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Reinhardt R, Leonard TA. A critical evaluation of protein kinase regulation by activation loop autophosphorylation. eLife 2023; 12:e88210. [PMID: 37470698 PMCID: PMC10359097 DOI: 10.7554/elife.88210] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/07/2023] [Indexed: 07/21/2023] Open
Abstract
Phosphorylation of proteins is a ubiquitous mechanism of regulating their function, localization, or activity. Protein kinases, enzymes that use ATP to phosphorylate protein substrates are, therefore, powerful signal transducers in eukaryotic cells. The mechanism of phosphoryl-transfer is universally conserved among protein kinases, which necessitates the tight regulation of kinase activity for the orchestration of cellular processes with high spatial and temporal fidelity. In response to a stimulus, many kinases enhance their own activity by autophosphorylating a conserved amino acid in their activation loop, but precisely how this reaction is performed is controversial. Classically, kinases that autophosphorylate their activation loop are thought to perform the reaction in trans, mediated by transient dimerization of their kinase domains. However, motivated by the recently discovered regulation mechanism of activation loop cis-autophosphorylation by a kinase that is autoinhibited in trans, we here review the various mechanisms of autoregulation that have been proposed. We provide a framework for critically evaluating biochemical, kinetic, and structural evidence for protein kinase dimerization and autophosphorylation, and share some thoughts on the implications of these mechanisms within physiological signaling networks.
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Affiliation(s)
- Ronja Reinhardt
- Max Perutz Labs, Vienna Biocenter Campus (VBC)ViennaAustria
- Medical University of Vienna, Center for Medical BiochemistryViennaAustria
| | - Thomas A Leonard
- Max Perutz Labs, Vienna Biocenter Campus (VBC)ViennaAustria
- Medical University of Vienna, Center for Medical BiochemistryViennaAustria
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2
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Abstract
BACKGROUND Insulin's discovery 100 years ago and its ongoing use since that time to treat diabetes belies the molecular complexity of its structure and that of its receptor. Advances in single-particle cryo-electron microscopy have over the past three years revolutionized our understanding of the atomic detail of insulin-receptor interactions. SCOPE OF REVIEW This review describes the three-dimensional structure of insulin and its receptor and details on how they interact. This review also highlights the current gaps in our structural understanding of the system. MAJOR CONCLUSIONS A near-complete picture has been obtained of the hormone receptor interactions, providing new insights into the kinetics of the interactions and necessitating a revision of the extant two-site cross-linking model of hormone receptor engagement. How insulin initially engages the receptor and the receptor's traversed trajectory as it undergoes conformational changes associated with activation remain areas for future investigation.
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Affiliation(s)
- Michael C Lawrence
- WEHI, Parkville, Victoria, 3052, Australia; Department of Medical Biology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, 3050, Australia.
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3
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Morimoto-Kamata R, Tsuji D, Yui S. Cathepsin G-Induced Insulin-Like Growth Factor (IGF) Elevation in MCF-7 Medium Is Caused by Proteolysis of IGF Binding Protein (IGFBP)-2 but Not of IGF-1. Biol Pharm Bull 2021; 43:1678-1686. [PMID: 33132312 DOI: 10.1248/bpb.b20-00389] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cathepsin G (CG), a neutrophil serine protease, induces cell migration and multicellular aggregation of human breast cancer MCF-7 cells. It has been suggested that tumor cell aggregates are associated with tumor embolism, thus CG-induced cell aggregation may promote tumor metastasis. We have revealed that cell aggregation is caused by elevated free insulin-like growth factor (IGF)-1 in the medium, followed by activation of IGF-1 receptor (IGF-1R). However, the molecular mechanism underlying IGF-1 elevation induced by CG remains unclear. Here, we aimed to elucidate the mechanism by examining the degradative effects of CG on IGF-1, and the IGF binding proteins (IGFBPs), which interfere with the binding of IGF-1 to its receptor. CG specifically evoked MCF-7 cell aggregation at less than 1 nM in a dose-dependent manner, however, neutrophil elastase (NE), chymotrypsin, and trypsin did not. Free IGF-1 concentration was continuously elevated in the medium of cells treated with CG, whereas treatments with other serine proteases resulted in only a transient or slight increase. IGFBP-2, the predominant IGFBP in MCF-7 cells, was gradually digested by CG. CG did not cleave IGF-1 for at least 48 h, whereas other proteases completely digested it. Moreover, CG induced continuous phosphorylation of IGF-1R and Akt, whereas NE-induced phosphorylation was transient, possibly due to insulin receptor substrate (IRS)-1 digestion. These results indicated that CG-specific IGF-1 elevation in the medium is caused by digestion of IGFBP-2, not IGF-1. Hence, this study clarifies the molecular mechanism of CG-specific cell aggregation.
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Affiliation(s)
| | - Daiki Tsuji
- Laboratory of Host Defense, Faculty of Pharma-Science, Teikyo University
| | - Satoru Yui
- Laboratory of Host Defense, Faculty of Pharma-Science, Teikyo University
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4
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Kavran JM, McCabe JM, Byrne PO, Connacher MK, Wang Z, Ramek A, Sarabipour S, Shan Y, Shaw DE, Hristova K, Cole PA, Leahy DJ. How IGF-1 activates its receptor. eLife 2014; 3:03772. [PMID: 25255214 PMCID: PMC4381924 DOI: 10.7554/elife.03772] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 09/23/2014] [Indexed: 12/20/2022] Open
Abstract
The type I insulin-like growth factor receptor (IGF1R) is involved in growth and survival of normal and neoplastic cells. A ligand-dependent conformational change is thought to regulate IGF1R activity, but the nature of this change is unclear. We point out an underappreciated dimer in the crystal structure of the related Insulin Receptor (IR) with Insulin bound that allows direct comparison with unliganded IR and suggests a mechanism by which ligand regulates IR/IGF1R activity. We test this mechanism in a series of biochemical and biophysical assays and find the IGF1R ectodomain maintains an autoinhibited state in which the TMs are held apart. Ligand binding releases this constraint, allowing TM association and unleashing an intrinsic propensity of the intracellular regions to autophosphorylate. Enzymatic studies of full-length and kinase-containing fragments show phosphorylated IGF1R is fully active independent of ligand and the extracellular-TM regions. The key step triggered by ligand binding is thus autophosphorylation.
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Affiliation(s)
- Jennifer M Kavran
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Jacqueline M McCabe
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Patrick O Byrne
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Mary Katherine Connacher
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Zhihong Wang
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Chemistry and Biochemistry, University of the Sciences, Philadelphia, United States
| | | | - Sarvenaz Sarabipour
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, United States
| | | | - David E Shaw
- DE Shaw Research, New York, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, United States
| | - Philip A Cole
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Daniel J Leahy
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, United States
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5
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Lee J, Miyazaki M, Romeo GR, Shoelson SE. Insulin receptor activation with transmembrane domain ligands. J Biol Chem 2014; 289:19769-77. [PMID: 24867955 DOI: 10.1074/jbc.m114.578641] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Complementary surfaces are buried when peptide hormones, growth factors, or cytokines bind and activate cellular receptors. Although these extended surfaces provide high affinity and specificity to the interactions, they also present great challenges to the design of small molecules that might either mimic or antagonize the process. We show that the insulin receptor (IR) and downstream signals can be activated by targeting a site outside of its ligand-binding domain. A 24-residue peptide having the IR transmembrane (TM) domain sequence activates IR, but not related growth factor receptors, through specific interactions with the receptor TM domain. Like insulin-dependent activation, IR-TM requires that IR have a competent ATP-binding site and kinase activation loop. IR-TM also activates mutated receptors from patients with severe insulin resistance, which do not respond to insulin. These results show that IR can be activated through a pathway that bypasses its canonical ligand-binding domain.
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Affiliation(s)
- Jongsoon Lee
- From the Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215
| | - Masaya Miyazaki
- From the Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215
| | - Giulio R Romeo
- From the Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215
| | - Steven E Shoelson
- From the Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215
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6
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Maruyama IN. Mechanisms of activation of receptor tyrosine kinases: monomers or dimers. Cells 2014; 3:304-30. [PMID: 24758840 PMCID: PMC4092861 DOI: 10.3390/cells3020304] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 04/10/2014] [Accepted: 04/11/2014] [Indexed: 02/06/2023] Open
Abstract
Receptor tyrosine kinases (RTKs) play essential roles in cellular processes, including metabolism, cell-cycle control, survival, proliferation, motility and differentiation. RTKs are all synthesized as single-pass transmembrane proteins and bind polypeptide ligands, mainly growth factors. It has long been thought that all RTKs, except for the insulin receptor (IR) family, are activated by ligand-induced dimerization of the receptors. An increasing number of diverse studies, however, indicate that RTKs, previously thought to exist as monomers, are present as pre-formed, yet inactive, dimers prior to ligand binding. The non-covalently associated dimeric structures are reminiscent of those of the IR family, which has a disulfide-linked dimeric structure. Furthermore, recent progress in structural studies has provided insight into the underpinnings of conformational changes during the activation of RTKs. In this review, I discuss two mutually exclusive models for the mechanisms of activation of the epidermal growth factor receptor, the neurotrophin receptor and IR families, based on these new insights.
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Affiliation(s)
- Ichiro N Maruyama
- Information Processing Biology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami, Okinawa 904-0495, Japan.
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7
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Panda AC, Grammatikakis I, Yoon JH, Abdelmohsen K. Posttranscriptional regulation of insulin family ligands and receptors. Int J Mol Sci 2013; 14:19202-29. [PMID: 24051403 PMCID: PMC3794829 DOI: 10.3390/ijms140919202] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/17/2013] [Accepted: 09/06/2013] [Indexed: 01/02/2023] Open
Abstract
Insulin system including ligands (insulin and IGFs) and their shared receptors (IR and IGFR) are critical regulators of insulin signaling and glucose homeostasis. Altered insulin system is associated with major pathological conditions like diabetes and cancer. The mRNAs encoding for these ligands and their receptors are posttranscriptionally controlled by three major groups of regulators; (i) alternative splicing regulatory factors; (ii) turnover and translation regulator RNA-binding proteins (TTR-RBPs); and (iii) non-coding RNAs including miRNAs and long non-coding RNAs (lncRNAs). In this review, we discuss the influence of these regulators on alternative splicing, mRNA stability and translation. Due to the pathological impacts of insulin system, we also discussed the possibilities of discovering new potential regulators which will improve understanding of insulin system and associated diseases.
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Affiliation(s)
- Amaresh C Panda
- Laboratory of Genetics, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA.
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8
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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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9
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Smit LS, Meyer DJ, Argetsinger LS, Schwartz J, Carter‐Su C. Molecular Events in Growth Hormone–Receptor Interaction and Signaling. Compr Physiol 2011. [DOI: 10.1002/cphy.cp070514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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10
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Rajawat YS, Hilioti Z, Bossis I. Aging: central role for autophagy and the lysosomal degradative system. Ageing Res Rev 2009; 8:199-213. [PMID: 19427410 DOI: 10.1016/j.arr.2009.05.001] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 05/01/2009] [Accepted: 05/01/2009] [Indexed: 12/19/2022]
Abstract
The lysosomal network is the major intracellular proteolytic system accounting for more than 98% of long-lived bulk protein degradation and recycling particularly in tissues such as liver and muscles. Lysosomes are the final destination of intracellular damaged structures, identified and sequestered by the processes of macroautophagy and chaperone-mediated autophagy (CMA). In the process of macroautophagy, long-lived proteins and other macromolecular aggregates and damaged intracellular organelles are first engulfed by autophagosomes. Autophagosomes themselves have limited degrading capacity and rely on fusion with lysosomes. Unlike macroautophagy, CMA does not require intermediate vesicle formation and the cytosolic proteins recognized by this pathway are directly translocated to the lysosomal membrane. Aging is a universal phenomenon characterized by progressive deterioration of cells and organs due to accumulation of macromolecular and organelle damage. The continuous removal of worn-out components and replacement with newly synthesized ones ensures cellular homeostasis and delays the aging process. Growing evidence indicate that the rate of autophagosome formation and maturation and the efficiency of autophagosome/lysosome fusion decline with age. In addition, a progressive increase in intralysosomal concentration of free radicals and the age pigment lipofuscin further diminish the efficiency of lysosomal protein degradation. Therefore, integrity of the autophagosomal-lysosomal network appears to be critical in the progression of aging. Discovery of the genes involved in the process of autophagy has provided insight into the various molecular pathways that may be involved in aging and senescence. In this review, we discuss the cellular and molecular mechanisms involved in autophagy and the role of autophagosome/lysosome network in the aging process.
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Affiliation(s)
- Yogendra S Rajawat
- University of Maryland, Department of Veterinary Medicine, College Park, MD 20742, United States
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11
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Compartmentalization and regulation of insulin signaling to GLUT4 by the cytoskeleton. VITAMINS AND HORMONES 2009; 80:193-215. [PMID: 19251039 DOI: 10.1016/s0083-6729(08)00608-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
One of the early events in the development of Type 2 diabetes appears to be an inhibition of insulin-mediated GLUT4 redistribution to the cell surface in tissues that express GLUT4. Understanding this process, and how it begins to breakdown in the development of insulin resistance is quite important as we face treatment and prevention of metabolic diseases. Over the past few years, and increasing number of laboratories have produced compelling data to demonstrate a role for both the actin and microtubule networks in the regulation of insulin-mediated GLUT4 redistribution to the cell surface. In this review, we explore this process from insulin-signal transduction to fusion of GLUT4 membrane vesicles, focusing on studies that have implicated a role for the cytoskeleton. We see from this body of work that both the actin network and the microtubule cytoskeleton play roles as targets of insulin action and effectors of insulin signaling leading to changes in GLUT4 redistribution to the cell surface and insulin-mediated glucose uptake.
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12
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Benyoucef S, Surinya K, Hadaschik D, Siddle K. Characterization of insulin/IGF hybrid receptors: contributions of the insulin receptor L2 and Fn1 domains and the alternatively spliced exon 11 sequence to ligand binding and receptor activation. Biochem J 2007; 403:603-13. [PMID: 17291192 PMCID: PMC1876384 DOI: 10.1042/bj20061709] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The IR (insulin receptor) and IGFR (type I insulin-like growth factor receptor) are found as homodimers, but the respective pro-receptors can also heterodimerize to form insulin-IGF hybrid receptors. There are conflicting data on the ligand affinity of hybrids, and especially on the influence of different IR isoforms. To investigate further the contribution of individual ligand binding epitopes to affinity and specificity in the IR/IGFR family, we generated hybrids incorporating both IR isoforms (A and B) and IR/IGFR domain-swap chimaeras, by ectopic co-expression of receptor constructs in Chinese hamster ovary cells, and studied ligand binding using both radioligand competition and bioluminescence resonance energy transfer assays. We found that IR-A-IGFR and IR-B-IGFR hybrids bound insulin with similar relatively low affinity, which was intermediate between that of homodimeric IR and homodimeric IGFR. However, both IR-A-IGFR and IR-B-IGFR hybrids bound IGF-I and IGF-II with high affinity, at a level comparable with homodimeric IGFR. Incorporation of a significant fraction of either IR-A or IR-B into hybrids resulted in abrogation of insulin- but not IGF-I-stimulated autophosphorylation. We conclude that the sequence of 12 amino acids encoded by exon 11 of the IR gene has little or no effect on ligand binding and activation of IR-IGFR hybrids, and that hybrid receptors bind IGFs but not insulin at physiological concentrations regardless of the IR isoform they contained. To reconstitute high affinity insulin binding within a hybrid receptor, chimaeras in which the IGFR L1 or L2 domains had been replaced by equivalent IR domains were co-expressed with full-length IR-A or IR-B. In the context of an IR-A-IGFR hybrid, replacement of IR residues 325-524 (containing the L2 domain and part of the first fibronectin domain) with the corresponding IGFR sequence increased the affinity for insulin by 20-fold. We conclude that the L2 and/or first fibronectin domains of IR contribute in trans with the L1 domain to create a high affinity insulin-binding site within a dimeric receptor.
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Affiliation(s)
- Samira Benyoucef
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QR, U.K
| | - Katharina H. Surinya
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QR, U.K
| | - Dirk Hadaschik
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QR, U.K
| | - Kenneth Siddle
- Department of Clinical Biochemistry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QR, U.K
- To whom correspondence should be addressed (email )
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13
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Blanquart C, Gonzalez-Yanes C, Issad T. Monitoring the Activation State of Insulin/Insulin-Like Growth Factor-1 Hybrid Receptors Using Bioluminescence Resonance Energy Transfer. Mol Pharmacol 2006; 70:1802-11. [PMID: 16926280 DOI: 10.1124/mol.106.026989] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In cells expressing both the insulin receptor isoform A (IRA) and the insulin-like growth factor-1 receptor (IGF1R), the presence of hybrid receptors, made up of an alphabeta-IRA chain associated with an alphabeta-IGF1R chain, has been demonstrated. These heterodimers are found in normal cells, and they also seem to play crucial roles in a number of cancers. However, they remain difficult to study, due to the concomitant presence of IRA and IGF1R homodimers. Using bioluminescence resonance energy transfer (BRET), we have developed assays to specifically monitor the activation state of IRA/IGF1R hybrids, both in vitro and in living cells. The first assay allowed the study of ligand-induced conformational changes within hybrid receptors purified from cells cotransfected with one type of receptor fused to Renilla reniformis luciferase (Rluc), and the other type of receptor fused to yellow fluorescent protein (YFP). In these conditions, only hybrid receptors were BRET-competent. In the second assay, the activation state of IRA/IGF1R hybrids was monitored in real time, in living cells, by cotransfection of kinase-dead versions of IRA-Rluc or IGF1R-Rluc, wild-type untagged IRA or IGF1R, and a YFP-tagged soluble version of the substrate-trapping mutant of protein tyrosine phosphatase 1B (YFP-PTP1B-D181A-Cter). In hybrid receptors, trans-phosphorylation of the kinase-dead alphabeta-Rluc moiety by the wild-type alphabeta moiety induced the recruitment of YFP-PTP1B-D181A-Cter, resulting in a hybrid-specific ligand-induced BRET signal. Therefore, both methods allow monitoring of the activity of IRA/IGF1R hybrid receptor and could be used to detect molecules of therapeutic interest for the treatment of cancer.
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Affiliation(s)
- Christophe Blanquart
- Department of Cell Biology, Institut Cochin, 22 Rue Méchain, 75014 Paris, France
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Nitert MD, Chisalita SI, Olsson K, Bornfeldt KE, Arnqvist HJ. IGF-I/insulin hybrid receptors in human endothelial cells. Mol Cell Endocrinol 2005; 229:31-7. [PMID: 15607526 DOI: 10.1016/j.mce.2004.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 10/07/2004] [Accepted: 10/12/2004] [Indexed: 10/26/2022]
Abstract
Vascular complications are common in diabetes. IGF-I receptors (IGF-IR) and insulin receptors (IR) in endothelial cells might respond to altered levels of IGF-I and insulin, resulting in altered endothelial function in diabetes. We therefore studied IGF-IR and IR gene expression, ligand binding, receptor protein, and phosphorylation in human umbilical vein endothelial cells (HUVEC). IGF-IR mRNA was more abundant than IR mRNA in freshly isolated HUVEC (IGF-IR/IR ratio 7.1 +/- 1.5) and in cultured HUVEC (ratio 3.5 +/- 0.51). Accordingly, specific binding of (125)I-IGF-I (0.64 +/- 0.25%) was higher than that of (125)I-insulin (0.25 +/- 0.09%). Protein was detected for both receptors and IGF-I/insulin hybrid receptors. IGF-IR phosphorylation was stimulated by 10(-10) to 10(-8) M IGF-I. IR were activated by 10(-9) to 10(-8) M insulin and IGF-I. We conclude that HUVEC express more IGF-IR than IR, and also express hybrid receptors. Both IGF-I and insulin phosphorylate their own receptors but only IGF-I seems to phosphorylate hybrid receptors.
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MESH Headings
- Cells, Cultured
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Humans
- Hypoglycemic Agents/metabolism
- Hypoglycemic Agents/pharmacology
- Insulin/pharmacology
- Insulin-Like Growth Factor I/pharmacology
- Iodine Radioisotopes
- Ligands
- Phosphorylation
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor, IGF Type 1/genetics
- Receptor, IGF Type 1/metabolism
- Receptor, Insulin/genetics
- Receptor, Insulin/metabolism
- Umbilical Veins/cytology
- Umbilical Veins/drug effects
- Umbilical Veins/metabolism
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Affiliation(s)
- Marloes Dekker Nitert
- Diabetes Research Center and Division of Cell Biology, Department of Biomedicine and Surgery, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden
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15
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Abstract
The incidence of type 2 diabetes mellitus (T2D) and obesity is increasing rapidly worldwide, reaching epidemic proportions. Insulin resistance is a key feature in both conditions and plays an important pathophysiological role. Over the last two decades a central role in the origin of insulin resistance has emerged for defects in the intracellular insulin signaling cascade leading to glucose uptake. Herein, we will 1) review insulin signaling pathways leading to glucose uptake, 2) review mouse models of insulin resistance that demonstrate the pathophysiologic importance of specific defects of these pathways and 3) discuss the molecular basis for insulin resistance in some human disease states known to be associated with insulin resistance. Finally, we will briefly mention some novel treatment targets for T2D stemming from this knowledge.
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Affiliation(s)
- Peter Vollenweider
- Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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16
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Moini H, Tirosh O, Park YC, Cho KJ, Packer L. R-alpha-lipoic acid action on cell redox status, the insulin receptor, and glucose uptake in 3T3-L1 adipocytes. Arch Biochem Biophys 2002; 397:384-91. [PMID: 11795898 DOI: 10.1006/abbi.2001.2680] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The insulin signaling pathway has been reported to mediate R-alpha-lipoic acid- (R-LA-)-stimulated glucose uptake into 3T3-L1 adipocytes and L6 myotubes. We investigated the role of the thiol antioxidant dihydrolipoic acid (DHLA) and intracellular glutathione (GSH) in R-LA-stimulated glucose transport and explored the hypothesis that R-LA could increase glucose uptake into 3T3-L1 adipocytes in an oxidant-mimetic manner. R-LA pretreatment of 3T3-L1 cells stimulated glucose transport at early time points (30 min - 6 h), whereas it inhibited glucose uptake at later time points. Analysis of the oxidized and reduced content of LA in cells and medium showed that >90% of lipoic acid present was in its oxidized form. Furthermore, all oxidized forms of LA (S-, R-, and racemic LA) stimulated glucose uptake, whereas the reduced form, dihydrolipoic acid, was ineffective. Intracellular GSH levels were not changed at the early time points (before 12 h), while longer preincubation (24 - 48 h) of cells with R-LA significantly increased intracellular GSH. Pretreatment of adipocytes with R-LA increased intracellular peroxide levels at early time points (30 min - 6 h), after which it was decreased (12 - 48 h). R-LA also increased tyrosine phosphorylation of immunoprecipitated insulin receptors from 3T3-L1 adipocytes. These results indicate that (i) 3T3-L1 adipocytes have a low capacity to reduce R-LA and the oxidized form of lipoic acid is responsible for stimulating glucose uptake, (ii) R-LA modulates glucose uptake by changing the intracellular redox status, and (iii) the insulin receptor is a potential cellular target for R-LA action.
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Affiliation(s)
- Hadi Moini
- Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, California 90033, USA
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17
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Emkey R, Kahn CR. Molecular Aspects of Insulin Signaling. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Czech MP, Van Renterghem B, Sleeman MW. Insulin Receptor Tyrosine Kinase. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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19
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Engh RA, Bossemeyer D. The protein kinase activity modulation sites: mechanisms for cellular regulation - targets for therapeutic intervention. ADVANCES IN ENZYME REGULATION 2001; 41:121-49. [PMID: 11384741 DOI: 10.1016/s0065-2571(00)00010-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- R A Engh
- Roche Diagnostics GmbH, Pharma Research Penzberg, Germany
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Lopaczynski W, Terry C, Nissley P. Autophosphorylation of the insulin-like growth factor I receptor cytoplasmic domain. Biochem Biophys Res Commun 2000; 279:955-60. [PMID: 11162456 DOI: 10.1006/bbrc.2000.4046] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cytoplasmic domain of the beta subunit of the insulin-like growth factor I receptor (amino acids 936-1337) was overexpressed in Sf9 insect cells using a baculovirus expression system, and the 6-His tagged receptor was purified by metal-affinity chromatography. Autophosphorylation of the receptor was concentration dependent, consistent with a trans phosphorylation mechanism. Phosphoamino acid analysis of the autophosphorylated receptor showed predominantly phosphotyrosine, but phosphoserine and phosphothreonine were also present. However, when the receptor was further purified by gel filtration on Sephadex G-100 and then autophosphorylated, phosphoamino acid analysis showed only phosphotyrosine. We conclude that the IGF-I receptor tyrosine kinase is not a dual-specificity kinase and that autophosphorylation of the beta subunit is by a trans mechanism.
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Affiliation(s)
- W Lopaczynski
- Metabolism Branch, National Cancer Institute, Bethesda, Maryland 20892, USA
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21
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Woldin CN, Hing FS, Lee J, Pilch PF, Shipley GG. Structural studies of the detergent-solubilized and vesicle-reconstituted insulin receptor. J Biol Chem 1999; 274:34981-92. [PMID: 10574975 DOI: 10.1074/jbc.274.49.34981] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin binding to the insulin receptor initiates a cascade of cellular events that are responsible for regulating cell metabolism, proliferation, and growth. We have investigated the structure of the purified, functionally active, human insulin receptor using negative stain and cryo-electron microscopy. Visualization of the detergent-solubilized and vesicle-reconstituted receptor shows the alpha(2)beta(2) heterotetrameric insulin receptor to be a three-armed pinwheel-like complex that exhibits considerable variability among individual receptors. The alpha-subunit of the receptor was labeled with an insulin analogue.streptavidin gold conjugate, which facilitated the identification of the receptor arm responsible for insulin binding. The gold label was localized to the tip of a single receptor arm of the three-armed complex. The beta-subunit of the insulin receptor was labeled with a maleimide-gold conjugate, which allowed orientation of the receptor complex in the membrane bilayer. The model derived from electron microscopic studies displays a "Y"-like morphology representing the predominant species identified in the reconstituted receptor images. The insulin receptor dimensions are approximately 12.2 nm by 20.0 nm, extending 9.7 nm above the membrane surface. The beta-subunit-containing arm is approximately 13.9 nm, and each alpha-subunit-containing arm is 8.6 nm in length. The model presented is the first description of the insulin receptor visualized in a fully hydrated state using cryo-electron microscopy.
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Affiliation(s)
- C N Woldin
- Department of Biophysics, Center for Advanced Biomedical Research, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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22
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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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23
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Elmendorf JS, Pessin JE. Insulin signaling regulating the trafficking and plasma membrane fusion of GLUT4-containing intracellular vesicles. Exp Cell Res 1999; 253:55-62. [PMID: 10579911 DOI: 10.1006/excr.1999.4675] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- J S Elmendorf
- Department of Physiology, University of Iowa, Iowa City, Iowa, 52242-1109, USA
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24
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Tsuda S, Kaihara M, Zhou X, Britos D, Arakaki R. The in vitro synthesized and processed human insulin receptor precursor binds insulin. FEBS Lett 1999; 457:13-7. [PMID: 10486554 DOI: 10.1016/s0014-5793(99)00995-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The cell-free examination of the human insulin receptor during biogenesis may provide a greater understanding of the elements that contribute to the acquisition of receptor function. The insulin receptor precursor components were produced in a cell-free system and the insulin binding ability of the [35S]methionine-labeled translation products was determined. The processed proreceptor represented by a 190 kDa band was retained on insulin-linked biotin-streptavidin agarose or an insulin column. The insulin binding 190 kDa band migrated slower than the non-binding 190 kDa band on SDS-PAGE which suggests that covalent modifications account for these differences. The trypsin-digested product of the 190 kDa proreceptor was also retained on insulin-linked biotin-streptavidin agarose, however the alpha-subunit precursor was retained on insulin agarose to a much lesser degree. We conclude that a significant fraction of the processed, in vitro translated insulin proreceptor acquires insulin binding ability.
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Affiliation(s)
- S Tsuda
- Department of Medicine, John A. Burns School of Medicine, University of Hawaii-Manoa, Honolulu 96813, USA
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25
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Oates AC, Lackmann M, Power MA, Brennan C, Down LM, Do C, Evans B, Holder N, Boyd AW. An early developmental role for eph-ephrin interaction during vertebrate gastrulation. Mech Dev 1999; 83:77-94. [PMID: 10381569 DOI: 10.1016/s0925-4773(99)00036-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Eph receptor tyrosine kinases (RTK) and their ephrin ligands are involved in the transmission of signals which regulate cytoskeletal organisation and cell migration, and are expressed in spatially restricted patterns at discrete phases during embryogenesis. Loss of function mutants of Eph RTK or ephrin genes result in defects in neuronal pathfinding or cell migration. In this report we show that soluble forms of human EphA3 and ephrin-A5, acting as dominant negative inhibitors, interfere with early events in zebrafish embryogenesis. Exogenous expression of both proteins results in dose-dependent defects in somite development and organisation of the midbrain-hindbrain boundary and hindbrain. The nature of the defects as well as the distribution and timing of expression of endogenous ligands/receptors for both proteins suggest that Eph-ephrin interaction is required for the organisation of embryonic structures by coordinating the cellular movements of convergence during gastrulation.
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Affiliation(s)
- A C Oates
- Ludwig Institute for Cancer Research (Melbourne Branch) Post Office, Royal Melbourne Hospital, Victoria 3050, Australia
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26
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Taylor SI, Arioglu E. Syndromes associated with insulin resistance and acanthosis nigricans. J Basic Clin Physiol Pharmacol 1999; 9:419-39. [PMID: 10212846 DOI: 10.1515/jbcpp.1998.9.2-4.419] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- S I Taylor
- Diabetes Branch, National Institute of Diabetes and Digestive, National Institutes of Health, Bethesda, MD 20892, USA.
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27
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Parast CV, Mroczkowski B, Pinko C, Misialek S, Khambatta G, Appelt K. Characterization and kinetic mechanism of catalytic domain of human vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR2 TK), a key enzyme in angiogenesis. Biochemistry 1998; 37:16788-801. [PMID: 9843450 DOI: 10.1021/bi981291f] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vascular endothelial growth factor (VEGF) is a dimeric protein which induces formation of new blood vessels (angiogenesis) through binding to VEGF-receptor-2 tyrosine kinase (VEGFR2 TK) or KDR (kinase insert domain-containing receptor) on the surface of endothelial cells. Angiogenesis has been shown to be essential for malignancy of tumors; therefore, VEGFR2 TK is a potential therapeutic target for the treatment of cancer. Sequence homology studies indicate that VEGFR2 TK contains three domains: extracellular (ligand-binding domain), transmembrane, and intracellular (catalytic domain). In this work, the catalytic domain of VEGFR2 TK was cloned and expressed in a soluble active form using a baculovirus expression system. In the absence of ligand, the enzyme is shown to catalyze its autophosphorylation in a time-dependent and enzyme-concentration-dependent manner, consistent with a trans mechanism for this reaction. Mass spectrometry analysis revealed incorporation of 5.5 +/- 0.5 mol of phosphate/mole of enzyme (monomer). In addition, the enzyme was shown to catalyze phosphorylation of a synthetic peptide, poly(E4Y). Using poly(E4Y) as substrate, the kinetic constants of both native and phosphorylated enzyme were determined. Enzyme phosphorylation increased catalytic efficiency of the enzyme by at least an order of magnitude. Furthermore, the enzyme was shown to catalyze the reverse reaction using phospho-poly(E4Y) as substrate. Cd2+ was found to be an inhibitor of the enzyme. Kinetic studies revealed that inhibition by Cd2+ was competitive with respect to Mg2+ and noncompetitive with respect to MgATP. These results indicate that Cd2+ competes for a second metal-binding site. Therefore, the reaction catalyzed by this enzyme was treated as a terreactant system. The kinetic mechanism of VEGFR2 TK was elucidated through the use of steady-state kinetic studies. According to these studies, the enzyme binds Mg2+ and MgATP in a random fashion followed by ordered addition of the peptide substrate. The release of product is also ordered, with MgADP being released last. The order of substrate binding was confirmed by using AMP-PCP, a dead-end inhibitor.
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Affiliation(s)
- C V Parast
- Agouron Pharmaceuticals, Incorporated, San Diego, California 92121, USA.
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28
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Abstract
OBJECTIVE To review the available information regarding the roles of insulin-like growth factor (IGF)-IGF binding protein (IGFBP) system in ovarian physiology. DESIGN Studies that specifically relate to the roles of ovarian folliculogenesis, oocyte maturation, and ovulation were identified through the literature and Medline searches. RESULTS Numerous actions of the IGFs have been demonstrated in the ovary, including an enhancement of cell proliferation, aromatase activity, and progesterone biosynthesis. The ovarian IGF system, comprised of IGF-I and IGF-II peptides, IGFBPs and IGF receptors, plays a significant role in the process of follicular development. In addition, IGF-I stimulates the meiotic maturation of follicle-enclosed oocytes in vitro via the IGF-I receptors. IGFBP-3 significantly inhibit gonadotropin-induced ovulation and oocyte maturation by neutralizing endogenously produced IGF-I. Thus, the intraovarian IGF-IGFBP system play a significant role in the processes of follicular development, oocyte maturation, and ovulation. CONCLUSION IGF-IGFBP systems have autocrine/paracrine regulatory actions in ovarian physiology. The disturbance of the IGF-IGFBP system in human ovaries may lead to an ovulation, disorders of androgen excess, and infertility.
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Affiliation(s)
- Y Yoshimura
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo, Japan
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29
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Hunter SJ, Garvey WT. Insulin action and insulin resistance: diseases involving defects in insulin receptors, signal transduction, and the glucose transport effector system. Am J Med 1998; 105:331-45. [PMID: 9809695 DOI: 10.1016/s0002-9343(98)00300-3] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- S J Hunter
- Department of Medicine, Medical University of South Carolina, Ralph H. Johnson Veterans Affairs Medical Center, Charleston 29425, USA
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30
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Cann AD, Bishop SM, Ablooglu AJ, Kohanski RA. Partial activation of the insulin receptor kinase domain by juxtamembrane autophosphorylation. Biochemistry 1998; 37:11289-300. [PMID: 9698376 DOI: 10.1021/bi9809122] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Increased enzymatic activity of receptor tyrosine kinases occurs after trans-phosphorylation of one or two tyrosines in the activation loop, located near the catalytic cleft. Partial activation of the insulin receptor's kinase domain was observed at dilute concentrations of kinase, suggesting that cis-autophosphorylation was occurring. Autophosphorylation during partial activation mapped to the juxtamembrane (JM) tyrosines and not to activation loop tyrosines. Furthermore, a double JM Tyr-to-Phe mutant kinase (JMY2F) did not undergo partial activation but catalyzed substrate phosphorylation at a very low rate. Steady-state kinetics of peptide phosphorylation were determined with and without JM autophosphorylation. The JMY2F mutant was used to prevent concurrent cis-autophosphorylation and therefore to approximate the basal state apoenzyme in the kinetic analysis. Partial activation was dominated by a decreased Michaelis constant for peptide substrate, from KM,PEP >/= 2.5 mM in the basal state to 0.2 mM in the partially activated state; the KM,ATP remained virtually unchanged at approximately 1 mM, and kcat increased from 180 to 600 min-1. The high KM,PEP suggests weak binding of peptide substrates to the apoenzyme. This was confirmed by Ki > 1 mM for peptide substrates used as inhibitors of JM autophosphorylation. The absence of comparably large changes in kcat and KM,ATP suggests that the JM region is primarily a strong barrier to the peptide entry step of trans-phosphorylation reactions. The JM region therefore functions as an intrasteric inhibitor in the basal state of the insulin receptor's kinase domain.
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Affiliation(s)
- A D Cann
- Department of Biochemistry, The Mount Sinai School of Medicine, New York 10029, USA
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31
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Lackmann M, Oates AC, Dottori M, Smith FM, Do C, Power M, Kravets L, Boyd AW. Distinct subdomains of the EphA3 receptor mediate ligand binding and receptor dimerization. J Biol Chem 1998; 273:20228-37. [PMID: 9685371 DOI: 10.1074/jbc.273.32.20228] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eph receptor tyrosine kinases and their ligands (ephrins) are highly conserved protein families implicated in patterning events during development, particularly in the nervous system. In a number of functional studies, strict conservation of structure and function across distantly related vertebrate species has been confirmed. In this study we make use of the observation that soluble human EphA3 (HEK) exerts a dominant negative effect on somite formation and axial organization during zebrafish embryogenesis to probe receptor function. Based on exon structure we have dissected the extracellular region of EphA3 receptor into evolutionarily conserved subdomains and used kinetic BIAcore analysis, mRNA injection into zebrafish embryos, and receptor transphosphorylation analysis to study their function. We show that ligand binding is restricted to the N-terminal region encoded by exon III, and we identify an independent, C-terminal receptor-dimerization domain. Recombinant proteins encoding either region in isolation can function as receptor antagonists in zebrafish. We propose a two-step mechanism of Eph receptor activation with distinct ligand binding and ligand-independent receptor-receptor oligomerization events.
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Affiliation(s)
- M Lackmann
- Ludwig Institute for Cancer Research (Melbourne Branch), Post Office, Royal Melbourne Hospital, Victoria 3050, Australia
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32
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Reinecke M, Collet C. The phylogeny of the insulin-like growth factors. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 183:1-94. [PMID: 9666565 DOI: 10.1016/s0074-7696(08)60142-4] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The insulin-like growth factors are major regulators of growth and development in mammals and their presence in lower vertebrates suggests that they played a similarly fundamental role throughout vertebrate evolution. While originally perceived simply as mediators of growth hormone, on-going research in mammals has revealed several hierarchical layers of complexity in the regulation of ligand bioavailability and signal transduction. Our understanding of the biological role and mechanisms of action of these important growth factors in mammals patently requires further elucidation of the IGF hormone system in the simple model systems that can be found in lower vertebrates and protochordates. This review contrasts our knowledge of the IGF hormone system in mammalian and nonmammalian models through comparison of tissue and developmental distributions and gene structures of IGF system components in different taxa. We also discuss the evolutionary origins of the system components and their possible evolutionary pathways.
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Affiliation(s)
- M Reinecke
- Division of Neuroendocrinology, University of Zürich, Switzerland
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33
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Abstract
It is now clear that PCOS is often associated with profound insulin resistance as well as with defects in insulin secretion. These abnormalities, together with obesity, explain the substantially increased prevalence of glucose intolerance in PCOS. Moreover, since PCOS is an extremely common disorder, PCOS-related insulin resistance is an important cause of NIDDM in women (Table 3). The insulin resistance in at least 50% of PCOS women appears to be related to excessive serine phosphorylation of the insulin receptor. A factor extrinsic to the insulin receptor, presumably a serine/threonine kinase, causes this abnormality and is an example of an important new mechanism for human insulin resistance related to factors controlling insulin receptor signaling. Serine phosphorylation appears to modulate the activity of the key regulatory enzyme of androgen biosynthesis, P450c17. It is thus possible that a single defect produces both the insulin resistance and the hyperandrogenism in some PCOS women (Fig. 19). Recent studies strongly suggest that insulin is acting through its own receptor (rather than the IGF-I receptor) in PCOS to augment not only ovarian and adrenal steroidogenesis but also pituitary LH release. Indeed, the defect in insulin action appears to be selective, affecting glucose metabolism but not cell growth. Since PCOS usually has a menarchal age of onset, this makes it a particularly appropriate disorder in which to examine the ontogeny of defects in carbohydrate metabolism and for ascertaining large three-generation kindreds for positional cloning studies to identify NIDDM genes. Although the presence of lipid abnormalities, dysfibrinolysis, and insulin resistance would be predicted to place PCOS women at high risk for cardiovascular disease, appropriate prospective studies are necessary to directly assess this.
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Affiliation(s)
- A Dunaif
- Pennsylvania State University College of Medicine, Hershey 17033, USA
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34
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Cann AD, Kohanski RA. Cis-autophosphorylation of juxtamembrane tyrosines in the insulin receptor kinase domain. Biochemistry 1997; 36:7681-9. [PMID: 9201908 DOI: 10.1021/bi970170x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Receptor tyrosine kinases undergo ligand-induced dimerization that promotes kinase domain trans-autophosphorylation. However, the kinase domains of the insulin receptor are effectively dimerized because of the covalent alpha2beta2 holomeric structure. This fact has made it difficult to determine the molecular mechanism of intraholomeric autophosphorylation, but there is evidence for both cis- and trans-autophosphorylation in the absence and presence of insulin. Here, using the cytoplasmic kinase domain (CKD) of the human insulin receptor, we demonstrate that autophosphorylation in the juxtamembrane (JM) subdomain follows a cis-reaction pathway. JM autophosphorylation was independent of CKD concentration over the range 6 nM-3 microM and was characterized kinetically: Half-saturation (K(ATP)) was observed at 75 microM ATP [5 mM Mn(CH3CO2)2] with a maximal rate of 0.24 mol of PO4 (mol of CKD)(-1) min(-1). Pairwise substitutions of Phe for Tyr in the other two autophosphorylation subdomains, generated by site-directed mutagenesis, altered the kinetics of JM autophosphorylation but did not change the pathway from a cis-reaction. Tyr(1328,1334) to Phe (in the carboxy-terminal subdomain) yielded <2-fold increase in the efficiency of JM autophosphorylation, whereas Tyr(1162,1163) to Phe (in the activation loop subdomain) yielded approximately 38-fold increased efficiency of JM autophosphorylation, due predominantly to a 23-fold decreased K(ATP). These findings demonstrate basal state binding of ATP to the CKD leading to cis-autophosphorylation and novel basal state regulatory interactions among the subdomains of the insulin receptor kinase. On the basis of these results and the crystal structure of the conserved catalytic core of this kinase [Hubbard, S. R., et al. (1994) Nature 372, 746], a model is proposed which reconciles the JM cis-reaction and the activation loop cis-inhibition/trans-reaction with the complex kinetics of insulin receptor autophosphorylation [Kohanski, R. A. (1993) Biochemistry 32, 5766].
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Affiliation(s)
- A D Cann
- Department of Biochemistry, The Mount Sinai School of Medicine, New York, New York 10029, USA
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35
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Chaika OV, Chaika N, Volle DJ, Wilden PA, Pirrucello SJ, Lewis RE. CSF-1 receptor/insulin receptor chimera permits CSF-1-dependent differentiation of 3T3-L1 preadipocytes. J Biol Chem 1997; 272:11968-74. [PMID: 9115260 DOI: 10.1074/jbc.272.18.11968] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A chimeric growth factor receptor (CSF1R/IR) was constructed by splicing cDNA sequences encoding the extracellular ligand binding domain of the human colony stimulating factor-1 (CSF-1) receptor to sequences encoding the transmembrane and cytoplasmic domains of the human insulin receptor. The addition of CSF-1 to cells transfected with the CSF1R/IR chimera cDNA stimulated the tyrosine phosphorylation of a protein that was immunoprecipitated by an antibody directed against the carboxyl terminus of the insulin receptor. Phosphopeptide maps of the 32P-labeled CSF1R/IR protein revealed the same pattern of phosphorylation observed in 32P-labeled insulin receptor beta subunits. CSF-1 stimulated the tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and Shc in cells expressing the CSF1R/IR chimera. Lipid accumulation and the expression of a differentiation-specific marker demonstrated that 3T3-L1 preadipocytes undergo CSF-1-dependent differentiation when transfected with the CSF1R/IR chimera cDNA but not when transfected with the expression vector alone. A 12-amino acid deletion within the juxtamembrane region of the CSF1R/IR (CSF1R/IRDelta960) blocked CSF-1-stimulated phosphorylation of IRS-1 and Shc but did not inhibit CSF-1-mediated differentiation of 3T3-L1 preadipocytes. These observations indicate that adipocyte differentiation can be initiated by intracellular pathways that do not require tyrosine phosphorylation of IRS-1 or Shc.
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Affiliation(s)
- O V Chaika
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA
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36
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Iwasaki Y, Nishiyama H, Suzuki K, Koizumi S. Sequential cis/trans autophosphorylation in TrkB tyrosine kinase. Biochemistry 1997; 36:2694-700. [PMID: 9054577 DOI: 10.1021/bi962057x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
TrkB, a member of the tyrosine kinase family of growth factor receptors, is activated by binding of brain-derived neurotrophic factor or neurotrophin 4/5. The intracellular kinase domain of TrkB (ICD-TrkB) was prepared by an insect cell expression system and characterized to identify the mechanism of autophosphorylation. The time course of autophosphorylation, which shows a biphasic progression with a slow nonlinear phase followed by a fast linear phase, indicates the existence of autophosphorylation-induced activation in ICD-TrkB. This is also supported by the finding that phosphorylated ICD-TrkB shows significantly higher activity than control naive ICD-TrkB. Interestingly, the autophosphorylation rate in the linear phase clearly depends on the ICD-TrkB concentration, whereas the rate of initial autophosphorylation is independent of the concentration of ICD-TrkB in the reaction mixture. This observation suggests a two-step autophosphorylation, first an intramolecular activating step and then an intermolecular step. This mechanism is confirmed by the result that only the later phase of autophos-phorylation is inhibited by addition of glycerol which interferes with intermolecular interactions. Therefore, we propose the mechanism of ICD-TrkB autophosphorylation as a sequential cis/trans phosphorylation.
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Affiliation(s)
- Y Iwasaki
- Bio-Organic Research Department, Ciba-Geigy (Japan) Limited, Takarazuka
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37
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Lee J, Pilch PF, Shoelson SE, Scarlata SF. Conformational changes of the insulin receptor upon insulin binding and activation as monitored by fluorescence spectroscopy. Biochemistry 1997; 36:2701-8. [PMID: 9054578 DOI: 10.1021/bi961815g] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have characterized the changes in intrinsic fluorescence that the insulin receptor undergoes upon ligand binding and autophosphorylation. The binding of insulin to its receptor results in an increase in the receptor's fluorescence intensity, emission energy and anisotropy. We monitored the time course of the anisotropy change, and these data, coupled with studies monitoring the energy transfer from insulin receptor tryptophan donors to a fluorescent-labeled insulin, allowed us to conclude that the change in anisotropy is due to a conformational change in the receptor induced by hormone binding. Since insulin association is very fast, the time course also allowed us to estimate the slower rate of formation of this conformationally-altered state. The time course of receptor autophosphorylation was measured under similar conditions and was found to be similar to the ligand-induced anisotropy time course. The simultaneous use of two fluorescent-labeled insulin analogs also allowed us to assess the maximum distance between the two hormones bound to the receptor. Addition of ATP produces a large, seemingly instantaneous increase in anisotropy. Our observation that ATP binds to the insulin receptor in the presence and absence of insulin supports the idea that the conformational change produced by insulin binding increases the rate of autophosphorylation rather than increases ATP affinity. A suggested model for these changes is presented.
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Affiliation(s)
- J Lee
- Department of Biochemistry, Boston University, School of Medicine, Massachusetts 02118, USA
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38
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Mynarcik DC, Williams PF, Schaffer L, Yu GQ, Whittaker J. Analog binding properties of insulin receptor mutants. Identification of amino acids interacting with the COOH terminus of the B-chain of the insulin molecule. J Biol Chem 1997; 272:2077-81. [PMID: 8999905 DOI: 10.1074/jbc.272.4.2077] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Recent studies utilizing alanine scanning mutagenesis have identified a major ligand binding domain of the secreted recombinant insulin receptor composed of two subdomains, one between amino acids 1 and 120 and the other between amino acids 704 and 716. In order to obtain a more detailed characterization of these subdomains, we examined the binding of an insulin superanalog, des-(B25-30)-[His-A8, Asp-B10, Tyr-B25 alpha-carboxamide]insulin, to alanine mutants of the ligand binding determinants of these subdomains. cDNAs encoding mutant secreted recombinant receptors were transiently expressed in 293 EBNA cells, and the binding properties for this analog of the expressed receptors were evaluated. In general des-(B25-30)-[His-A8, Asp-B10, Tyr-B25 alpha-carboxamide]insulin binding correlated with insulin binding, suggesting that both peptides bound to the receptor in a similar manner. Alanine mutations of eight amino acids (Asn15, Phe64, Phe705, Glu706, Tyr708, Leu709, Asn711, and Phe714) of the receptor produced the most profound decreases in affinity for des-(B25-30)-[His-A8, Asp-B10, Tyr-B25 alpha-carboxamide]insulin, suggesting that interactions with these amino acids contributed the major part of the free energy of the ligand-receptor interaction. Mutation of Arg14 and His710 to Ala produced receptors with undetectable insulin binding but an affinity for des-(B25-30)-[His-A8, Asp-B10, Tyr-B25 alpha-carboxamide]insulin only 8-23-fold less than for native receptor. Further analog studies were performed to elucidate this paradox. The receptor binding potencies of His-A8 and Asp-B10 insulins for these receptor mutants appeared to parallel their relative potencies for native receptor. In contrast the receptor binding potency of des-(B25-30)-[Tyr-B25 alpha-carboxamide]insulin was disproportionately increased for these mutants when compared with its potency for native receptor.
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Affiliation(s)
- D C Mynarcik
- Department of Medicine and Physiology, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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39
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Takata Y, Imamura T, Haruta T, Sasaoka T, Morioka H, Ishihara H, Sawa T, Usui I, Ishiki M, Kobayashi M. The dominant negative effect of a kinase-defective insulin receptor on insulin-like growth factor-I-stimulated signaling in Rat-1 fibroblasts. Metabolism 1996; 45:1474-82. [PMID: 8969279 DOI: 10.1016/s0026-0495(96)90175-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
To study the interaction between insulin receptor (IR) and insulin-like growth factor-I (IGF-I) receptor (IGF-IR) tyrosine kinases, we examined IGF-I action in Rat-1 cells expressing a naturally occurring tyrosine kinase-deficient mutant IR (Asp 1048 IR). IGF-I normally stimulated receptor autophosphorylation, IRS-I phosphorylation, and glycogen synthesis in cells expressing Asp 1048 IR. However, the Asp 1048 IR inhibited IGF-I-stimulated thymidine uptake by 45% to 52% and amino acid uptake (aminoisobutyric acid [AIB]) by 58% in Asp 1048 IR cells. Furthermore, IGF-I-stimulated tyrosine kinase activity toward synthetic polymers, Shc phosphorylation, and mitogen-activated protein (MAP) kinase activity was inhibited. The inhibition of mitogenesis and AIB uptake was restored with the amelioration of the impaired tyrosine kinase activity and Shc phosphorylation by the introduction of abundant wild-type IGF-IR in Asp 1048 IR cells. These results suggest that the Asp 1048 IR causes a dominant negative effect on IGF-IR in transmitting signals to Shc and MAP kinase activation, which leads to decreased IGF-I-stimulated DNA synthesis, and that the kinase-defective insulin receptor does not affect IGF-I-stimulated IRS-I phosphorylation, which leads to the normal IGF-I-stimulated glycogen synthesis.
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Affiliation(s)
- Y Takata
- First Department of Medicine, Toyama Medical and Pharmaceutical University, Japan
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40
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Mynarcik DC, Yu GQ, Whittaker J. Alanine-scanning mutagenesis of a C-terminal ligand binding domain of the insulin receptor alpha subunit. J Biol Chem 1996; 271:2439-42. [PMID: 8576204 DOI: 10.1074/jbc.271.5.2439] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
A recent affinity labeling study has suggested that amino acids 704-717 of the C terminus of the insulin receptor represent a contact site for insulin. To determine whether these amino acids are part of a ligand binding site, we have performed alanine-scanning mutagenesis of this region. Mutant cDNAs encoding recombinant secreted receptors were transiently expressed in 293 EBNA cells, and their insulin binding properties were evaluated. Of the 14 residues in this region only 4 amino acids, Asp-707, Val-712, Pro-716, and Arg-717, could be mutated to alanine without compromising insulin binding. The reduction in affinity resulting from the individual mutation of the remaining amino acids varied from an increase in Kd to 3.69 x 10(-9) M (Asn-711) to greater than 10(-6) M (Thr-704, Phe-705, Glu-706, and His-710); the Kd of native secreted recombinant receptor is 0.56 x 10(-9) M.
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Affiliation(s)
- D C Mynarcik
- Department of Medicine, State University of New York, Stony Brook 11794, USA
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41
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Accili D, Drago J, Lee EJ, Johnson MD, Cool MH, Salvatore P, Asico LD, José PA, Taylor SI, Westphal H. Early neonatal death in mice homozygous for a null allele of the insulin receptor gene. Nat Genet 1996; 12:106-9. [PMID: 8528241 DOI: 10.1038/ng0196-106] [Citation(s) in RCA: 374] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- D Accili
- Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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42
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Abstract
The solution of crystal structures from half a dozen protein kinases during the last four years in different laboratories has deepened our understanding of the catalysis and regulation of this enzyme class, and given a vigorous impetus to the whole field. Due to the great degree of sequence conservation among protein kinases the informational yield with every new structure is high, as each is a representative of the enzyme family in general and most often of a subclass in particular. This review will focus on the active site structure of cAMP-dependent protein kinase (cAPK) with special regard to two new crystal structures; one of an active protein kinase CK1*, which may represent an as yet unsolved step in the kinetic pathway, and the other of the insulin receptor kinase domain, the first structure of a tyrosine kinase.
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Affiliation(s)
- D Bossemeyer
- Department of Pathochemistry, German Cancer Research Centre, Heidelberg
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43
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Bevan AP, Burgess JW, Drake PG, Shaver A, Bergeron JJ, Posner BI. Selective activation of the rat hepatic endosomal insulin receptor kinase. Role for the endosome in insulin signaling. J Biol Chem 1995; 270:10784-91. [PMID: 7537739 DOI: 10.1074/jbc.270.18.10784] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Insulin administration activates the insulin receptor kinase (IRK) in both plasma membrane (PM) and endosomes (ENs) raising the possibility of transmembrane signaling occurring in the endosomal compartment. Peroxovanadium compounds activate the IRK by inhibiting IR-associated phosphotyrosine phosphatase(s). Following the administration of the phosphotyrosine phosphatase inhibitor bisperoxo(1,10-phenanthroline)-oxovanadate (V) anion (bpV(phen)) activation of the hepatic IRK in ENs preceded that in PM by 5 min. When colchicine treatment preceded bpV(phen) administration IRK activation in ENs was unaffected but was totally abrogated in PM. Insulin receptor substrate-1 tyrosine phosphorylation followed the kinetics of IRK activation in ENs not PM and a hypoglycemic response similar to that achieved with a pharmacological dose of insulin ensued. These studies demonstrate that ENs constitute a site for IR-mediated signal transduction.
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Affiliation(s)
- A P Bevan
- Polypeptide Hormone Laboratory, McGill University, Montreal, Quebec, Canada
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44
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Wei L, Hubbard SR, Hendrickson WA, Ellis L. Expression, characterization, and crystallization of the catalytic core of the human insulin receptor protein-tyrosine kinase domain. J Biol Chem 1995; 270:8122-30. [PMID: 7713916 DOI: 10.1074/jbc.270.14.8122] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The deduced primary sequence of the cytoplasmic protein-tyrosine kinase domain of the insulin receptor contains a conserved kinase homology region (receptor residues 1002-1257) flanked by a juxtamembrane region and a C-terminal tail. A soluble 48-kDa derivative (residues 959-1355) containing these regions but lacking the first six residues of the juxtamembrane region had earlier been synthesized in Sf9 cells using a baculovirus expression system. The catalytic core of the kinase domain was studied first by proteolytic analysis of the 48-kDa kinase and then by expressing a series of truncated kinase domains in transiently transfected COS cells. Based on these studies, two core kinases of 34 (residues 985-1283) and 35 (residues 978-1283) kDa, respectively, were overexpressed in Sf9 cells. Biochemical characterization of the 35-kDa kinase revealed that the core kinase conserved the major functional properties of the native receptor kinase domain. Activity of the 35-kDa kinase toward a synthetic peptide increased more than 200-fold upon autophosphorylation, which occurred exclusively at Tyr-1158, Tyr-1162, and Tyr-1163; the largest increase was observed between bis- and trisphosphorylation of the kinase. The activated 35- and 48-kDa kinases were similar with respect to specific activity and ATP and Mg2+ requirements for peptide phosphorylation. Moreover, autophosphorylation appeared to initiate predominantly at Tyr-1162, immediately followed by phosphorylation at Tyr-1158 and then at Tyr-1163. The rate of autophosphorylation was dependent on enzyme concentration, consistent with a trans-phosphorylation mechanism. Finally, the 35-kDa kinase was crystallized, making possible elucidation of its three-dimensional structure by x-ray crystallography.
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Affiliation(s)
- L Wei
- W. M. Keck Center for Genome Informatics, Texas A & M University, Houston 77030, USA
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45
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Affiliation(s)
- D Accili
- Diabetes Branch, NIDDK, Bethesda, MD 20892, USA
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46
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McDonald NQ, Murray-Rust J, Blundell TL. The first structure of a receptor tyrosine kinase domain: a further step in understanding the molecular basis of insulin action. Structure 1995; 3:1-6. [PMID: 7743124 DOI: 10.1016/s0969-2126(01)00129-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Both the observed cis-inhibition and the proposed trans-activation of the insulin receptor tyrosine kinase help explain insulin signalling through its receptor.
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Affiliation(s)
- N Q McDonald
- Department of Crystallography, Birkbeck College, London, UK
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47
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Hubbard SR, Wei L, Ellis L, Hendrickson WA. Crystal structure of the tyrosine kinase domain of the human insulin receptor. Nature 1994; 372:746-54. [PMID: 7997262 DOI: 10.1038/372746a0] [Citation(s) in RCA: 796] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The X-ray crystal structure of the tyrosine kinase domain of the human insulin receptor has been determined by multiwavelength anomalous diffraction phasing and refined to 2.1 A resolution. The structure reveals the determinants of substrate preference for tyrosine rather than serine or threonine and a novel autoinhibition mechanism whereby one of the tyrosines that is autophosphorylated in response to insulin, Tyr 1,162, is bound in the active site.
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Affiliation(s)
- S R Hubbard
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032
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48
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Haft CR, Taylor SI. Deletion of 343 amino acids from the carboxyl terminus of the beta-subunit of the insulin receptor inhibits insulin signaling. Biochemistry 1994; 33:9143-51. [PMID: 8049217 DOI: 10.1021/bi00197a017] [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: 01/28/2023]
Abstract
Naturally occurring mutations in the insulin receptor gene that impair the receptor tyrosine kinase activity cause insulin resistance in vivo in a dominant fashion. Previously, two unrelated families have been described that express an insulin receptor with a truncation due to a premature chain termination at codon 1000 (delta 1000), thereby deleting 343 amino acids from the carboxyl terminus of the beta-subunit. While clinical findings suggest that the truncated receptor does not mediate insulin action in vivo, a recent study suggested that a similarly truncated receptor enhanced insulin sensitivity in transfected cells by augmenting the signaling by endogenous receptors [Sasaoka, T., Takata, Y., Kusari, J., Anderson, C. M., Langlois, W. J., & Olefsky, J. M. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 4379-4383]. To investigate these paradoxical data, we studied the structure and function of delta 1000 truncated insulin receptors when expressed in NIH-3T3 cells. We found that, despite the deletion of most of the tyrosine kinase domain and all of the C-terminal domain of the beta-subunit of the insulin receptor, the delta 1000 mutant receptors were processed normally and were transported to the plasma membrane where they bind insulin with high affinity. Following ligand addition, the truncated receptors are degraded with a normal half-life. However, they fail to undergo insulin-stimulated internalization, do not regulate the phosphorylation of insulin receptor substrate 1, and are unable to mediate an insulin-stimulated increase in DNA synthesis and c-jun and c-fos expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C R Haft
- Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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49
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Smith JE, Sheng ZF, Kallen RG. Effects of tyrosine-->phenylalanine mutations on auto- and trans-phosphorylation reactions catalyzed by the insulin receptor beta-subunit cytoplasmic domain. DNA Cell Biol 1994; 13:593-604. [PMID: 8024702 DOI: 10.1089/dna.1994.13.593] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Activation of the insulin receptor kinase is closely associated with autophosphorylation of several tyrosine residues in the cytoplasmic domain of the receptor's two beta-subunits. To determine the contribution of these tyrosine phosphorylations to autoactivation of the receptor kinase, we have blocked phosphorylation at specific tyrosine by replacing these tyrosine residues, individually and in combination, with phenylalanine in a soluble 45-kD analog of the cytoplasmic insulin receptor kinase domain (CIRK). Kinetic studies of auto- and transphosphorylation with this panel of mutated CIRKs indicate that: (i) None of the tyrosines (953, 960, 1,146, 1,150, 1,151, 1,316, or 1,322) are necessary for catalysis: all single Y-->F mutants retain the ability to autoactivate comparable to the parent CIRK. (ii) Two of the tyrosine autophosphorylation sites, either tyrosine 1,150 or 1,151, contribute most (70-80%) of the autoactivation, because replacement of these two tyrosines by phenylalanine was the minimal change that abolishes autoactivation. (iii) A mutant CIRK having all seven reported tyrosine phosphorylation sites replaced by phenylalanine retained basal kinase activity but was incapable of autoactivation. These findings imply that autoactivation can occur without phosphorylation having occurred at any single site (953, 960, 1,146, 1,150, 1,151, 1,316, or 1,322), and autophosphorylation need not follow an ordered, sequential pathway beginning, for example, at tyrosine 1,146 as proposed for the intact insulin receptor.
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Affiliation(s)
- J E Smith
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104-6059
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50
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Taouis M, Levy-Toledano R, Roach P, Taylor S, Gorden P. Structural basis by which a recessive mutation in the alpha-subunit of the insulin receptor affects insulin binding. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36552-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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