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Abstract
The molecular mechanisms of cellular insulin action have been the focus of much investigation since the discovery of the hormone 100 years ago. Insulin action is impaired in metabolic syndrome, a condition known as insulin resistance. The actions of the hormone are initiated by binding to its receptor on the surface of target cells. The receptor is an α2β2 heterodimer that binds to insulin with high affinity, resulting in the activation of its tyrosine kinase activity. Once activated, the receptor can phosphorylate a number of intracellular substrates that initiate discrete signaling pathways. The tyrosine phosphorylation of some substrates activates phosphatidylinositol-3-kinase (PI3K), which produces polyphosphoinositides that interact with protein kinases, leading to activation of the kinase Akt. Phosphorylation of Shc leads to activation of the Ras/MAP kinase pathway. Phosphorylation of SH2B2 and of Cbl initiates activation of G proteins such as TC10. Activation of Akt and other protein kinases produces phosphorylation of a variety of substrates, including transcription factors, GTPase-activating proteins, and other kinases that control key metabolic events. Among the cellular processes controlled by insulin are vesicle trafficking, activities of metabolic enzymes, transcriptional factors, and degradation of insulin itself. Together these complex processes are coordinated to ensure glucose homeostasis.
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O'Rahilly S. "Treasure Your Exceptions"-Studying Human Extreme Phenotypes to Illuminate Metabolic Health and Disease: The 2019 Banting Medal for Scientific Achievement Lecture. Diabetes 2021; 70:29-38. [PMID: 33355307 PMCID: PMC7881844 DOI: 10.2337/dbi19-0037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The study of humans with genetic mutations which lead to a substantial disturbance of physiological processes has made a contribution to biomedical science that is disproportionate to the rarity of affected individuals. In this lecture, I discuss examples of where such studies have helped to illuminate two areas of human metabolism. First, the control of insulin sensitivity and its disruption in states of insulin resistance and second, the regulation of energy balance and its disturbances in obesity.
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Affiliation(s)
- Stephen O'Rahilly
- MRC Metabolic Diseases Unit, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Treatment Centre, University of Cambridge, Cambridge, U.K.
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Brierley GV, Webber H, Rasijeff E, Grocott S, Siddle K, Semple RK. Anti-Insulin Receptor Antibodies Improve Hyperglycemia in a Mouse Model of Human Insulin Receptoropathy. Diabetes 2020; 69:2481-2489. [PMID: 32816962 PMCID: PMC7576564 DOI: 10.2337/db20-0345] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 08/11/2020] [Indexed: 02/07/2023]
Abstract
Loss-of-function mutations in both alleles of the human insulin receptor gene (INSR) cause extreme insulin resistance (IR) and usually death in childhood, with few effective therapeutic options. Bivalent antireceptor antibodies can elicit insulin-like signaling by mutant INSR in cultured cells, but whether this translates into meaningful metabolic benefits in vivo, wherein the dynamics of insulin signaling and receptor recycling are more complex, is unknown. To address this, we adopted a strategy to model human insulin receptoropathy in mice, using Cre recombinase delivered by adeno-associated virus to knockout endogenous hepatic Insr acutely in floxed Insr mice (liver insulin receptor knockout [L-IRKO] + GFP), before adenovirus-mediated add back of wild-type (WT) or mutant human INSR Two murine anti-INSR monoclonal antibodies, previously shown to be surrogate agonists for mutant INSR, were then tested by intraperitoneal injections. As expected, L-IRKO + GFP mice showed glucose intolerance and severe hyperinsulinemia. This was fully corrected by add back of WT but not with either D734A or S350L mutant INSR. Antibody injection improved glucose tolerance in D734A INSR-expressing mice and reduced hyperinsulinemia in both S350L and D734A INSR-expressing animals. It did not cause hypoglycemia in WT INSR-expressing mice. Antibody treatment also downregulated both WT and mutant INSR protein, attenuating its beneficial metabolic effects. Anti-INSR antibodies thus improve IR in an acute model of insulin receptoropathy, but these findings imply a narrow therapeutic window determined by competing effects of antibodies to stimulate receptors and induce their downregulation.
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Affiliation(s)
- Gemma V Brierley
- The University of Cambridge Metabolic Research Laboratories, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K.
| | - Hannah Webber
- MRC Disease Model Core, Metabolic Research Laboratories, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Eerika Rasijeff
- MRC Disease Model Core, Metabolic Research Laboratories, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Sarah Grocott
- MRC Disease Model Core, Metabolic Research Laboratories, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Kenneth Siddle
- The University of Cambridge Metabolic Research Laboratories, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K
| | - Robert K Semple
- The University of Cambridge Metabolic Research Laboratories, Wellcome-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, U.K.
- University of Edinburgh Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, U.K
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Ding Q, Liang M. Arg1201Gln mutation of insulin receptor impairs tyrosine kinase activity and causes insulin resistance: a case report. Gynecol Endocrinol 2020; 36:558-560. [PMID: 31899992 DOI: 10.1080/09513590.2019.1707794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Type A insulin resistance syndrome (TAIRS) is a rare subtype of congenital insulin resistance (IR), which is characterized by specific clinical manifestations without clear diagnostic criteria and is easily misdiagnosed or overlooked. Herein we present a case of TAIRS with acanthosis nigricans (AN), severe IR, polycystic ovaries, hyperandrogenism and its consequence such as menstrual disturbances, acne and hirsutism. A heterozygous mutation, p.Arg1201Gln, in the insulin receptor (INSR) was detected. This mutation in the tyrosine kinase domain has been described before and shown to impair tyrosine kinase activity and is responsible for IR.
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Affiliation(s)
- Qinpei Ding
- Department of Endocrinology, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Min Liang
- Department of Endocrinology, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
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Li X, Itani OA, Haataja L, Dumas KJ, Yang J, Cha J, Flibotte S, Shih HJ, Delaney CE, Xu J, Qi L, Arvan P, Liu M, Hu PJ. Requirement for translocon-associated protein (TRAP) α in insulin biogenesis. SCIENCE ADVANCES 2019; 5:eaax0292. [PMID: 31840061 PMCID: PMC6892615 DOI: 10.1126/sciadv.aax0292] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 10/07/2019] [Indexed: 05/26/2023]
Abstract
The mechanistic basis for the biogenesis of peptide hormones and growth factors is poorly understood. Here, we show that the conserved endoplasmic reticulum membrane translocon-associated protein α (TRAPα), also known as signal sequence receptor 1, plays a critical role in the biosynthesis of insulin. Genetic analysis in the nematode Caenorhabditis elegans and biochemical studies in pancreatic β cells reveal that TRAPα deletion impairs preproinsulin translocation while unexpectedly disrupting distal steps in insulin biogenesis including proinsulin processing and secretion. The association of common intronic single-nucleotide variants in the human TRAPα gene with susceptibility to type 2 diabetes and pancreatic β cell dysfunction suggests that impairment of preproinsulin translocation and proinsulin trafficking may contribute to the pathogenesis of type 2 diabetes.
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Affiliation(s)
- Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Omar A. Itani
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Leena Haataja
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Kathleen J. Dumas
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jing Yang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Jeeyeon Cha
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
- Division of Diabetes, Endocrinology and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Stephane Flibotte
- Departments of Zoology and Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hung-Jen Shih
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Colin E. Delaney
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jialu Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Ling Qi
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Peter Arvan
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Patrick J. Hu
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA
- Division of Hematology and Oncology, Vanderbilt University Medical Center, Nashville, TN, USA
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Brierley GV, Siddle K, Semple RK. Evaluation of anti-insulin receptor antibodies as potential novel therapies for human insulin receptoropathy using cell culture models. Diabetologia 2018; 61:1662-1675. [PMID: 29700562 PMCID: PMC6445487 DOI: 10.1007/s00125-018-4606-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/06/2018] [Indexed: 12/28/2022]
Abstract
AIMS/HYPOTHESIS Bi-allelic loss-of-function mutations in the INSR gene (encoding the insulin receptor [INSR]) commonly cause extreme insulin resistance and early mortality. Therapeutic options are limited, but anti-INSR antibodies have been shown to activate two mutant receptors, S323L and F382V. This study evaluates four well-characterised murine anti-INSR monoclonal antibodies recognising distinct epitopes (83-7, 83-14, 18-44, 18-146) as surrogate agonists for potential targeted treatment of severe insulin resistance arising from insulin receptoropathies. METHODS Ten naturally occurring mutant human INSRs with defects affecting different aspects of receptor function were modelled and assessed for response to insulin and anti-INSR antibodies. A novel 3T3-L1 adipocyte model of insulin receptoropathy was generated, permitting conditional knockdown of endogenous mouse Insr by lentiviral expression of species-specific short hairpin (sh)RNAs with simultaneous expression of human mutant INSR transgenes. RESULTS All expressed mutant INSR bound to all antibodies tested. Eight mutants showed antibody-induced autophosphorylation, while co-treatment with antibody and insulin increased maximal phosphorylation compared with insulin alone. After knockdown of mouse Insr and expression of mutant INSR in 3T3-L1 adipocytes, two antibodies (83-7 and 83-14) activated signalling via protein kinase B (Akt) preferentially over signalling via extracellular signal-regulated kinase 1/2 (ERK1/2) for seven mutants. These antibodies stimulated glucose uptake via P193L, S323L, F382V and D707A mutant INSRs, with antibody response greater than insulin response for D707A. CONCLUSIONS/INTERPRETATION Anti-INSR monoclonal antibodies can activate selected naturally occurring mutant human insulin receptors, bringing closer the prospect of novel therapy for severe insulin resistance caused by recessive mutations.
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Affiliation(s)
- Gemma V Brierley
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, UK
- National Institute for Health Research Cambridge Biomedical Research Centre, Addenbrooke's Hospital, Cambridge, UK
| | - Kenneth Siddle
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, UK
- National Institute for Health Research Cambridge Biomedical Research Centre, Addenbrooke's Hospital, Cambridge, UK
| | - Robert K Semple
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, UK.
- National Institute for Health Research Cambridge Biomedical Research Centre, Addenbrooke's Hospital, Cambridge, UK.
- University of Edinburgh Centre for Cardiovascular Science, Queen's Medical Research Institute, Little France Crescent, Edinburgh, EH16 4TJ, UK.
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Abstract
A continuous supply of glucose is necessary to ensure proper function and survival of all organs. Plasma glucose levels are thus maintained in a narrow range around 5 mM, which is considered the physiological set point. Glucose homeostasis is controlled primarily by the liver, fat, and skeletal muscle. Following a meal, most glucose disposals occur in the skeletal muscle, whereas fasting plasma glucose levels are determined primarily by glucose output from the liver. The balance between the utilization and production of glucose is primarily maintained at equilibrium by two opposing hormones, insulin and glucagon. In response to an elevation in plasma glucose and amino acids (after consumption of a meal), insulin is released from the beta cells of the islets of Langerhans in the pancreas. When plasma glucose falls (during fasting or exercise), glucagon is secreted by α cells, which surround the beta cells in the pancreas. Both cell types are extremely sensitive to glucose concentrations, can regulate hormone synthesis, and are released in response to small changes in plasma glucose levels. At the same time, insulin serves as the major physiological anabolic agent, promoting the synthesis and storage of glucose, lipids, and proteins and inhibiting their degradation and release back into the circulation. This chapter will focus mainly on signal transduction mechanisms by which insulin exerts its plethora of effects in liver, muscle, and fat cells, focusing on those pathways that are crucial in the control of glucose and lipid homeostasis.
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Affiliation(s)
- Alan R Saltiel
- Life Sciences Institute, University of Michigan, AnnArbor, MI, USA.
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Ma GS, Lopez-Sanchez I, Aznar N, Kalogriopoulos N, Pedram S, Midde K, Ciaraldi TP, Henry RR, Ghosh P. Activation of G proteins by GIV-GEF is a pivot point for insulin resistance and sensitivity. Mol Biol Cell 2015; 26:4209-23. [PMID: 26378251 PMCID: PMC4642855 DOI: 10.1091/mbc.e15-08-0553] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 09/11/2015] [Indexed: 11/11/2022] Open
Abstract
A long-held tenet in the field of diabetes is that the tipping point between insulin sensitivity and resistance resides at the level of insulin receptor/insulin receptor substrate–adaptor complexes. Here it is shown that activation of Gαi by GIV/Girdin is a decisive event within the metabolic insulin signaling cascade that reversibly orchestrates insulin sensitivity or resistance. Insulin resistance (IR) is a metabolic disorder characterized by impaired insulin signaling and cellular glucose uptake. The current paradigm for insulin signaling centers upon the insulin receptor (InsR) and its substrate IRS1; the latter is believed to be the sole conduit for postreceptor signaling. Here we challenge that paradigm and show that GIV/Girdin, a guanidine exchange factor (GEF) for the trimeric G protein Gαi, is another major hierarchical conduit for the metabolic insulin response. By virtue of its ability to directly bind InsR, IRS1, and phosphoinositide 3-kinase, GIV serves as a key hub in the immediate postreceptor level, which coordinately enhances the metabolic insulin response and glucose uptake in myotubes via its GEF function. Site-directed mutagenesis or phosphoinhibition of GIV-GEF by the fatty acid/protein kinase C-theta pathway triggers IR. Insulin sensitizers reverse phosphoinhibition of GIV and reinstate insulin sensitivity. We also provide evidence for such reversible regulation of GIV-GEF in skeletal muscles from patients with IR. Thus GIV is an essential upstream component that couples InsR to G-protein signaling to enhance the metabolic insulin response, and impairment of such coupling triggers IR. We also provide evidence that GIV-GEF serves as therapeutic target for exogenous manipulation of physiological insulin response and reversal of IR in skeletal muscles.
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Affiliation(s)
- Gary S Ma
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Inmaculada Lopez-Sanchez
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Nicolas Aznar
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Nicholas Kalogriopoulos
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Shabnam Pedram
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Krishna Midde
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Theodore P Ciaraldi
- Department of Veterans Affairs, VA San Diego Healthcare System, San Diego, CA 92161
| | - Robert R Henry
- Department of Veterans Affairs, VA San Diego Healthcare System, San Diego, CA 92161
| | - Pradipta Ghosh
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093 Department of Veterans Affairs, VA San Diego Healthcare System, San Diego, CA 92161 Department of Cell and Molecular Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
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Fatchiyah F, Christian N, Soeatmadji D. Reducing IRS-1 Activation Cause Mutation of Tyrosine Kinase Domain hINSR Gene on Type-2 Diabetes Mellitus Patients. Bioinformation 2013; 9:853-7. [PMID: 24250111 PMCID: PMC3819570 DOI: 10.6026/97320630009853] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 09/30/2013] [Indexed: 11/23/2022] Open
Abstract
The purpose of this study is to examine the effect of mutation on tyrosine kinase hINSR gene of DM Type 2 patients reduce the IRS- 1 activation by in silico analysis. Blood DNA of DM Type 2 patients from Saeful Anwar Hospital Malang were amplified and sequenced by specific primers of tyrosine kinase domain of hINSR gene. These gene sequences were converted to protein sequence by BLAST and the IRS-1 protein sequence is retrieved from NCBI database. Both of the protein sequence was aligned by using Bio edit version 5.0.6. The model of three dimension protein was predicted by SWISS MODEL webserver, and visualized the structure alteration by using Pymol 0.99rc6 and Hex 5.0, and then superimpose of the hINSR and IRS-1 interaction were examined by docking using Hex 5.0. The results showed that one substitution and one deletion of 8-3F patient exon-22 hINSR gene tyrosine kinase domain cause loss of four helixes and three coils structures on tyrosine kinase hINSR protein. Six-deletions and six-substitutions on same gene domain of DMK9 patient changed the two helixes became coil structure. The binding energy of hINSR tyrosine kinase with IRS-1 of normal is E= -494.67 kJ/mol, DMK9 patient is E= -458.4 kJ/mol, and 8-3F patient is E=-544.20 kJ/mol. The DMK9 patient prognosis has better physiological condition than 8-3F patient. Interaction between 8-3F of hINSR tyrosine kinase domain mutation and PTB domain IRS-1 is more spontaneous than DMK9, but both of them were reduced on IRS-1 activation respectively.
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Affiliation(s)
- Fatchiyah Fatchiyah
- Department of Biology, Faculty of Mathematics and Natural Sciences, Brawijaya University, Jl Veteran, Malang, East Java 65145,Indonesia
| | - Nur Christian
- Department of Biology, Faculty of Mathematics and Natural Sciences, Brawijaya University, Jl Veteran, Malang, East Java 65145,Indonesia
| | - DjokoWahono Soeatmadji
- Department of Endocrinology, Saeful Anwar Hospital, Jl. Jaksa Agung Suprapto No. 2 Malang, East Java, Indonesia
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Molecular Mechanisms of Insulin Resistance in Diabetes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 771:240-51. [DOI: 10.1007/978-1-4614-5441-0_19] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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STAGSTED JAN. Journey beyond immunology. Regulation of receptor internalization by major histocompatibility complex class I (MHC-I) and effect of peptides derived from MHC-I. APMIS 2011. [DOI: 10.1111/j.1600-0463.1998.tb05657.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Semple RK, Sleigh A, Murgatroyd PR, Adams CA, Bluck L, Jackson S, Vottero A, Kanabar D, Charlton-Menys V, Durrington P, Soos MA, Carpenter TA, Lomas DJ, Cochran EK, Gorden P, O'Rahilly S, Savage DB. Postreceptor insulin resistance contributes to human dyslipidemia and hepatic steatosis. J Clin Invest 2009; 119:315-22. [PMID: 19164855 DOI: 10.1172/jci37432] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Accepted: 12/10/2008] [Indexed: 12/17/2022] Open
Abstract
Metabolic dyslipidemia is characterized by high circulating triglyceride (TG) and low HDL cholesterol levels and is frequently accompanied by hepatic steatosis. Increased hepatic lipogenesis contributes to both of these problems. Because insulin fails to suppress gluconeogenesis but continues to stimulate lipogenesis in both obese and lipodystrophic insulin-resistant mice, it has been proposed that a selective postreceptor defect in hepatic insulin action is central to the pathogenesis of fatty liver and hypertriglyceridemia in these mice. Here we show that humans with generalized insulin resistance caused by either mutations in the insulin receptor gene or inhibitory antibodies specific for the insulin receptor uniformly exhibited low serum TG and normal HDL cholesterol levels. This was due at least in part to surprisingly low rates of de novo lipogenesis and was associated with low liver fat content and the production of TG-depleted VLDL cholesterol particles. In contrast, humans with a selective postreceptor defect in AKT2 manifest increased lipogenesis, elevated liver fat content, TG-enriched VLDL, hypertriglyceridemia, and low HDL cholesterol levels. People with lipodystrophy, a disorder characterized by particularly severe insulin resistance and dyslipidemia, demonstrated similar abnormalities. Collectively these data from humans with molecularly characterized forms of insulin resistance suggest that partial postreceptor hepatic insulin resistance is a key element in the development of metabolic dyslipidemia and hepatic steatosis.
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Affiliation(s)
- Robert K Semple
- Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
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Bouzakri K, Austin R, Rune A, Lassman ME, Garcia-Roves PM, Berger JP, Krook A, Chibalin AV, Zhang BB, Zierath JR. Malonyl CoenzymeA decarboxylase regulates lipid and glucose metabolism in human skeletal muscle. Diabetes 2008; 57:1508-16. [PMID: 18314420 DOI: 10.2337/db07-0583] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Malonyl coenzyme A (CoA) decarboxylase (MCD) is a key enzyme responsible for malonyl-CoA turnover and functions in the control of the balance between lipid and glucose metabolism. We utilized RNA interference (siRNA)-based gene silencing to determine the direct role of MCD on metabolic responses in primary human skeletal muscle. RESEARCH DESIGN AND METHODS We used siRNA to silence MCD gene expression in cultured human myotubes from healthy volunteers (seven male and seven female) with no known metabolic disorders. Thereafter, we determined lipid and glucose metabolism and signal transduction under basal and insulin-stimulated conditions. RESULTS RNA interference-based silencing of MCD expression (75% reduction) increased malonyl-CoA levels twofold and shifted substrate utilization from lipid to glucose oxidation. RNA interference-based depletion of MCD reduced basal palmitate oxidation. In parallel with this reduction, palmitate uptake was decreased under basal (40%) and insulin-stimulated (49%) conditions compared with myotubes transfected with a scrambled sequence. MCD silencing increased basal and insulin-mediated glucose oxidation 1.4- and 2.6-fold, respectively, compared with myotubes transfected with a scrambled sequence. In addition, glucose transport and cell-surface GLUT4 content was increased. In contrast, insulin action on IRS-1 tyrosine phosphorylation, tyrosine-associated phosphatidylinositol (PI) 3-kinase activity, Akt, and glycogen synthase kinase (GSK) phosphorylation was unaltered between myotubes transfected with siRNA against MCD versus a scrambled sequence. CONCLUSIONS These results provide evidence that MCD silencing suppresses lipid uptake and enhances glucose uptake in primary human myotubes. In conclusion, MCD expression plays a key reciprocal role in the balance between lipid and glucose metabolism.
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Affiliation(s)
- Karim Bouzakri
- Department of Molecular Medicine and Surgery, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden
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Clustering of genetically defined allele classes in the Caenorhabditis elegans DAF-2 insulin/IGF-1 receptor. Genetics 2008; 178:931-46. [PMID: 18245374 PMCID: PMC2248335 DOI: 10.1534/genetics.107.070813] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The DAF-2 insulin/IGF-1 receptor regulates development, metabolism, and aging in the nematode Caenorhabditis elegans. However, complex differences among daf-2 alleles complicate analysis of this gene. We have employed epistasis analysis, transcript profile analysis, mutant sequence analysis, and homology modeling of mutant receptors to understand this complexity. We define an allelic series of nonconditional daf-2 mutants, including nonsense and deletion alleles, and a putative null allele, m65. The most severe daf-2 alleles show incomplete suppression by daf-18(0) and daf-16(0) and have a range of effects on early development. Among weaker daf-2 alleles there exist distinct mutant classes that differ in epistatic interactions with mutations in other genes. Mutant sequence analysis (including 11 newly sequenced alleles) reveals that class 1 mutant lesions lie only in certain extracellular regions of the receptor, while class 2 (pleiotropic) and nonconditional missense mutants have lesions only in the ligand-binding pocket of the receptor ectodomain or the tyrosine kinase domain. Effects of equivalent mutations on the human insulin receptor suggest an altered balance of intracellular signaling in class 2 alleles. These studies consolidate and extend our understanding of the complex genetics of daf-2 and its underlying molecular biology.
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Hirschberg R, Maroni BJ. Protein and Energy Metabolism in Acute Renal Failure. Semin Dial 2007. [DOI: 10.1111/j.1525-139x.1997.tb00859.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Glund S, Deshmukh A, Long YC, Moller T, Koistinen HA, Caidahl K, Zierath JR, Krook A. Interleukin-6 directly increases glucose metabolism in resting human skeletal muscle. Diabetes 2007; 56:1630-7. [PMID: 17363741 DOI: 10.2337/db06-1733] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Interleukin (IL)-6 is a proinflammatory cytokine shown to modify insulin sensitivity. Elevated plasma levels of IL-6 are observed in insulin-resistant states. Interestingly, plasma IL-6 levels also increase during exercise, with skeletal muscle being the predominant source. Thus, IL-6 has also been suggested to promote insulin-mediated glucose utilization. In this study, we determined the direct effects of IL-6 on glucose transport and signal transduction in human skeletal muscle. Skeletal muscle strips were prepared from vastus lateralis biopsies obtained from 22 healthy men. Muscle strips were incubated with or without IL-6 (120 ng/ml). We found that IL-6 increased glucose transport in human skeletal muscle 1.3-fold (P < 0.05). A 30-min pre-exposure to IL-6 did not affect insulin-stimulated glucose transport. IL-6 also increased skeletal muscle glucose incorporation into glycogen, as well as glucose oxidation (1.5- and 1.3-fold, respectively; P < 0.05). IL-6 increased phosphorylation of STAT3 (signal transducer and activator of transcription 3; P < 0.05), AMP-activated protein kinase (P = 0.063), and p38 mitogen-activated protein kinase (P < 0.05) and reduced phosphorylation of S6 ribosomal protein (P < 0.05). In contrast, phosphorylation of protein kinase B/Akt, AS160 (Akt substrate of 160 kDa), and GSK3alpha/beta (glycogen synthase kinase 3alpha/beta) as well as insulin receptor substrate 1-associated phosphatidylinositol 3-kinase activity remained unaltered. In conclusion, acute IL-6 exposure increases glucose metabolism in resting human skeletal muscle. Insulin-stimulated glucose transport and insulin signaling were unchanged after IL-6 exposure.
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Affiliation(s)
- Stephan Glund
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden
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17
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Le Foll C, Corporeau C, Le Guen V, Gouygou JP, Bergé JP, Delarue J. Long-chain n-3 polyunsaturated fatty acids dissociate phosphorylation of Akt from phosphatidylinositol 3'-kinase activity in rats. Am J Physiol Endocrinol Metab 2007; 292:E1223-30. [PMID: 17179391 DOI: 10.1152/ajpendo.00446.2006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined whether a low amount of dietary long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) modulated phosphatidylinositol 3'-kinase (PI 3-kinase) activity and downstream Akt phosphorylation differently in normal or insulin-resistant rats. Rats were fed for 28 days with either a control diet containing 14.6% of metabolizable energy (ME) as peanut-rape oil (PR) or an n-3 diet where 4.9% of ME as PR was replaced by fish oil. Over the last 5 days, rats received 9 per thousand NaCl or dexamethasone (1 mg/kg). Insulin stimulation of both PI 3-kinase activity and Akt serine(473) phosphorylation and modulation of GLUT4 content were studied in liver, muscle, and adipose tissue (AT). Glucose tolerance and insulin sensitivity were determined by an oral glucose challenge. In muscle and AT, LC n-3 PUFA abolished insulin-stimulated PI 3-kinase activity. These effects were not paralleled by defects in Akt serine(473) phosphorylation, which was even increased in AT. Dexamethasone abolished insulin-stimulated PI 3-kinase activity in all tissues, whereas Akt serine(473) phosphorylation was markedly reduced in muscle but unaltered in liver and AT. Such tissue-specific dissociating effects of LC n-3 PUFA on PI 3-kinase/Akt activation took place without alteration of glucose metabolism. Maintenance of a normal glucose metabolism by the n-3 diet despite abolition of PI 3-kinase activation was likely explained by a compensatory downstream Akt serine(473) phosphorylation. The inability of LC n-3 PUFA to prevent insulin resistance by dexamethasone could result from the lack of such a dissociation.
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18
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Al-Khalili L, Bouzakri K, Glund S, Lönnqvist F, Koistinen HA, Krook A. Signaling specificity of interleukin-6 action on glucose and lipid metabolism in skeletal muscle. Mol Endocrinol 2006; 20:3364-75. [PMID: 16945991 DOI: 10.1210/me.2005-0490] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We identified signaling pathways by which IL-6 regulates skeletal muscle differentiation and metabolism. Primary human skeletal muscle cells were exposed to IL-6 (25 ng/ml either acutely or for several days), and small interfering RNA gene silencing was applied to measure glucose and fat metabolism. Chronic IL-6 exposure increased myotube fusion and formation and the mRNA expression of glucose transporter 4, peroxisome proliferator activated receptor (PPAR)alpha, PPARdelta, PPARgamma, PPARgamma coactivator 1, glycogen synthase, myocyte enhancer factor 2D, uncoupling protein 2, fatty acid transporter 4, and IL-6 (P < 0.05), whereas glucose transporter 1, CCAAT/enhancer-binding protein-alpha, and uncoupling protein 3 were decreased. IL-6 increased glucose incorporation into glycogen, glucose uptake, lactate production, and fatty acid uptake and oxidation, concomitant with increased phosphorylation of AMP-activated protein kinase (AMPK), signal transducer and activator of transcription 3, and ERK1/2. IL-6 also increased phosphatidylinositol (PI) 3-kinase activity (450%; P < 0.05), which was blunted by subsequent insulin-stimulation (P < 0.05). IL-6-mediated glucose metabolism was suppressed, but lipid metabolism was unaltered, by inhibition of PI3-kinase with LY294002. The small interfering RNA-directed depletion of AMPK reduced IL-6-mediated fatty acid oxidation and palmitate uptake but did not reduce glycogen synthesis. In summary, IL-6 increases glycogen synthesis via a PI3-kinase-dependent mechanism and enhances lipid oxidation via an AMPK-dependent mechanism in skeletal muscle. Thus, IL-6 directly promotes skeletal muscle differentiation and regulates muscle substrate utilization, promoting glycogen storage and lipid oxidation.
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Affiliation(s)
- Lubna Al-Khalili
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
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19
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Højlund K, Wojtaszewski JFP, Birk J, Hansen BF, Vestergaard H, Beck-Nielsen H. Partial rescue of in vivo insulin signalling in skeletal muscle by impaired insulin clearance in heterozygous carriers of a mutation in the insulin receptor gene. Diabetologia 2006; 49:1827-37. [PMID: 16761106 DOI: 10.1007/s00125-006-0312-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 04/24/2006] [Indexed: 11/30/2022]
Abstract
AIMS/HYPOTHESIS Recently we reported the coexistence of postprandial hypoglycaemia and moderate insulin resistance in heterozygous carriers of the Arg1174Gln mutation in the insulin receptor gene (INSR). Controlled studies of in vivo insulin signalling in humans with mutant INSR are unavailable, and therefore the cellular mechanisms underlying insulin resistance in Arg1174Gln carriers remain to be clarified. SUBJECTS, MATERIALS AND METHODS We studied glucose metabolism and insulin signalling in skeletal muscle from six Arg1174Gln carriers and matched control subjects during a euglycaemic-hyperinsulinaemic clamp. RESULTS Impaired clearance of exogenous insulin caused four-fold higher clamp insulin levels in Arg1174Gln carriers compared with control subjects (p<0.05). In Arg1174Gln carriers insulin increased glucose disposal and non-oxidative glucose metabolism (p<0.05), but to a lower extent than in controls (p<0.05). Insulin increased Akt phosphorylation at Ser473 and Thr308, inhibited glycogen synthase kinase-3alpha activity, reduced phosphorylation of glycogen synthase at sites 3a+3b, and increased glycogen synthase activity in Arg1174Gln carriers (all p<0.05). In the insulin-stimulated state, Akt phosphorylation at Thr308 and glycogen synthase activity were reduced in Arg1174Gln carriers compared with controls (p<0.05), whereas glycogen synthase kinase-3alpha activity and phosphorylation of glycogen synthase at sites 3a+3b were similar in the two groups. CONCLUSIONS/INTERPRETATION In vivo insulin signalling in skeletal muscle of patients harbouring the Arg1174Gln mutation is surprisingly intact, with modest impairments in insulin-stimulated activity of Akt and glycogen synthase explaining the moderate degree of insulin resistance. Our data suggest that impaired insulin clearance in part rescues in vivo insulin signalling in muscle in these carriers of a mutant INSR, probably by increasing insulin action on the non-mutated insulin receptors.
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Affiliation(s)
- K Højlund
- Diabetes Research Centre, Department of Endocrinology, Odense University Hospital, Odense, Denmark
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20
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Al-Khalili L, Krook A, Zierath JR, Cartee GD. Prior serum- and AICAR-induced AMPK activation in primary human myocytes does not lead to subsequent increase in insulin-stimulated glucose uptake. Am J Physiol Endocrinol Metab 2004; 287:E553-7. [PMID: 15149951 DOI: 10.1152/ajpendo.00161.2004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exposing isolated rat skeletal muscle to 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside [AICAR, a pharmacological activator of AMP-activated protein kinase (AMPK)] plus serum leads to a subsequent increase in insulin-stimulated glucose transport (Fisher JS, Gao J, Han DH, Holloszy JO, and Nolte LA. Am J Physiol Endocrinol Metab 282: E18-E23, 2002). Our goal was to determine whether preincubation of primary human skeletal muscle cells with human serum and AICAR (Serum+AICAR) would also induce a subsequent elevation in insulin-stimulated glucose uptake. Cells were preincubated for 1 h under 4 conditions: 1) without AICAR or serum (Control), 2) with serum, 3) with AICAR, or 4) with Serum+AICAR. Some cells were then collected for immunoblot analysis to assess phosphorylation of AMPK (pAMPK) and its substrate acetyl-CoA carboxylase (ACC). Other cells were incubated for an additional 4 h without AICAR or serum and then used to measure basal or insulin-stimulated 2-deoxyglucose (2-DG) uptake. Level of pAMPK was increased (P < 0.01) for myotubes exposed to Serum+AICAR vs. all other groups. Phosphorylated ACC (pACC) levels were higher for both Serum+AICAR (P < 0.05) and AICAR (P < 0.05) vs. Control and Serum groups. Basal (P < 0.05) and 1.2 nM insulin-stimulated (P < 0.005) 2-DG uptake was higher for Serum vs. all other preincubation conditions at equal insulin concentration. Regardless of insulin concentration (0, 1.2, or 18 nM), 2-DG was unaltered in cells preincubated with Serum+AICAR vs. Control cells. In contrast to results with isolated rat skeletal muscle, increasing the pAMPK and pACC in human myocytes via preincubation with Serum+AICAR was insufficient to lead to a subsequent enhancement in insulin-stimulated glucose uptake.
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Affiliation(s)
- Lubna Al-Khalili
- Department of Surgical Science, Karolinska Institute, Stockholm, Sweden
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21
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Højlund K, Hansen T, Lajer M, Henriksen JE, Levin K, Lindholm J, Pedersen O, Beck-Nielsen H. A novel syndrome of autosomal-dominant hyperinsulinemic hypoglycemia linked to a mutation in the human insulin receptor gene. Diabetes 2004; 53:1592-8. [PMID: 15161766 DOI: 10.2337/diabetes.53.6.1592] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Recently, various subtypes of familial hyperinsulinemic hypoglycemia with an autosomal-dominant inheritance have been etiologically characterized. In the present study, we have delineated the genetics and metabolic phenotype of a novel form of hypoglycemia in a large pedigree with an apparent autosomal-dominant transmission. After initial investigations of the proband, her mother, and a sister, the study was extended to 19 family members in three generations. Glucose tolerance was assessed by a 5-h oral glucose tolerance test (OGTT) and insulin sensitivity by euglycemic-hyperinsulinemic clamp in six affected family members and six control subjects. To identify the genetic cause of hypoglycemia, linkage analysis and mutation analysis of genomic DNA from all family members were performed. All affected family members were characterized by postprandial hypoglycemia, fasting hyperinsulinemia, and an elevated serum insulin-to-C-peptide ratio. The 5-h OGTT demonstrated hyperinsulinemic hypoglycemia, and the clamp studies showed reduced insulin sensitivity and clearance of serum insulin in affected family members compared with control subjects. Linkage analysis and subsequent mutation screening revealed a missense mutation (Arg1174Gln) in the tyrosine kinase domain of the insulin receptor gene that cosegregated with the disease phenotype (logarithm of odds [LOD] score 3.21). In conclusion, we report a novel syndrome of autosomal-dominant hyperinsulinemic hypoglycemia. The findings demonstrate the coexistence of severe postprandial hypoglycemia, insulin resistance, and impaired insulin clearance and suggest that hypoglycemia should be considered as a phenotype linked to heterozygote mutations in the insulin receptor gene.
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Affiliation(s)
- Kurt Højlund
- Diabetes Research Centre, Department of Endocrinology, Odense University Hospital, Kloevervaenget 6, DK-5000, Odense C, Denmark.
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22
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Al-Khalili L, Cartee GD, Krook A. RNA interference-mediated reduction in GLUT1 inhibits serum-induced glucose transport in primary human skeletal muscle cells. Biochem Biophys Res Commun 2003; 307:127-32. [PMID: 12849991 DOI: 10.1016/s0006-291x(03)01124-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Using RNA interference (RNAi), we specifically down-regulate protein expression in differentiated human skeletal myotube cultures. Serum stimulation of myotubes increases glucose uptake. Using a sensitive photolabeling technique, we demonstrate that this increase in glucose uptake is accompanied by increased cell-surface content of glucose transporter (GLUT) 1. Using RNAi, we specifically reduce GLUT1 mRNA and protein expression, leading to inhibition of serum-mediated increase in glucose transport. Thus, we demonstrate the utility of RNAi in a primary human differentiated cell system, and apply this methodology to demonstrate that serum-mediated increase in glucose transport in human skeletal muscle cells is dependent on GLUT1.
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Affiliation(s)
- Lubna Al-Khalili
- Department of Surgical Science, Karolinska Institute, S-171 77, Stockholm, Sweden
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23
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Sbrissa D, Ikonomov O, Shisheva A. Selective insulin-induced activation of class I(A) phosphoinositide 3-kinase in PIKfyve immune complexes from 3T3-L1 adipocytes. Mol Cell Endocrinol 2001; 181:35-46. [PMID: 11476939 DOI: 10.1016/s0303-7207(01)00539-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A diverse range of insulin-regulated cellular processes are dependent on class I(A) phosphatidylinositol 3-kinases (PI 3-Ks) and their association with and activation by up-stream signaling molecules. Here we report on the identification of the phosphoinositide 5'-kinase PIKfyve as a partner of class I(A) PI 3-K. Thus, both p85 and p110 subunits (class I(A)) of PI 3-Ks co-precipitated with anti-PIKfyve antibodies from lysates of resting 3T3-L1 adipocytes and, vice versa, PIKfyve co-precipitated with anti-p85 PI 3-K antibodies. Assignment to class I(A) PI 3-K enzymatic activity was further substantiated by the inhibition of PtdIns 3-P production in PIKfyve immune complexes by low concentrations of wortmannin and Triton X-100, and its preferences for Mg(2+) versus Mn(2+). Insulin but not PDGF or EGF stimulation of 3T3-L1 adipocytes markedly increased the PtdIns 3-P production (4.2-fold) in PIKfyve immune complexes, primarily as a result of increased PI 3-K intrinsic enzymatic activity. Intriguingly, while both insulin and PDGF caused an increase of class I(A) PI 3-K activity co-immunoprecipitated with tyrosine phosphorylated proteins, only insulin treatment yielded an activation of class I(A) PI 3-K in PIKfyve immune complexes. Studies aiming at identifying the underlying mechanism revealed that PIKfyve-class I(A) PI 3-K association and the insulin-induced activation likely operate independently of tyrosine phosphorylated insulin receptor substrate proteins. Together, these results establish PIKfyve as a novel source of activated class I(A) PI 3-K molecules that may be relevant in the insulin-signal transduction pathway.
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Affiliation(s)
- D Sbrissa
- Department of Physiology, Wayne State University School of Medicine, 4237 Scott Mall, 540 E. Canfield, Detroit, MI 48201, USA
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24
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Mounier C, Lavoie L, Dumas V, Mohammad-Ali K, Wu J, Nantel A, Bergeron JJ, Thomas DY, Posner BI. Specific inhibition by hGRB10zeta of insulin-induced glycogen synthase activation: evidence for a novel signaling pathway. Mol Cell Endocrinol 2001; 173:15-27. [PMID: 11223174 DOI: 10.1016/s0303-7207(00)00439-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Grb10 is a member of a family of adapter proteins that binds to tyrosine-phosphorylated receptors including the insulin receptor kinase (IRK). In this study recombinant adenovirus was used to over-express hGrb10zeta, a new Grb10 isoform, in primary rat hepatocytes and the consequences for insulin signaling were evaluated. Over-expression of hGrb10zeta resulted in 50% inhibition of insulin-stimulated IRK autophosphorylation and activation. Analysis of downstream events showed that hGrb10zeta over-expression specifically inhibits insulin-stimulated glycogen synthase (GS) activity and glycogen synthesis without affecting insulin-induced IRS1/2 phosphorylation, PI3-kinase activation, insulin like growth factor binding protein-1 (IGFBP-1) mRNA expression, and ERK1/2 MAP kinase activity. The classical pathway from PI3-kinase through Akt-PKB/GSK-3 leading to GS activation by insulin was also not affected by hGrb10zeta over-expression. These results indicate that hGrb10zeta inhibits a novel and presently unidentified insulin signaling pathway leading to GS activation in liver.
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Affiliation(s)
- C Mounier
- The Polypeptide Hormone Laboratory, McGill University, Strathcona Building, 3640 University Street, Quebec, H3A 2B2, Montreal, Canada
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25
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Hemming R, Agatep R, Badiani K, Wyant K, Arthur G, Gietz RD, Triggs-Raine B. Human growth factor receptor bound 14 binds the activated insulin receptor and alters the insulin-stimulated tyrosine phosphorylation levels of multiple proteins. Biochem Cell Biol 2001. [DOI: 10.1139/o00-090] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To identify proteins interacting in the insulin-signaling pathway that might define new pathways or regulate existing ones, we have employed the yeast two-hybrid system. In a two-hybrid screen of a human liver cDNA library, we identified the human growth factor receptor bound 14 (hGrb14) adaptor protein as a partner of the activated insulin receptor. Additional analysis of the insulin receptor - hGrb14 interaction in the yeast two-hybrid system revealed that the SH2 domain of hGrb14 was not the sole region involved in binding the activated insulin receptor. The insulin-stimulated interaction between hGrb14 and the insulin receptor was also observed in different mammalian cultured cell lines. This association was detected at 1 min of insulin stimulation and was maximal at 10 nM and greater concentrations of insulin. Chinese hamster ovary cells stably expressing the insulin receptor (CHO-IR) and hGrb14 were used to examine the effects of hGrb14 overexpression on insulin-stimulated tyrosine phosphorylation of proteins; in general, increasing levels of hGrb14 expression resulted in a reduction in tyrosine phosphorylation. This decrease was demonstrated for the specific proteins src homology-containing and collagen-related protein (Shc), insulin receptor substrate-1 (IRS-1), and Downstream of tyrosine Kinase (Dok). The broad effects of hGrb14 overexpression on insulin-stimulated tyrosine phosphorylation suggest that it acts early in the insulin-signaling pathway.Key words: insulin signaling, growth factor receptor bound 14, Grb14, adaptor protein, insulin receptor.
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26
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Vorwerk P, Christoffersen CT, Müller J, Vestergaard H, Pedersen O, De Meyts P. Alternative splicing of exon 17 and a missense mutation in exon 20 of the insulin receptor gene in two brothers with a novel syndrome of insulin resistance (congenital fiber-type disproportion myopathy). HORMONE RESEARCH 2000; 52:211-20. [PMID: 10844410 DOI: 10.1159/000023464] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The insulin receptor (IR) in two brothers with a rare syndrome of congenital muscle fiber type disproportion myopathy (CFTDM) associated with diabetes and severe insulin resistance was studied. By direct sequencing of Epstein-Barr virus-transformed lymphocytes both patients were found to be compound heterozygotes for mutations in the IR gene. The maternal allele was alternatively spliced in exon 17 due to a point mutation in the -1 donor splice site of the exon. The abnormal skipping of exon 17 shifts the amino acid reading frame and leads to a truncated IR, missing the entire tyrosine kinase domain. In the correct spliced variant, the point mutation is silent and results in a normally translated IR. The paternal allele carries a missense mutation in the tyrosine kinase domain. All three cDNA variants were present in the lymphocytes of the patients. Purified IR from 293 cells overexpressing either of the two mutated receptors lacked basal or stimulated IR beta-subunit autophosphorylation. A third brother who inherited both normal alleles has an normal muscle phenotype and insulin sensitivity, suggesting a direct linkage of these IR mutations with the CFTDM phenotype.
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MESH Headings
- Adolescent
- Alleles
- Alternative Splicing
- Base Sequence
- Child
- DNA Primers/genetics
- DNA, Complementary/genetics
- Exons
- Female
- Heterozygote
- Humans
- In Vitro Techniques
- Insulin/metabolism
- Insulin Resistance/genetics
- Male
- Mutagenesis, Site-Directed
- Mutation, Missense
- Myopathies, Structural, Congenital/genetics
- Myopathies, Structural, Congenital/metabolism
- Pedigree
- Phenotype
- Point Mutation
- Polymorphism, Genetic
- Protein Structure, Tertiary/genetics
- Protein-Tyrosine Kinases/genetics
- Receptor, Insulin/genetics
- Receptor, Insulin/metabolism
- Syndrome
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Affiliation(s)
- P Vorwerk
- Department of Pediatric Hematology and Oncology, Otto von Guericke University, Magdeburg, Germany.
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27
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Venable CL, Frevert EU, Kim YB, Fischer BM, Kamatkar S, Neel BG, Kahn BB. Overexpression of protein-tyrosine phosphatase-1B in adipocytes inhibits insulin-stimulated phosphoinositide 3-kinase activity without altering glucose transport or Akt/Protein kinase B activation. J Biol Chem 2000; 275:18318-26. [PMID: 10751417 DOI: 10.1074/jbc.m908392199] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies suggested that protein-tyrosine phosphatase 1B (PTP1B) antagonizes insulin action by catalyzing dephosphorylation of the insulin receptor (IR) and/or other key proteins in the insulin signaling pathway. In adipose tissue and muscle of obese humans and rodents, PTP1B expression is increased, which led to the hypothesis that PTP1B plays a role in the pathogenesis of insulin resistance. Consistent with this, mice in which the PTP1B gene was disrupted exhibit increased insulin sensitivity. To test whether increased expression of PTP1B in an insulin-sensitive cell type could contribute to insulin resistance, we overexpressed wild-type PTP1B in 3T3L1 adipocytes using adenovirus-mediated gene delivery. PTP1B expression was increased approximately 3-5-fold above endogenous levels at 16 h, approximately 14-fold at 40 h, and approximately 20-fold at 72 h post-transduction. Total protein-tyrosine phosphatase activity was increased by 50% at 16 h, 3-4-fold at 40 h, and 5-6-fold at 72 h post-transduction. Compared with control cells, cells expressing high levels of PTP1B showed a 50-60% decrease in maximally insulin-stimulated tyrosyl phosphorylation of IR and insulin receptor substrate-1 (IRS-1) and phosphoinositide 3-kinase (PI3K) activity associated with IRS-1 or with phosphotyrosine. Akt phosphorylation and activity were unchanged. Phosphorylation of p42 and p44 MAP kinase (MAPK) was reduced approximately 32%. Overexpression of PTP1B had no effect on basal, submaximally or maximally (100 nm) insulin-stimulated glucose transport or on the EC(50) for transport. Our results suggest that: 1) insulin stimulation of glucose transport in adipocytes requires </=45% of maximal tyrosyl phosphorylation of IR or IRS-1 and <50% of maximal activation of PI3K, 2) a novel PI3K-independent pathway may play a role in insulin-induced glucose transport in adipocytes, and 3) overexpression of PTP1B alone in adipocytes does not impair glucose transport.
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Affiliation(s)
- C L Venable
- Diabetes Unit, Division of Endocrinology and Cancer Biology Program, Division of Hematology-Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, Massachusetts 02215, USA
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28
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Yau L, Lukes H, McDiarmid H, Werner J, Zahradka P. Insulin-like growth factor-I (IGF-I)-dependent activation of pp42/44 mitogen-activated protein kinase occurs independently of IGF-I receptor kinase activation and IRS-1 tyrosine phosphorylation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 266:1147-57. [PMID: 10583412 DOI: 10.1046/j.1432-1327.1999.00968.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The proliferation and metabolism of H4IIE hepatoma cells is apparently mediated through the insulin receptor. These cells, however, also have high-affinity binding sites for insulin-like growth factor-I (IGF-I). Addition of insulin to H4IIE cells increased RNA synthesis, DNA synthesis and cell number. IGF-I, on the other hand, was ineffective at concentrations equivalent to the lowest effective insulin dose, although stimulation was observed with concentrations 100-fold higher. Similar results were obtained when glucose uptake was measured. Western blot analysis demonstrated that tyrosine phosphorylation patterns produced by insulin and IGF-I differed. In particular, phosphorylation of insulin receptor substrate-1 (IRS-1) was evident after treatment with insulin, but not after treatment with IGF-I. Correspondingly, insulin, but not IGF-I, stimulated receptor tyrosine kinase activity. In contrast with these results, both insulin and IGF-I induced mitogen-activated protein (MAP) kinase phosphorylation and activity at a concentration of 10 nM. The correlation between insulin-dependent and IGF-I-dependent MAP kinase activation was confirmed by Western blot analysis of phosphorylated MAP kinase kinase (MEK). These results suggest that phosphorylation of IRS-1 is essential for both cell proliferation and glucose metabolism, but is uncoupled from the MAP kinase cascade. Furthermore, stimulation of MEK and MAP kinase is independent of receptor tyrosine kinase activity.
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Affiliation(s)
- L Yau
- Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Canada
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29
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Hawkins M, Hu M, Yu J, Eder H, Vuguin P, She L, Barzilai N, Leiser M, Backer JM, Rossetti L. Discordant effects of glucosamine on insulin-stimulated glucose metabolism and phosphatidylinositol 3-kinase activity. J Biol Chem 1999; 274:31312-9. [PMID: 10531330 DOI: 10.1074/jbc.274.44.31312] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The impact of increased GlcN availability on insulin-stimulated p85/p110 phosphatidylinositol 3-kinase (PI3K) activity in skeletal muscle was examined in relation to GlcN-induced defects in peripheral insulin action. Primed continuous GlcN infusion (750 micromol/kg bolus; 30 micromol/kg.min) in conscious rats limited both maximal stimulation of muscle PI3K by acute insulin (I) (1 unit/kg) bolus (I + GlcN = 1.9-fold versus saline = 3.3-fold above fasting levels; p < 0.01) and chronic activation of PI3K following 3-h euglycemic, hyperinsulinemic (18 milliunits/kg.min) clamp studies (I + GlcN = 1.2-fold versus saline = 2.6-fold stimulation; p < 0.01). To determine the time course of GlcN-induced defects in insulin-stimulated PI3K activity and peripheral insulin action, GlcN was administered for 30, 60, 90, or 120 min during 2-h euglycemic, hyperinsulinemic clamp studies. Activation of muscle PI3K by insulin was attenuated following only 30 min of GlcN infusion (GlcN 30 min = 1.5-fold versus saline = 2.5-fold stimulation; p < 0.05). In contrast, the first impairment in insulin-mediated glucose uptake (Rd) developed following 110 min of GlcN infusion (110 min = 39.9 +/- 1.8 versus 30 min = 42.8 +/- 1.4 mg/kg.min, p < 0.05). However, the ability of insulin to stimulate phosphatidylinositol 3,4, 5-trisphosphate production and to activate glycogen synthase in skeletal muscle was preserved following up to 180 min of GlcN infusion. Thus, increased GlcN availability induced (a) profound and early inhibition of proximal insulin signaling at the level of PI3K and (b) delayed effects on insulin-mediated glucose uptake, yet (c) complete sparing of insulin-mediated glycogen synthase activation. The pattern and time sequence of GlcN-induced defects suggest that the etiology of peripheral insulin resistance may be distinct from the rapid and marked impairment in insulin signaling.
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Affiliation(s)
- M Hawkins
- Division of Endocrinology, Diabetes Research and Training Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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30
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Rau H, Reaves BJ, O'Rahilly S, Whitehead JP. Truncated human leptin (delta133) associated with extreme obesity undergoes proteasomal degradation after defective intracellular transport. Endocrinology 1999; 140:1718-23. [PMID: 10098508 DOI: 10.1210/endo.140.4.6670] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We recently described a homozygous frameshift mutation in the human leptin (ob) gene associated with undetectable serum leptin and extreme obesity in two individuals. This represented the first identified genetic cause of morbid obesity in humans. Preliminary data suggested a defect in the secretion of this truncated (delta133) mutant leptin. In the present investigation, we have examined the mechanisms underlying the defective secretion of the delta133 leptin in transient transfection studies in Chinese hamster ovary and monkey kidney epithelium cells. Consistent with our previous observations, only immunoreactive wild-type (wt) leptin was secreted. In pulse chase experiments, intracellular wt leptin levels decreased, concomitant with secretion into the medium. In contrast, though immunoreactive delta133 leptin disappeared from cell lysates with kinetics similar to those of wt leptin (half-life, 45 min), it was not detected in the medium. Inhibition of the proteasome, using the inhibitor clastolactacystin beta-lactone, led to a significant increase in the intracellular levels of delta133 leptin, indicating a role for the proteasome in the degradation pathway. Although intracellular immunoprecipitated wt and delta133 leptin levels were comparable, analysis of total cell lysates revealed a 7-fold increase in total intracellular delta133 leptin, compared with wt leptin. Size-exclusion membrane filtration demonstrated that intracellular delta133 leptin accumulated in an aggregated form, presumably as a result of misfolding in the endoplasmic reticulum. Consistent with this, an endoplasmic reticulum-like localization for delta133 leptin was detected by immunofluorescence microscopy. In conclusion, the delta133 mutant leptin is not secreted but accumulates intracellularly, as a consequence of misfolding/aggregation, and is subsequently degraded by the proteasome. These studies further define the genotype/phenotype correlation in this paradigmatic case of human leptin deficiency.
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Affiliation(s)
- H Rau
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, United Kingdom
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31
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Kuno S, Kawamoto M, Okuyama M, Yasumasu I. Outgrowth of pseudopodial cables induced by all-trans retinoic acid in micromere-derived cells isolated from sea urchin embryos. Dev Growth Differ 1999; 41:193-9. [PMID: 10223715 DOI: 10.1046/j.1440-169x.1999.00416.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cultured cells derived from micromeres of sea urchin embryos underwent pseudopodial cable growth without spicule rod formation in the presence of all-trans retinoic acid (tRA) or insulin. Pseudopodial cable growth caused by tRA or insulin was inhibited by genistein, a protein tyrosine kinase inhibitor. Phosphorylation of protein tyrosine residue was augmented in the cells treated with tRA or insulin and was inhibited by genistein. Probably, protein tyrosine kinase takes an indispensable part in signal transduction systems for tRA and insulin in these cells. In tRA-treated cells, augmentation of the phosphorylation of protein tyrosine residue was accompanied by an increase in the activity of protein tyrosine kinase and was inhibited by actinomycin D, inhibiting cable growth. Activation of this enzyme in tRA-treated cells probably depends on RNA synthesis. In insulin-treated cells, augmentation of tyrosine residue phosphorylation occurred without any appreciable change in this enzyme's activity and was hardly affected by actinomycin D. Phosphorylation of protein tyrosine residue seems to be activated by the binding of insulin to an insulin receptor. Pseudopodial cable growth in these cells treated with tRA or insulin was inhibited by wortmannin. Phosphatidylinositol 3 kinase probably participates in tRA and insulin signal transduction systems.
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Affiliation(s)
- S Kuno
- Department of Biology, School of Education, Waseda University, Tokyo, Japan
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32
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Staubs PA, Nelson JG, Reichart DR, Olefsky JM. Platelet-derived growth factor inhibits insulin stimulation of insulin receptor substrate-1-associated phosphatidylinositol 3-kinase in 3T3-L1 adipocytes without affecting glucose transport. J Biol Chem 1998; 273:25139-47. [PMID: 9737973 DOI: 10.1074/jbc.273.39.25139] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Phosphatidylinositol 3-kinase (PI3K) activation is necessary for insulin-responsive glucose transporter (GLUT4) translocation and glucose transport. Insulin and platelet-derived growth factor (PDGF) stimulate PI3K activity in 3T3-L1 adipocytes, but only insulin is capable of stimulating GLUT4 translocation and glucose transport. We found that PDGF causes serine/threonine phosphorylation of insulin receptor substrate 1 (IRS-1) in 3T3-L1 cells, measured by altered mobility on SDS-polyacrylamide gel, and this leads to a decrease in insulin-stimulated tyrosine phosphorylation of IRS-1. The PI3K inhibitors wortmannin and LY294002 inhibit the PDGF-induced phosphorylation of IRS-1, whereas the MEK inhibitor PD98059 was without a major effect. PDGF pretreatment for 60-90 min led to a marked 80-90% reduction in insulin stimulatable phosphotyrosine and IRS-1-associated PI3K activity. We examined the functional consequences of this decrease in IRS-1-associated PI3K activity. Interestingly, insulin stimulation of GLUT4 translocation and glucose transport was unaffected by 60-90 min of PDGF preincubation. Furthermore, insulin activation of Akt and p70(s6kinase), kinases downstream of PI3K, was unaffected by PDGF pretreatment. Wortmannin was capable of blocking these insulin actions following PDGF pretreatment, suggesting that PI3K was still necessary for these effects. In conclusion, 1) PDGF causes serine/threonine phosphorylation of IRS-1, and PI3K, or a kinase downstream of PI3K, mediates this phosphorylation. 2) This PDGF-induced phosphorylation of IRS-1 leads to a significant decrease in insulin-stimulated PI3K activity. 3) PDGF has no effect on insulin stimulation of Akt, p70(s6kinase), GLUT4 translocation, or glucose transport. 4) This suggests the existence of an IRS-1-independent pathway leading to the activation of PI3K, Akt, and p70(s6kinase); GLUT4 translocation; and glucose transport.
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Affiliation(s)
- P A Staubs
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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33
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Sharma PM, Egawa K, Huang Y, Martin JL, Huvar I, Boss GR, Olefsky JM. Inhibition of phosphatidylinositol 3-kinase activity by adenovirus-mediated gene transfer and its effect on insulin action. J Biol Chem 1998; 273:18528-37. [PMID: 9660823 DOI: 10.1074/jbc.273.29.18528] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Phosphatidylinositol 3-kinase (PI 3-K) is implicated in cellular events including glucose transport, glycogen synthesis, and protein synthesis. It is activated in insulin-stimulated cells by binding of the Src homology 2 (SH2) domains in its 85-kDa regulatory subunit to insulin receptor substrate-1 (IRS-1), and, others. We have previously shown that IRS-1-associated PI 3-kinase activity is not essential for insulin-stimulated glucose transport in 3T3-L1 adipocytes, and that alternate pathways exist in these cells. We now show that adenovirus-mediated overexpression of the p85N-SH2 domain in these cells behaves in a dominant-negative manner, interfering with complex formation between endogenous PI 3-K and its SH2 binding targets. This not only inhibited insulin-stimulated IRS-1-associated PI 3-kinase activity, but also completely blocked anti-phosphotyrosine-associated PI 3-kinase activity, which would include the non-IRS-1-associated activity. This resulted in inhibition of insulin-stimulated glucose transport, glycogen synthase activity and DNA synthesis. Further, Ser/Thr phosphorylation of downstream molecules Akt and p70 S6 kinase was inhibited. However, co-expression of a membrane-targeted p110(C) with the p85N-SH2 protein rescued glucose transport, supporting our argument that the p85N-SH2 protein specifically blocks insulin-mediated PI 3-kinase activity, and, that the signaling pathways downstream of PI 3-kinase are intact. Unexpectedly, GTP-bound Ras was elevated in the basal state. Since p85 is known to interact with GTPase-activating protein in 3T3-L1 adipocytes, the overexpressed p85N-SH2 peptide could titrate out cellular GTPase-activating protein by direct association, such that it is unavailable to hydrolyze GTP-bound Ras. However, insulin-induced mitogen-activated protein kinase phosphorylation was inhibited. Thus, PI 3-kinase may be required for this action at a step independent of and downstream of Ras. We conclude that, in 3T3-L1 adipocytes, non-IRS-1-associated PI 3-kinase activity is crucial for insulin's metabolic signaling, and that overexpressed p85N-SH2 protein inhibits a variety of insulin's ultimate biological effects.
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Affiliation(s)
- P M Sharma
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, California 92093, USA
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Gagnon AM, Chabot J, Pardasani D, Sorisky A. Extracellular matrix induced by TGFbeta impairs insulin signal transduction in 3T3-L1 preadipose cells. J Cell Physiol 1998; 175:370-8. [PMID: 9572482 DOI: 10.1002/(sici)1097-4652(199806)175:3<370::aid-jcp15>3.0.co;2-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
When 3T3-L1 preadipose cells are exposed to transforming growth factor beta (TGFbeta), they synthesize more extracellular matrix (ECM) and resist differentiation-inducing stimuli. The mechanism by which ECM suppresses adipose cell differentiation (adipogenesis) remains unknown. Since adipogenesis is an insulin/insulin-like growth factor-1 (IGF-1)-dependent process, we investigated whether TGFbeta-induced ECM inhibits insulin signaling. When preadipose cells were pretreated overnight with TGFbeta, we observed a 75% decrease in insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) compared to that in control cells. Culturing 3T3-L1 preadipose cells on fibronectin, a component of the ECM induced by TGFbeta, also inhibited insulin-dependent IRS-1 tyrosine phosphorylation and adipogenesis, supporting a role for ECM in mediating TGFbeta's inhibitory effect on insulin signaling. Since the insulin-stimulated association of phosphoinositide (PI) 3-kinase with IRS-1 depends on IRS-1 tyrosine phosphorylation, we measured the presence of the PI 3-kinase 85 kDa regulatory subunit in anti-IRS-1 immunoprecipitates. Following insulin stimulation, PI 3-kinase-IRS-1 association was reduced by 70% in TGFbeta pretreated vs. control preadipose cells. However, insulin-stimulated cellular production of PI(3,4,5)P3 was unaltered by TGFbeta pretreatment. This suggests that IRS-1-associated p85-type PI 3-kinase may represent a particular subset of total cellular PI 3-kinase that is specifically inhibited by TGFbeta. Reduction of insulin-stimulated association of IRS-1 with p85-type PI 3-kinase by TGFbeta may be one potential mechanism through which TGFbeta blocks 3T3-L1 adipose cell differentiation.
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Affiliation(s)
- A M Gagnon
- Ottawa Civic Hospital Loeb Research Institute, Department of Medicine, University of Ottawa, Canada
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35
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Gagnon A, Sorisky A. The effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation. OBESITY RESEARCH 1998; 6:157-63. [PMID: 9545023 DOI: 10.1002/j.1550-8528.1998.tb00330.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We examined the effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation. Oil Red O staining of neutral lipid, cellular triglyceride mass, and glycerol phosphate dehydrogenase (GPDH) activity, were greater in 3T3-L1 cells cultured at 5 mM vs. 25 mM glucose. GPDH activity was 2- to 4-fold higher at 5 mM vs. 25 mM glucose over a range of insulin concentrations (0.1 to 100 nM). Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) was 1.7-fold greater, and insulin-stimulated phosphoinositide 3-kinase association with IRS-1 was 2.3-fold higher, at 5 mM vs. 25 mM glucose. These effects of glucose were not caused by alterations in IRS-1 mass or cell-surface insulin binding. In preadipose cells at 5 mM glucose, expression of the leukocyte antigen-related (LAR) protein tyrosine phosphatase (negative regulator of insulin signaling) was 63% of the level at 25 mM glucose. Our data demonstrate that glucose concentration affects insulin-induced 3T3-L1 adipose cell differentiation as well as differentiation-directed insulin signaling pathways. Alterations in LAR expression potentially may be involved in modulating these responses.
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Affiliation(s)
- A Gagnon
- Ottawa Civic Hospital Loeb Research Institute, Department of Medicine, University of Ottawa, Ontario, Canada
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36
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Wang J, Riedel H. Insulin-like growth factor-I receptor and insulin receptor association with a Src homology-2 domain-containing putative adapter. J Biol Chem 1998; 273:3136-9. [PMID: 9452421 DOI: 10.1074/jbc.273.6.3136] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Insulin receptor (IR) and the related insulin-like growth factor-I (IGF-I) receptor (IGF-IR) mediate a variety of metabolic and mitogenic cellular responses, some of which may involve unidentified receptor targets. A Src homology-2 (SH2) domain-coding region of a mouse protein was cloned based on its interaction with IR. It was designated mSH2-B based on its high similarity to an earlier reported rat sequence SH2-B. A role of mSH2-B in IGF-I and insulin action was suggested by the interaction of the SH2 domain with activated IGF-IR and IR catalytic fragments but not with an inactive IR catalytic fragment in the yeast two-hybrid system in vivo and by the hormone-dependent association of a glutathione S-transferase (GST) SH2 domain fusion protein of mSH2-B with both receptors in cell extracts. A comparison of IGF-IR and IR mutants lacking individual Tyr autophosphorylation sites for association with GST mSH2-B showed that homologous juxtamembrane (IR960/IGF-IR950) and C-terminal (IR1322/IGF-IR1316) receptor motifs were required. Synthetic phosphopeptides representing IR960 and IR1322 competed for GST mSH2-B binding to the receptor, suggesting that both motifs participate in the association with mSH2-B. Antibodies raised against GST mSH2-B identified a cellular protein of 92 kDa that was not found to be phosphorylated on Tyr. It co-immunoprecipitated with IGF-IR or IR, which was strictly dependent on receptor activation. IR and IGF-IR Tyr phosphorylation motifs were not identified in the complete SH2-B primary structure, suggesting that it may participate as an adapter rather than a substrate in the IGF-I and insulin signaling pathways.
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Affiliation(s)
- J Wang
- Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202, USA
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37
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Maggi D, Andraghetti G, Carpentier JL, Cordera R. Cys860 in the extracellular domain of insulin receptor beta-subunit is critical for internalization and signal transduction. Endocrinology 1998; 139:496-504. [PMID: 9449617 DOI: 10.1210/endo.139.2.5744] [Citation(s) in RCA: 11] [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: 02/05/2023]
Abstract
The C860S mutation (IRC860S) in the extracellular domain of the insulin receptor beta-subunit has previously been shown to result in an inhibition of insulin receptor internalization. The present work aims at further dissecting the consequences of this mutation not only on insulin receptor internalization, but also on the signaling of the receptor. Following transfection of Chinese hamster ovary (CHO) cells with insulin receptors with the C860S mutation (CHO-IRC860S) and quantitative electron microscopic analysis of [125I]insulin localization in these cells, the inhibition of receptor internalization appears to be due to an inhibition of the lateral translocation of the receptor from microvilli to nonvillous domains of the cell surface. At 37 C, insulin-stimulated insulin receptor substrate-1 (IRS-1) phosphorylation is inhibited by 50% in CHO-IRC860S, whereas Shc phosphorylation remains unaffected. The inhibition of IRS-1 phosphorylation is still present when experiments are conducted at 4 C, a temperature at which insulin receptor internalization is prevented, suggesting that the defect in IRS-1 phosphorylation is not due to the reduced internalization of the receptor. In terms of biological effects, the mutation has negative consequences on insulin-stimulated c-fos expression and DNA synthesis as well as on glycogen synthase activity. Eventually, the events observed are specific for Cys860, as individual substitution of the two more proximal Cys residues (795 and 872) to Ser is not accompanied by any change in either insulin-induced insulin receptor internalization or IRS-1 phosphorylation. Thus, the present analysis of CHO-IRC860S 1) reveals that insulin receptor surface redistribution is not solely dependent on receptor autophosphorylation, 2) emphasizes that IRS-1 phosphorylation is not dependent on receptor internalization and can be triggered from microvilli, and 3) stresses divergent aspects between two of the major signaling pathways of the insulin receptor.
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Affiliation(s)
- D Maggi
- Department of Endocrinology and Metabolism, University of Genova, Italy
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38
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Krook A, Whitehead JP, Dobson SP, Griffiths MR, Ouwens M, Baker C, Hayward AC, Sen SK, Maassen JA, Siddle K, Tavaré JM, O'Rahilly S. Two naturally occurring insulin receptor tyrosine kinase domain mutants provide evidence that phosphoinositide 3-kinase activation alone is not sufficient for the mediation of insulin's metabolic and mitogenic effects. J Biol Chem 1997; 272:30208-14. [PMID: 9374504 DOI: 10.1074/jbc.272.48.30208] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have recently reported (1) that two naturally occurring mutants of the insulin receptor tyrosine kinase domain, Arg-1174 --> Gln and Pro-1178 --> Leu (Gln-1174 and Leu1178, respectively), both found in patients with inherited severe insulin resistance, markedly impaired receptor tyrosine autophosphorylation, with both mutant receptors being unable to mediate the stimulation of glycogen synthesis or mitogenesis by insulin when expressed in Chinese hamster ovary cells. However, these mutations did not fully prevent IRS-1 phosphorylation in response to insulin in these cells, suggesting that IRS-1 alone may not be sufficient to mediate insulin's metabolic and mitogenic effects. In the present study, we have demonstrated that these mutations also impair the ability of the insulin receptor to activate the transcription factor Elk-1 and promote GLUT4 translocation to the plasma membrane. Although at low concentrations of insulin, the mutant receptors were impaired in their ability to stimulate the tyrosine phosphorylation of IRS-1, at higher insulin concentrations we confirmed that the cells expressing the mutant receptors showed significantly increased tyrosine phosphorylation of IRS-1 compared with parental nontransfected cells. In addition, at comparable insulin concentrations, the association of the p85alpha subunit of phosphoinositide 3-kinase (PI3-kinase) with IRS-1 and the enzymatic activity of IRS-1-associated PI3-kinase were significantly enhanced in cells expressing the mutant receptors. In contrast, no significant stimulation of the tyrosine phosphorylation of Shc, GTP loading of Ras, or mitogen-activated protein kinase phosphorylation was seen in cell lines expressing these mutant receptors. Thus, no activation of any measurable mitogenic or metabolic response was detectable, despite significant insulin-induced phosphorylation of IRS-1 and its association with PI3-kinase in cells stably expressing the mutant insulin receptors. These findings suggest that PI3-kinase activation alone may be insufficient to mediate a wide range of the metabolic and mitogenic effects of insulin. Additionally, the data provide support for the notion that insulin activation of Ras is more closely linked with Shc, and not IRS-1, phosphorylation.
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Affiliation(s)
- A Krook
- Department of Medicine, Cambridge University, Addenbrookes Hospital, Hills Road, CB2 2QR, Cambridge, United Kingdom.
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Kalloo-Hosein HE, Whitehead JP, Soos M, Tavaré JM, Siddle K, O'Rahilly S. Differential signaling to glycogen synthesis by the intracellular domain of the insulin versus the insulin-like growth factor-1 receptor. Evidence from studies of TrkC-chimeras. J Biol Chem 1997; 272:24325-32. [PMID: 9305889 DOI: 10.1074/jbc.272.39.24325] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Insulin and insulin-like growth factor-1 (IGF-1) have similar cell-surface receptors yet subserve different physiological functions. To examine whether these differences relate to intrinsic signaling properties of the intracellular domains of their respective receptors, chimeric receptors were constructed using the extracellular domain of the neurotrophin-3 (NT-3) receptor, TrkC, and the intracellular domain of either the insulin receptor or the IGF-1 receptor. TrkC-IR (TIR) and TrkC-IGF-1R (TIGR) were stably expressed in 3T3-L1 cells. While TIR and TIGR cell lines expressing similar numbers of chimeric receptors showed a similar dose-response relationship in NT-3 stimulated DNA synthesis, NT-3 stimulated glycogen synthesis was greater in TIR than in TIGR cells (maximum TIGR response was 35% of maximum TIR response). Additionally, the concentration of NT-3 at which significant stimulation of glycogen synthesis was seen was 0.1 ng/ml in TIR and 1 ng/ml in TIGR cells. Basal levels of thymidine incorporation but not glycogen synthesis were consistently higher in TIR than in TIGR expressing cells. No detectable basal autophosphorylation of chimeric receptors was seen in any of the cell lines. However, exposure of cell lines to the phosphatase inhibitor bisperoxovanadate resulted in greater basal autophosphorylation of the TIR and endogenous murine IR than the TIGR and endogenous murine IGF-1R. Thus, in this system, the intracellular domain of the IR appears to couple more effectively to glycogen synthesis than that of the IGF-1R, whereas the intracellular domains of both receptors have a similar capacity to stimulate DNA synthesis.
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Affiliation(s)
- H E Kalloo-Hosein
- University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QR United Kingdom
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