in the literature concerning a possible relationship between stress, depression and bereavement, and carcinoma. We shall propose a causal model in which the relationship between stress, depression and carcinoma is clarified. This relationship is grounded on dysregulation of the inflammatory cytokines in stress and depression. Stress is associated with increased expression of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha), and reduced expression of IL-2, interferon-gamma (IFN-gamma), major histocompatability complex (MHC) class II molecules and natural killer cell activity (NKA). Depression is associated with elevated IFN-gamma and IL-1 beta, downregulated IL-2, and reduced NKA. Most organ-related carcinomas are associated with elevated TNF-alpha, which inhibits the activity of protein tyrosine phosphatase (PTPase), the enzyme that initiates activation of the MHC class I pathway. Sustained elevation of TNF-alpha inhibits the activity of PTPase which results in diminished expression of the MHC class I antigen on the cell surface and thus, malignant cells escape immune surveillance. Therefore, stress and depression can foster tumor progression by means of inhibiting the expression of MHC class I and II molecules and through the reduction of NKA.
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Affiliation(s)
- R J Holden
- Medical Research Unit, University of Wollongong, NSW, Australia
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36
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Okada Y, Yoshida M, Baba S, Shii K. Development of vanadate sensitive human erythrocytes insulin receptor tyrosine phosphatase assay. Diabetes Res Clin Pract 1998; 41:157-63. [PMID: 9829343 DOI: 10.1016/s0168-8227(98)00076-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aim of this study was to investigate the effect of sodium orthovanadate on the alterations of human erythrocytes insulin receptor autophosphorylation. Human erythrocytes were incubated with insulin in a cell system and then lysed. The autophosphorylated insulin receptors were measured with the aid of a two-site immunofluorometric assay and using a monoclonal anti-insulin receptor antibody to label the insulin receptors and a monoclonal anti-phosphotyrosine antibody to assess tyrosine phosphorylation. When the erythrocytes were treated with insulin and then reincubated in insulin-free medium, vanadate completely inhibited insulin receptor dephosphorylation, although it had no effect on in vitro receptor autophosphorylation. Thus insulin receptor tyrosine phosphatase activity is postulated to be [% (autophosphorylated insulin receptors with vanadate - autophosphorylated insulin receptors without vanadate)/total insulin receptors] under overall steady conditions in a cell system. Using this assay, the insulin receptor tyrosine phosphatase activities of 25 control and 32 diabetic subjects were studied. There was no significant difference in insulin receptor tyrosine phosphatase activity between control subjects and diabetic subjects (0.173 +/- 0.062 vs 0.209 - +/- 0.057 autophosphorylated insulin receptors units/insulin receptors units). The assay used in this study requires only 0.6 ml of whole blood, and so should be a useful tool for detecting patients who are insulin-resistant due to abnormal insulin receptor tyrosine phosphatase activity.
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Affiliation(s)
- Y Okada
- Hyogo Institute of Clinical Research, Akashi, Japan
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37
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Goldstein BJ, Li PM, Ding W, Ahmad F, Zhang WR. Regulation of insulin action by protein tyrosine phosphatases. VITAMINS AND HORMONES 1998; 54:67-96. [PMID: 9529974 DOI: 10.1016/s0083-6729(08)60922-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- B J Goldstein
- Dorrance H. Hamilton Research Laboratories, Department of Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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38
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Norris K, Norris F, Kono DH, Vestergaard H, Pedersen O, Theofilopoulos AN, Møller NP. Expression of protein-tyrosine phosphatases in the major insulin target tissues. FEBS Lett 1997; 415:243-8. [PMID: 9357975 DOI: 10.1016/s0014-5793(97)01133-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Protein-tyrosine phosphatases (PTPs) are key regulators of the insulin receptor signal transduction pathway. We have performed a detailed analysis of PTP expression in the major human insulin target tissues or cells (liver, adipose tissue, skeletal muscle and endothelial cells). To obtain a representative picture, all tissues were analyzed by PCR using three different primer sets corresponding to conserved regions of known PTPs. A total of 24 different PTPs were identified. A multiprobe RNase protection assay was developed to obtain a semiquantitative measure of the expression levels of selected PTPs. Surprisingly, PTP-LAR, previously suggested to be a major regulator of the insulin receptor tyrosine kinase, was expressed in extremely low levels in skeletal muscle, whereas the related receptor-type PTP-sigma and PTP-alpha were expressed in relatively high levels in all four tissues. The low levels of LAR PTP mRNA in skeletal muscle were further confirmed by Northern blot analysis.
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MESH Headings
- Adipose Tissue/enzymology
- Adipose Tissue/metabolism
- Blotting, Northern
- DNA Primers
- Endothelium, Vascular/enzymology
- Endothelium, Vascular/metabolism
- Gene Expression Regulation, Enzymologic
- Humans
- Isoenzymes/biosynthesis
- Isoenzymes/genetics
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/metabolism
- Placenta/enzymology
- Placenta/metabolism
- Polymerase Chain Reaction
- Protein Tyrosine Phosphatases/biosynthesis
- Protein Tyrosine Phosphatases/genetics
- RNA Probes
- RNA, Messenger/analysis
- Receptor, Insulin/physiology
- Receptor-Like Protein Tyrosine Phosphatases, Class 4
- Receptors, Cell Surface
- Ribonucleases/metabolism
- Signal Transduction
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Affiliation(s)
- K Norris
- Vessel Wall Biology, Novo Nordisk, Gentofte, Denmark.
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39
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40
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Nakagawa Y, Oxford GE, Ishibashi K, Yamamoto H, Maeda N, Bowen E, Brayer J, Humphreys-Beher MG. Gastrointestinal absorption of insulin-like growth factor in the mouse in the absence of salivary insulin-like growth factor binding protein. Biochem Pharmacol 1997; 53:233-40. [PMID: 9037256 DOI: 10.1016/s0006-2952(96)00733-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Based on previous observations of the presence of both insulin-like growth factors I and II (IGF-I and IGF-II) in murine saliva (kerr et al., Biochem Pharmacol 49: 1521-1531, 1995), the saliva from BALB/c and Non-obese diabetic (NOD) mice was examined for the presence of insulin-like growth factor binding proteins (IGFBPs). Using a western-blot type ligand binding assay with 125I-labeled IGF-I, a series of binding proteins with molecular masses (M), between 25 and 45 kDa were detected in the sera, but not saliva, from both BALB/c and diabetic NOD mice. In the diabetic NOD mice, there were detectable changes in the concentrations of several of the IGFBPs relative to BALB/c mice. Using specific antibody to the binding proteins, one of these was identified as IGFBP-2. Gavage administration of [125I]IGFI indicated substantial uptake from the gastrointestinal tract and significant tissue distribution. There was an increase in serum concentrations of radiolabeled IGF-I in diabetic NOD mice over that in BALB/c mice but less recovered from most of the tissues. Intact 125I-labeled IGF-I was extracted and purified from various tissues, following gavage, and shown to retain biological activity. Thus, the uptake of biologically active IGFs from saliva would appear to take place independently of specific binding proteins.
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Affiliation(s)
- Y Nakagawa
- Department of Oral and Maxillofacial Surgery, Tsurumi University Dental School, Yokohama, Japan
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41
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Bandyopadhyay D, Kusari A, Kenner KA, Liu F, Chernoff J, Gustafson TA, Kusari J. Protein-tyrosine phosphatase 1B complexes with the insulin receptor in vivo and is tyrosine-phosphorylated in the presence of insulin. J Biol Chem 1997; 272:1639-45. [PMID: 8999839 DOI: 10.1074/jbc.272.3.1639] [Citation(s) in RCA: 206] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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). To characterize these proteins, lysates from control and insulin-treated cells expressing catalytically inactive PTPase 1B (CS) were immunoadsorbed and subsequently immunoblotted using various combinations of phosphotyrosine, PTPase 1B, and insulin receptor (IR) antibodies. Anti-PTPase 1B antibodies coprecipitated a 95-kDa PY protein from insulin-stimulated cells, subsequently identified as the IR beta-subunit. Similarly, anti-IR antibodies coprecipitated the 50-kDa PY-PTPase 1B protein from insulin-treated cells. To identify PTPase 1B tyrosine (Tyr) residues that are phosphorylated in response to insulin, three candidate sites (Tyr66, Tyr152, and Tyr153) were replaced with phenylalanine. Replacing Tyr66 or Tyr152 and Tyr153 significantly reduced insulin-stimulated PTPase 1B phosphotyrosine content, as well as its association with the IR. 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.
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Affiliation(s)
- D Bandyopadhyay
- Department of Physiology, Tulane University Medical Center, New Orleans, Louisiana 70112-2699, USA
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42
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Inoue G, Cheatham B, Kahn CR. Different pathways of postreceptor desensitization following chronic insulin treatment and in cells overexpressing constitutively active insulin receptors. J Biol Chem 1996; 271:28206-11. [PMID: 8910437 DOI: 10.1074/jbc.271.45.28206] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have reported previously that substitution of the transmembrane domain of the insulin receptor with that of the erbB-2 oncogene (IRerbV-->E) results in constitutive activation of the insulin receptor kinase. Compared to NIH3T3 cells overexpressing wild-type insulin receptors (IRwt), cells overexpressing IRerbV-->E displayed a decrease in IRS-1 protein content by 55%, but basal tyrosine phosphorylation of IRS-1 was increased. This resulted in an increased association of IRS-1 with the p85 subunit of phosphatidylinositol 3-kinase, increased phosphatidylinositol 3-kinase activity in anti-IRS-1 immunoprecipitates, constitutive activation of p70 S6 protein kinase, and an increased association of Grb2 with Shc in the absence of ligand. However, Grb2 association with IRS-1 could not be detected in the basal or insulin-stimulated states, and mitogen-activated protein kinase (MAPK) activity could not be stimulated by insulin, epidermal growth factor, or platelet-derived growth factor. In contrast to IRerbV-->E, the insulin receptor content and its tyrosine phosphorylation were significantly decreased in IRwt cells chronically stimulated (>24 h) with insulin. With decreased IRS-1 content, tyrosine phosphorylation of IRS-1 was decreased by over 75%, leading to decreased IRS-1-associated PI 3-kinase and Grb2. In addition, Grb2 association with Shc and activation of MAPK and the p70 S6 kinase were insensitive to insulin stimulation. By contrast, association of Grb2 with Shc and activation of MAPK, but not the p70 S6 kinase, could be stimulated by epidermal growth factor or platelet-derived growth factor. These data suggest that there are multiple levels of postreceptor desensitization to insulin action. These are used somewhat differently in these two different models, probably due in part to the difference in receptor down-regulation.
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Affiliation(s)
- G Inoue
- Research Division, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02215, USA
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43
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Kenner KA, Anyanwu E, Olefsky JM, Kusari J. Protein-tyrosine phosphatase 1B is a negative regulator of insulin- and insulin-like growth factor-I-stimulated signaling. J Biol Chem 1996; 271:19810-6. [PMID: 8702689 DOI: 10.1074/jbc.271.33.19810] [Citation(s) in RCA: 343] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
To understand the physiological role of protein-tyrosine phosphatase 1B (PTPase 1B) in insulin and insulin-like growth factor-I (IGF-I) signaling, we established clonal cell lines overexpressing wild type or inactive mutant (C215S) PTPase 1B in cells overexpressing insulin (Hirc) or IGF-I (CIGFR) receptors. PTPase 1B overexpression in transfected cells was verified by immunoblot analysis with a monoclonal PTPase 1B antibody. Subfractionation of parental cells demonstrated that greater than 90% of PTPase activity was localized in the Triton X-100-soluble particulate (P1) cell fraction. PTPase activity in the P1 fraction of cells overexpressing wild type PTPase 1B was 3-6-fold higher than parental cells but was unaltered in all fractions from C215S PTPase 1B-containing cells. The overexpression of wild type and C215S PTPase 1B had no effects on intrinsic receptor kinase activity, growth rate, or general cell morphology. The effects of PTPase 1B overexpression on cellular protein tyrosine phosphorylation were examined by anti-phosphotyrosine immunoblot analysis. No differences were apparent under basal conditions, but hormone-stimulated receptor autophosphorylation and/or insulin receptor substrate tyrosine phosphorylation were inhibited in cells overexpressing wild type PTPase 1B and increased in cells expressing mutant PTPase 1B, in comparison with parental cells. Metabolic signaling, assessed by ligand-stimulated [14C]glucose incorporation into glycogen, was also inhibited in cells overexpressing active PTPase 1B and enhanced in cells containing C215S PTPase 1B. These data strongly suggest that PTPase 1B acts as a negative regulator of insulin and IGF-I signaling.
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Affiliation(s)
- K A Kenner
- Department of Physiology, Tulane University Medical Center, New Orleans, Louisiana 70112-2699, USA
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44
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Saltiel AR. Diverse signaling pathways in the cellular actions of insulin. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:E375-85. [PMID: 8638681 DOI: 10.1152/ajpendo.1996.270.3.e375] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Insulin is one of the most important regulators of glucose and lipid homeostasis. Many of its cellular actions are mediated by changes in protein phosphorylation. The consequences of these phosphorylation events extend from a series of different short-term metabolic actions to longer-term effects of the hormone on cellular growth and differentiation. Although the insulin receptor itself is a tyrosine kinase that is activated upon hormone binding, the ensuing changes in phosphorylation occur predominantly on serine and threonine residues. Moreover, insulin can simultaneously stimulate the phosphorylation of some proteins and the dephosphorylation of others. These paradoxical effects of insulin suggest that separate signal transduction pathways may emanate from the receptor itself to produce the pleiotropic actions of the hormone.
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Affiliation(s)
- A R Saltiel
- Department of Signal Transduction, Parke-Davis Pharmaceutical Research, Warner-Lambert, Ann Arbor, Michigan 48105, USA
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45
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LeRoith D. Insulin-like growth factor receptors and binding proteins. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1996; 10:49-73. [PMID: 8734451 DOI: 10.1016/s0950-351x(96)80298-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The insulin-like growth factor receptors are integral membrane proteins and demonstrate separate, but important effects on the regulation of cellular processes. The IGF-I receptor signals multiple cascades via its inherent tyrosine kinase activity. The IGF-II/M-6-P receptor on the other hand is primarily involved in targeting of enzymes to various subcellular compartments. In contrast, the insulin-like binding proteins are secreted by the cells and accumulate in the extracellular matrix or on the external surface of the cell. They are also involved in regulating cellular processes more indirectly. They modulate the interactions of the IGFs with their receptors, and in addition, may have some IGF-independent effects probably by direct interaction with integrin and other cell membrane receptor proteins. The recent studies, as outlined in this review, strongly suggest an important, if not essential role for the IGF system in normal physiology and disease states. The challenge now is to define the mechanisms involved in these effects. More studies are required to fully understand the post-receptor mechanism involved in IGF-I receptor signal transduction and the mechanisms whereby the IGFBPs exert their interesting effects. Understanding these mechanisms will enable investigators to create new therapeutic modalities for diseases that are affected by the IGF system.
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Affiliation(s)
- D LeRoith
- Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1770, USA
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46
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Abstract
Numerous growth factors and receptors that alter proliferation have been identified in lung cancer. In non-small cell lung cancer (NSCLC) cell lines, high levels of vasoactive intestinal peptide (VIP) mRNA have been detected by Northern analysis, and immunoreactive VIP is present. VIP elevates intracellular cAMP and stimulates the clonal growth of NSCLC cells. Also, transforming growth factor alpha (TGF-alpha) mRNA is present in NSCLC cells and TGF-alpha is present in conditioned media exposed to NSCLC cells. TGF-alpha binds with high affinity to epidermal growth factor (EGF) receptors present on NSCLC cells. EGF stimulates tyrosine kinase activity and growth in NSCLC cells. Synthetic peptide antagonists and monoclonal antibodies have been identified that disrupt autocrine growth pathways and inhibit NSCLC growth. These data suggest that VIP and TGF-alpha are important autocrine growth factors for NSCLC.
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Affiliation(s)
- T W Moody
- National Cancer Institute, Biomarkers and Prevention Research Branch, Rockville, MD 20850, USA
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47
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Xiaodong Cao, Moran EJ, Siev D, Lio A, Ohashi C, Mjalli AM. Synthesis of Nh-acyl-α-aminoamides on rink resin: Inhibitors of the hematopoietic protein tyrosine phosphatase (HePTP). Bioorg Med Chem Lett 1995. [DOI: 10.1016/0960-894x(95)00533-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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48
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Kosaki A, Pillay TS, Xu L, Webster NJ. The B isoform of the insulin receptor signals more efficiently than the A isoform in HepG2 cells. J Biol Chem 1995; 270:20816-23. [PMID: 7657666 DOI: 10.1074/jbc.270.35.20816] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have demonstrated previously that dexamethasone treatment of HepG2 cells caused an enhancement of insulin's metabolic effects (Kosaki, A., and Webster, N. J. (1993) J. Biol. Chem. 268, 21990-21996). This correlated with increased expression of the mRNA encoding the B isoform of the insulin receptor (IR). In the present study, we have demonstrated that dexamethasone treatment caused in addition an enhancement in insulin-stimulated immediate-early gene expression (c-fos and egr-1). Dexamethasone treatment caused an increase in in vivo IR autophosphorylation and insulin receptor substrate-1 (IRS-1) phosphorylation both early events in the insulin signaling pathway. Furthermore, the IRS-1 phosphorylation was distinctly left shifted, although the level of IRS-1 protein was unchanged. Total cellular tyrosine phosphatase activity was unaltered when assayed with 32P-labeled IR and IRS-1. Studies in vitro on wheat-germ agglutinin-purified receptors showed that the B isoform of the IR had increased kinase activity both toward itself and the exogenous substrates poly.glu4:tyr1 and recombinant IRS-1 protein. In addition, two-dimensional tryptic phosphopeptide maps indicated that the B isoform has an additional phosphopeptide that is not seen for the A isoform. In conclusion, it appears that the B isoform of the IR signals more efficiently than the A isoform in HepG2 cells.
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Affiliation(s)
- A Kosaki
- Department of Medicine, University of California, San Diego, La Jolla 92093, USA
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49
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Kerr M, Lee A, Wang PL, Purushotham KR, Chegini N, Yamamoto H, Humphreys-Beher MG. Detection of insulin and insulin-like growth factors I and II in saliva and potential synthesis in the salivary glands of mice. Effects of type 1 diabetes mellitus. Biochem Pharmacol 1995; 49:1521-31. [PMID: 7763295 DOI: 10.1016/0006-2952(95)00017-t] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The salivary glands of mammals synthesize and secrete a number of peptide growth factors that play important roles in cell/tissue homeostasis and embryonic development. Using a radioimmunoassay, insulin, insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II) were detected in saliva from mice. Unlike epidermal growth factor (EGF), there was no sexual dimorphism in the concentrations of the insulin growth factor family. Immunohistochemical localization of IGF-I and IGF-II was confined to the duct cells of both the parotid and the submandibular glands. Reverse transcriptase-polymerase chain reaction amplification of total RNA from parotid and submandibular glands confirmed the presence of all three hormone/growth factor mRNAs in both glands. The levels of insulin and IGF-I were higher in saliva from an animal model for autoimmune type 1 diabetes, the non-obese diabetic (NOD) mouse, than in a second inbred strain, BALB/c. In contrast, the IGF-II levels were decreased relative to the BALB/c strain. With the onset of diabetes in NOD mice, insulin levels declined, while IGF-I and IGF-II levels showed trends toward lower levels of these growth factors when compared with non-diabetic animals. These changes were reflected in the concentrations from parotid and submandibular gland cell lysates.
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Affiliation(s)
- M Kerr
- Department of Oral Biology, University of Florida, Gainesville 32610, USA
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50
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Ahmad F, Goldstein BJ. Alterations in specific protein-tyrosine phosphatases accompany insulin resistance of streptozotocin diabetes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 268:E932-40. [PMID: 7762648 DOI: 10.1152/ajpendo.1995.268.5.e932] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
To test whether protein tyrosine phosphatases (PTPases) may play a role in the insulin resistance of insulinopenic diabetes, we assessed PTPase activity as well as the protein and mRNA abundance of three major candidate PTPases in subcellular fractions of liver and skeletal muscle of streptozotocin-diabetic rats before and after insulin treatment. PTPase activity against the insulin receptor in liver and muscle cytosol increased to 120-125% of control in the diabetic animals and by an additional 5-10% after insulin treatment. In the particulate fraction, PTPase activity decreased to 65-70% of control in diabetic liver and muscle and increased to 115-120% of control after insulin treatment. Protein for the leukocyte common antigen-related PTPase paralleled the changes in the PTPase activity in the particulate fraction. SH-PTP2/syp and PTPase 1B were both significantly increased in diabetes. SH-PTP2/syp also exhibited an increased ratio of particulate to cytosol distribution in diabetic tissues (1.8-1.9) that was reversed after insulin treatment (0.79-0.95). Northern analysis suggested that the PTPases were regulated at a pretranslational level. These changes in the abundance and distribution of specific PTPases may be involved in the pathogenesis of insulin resistance in insulinopenic diabetes.
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Affiliation(s)
- F Ahmad
- Dorrance H. Hamilton Research Laboratories, Department of Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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