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Krishnan H, Ahmed S, Hubbard SR, Miller WT. Biochemical characterization of the Drosophila insulin receptor kinase and longevity-associated mutants. FASEB J 2024; 38:e23355. [PMID: 38071609 PMCID: PMC11284340 DOI: 10.1096/fj.202301948r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 11/13/2023] [Accepted: 11/20/2023] [Indexed: 12/18/2023]
Abstract
Drosophila melanogaster (fruit fly) insulin receptor (D-IR) is highly homologous to the human counterpart. Like the human pathway, D-IR responds to numerous insulin-like peptides to activate cellular signals that regulate growth, development, and lipid metabolism in fruit flies. Allelic mutations in the D-IR kinase domain elevate life expectancy in fruit flies. We developed a robust heterologous expression system to express and purify wild-type and longevity-associated mutant D-IR kinase domains to investigate enzyme kinetics and substrate specificities. D-IR exhibits remarkable similarities to the human insulin receptor kinase domain but diverges in substrate preferences. We show that longevity-associated mutations reduce D-IR catalytic activity. Deletion of the unique kinase insert domain portion or mutations proximal to activating tyrosines do not influence kinase activity, suggesting their potential role in substrate recruitment and downstream signaling. Through biochemical investigations, this study enhances our comprehension of D-IR's role in Drosophila physiology, complementing genetic studies and expanding our knowledge on the catalytic functions of this conserved signaling pathway.
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Affiliation(s)
- Harini Krishnan
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York, USA
| | - Sultan Ahmed
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York, USA
| | - Stevan R. Hubbard
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, New York, USA
| | - W. Todd Miller
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York, USA
- Department of Veterans Affairs Medical Center, Northport, New York, USA
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2
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Tatar M. Aging Regulated Through a Stability Model of Insulin/Insulin Growth Factor Receptor Function. Front Endocrinol (Lausanne) 2021; 12:649880. [PMID: 33776941 PMCID: PMC7991905 DOI: 10.3389/fendo.2021.649880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 02/08/2021] [Indexed: 01/04/2023] Open
Abstract
Mutations of the insulin-like receptor in Drosophila extend lifespan. New research suggests this receptor operates in two modes. The first extends lifespan while slowing reproduction and reducing growth. The second strongly extends lifespan without impairing growth or reproduction; it confers longevity assurance. The mutation that confers longevity assurance resides in the kinase insert domain, which contains a potential SH2 binding site for substrate proteins. We apply a recent model for the function of receptor tyrosine kinases to propose how insulin receptor structure can modulate aging. This concept hypothesizes that strong insulin-like ligands promote phosphorylation of high threshold substrate binding sites to robustly induce reproduction, which impairs survival as a consequence of trade-offs. Lower levels of receptor stimulation provide less kinase dimer stability, which reduces reproduction and extends lifespan by avoiding reproductive costs. Environmental conditions that favor diapause alter the expression of insulin ligands to further repress the stability of the interacting kinase domains, block phosphorylation of low threshold substrates and thus induce a unique molecular program that confers longevity assurance. Mutations of the insulin receptor that block low-phosphorylation site interactions, such as within the kinase insert domain, can extend lifespan while maintaining overall dimer stability. These flies are long-lived while maintaining reproduction and growth. The kinase insert domain of Drosophila provides a novel avenue from which to seek signaling of the insulin/insulin-like growth factor system of humans that modulate aging without impacting reproduction and growth, or incurring insulin resistance pathology.
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3
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Willoughby LF, Manent J, Allan K, Lee H, Portela M, Wiede F, Warr C, Meng TC, Tiganis T, Richardson HE. Differential regulation of protein tyrosine kinase signalling by Dock and the PTP61F variants. FEBS J 2017; 284:2231-2250. [PMID: 28544778 DOI: 10.1111/febs.14118] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 04/12/2017] [Accepted: 05/19/2017] [Indexed: 01/01/2023]
Abstract
Tyrosine phosphorylation-dependent signalling is coordinated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). There is a growing list of adaptor proteins that interact with PTPs and facilitate the dephosphorylation of substrates. The extent to which any given adaptor confers selectivity for any given substrate in vivo remains unclear. Here we have taken advantage of Drosophila melanogaster as a model organism to explore the influence of the SH3/SH2 adaptor protein Dock on the abilities of the membrane (PTP61Fm)- and nuclear (PTP61Fn)-targeted variants of PTP61F (the Drosophila othologue of the mammalian enzymes PTP1B and TCPTP respectively) to repress PTK signalling pathways in vivo. PTP61Fn effectively repressed the eye overgrowth associated with activation of the epidermal growth factor receptor (EGFR), PTK, or the expression of the platelet-derived growth factor/vascular endothelial growth factor receptor (PVR) or insulin receptor (InR) PTKs. PTP61Fn repressed EGFR and PVR-induced mitogen-activated protein kinase signalling and attenuated PVR-induced STAT92E signalling. By contrast, PTP61Fm effectively repressed EGFR- and PVR-, but not InR-induced tissue overgrowth. Importantly, coexpression of Dock with PTP61F allowed for the efficient repression of the InR-induced eye overgrowth, but did not enhance the PTP61Fm-mediated inhibition of EGFR and PVR-induced signalling. Instead, Dock expression increased, and PTP61Fm coexpression further exacerbated the PVR-induced eye overgrowth. These results demonstrate that Dock selectively enhances the PTP61Fm-mediated attenuation of InR signalling and underscores the specificity of PTPs and the importance of adaptor proteins in regulating PTP function in vivo.
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Affiliation(s)
| | - Jan Manent
- Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Kirsten Allan
- Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Han Lee
- Institute of Biochemical Sciences, National Taiwan University, and Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Marta Portela
- Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Florian Wiede
- Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Coral Warr
- School of Biomedical Sciences, Monash University, Clayton, Victoria, Australia
| | - Tzu-Ching Meng
- Institute of Biochemical Sciences, National Taiwan University, and Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Tony Tiganis
- Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Helena E Richardson
- Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.,Peter MacCallum Department of Oncology, University of Melbourne, Victoria, Australia.,Department of Biochemistry & Molecular Biology, University of Melbourne, Victoria, Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Victoria, Australia
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4
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Altintas O, Park S, Lee SJV. The role of insulin/IGF-1 signaling in the longevity of model invertebrates, C. elegans and D. melanogaster. BMB Rep 2016; 49:81-92. [PMID: 26698870 PMCID: PMC4915121 DOI: 10.5483/bmbrep.2016.49.2.261] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Indexed: 01/08/2023] Open
Abstract
Insulin/insulin-like growth factor (IGF)-1 signaling (IIS) pathway regulates
aging in many organisms, ranging from simple invertebrates to mammals, including
humans. Many seminal discoveries regarding the roles of IIS in aging and
longevity have been made by using the roundworm Caenorhabditis
elegans and the fruit fly Drosophila melanogaster. In this
review, we describe the mechanisms by which various IIS components regulate
aging in C. elegans and D. melanogaster. We
also cover systemic and tissue-specific effects of the IIS components on the
regulation of lifespan. We further discuss IIS-mediated physiological processes
other than aging and their effects on human disease models focusing on
C. elegans studies. As both C. elegans and
D. melanogaster have been essential for key findings
regarding the effects of IIS on organismal aging in general, these invertebrate
models will continue to serve as workhorses to help our understanding of
mammalian aging. [BMB Reports 2016; 49(2): 81-92]
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Affiliation(s)
- Ozlem Altintas
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Sangsoon Park
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Seung-Jae V Lee
- School of Interdisciplinary Bioscience and Bioengineering, Department of Life Sciences, and Information Technology Convergence Engineering, Pohang University of Science and Technology, Pohang 37673, Korea
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5
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Sopko R, Lin YB, Makhijani K, Alexander B, Perrimon N, Brückner K. A systems-level interrogation identifies regulators of Drosophila blood cell number and survival. PLoS Genet 2015; 11:e1005056. [PMID: 25749252 PMCID: PMC4352040 DOI: 10.1371/journal.pgen.1005056] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 02/05/2015] [Indexed: 12/12/2022] Open
Abstract
In multicellular organisms, cell number is typically determined by a balance of intracellular signals that positively and negatively regulate cell survival and proliferation. Dissecting these signaling networks facilitates the understanding of normal development and tumorigenesis. Here, we study signaling by the Drosophila PDGF/VEGF Receptor (Pvr) in embryonic blood cells (hemocytes) and in the related cell line Kc as a model for the requirement of PDGF/VEGF receptors in vertebrate cell survival and proliferation. The system allows the investigation of downstream and parallel signaling networks, based on the ability of Pvr to activate Ras/Erk, Akt/TOR, and yet-uncharacterized signaling pathway/s, which redundantly mediate cell survival and contribute to proliferation. Using Kc cells, we performed a genome wide RNAi screen for regulators of cell number in a sensitized, Pvr deficient background. We identified the receptor tyrosine kinase (RTK) Insulin-like receptor (InR) as a major Pvr Enhancer, and the nuclear hormone receptors Ecdysone receptor (EcR) and ultraspiracle (usp), corresponding to mammalian Retinoid X Receptor (RXR), as Pvr Suppressors. In vivo analysis in the Drosophila embryo revealed a previously unrecognized role for EcR to promote apoptotic death of embryonic blood cells, which is balanced with pro-survival signaling by Pvr and InR. Phosphoproteomic analysis demonstrates distinct modes of cell number regulation by EcR and RTK signaling. We define common phosphorylation targets of Pvr and InR that include regulators of cell survival, and unique targets responsible for specialized receptor functions. Interestingly, our analysis reveals that the selection of phosphorylation targets by signaling receptors shows qualitative changes depending on the signaling status of the cell, which may have wide-reaching implications for other cell regulatory systems.
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Affiliation(s)
- Richelle Sopko
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - You Bin Lin
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, California, United States of America
| | - Kalpana Makhijani
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, California, United States of America
| | - Brandy Alexander
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, California, United States of America
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Katja Brückner
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, California, United States of America
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, California, United States of America
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California, United States of America
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6
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Li CR, Guo D, Pick L. Independent signaling by Drosophila insulin receptor for axon guidance and growth. Front Physiol 2014; 4:385. [PMID: 24478707 PMCID: PMC3895810 DOI: 10.3389/fphys.2013.00385] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 12/09/2013] [Indexed: 12/29/2022] Open
Abstract
The Drosophila insulin receptor (DInR) regulates a diverse array of biological processes including growth, axon guidance, and sugar homeostasis. Growth regulation by DInR is mediated by Chico, the Drosophila homolog of vertebrate insulin receptor substrate proteins IRS1-4. In contrast, DInR regulation of photoreceptor axon guidance in the developing visual system is mediated by the SH2-SH3 domain adaptor protein Dreadlocks (Dock). In vitro studies by others identified five NPXY motifs, one in the juxtamembrane region and four in the signaling C-terminal tail (C-tail), important for interaction with Chico. Here we used yeast two-hybrid assays to identify regions in the DInR C-tail that interact with Dock. These Dock binding sites were in separate portions of the C-tail from the previously identified Chico binding sites. To test whether these sites are required for growth or axon guidance in whole animals, a panel of DInR proteins, in which the putative Chico and Dock interaction sites had been mutated individually or in combination, were tested for their ability to rescue viability, growth and axon guidance defects of dinr mutant flies. Sites required for viability were identified. Unexpectedly, mutation of both putative Dock binding sites, either individually or in combination, did not lead to defects in photoreceptor axon guidance. Thus, either sites also required for viability are necessary for DInR function in axon guidance and/or there is redundancy built into the DInR/Dock interaction such that Dock is able to interact with multiple regions of DInR. We also found that simultaneous mutation of all five NPXY motifs implicated in Chico interaction drastically decreased growth in both male and female adult flies. These animals resembled chico mutants, supporting the notion that DInR interacts directly with Chico in vivo to control body size. Mutation of these five NPXY motifs did not affect photoreceptor axon guidance, segregating the roles of DInR in the processes of growth and axon guidance.
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Affiliation(s)
- Caroline R Li
- Department of Entomology and Program in Molecular and Cell Biology, University of Maryland College Park, MD, USA
| | - Dongyu Guo
- Department of Entomology and Program in Molecular and Cell Biology, University of Maryland College Park, MD, USA
| | - Leslie Pick
- Department of Entomology and Program in Molecular and Cell Biology, University of Maryland College Park, MD, USA
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7
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Abstract
PTP1B (protein tyrosine phosphatase 1B) is a negative regulator of IR (insulin receptor) activation and glucose homoeostasis, but the precise molecular mechanisms governing PTP1B substrate selectivity and the regulation of insulin signalling remain unclear. In the present study we have taken advantage of Drosophila as a model organism to establish the role of the SH3 (Src homology 3)/SH2 adaptor protein Dock (Dreadlocks) and its mammalian counterpart Nck in IR regulation by PTPs. We demonstrate that the PTP1B orthologue PTP61F dephosphorylates the Drosophila IR in S2 cells in vitro and attenuates IR-induced eye overgrowth in vivo. Our studies indicate that Dock forms a stable complex with PTP61F and that Dock/PTP61F associate with the IR in response to insulin. We report that Dock is required for effective IR dephosphorylation and inactivation by PTP61F in vitro and in vivo. Furthermore, we demonstrate that Nck interacts with PTP1B and that the Nck/PTP1B complex inducibly associates with the IR for the attenuation of IR activation in mammalian cells. Our studies reveal for the first time that the adaptor protein Dock/Nck attenuates insulin signalling by recruiting PTP61F/PTP1B to its substrate, the IR.
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8
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Sundararajan C, Besanger TR, Labiris R, Guenther KJ, Strack T, Garafalo R, Kawabata TT, Finco-Kent D, Zubieta J, Babich JW, Valliant JF. Synthesis and Characterization of Rhenium and Technetium-99m Labeled Insulin. J Med Chem 2010; 53:2612-21. [DOI: 10.1021/jm100096c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chitra Sundararajan
- Departments of Chemistry and Medical Physics & Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Travis R. Besanger
- Departments of Chemistry and Medical Physics & Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Renee Labiris
- Department of Medicine, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Katharina J. Guenther
- Departments of Chemistry and Medical Physics & Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Thomas Strack
- Pfizer, Inc., 235 East 42nd Street 3/58, New York, New York 10017
| | - Robert Garafalo
- Pfizer, Inc., 235 East 42nd Street 3/58, New York, New York 10017
| | | | | | - Jon Zubieta
- Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, New York 13244
| | - John W. Babich
- Molecular Insight Pharmaceuticals, Inc., Cambridge, Massachusetts 02142
| | - John F. Valliant
- Departments of Chemistry and Medical Physics & Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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9
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Abstract
Insulin-like peptides (ILPs) exist in insects and are encoded by multigene families that are expressed in the brain and other tissues. Upon secretion, these peptides likely serve as hormones, neurotransmitters, and growth factors, but to date, few direct functions have been demonstrated. In Drosophila melanogaster, molecular genetic studies have revealed elements of a conserved insulin signaling pathway, and as in other animal models, it appears to play a key role in metabolism, growth, reproduction, and aging. This review offers (a) an integrated summary of the efforts to characterize the distribution of ILPs in insects and to define this pathway and its functions in Drosophila and (b) a few considerations for future studies of ILP endocrinology in insects.
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Affiliation(s)
- Qi Wu
- Department of Cellular Biology, University of Georgia, Athens.
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10
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Abstract
Studies in the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans have revealed that components of the insulin signaling pathway have been highly conserved during evolution. Genetic analysis in Drosophila suggests that structural conservation also extends to the functional level. Flies carrying mutations that reduce insulin signaling have a growth deficiency phenotype similar to that seen in mice with disruptions of genes encoding insulin-like growth factors (IGFs) or the IGF-I receptor. Recent studies in flies have demonstrated a role for the insulin signaling pathway in the regulation of metabolism, reproduction and lifespan via modulation of central neuroendocrine pathways. Similarly, mice with loss of brain insulin receptors or insulin receptor substrate 2 deficiency exhibit neuroendocrine defects and female infertility. These parallels suggest that the insulin system has multiple conserved roles, acting directly to modulate growth and indirectly, via the neuroendocrine system, to modulate peripheral physiology in response to changes in nutrient availability.
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Affiliation(s)
- Robert S Garofalo
- Dept Cardiovascular and Metabolic Diseases, Pfizer Global Research and Development, MS-3220-3082, Groton, CT 06340, USA.
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11
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Abstract
The family of docker proteins containing phosphotyrosine-binding (PTB) domains appears to represent a family of critically positioned and exquisitely controlled signalling proteins that relay signals from the activated receptors to downstream pathways. These proteins all have a membrane attachment domain, a PTB domain that targets the protein to a subset of receptors and a number of phosphorylatable tyrosines that dock other signalling proteins. Evidence is accruing that suggests that the PTB domain has evolved from a pleckstrin homology (PH) domain to bind to a range of sequences that, while bestowing specificity, allows switching of the docker protein between receptors or signalling systems. The history of the PTB domain and how it influences the participation of docker protein in various signalling pathways are discussed.
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Affiliation(s)
- Graeme R Guy
- Signal Transduction Laboratory, Institute of Molecular and Cell Biology, 30 Medical Drive 117609, Singapore.
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12
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Abstract
Targeted gene mutations have established distinct, yet overlapping, developmental roles for receptors of the insulin/IGF family. IGF-I receptor mediates IGF-I and IGF-II action on prenatal growth and IGF-I action on postnatal growth. Insulin receptor mediates prenatal growth in response to IGF-II and postnatal metabolism in response to insulin. In rodents, unlike humans, insulin does not participate in embryonic growth until late gestation. The ability of the insulin receptor to act as a bona fide IGF-II-dependent growth promoter is underscored by its rescue of double knockout Igf1r/Igf2r mice. Thus, IGF-II is a true bifunctional ligand that is able to stimulate both insulin and IGF-I receptor signaling, although with different potencies. In contrast, the IGF-II/cation-independent mannose-6-phosphate receptor regulates IGF-II clearance. The growth retardation of mice lacking IGF-I and/or insulin receptors is due to reduced cell number, resulting from decreased proliferation. Evidence from genetically engineered mice does not support the view that insulin and IGF receptors promote cellular differentiation in vivo or that they are required for early embryonic development. The phenotypes of insulin receptor gene mutations in humans and in mice indicate important differences between the developmental roles of insulin and its receptor in the two species.
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Affiliation(s)
- J Nakae
- Naomi Berrie Diabetes Center, Department of Medicine, College of Physicians & Surgeons of Columbia University, New York, New York 10032, USA
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13
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Abstract
Insulin signaling at the target tissue results in a large array of biological outcomes. These events are essential for normal growth and development and for normal homeostasis of glucose, fat, and protein metabolism. Elucidating the intracellular events after activation of the IR has been the primary focus of a large number of investigators for decades, and for excellent reasons. Understanding the signaling pathways involved in insulin action could lead to a better understanding of the pathophysiology of insulin resistance associated with obesity and type 2 diabetes, and identifying key molecules and processes could lead to newer and more effective therapeutic agents for treating these common disorders.
This review summarizes our previous understanding of how insulin acts and outlines some recent developments in our understanding of insulin action and insulin resistance at the cellular level, beginning with a discussion on the discovery of evolutionarily conserved molecules of the insulin signaling pathways. This article will also provide a summary of a few in vitro and cellular models of insulin resistance and a description of some new paradigms in the cellular mechanisms of insulin action.
This review will not attempt to be all-inclusive; for a more comprehensive understanding, readers are referred to more complete reviews on insulin action (1–5).
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Affiliation(s)
- D Le Roith
- Clinical Endocrinology Branch, National Institutes of Health, Bethesda, Maryland, USA.
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14
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Poltilove RM, Jacobs AR, Haft CR, Xu P, Taylor SI. Characterization of Drosophila insulin receptor substrate. J Biol Chem 2000; 275:23346-54. [PMID: 10801879 DOI: 10.1074/jbc.m003579200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin receptor substrate (IRS) proteins are phosphorylated by multiple tyrosine kinases, including the insulin receptor. Phosphorylated IRS proteins bind to SH2 domain-containing proteins, thereby triggering downstream signaling pathways. The Drosophila insulin receptor (dIR) C-terminal extension contains potential binding sites for signaling molecules, suggesting that dIR might not require an IRS protein to accomplish its signaling functions. However, we obtained a cDNA encoding Drosophila IRS (dIRS), and we demonstrated expression of dIRS in a Drosophila cell line. Like mammalian IRS proteins, the N-terminal portion of dIRS contains a pleckstrin homology domain and a phosphotyrosine binding domain that binds to phosphotyrosine residues in both human and Drosophila insulin receptors. When coexpressed with dIRS in COS-7 cells, a chimeric receptor (the extracellular domain of human IR fused to the cytoplasmic domain of dIR) mediated insulin-stimulated tyrosine phosphorylation of dIRS. Mutating the juxtamembrane NPXY motif markedly reduced the ability of the receptor to phosphorylate dIRS. In contrast, the NPXY motifs in the C-terminal extension of dIR were required for stable association with dIRS. Coimmunoprecipitation experiments demonstrated insulin-dependent binding of dIRS to phosphatidylinositol 3-kinase and SHP2. However, we did not detect interactions with Grb2, SHC, or phospholipase C-gamma. Taken together with published genetic studies, these biochemical data support the hypothesis that dIRS functions directly downstream from the insulin receptor in Drosophila.
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Affiliation(s)
- R M Poltilove
- Diabetes Branch, NIDDKD, National Institutes of Health, Bethesda, Maryland 20892, USA
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15
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Abstract
The insulin receptor substrates function at the heart of the insulin signalling network. It has recently become apparent that the intracellular localisation of these molecules is regulated in a precise manner that is critical for both the generation and the termination of the insulin signal. Some insulin receptor substrate isoforms appear to be associated with an insoluble matrix that resembles the cytoskeleton. When inappropriately dissociated from this matrix the signalling network collapses concomitant with loss of insulin sensitivity.
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Affiliation(s)
- J P Whitehead
- The Centre for Molecular and Cellular Biology, University of Queensland, Brisbane, 4072, Australia.
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