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Tundo GR, Grasso G, Persico M, Tkachuk O, Bellia F, Bocedi A, Marini S, Parravano M, Graziani G, Fattorusso C, Sbardella D. The Insulin-Degrading Enzyme from Structure to Allosteric Modulation: New Perspectives for Drug Design. Biomolecules 2023; 13:1492. [PMID: 37892174 PMCID: PMC10604886 DOI: 10.3390/biom13101492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 09/11/2023] [Accepted: 09/17/2023] [Indexed: 10/29/2023] Open
Abstract
The insulin-degrading enzyme (IDE) is a Zn2+ peptidase originally discovered as the main enzyme involved in the degradation of insulin and other amyloidogenic peptides, such as the β-amyloid (Aβ) peptide. Therefore, a role for the IDE in the cure of diabetes and Alzheimer's disease (AD) has been long envisaged. Anyway, its role in degrading amyloidogenic proteins remains not clearly defined and, more recently, novel non-proteolytic functions of the IDE have been proposed. From a structural point of view, the IDE presents an atypical clamshell structure, underscoring unique enigmatic enzymological properties. A better understanding of the structure-function relationship may contribute to solving some existing paradoxes of IDE biology and, in light of its multifunctional activity, might lead to novel therapeutic approaches.
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Affiliation(s)
- Grazia Raffaella Tundo
- Department of Clinical Science and Traslational Medicine, University of Rome Tor Vergata, Via Della Ricerca Scientifica 1, 00133 Rome, Italy; (G.R.T.)
| | - Giuseppe Grasso
- Department of Chemical Sciences, University of Catania, Viale Andrea Doria 6, 95125 Catania, Italy;
| | - Marco Persico
- Department of Pharmacy, University of Naples “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy; (M.P.); (O.T.)
| | - Oleh Tkachuk
- Department of Pharmacy, University of Naples “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy; (M.P.); (O.T.)
| | - Francesco Bellia
- Institute of Crystallography, CNR, Via Paolo Gaifami 18, 95126 Catania, Italy
| | - Alessio Bocedi
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
| | - Stefano Marini
- Department of Clinical Science and Traslational Medicine, University of Rome Tor Vergata, Via Della Ricerca Scientifica 1, 00133 Rome, Italy; (G.R.T.)
| | | | - Grazia Graziani
- Department of Systems Medicine, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy;
| | - Caterina Fattorusso
- Department of Pharmacy, University of Naples “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy; (M.P.); (O.T.)
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Leissring MA, González-Casimiro CM, Merino B, Suire CN, Perdomo G. Targeting Insulin-Degrading Enzyme in Insulin Clearance. Int J Mol Sci 2021; 22:ijms22052235. [PMID: 33668109 PMCID: PMC7956289 DOI: 10.3390/ijms22052235] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/20/2021] [Accepted: 02/21/2021] [Indexed: 02/07/2023] Open
Abstract
Hepatic insulin clearance, a physiological process that in response to nutritional cues clears ~50–80% of circulating insulin, is emerging as an important factor in our understanding of the pathogenesis of type 2 diabetes mellitus (T2DM). Insulin-degrading enzyme (IDE) is a highly conserved Zn2+-metalloprotease that degrades insulin and several other intermediate-size peptides. Both, insulin clearance and IDE activity are reduced in diabetic patients, albeit the cause-effect relationship in humans remains unproven. Because historically IDE has been proposed as the main enzyme involved in insulin degradation, efforts in the development of IDE inhibitors as therapeutics in diabetic patients has attracted attention during the last decades. In this review, we retrace the path from Mirsky’s seminal discovery of IDE to the present, highlighting the pros and cons of the development of IDE inhibitors as a pharmacological approach to treating diabetic patients.
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Affiliation(s)
- Malcolm A. Leissring
- Institute for Memory Impairments and Neurological Disorders, University of California, Irvine (UCI MIND), Irvine, CA 92697-4545, USA
- Correspondence: (M.A.L.); (G.P.); Tel.: +1-904-254-3050 (M.A.L.); +34-983-184-805 (G.P.)
| | - Carlos M. González-Casimiro
- Instituto de Biología y Genética Molecular (University of Valladolid-CSIC), 47003 Valladolid, Spain; (C.M.G.-C.); (B.M.)
| | - Beatriz Merino
- Instituto de Biología y Genética Molecular (University of Valladolid-CSIC), 47003 Valladolid, Spain; (C.M.G.-C.); (B.M.)
| | - Caitlin N. Suire
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306-4300, USA;
| | - Germán Perdomo
- Instituto de Biología y Genética Molecular (University of Valladolid-CSIC), 47003 Valladolid, Spain; (C.M.G.-C.); (B.M.)
- Correspondence: (M.A.L.); (G.P.); Tel.: +1-904-254-3050 (M.A.L.); +34-983-184-805 (G.P.)
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3
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Modulation of Insulin Sensitivity by Insulin-Degrading Enzyme. Biomedicines 2021; 9:biomedicines9010086. [PMID: 33477364 PMCID: PMC7830943 DOI: 10.3390/biomedicines9010086] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 01/14/2021] [Accepted: 01/15/2021] [Indexed: 12/15/2022] Open
Abstract
Insulin-degrading enzyme (IDE) is a highly conserved and ubiquitously expressed metalloprotease that degrades insulin and several other intermediate-size peptides. For many decades, IDE had been assumed to be involved primarily in hepatic insulin clearance, a key process that regulates availability of circulating insulin levels for peripheral tissues. Emerging evidence, however, suggests that IDE has several other important physiological functions relevant to glucose and insulin homeostasis, including the regulation of insulin secretion from pancreatic β-cells. Investigation of mice with tissue-specific genetic deletion of Ide in the liver and pancreatic β-cells (L-IDE-KO and B-IDE-KO mice, respectively) has revealed additional roles for IDE in the regulation of hepatic insulin action and sensitivity. In this review, we discuss current knowledge about IDE’s function as a regulator of insulin secretion and hepatic insulin sensitivity, both evaluating the classical view of IDE as an insulin protease and also exploring evidence for several non-proteolytic functions. Insulin proteostasis and insulin sensitivity have both been highlighted as targets controlling blood sugar levels in type 2 diabetes, so a clearer understanding the physiological functions of IDE in pancreas and liver could led to the development of novel therapeutics for the treatment of this disease.
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4
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Stewart MP, Langer R, Jensen KF. Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts. Chem Rev 2018; 118:7409-7531. [PMID: 30052023 PMCID: PMC6763210 DOI: 10.1021/acs.chemrev.7b00678] [Citation(s) in RCA: 399] [Impact Index Per Article: 66.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.
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Affiliation(s)
- Martin P. Stewart
- Department of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, USA
- The Koch Institute for Integrative Cancer Research,
Massachusetts Institute of Technology, Cambridge, USA
| | - Robert Langer
- Department of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, USA
- The Koch Institute for Integrative Cancer Research,
Massachusetts Institute of Technology, Cambridge, USA
| | - Klavs F. Jensen
- Department of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, USA
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5
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Abdul-Hay SO, Bannister TD, Wang H, Cameron MD, Caulfield TR, Masson A, Bertrand J, Howard EA, McGuire MP, Crisafulli U, Rosenberry TR, Topper CL, Thompson CR, Schürer SC, Madoux F, Hodder P, Leissring MA. Selective Targeting of Extracellular Insulin-Degrading Enzyme by Quasi-Irreversible Thiol-Modifying Inhibitors. ACS Chem Biol 2015; 10:2716-24. [PMID: 26398879 PMCID: PMC10127574 DOI: 10.1021/acschembio.5b00334] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Many therapeutically important enzymes are present in multiple cellular compartments, where they can carry out markedly different functions; thus, there is a need for pharmacological strategies to selectively manipulate distinct pools of target enzymes. Insulin-degrading enzyme (IDE) is a thiol-sensitive zinc-metallopeptidase that hydrolyzes diverse peptide substrates in both the cytosol and the extracellular space, but current genetic and pharmacological approaches are incapable of selectively inhibiting the protease in specific subcellular compartments. Here, we describe the discovery, characterization, and kinetics-based optimization of potent benzoisothiazolone-based inhibitors that, by virtue of a unique quasi-irreversible mode of inhibition, exclusively inhibit extracellular IDE. The mechanism of inhibition involves nucleophilic attack by a specific active-site thiol of the enzyme on the inhibitors, which bear an isothiazolone ring that undergoes irreversible ring opening with the formation of a disulfide bond. Notably, binding of the inhibitors is reversible under reducing conditions, thus restricting inhibition to IDE present in the extracellular space. The identified inhibitors are highly potent (IC50(app) = 63 nM), nontoxic at concentrations up to 100 μM, and appear to preferentially target a specific cysteine residue within IDE. These novel inhibitors represent powerful new tools for clarifying the physiological and pathophysiological roles of this poorly understood protease, and their unusual mechanism of action should be applicable to other therapeutic targets.
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Affiliation(s)
- Samer O. Abdul-Hay
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | | | | | | | - Thomas R. Caulfield
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Amandine Masson
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Juliette Bertrand
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Erin A. Howard
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Michael P. McGuire
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Umberto Crisafulli
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Terrone R. Rosenberry
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
| | - Caitlyn L. Topper
- Institute
for Memory Impairments and Neurological Disorders (UCI MIND), University of California, Irvine, California 92697, United States
| | - Caroline R. Thompson
- Institute
for Memory Impairments and Neurological Disorders (UCI MIND), University of California, Irvine, California 92697, United States
| | - Stephan C. Schürer
- Department
of Molecular and Cellular Pharmacology, University of Miami, Miller School of Medicine, Miami, Florida 33136, United States
| | | | | | - Malcolm A. Leissring
- Department
of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida 32224, United States
- Institute
for Memory Impairments and Neurological Disorders (UCI MIND), University of California, Irvine, California 92697, United States
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6
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Beuzelin C, Evnouchidou I, Rigolet P, Cauvet-Burgevin A, Girard PM, Dardalhon D, Culina S, Gdoura A, van Endert P, Francesconi S. Deletion of the fission yeast homologue of human insulinase reveals a TORC1-dependent pathway mediating resistance to proteotoxic stress. PLoS One 2013; 8:e67705. [PMID: 23826334 PMCID: PMC3691139 DOI: 10.1371/journal.pone.0067705] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 05/21/2013] [Indexed: 01/06/2023] Open
Abstract
Insulin Degrading Enzyme (IDE) is a protease conserved through evolution with a role in diabetes and Alzheimer's disease. The reason underlying its ubiquitous expression including cells lacking identified IDE substrates remains unknown. Here we show that the fission yeast IDE homologue (Iph1) modulates cellular sensitivity to endoplasmic reticulum (ER) stress in a manner dependent on TORC1 (Target of Rapamycin Complex 1). Reduced sensitivity to tunicamycin was associated with a smaller number of cells undergoing apoptosis. Wild type levels of tunicamycin sensitivity were restored in iph1 null cells when the TORC1 complex was inhibited by rapamycin or by heat inactivation of the Tor2 kinase. Although Iph1 cleaved hallmark IDE substrates including insulin efficiently, its role in the ER stress response was independent of its catalytic activity since expression of inactive Iph1 restored normal sensitivity. Importantly, wild type as well as inactive human IDE complemented gene-invalidated yeast cells when expressed at the genomic locus under the control of iph1+ promoter. These results suggest that IDE has a previously unknown function unrelated to substrate cleavage, which links sensitivity to ER stress to a pro-survival role of the TORC1 pathway.
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Affiliation(s)
- Clémentine Beuzelin
- Institut Curie, Centre de Recherche, Orsay, France
- Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 3348, Centre Universitaire, Orsay, France
- Université Paris-sud XI, Orsay, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris, France
- Institut National de la Santé et de la Recherche Médicale, Unité 1013, Paris, France
| | - Irini Evnouchidou
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris, France
- Institut National de la Santé et de la Recherche Médicale, Unité 1013, Paris, France
| | - Pascal Rigolet
- Institut Curie, Centre de Recherche, Orsay, France
- Université Paris-sud XI, Orsay, France
| | - Anne Cauvet-Burgevin
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris, France
- Institut National de la Santé et de la Recherche Médicale, Unité 1013, Paris, France
| | - Pierre-Marie Girard
- Institut Curie, Centre de Recherche, Orsay, France
- Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 3348, Centre Universitaire, Orsay, France
| | - Delphine Dardalhon
- Institut Curie, Centre de Recherche, Orsay, France
- Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 3348, Centre Universitaire, Orsay, France
| | - Slobodan Culina
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris, France
- Institut National de la Santé et de la Recherche Médicale, Unité 1013, Paris, France
| | - Abdelaziz Gdoura
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris, France
- Institut National de la Santé et de la Recherche Médicale, Unité 1013, Paris, France
| | - Peter van Endert
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris, France
- Institut National de la Santé et de la Recherche Médicale, Unité 1013, Paris, France
| | - Stefania Francesconi
- Institut Curie, Centre de Recherche, Orsay, France
- Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 3348, Centre Universitaire, Orsay, France
- * E-mail:
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7
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Song ES, Rodgers DW, Hersh LB. Mixed dimers of insulin-degrading enzyme reveal a cis activation mechanism. J Biol Chem 2011; 286:13852-8. [PMID: 21343292 DOI: 10.1074/jbc.m110.191668] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin-degrading enzyme (IDE) exists primarily as a dimer being unique among the zinc metalloproteases in that it exhibits allosteric kinetics with small synthetic peptide substrates. In addition the IDE reaction rate is increased by small peptides that bind to a distal site within the substrate binding site. We have generated mixed dimers of IDE in which one or both subunits contain mutations that affect activity. The mutation Y609F in the distal part of the substrate binding site of the active subunit blocks allosteric activation regardless of the activity of the other subunit. This effect shows that substrate or small peptide activation occurs through a cis effect. A mixed dimer composed of one wild-type subunit and the other subunit containing a mutation that neither permits substrate binding nor catalysis (H112Q) exhibits the same turnover number per active subunit as wild-type IDE. In contrast, a mixed dimer in which one subunit contains the wild-type sequence and the other contains a mutation that permits substrate binding, but not catalysis (E111F), exhibits a decrease in turnover number. This indicates a negative trans effect of substrate binding at the active site. On the other hand, activation in trans is observed with extended substrates that occupy both the active and distal sites. Comparison of the binding of an amyloid β peptide analog to wild-type IDE and to the Y609F mutant showed no difference in affinity, indicating that Y609 does not play a significant role in substrate binding at the distal site.
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Affiliation(s)
- Eun Suk Song
- Department of Molecular and Cellular Biochemistry and the Center for Structural Biology, University of Kentucky, Lexington, Kentucky 40536, USA
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8
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9
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Ralat LA, Kalas V, Zheng Z, Goldman RD, Sosnick TR, Tang WJ. Ubiquitin is a novel substrate for human insulin-degrading enzyme. J Mol Biol 2010; 406:454-66. [PMID: 21185309 DOI: 10.1016/j.jmb.2010.12.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 12/16/2010] [Accepted: 12/17/2010] [Indexed: 01/22/2023]
Abstract
Insulin-degrading enzyme (IDE) can degrade insulin and amyloid-β, peptides involved in diabetes and Alzheimer's disease, respectively. IDE selects its substrates based on size, charge, and flexibility. From these criteria, we predict that IDE can cleave and inactivate ubiquitin (Ub). Here, we show that IDE cleaves Ub in a biphasic manner, first, by rapidly removing the two C-terminal glycines (k(cat)=2 s(-1)) followed by a slow cleavage between residues 72 and 73 (k(cat)=0.07 s(-1)), thereby producing the inactive 1-74 fragment of Ub (Ub1-74) and 1-72 fragment of Ub (Ub1-72). IDE is a ubiquitously expressed cytosolic protein, where monomeric Ub is also present. Thus, Ub degradation by IDE should be regulated. IDE is known to bind the cytoplasmic intermediate filament protein nestin with high affinity. We found that nestin potently inhibits the cleavage of Ub by IDE. In addition, Ub1-72 has a markedly increased affinity for IDE (∼90-fold). Thus, the association of IDE with cellular regulators and product inhibition by Ub1-72 can prevent inadvertent proteolysis of cellular Ub by IDE. Ub is a highly stable protein. However, IDE instead prefers to degrade peptides with high intrinsic flexibility. Indeed, we demonstrate that IDE is exquisitely sensitive to Ub stability. Mutations that only mildly destabilize Ub (ΔΔG<0.6 kcal/mol) render IDE hypersensitive to Ub with rate enhancements greater than 12-fold. The Ub-bound IDE structure and IDE mutants reveal that the interaction of the exosite with the N-terminus of Ub guides the unfolding of Ub, allowing its sequential cleavages. Together, our studies link the control of Ub clearance with IDE.
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Affiliation(s)
- Luis A Ralat
- Ben May Department for Cancer Research, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
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10
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Insulin-degrading enzyme binds to the nonglycosylated precursor of varicella-zoster virus gE protein found in the endoplasmic reticulum. J Virol 2009; 84:847-55. [PMID: 19864391 DOI: 10.1128/jvi.01801-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Insulin degradation enzyme (IDE) is a 110-kDa zinc metalloprotease found in the cytosol of all cells. IDE degrades insulin and a variety of small proteins including amyloid-beta. Recently, IDE has been proposed as the receptor for varicella-zoster virus (VZV) attachment. During our reassessment, some of the original studies were repeated and expanded in scope. We first confirmed that IDE antibody reduced VZV spread. For additional controls, we repeated the same experiments with herpes simplex virus (HSV)-infected cells as well as uninfected cells. There was a visible reduction in HSV spread but less than seen in the VZV system. Of greater importance, IDE antibody also inhibited the growth of uninfected cells. Second, we repeated the coprecipitation assays. We confirmed that antibodies to VZV gE (open reading frame 68) coprecipitated IDE and that anti-IDE antibody coprecipitated gE. However, the detected gE protein was not the mature 98-kDa form; rather, it was a precursor 73-kDa gE form found in the endoplasmic reticulum. Additional control experiments included VZV-infected cell cultures treated with tunicamycin to block gE glycosylation in the endoplasmic reticulum; again, the anti-IDE antibody coprecipitated a 73-kDa gE product. Finally, Orbitrap mass spectrometry analysis of a chromatographically purified gE sample revealed four cellular proteins associated with the unfolded protein response: BiP (HSPA5), HSPA8, HSPD1, and PPIA (peptidyl-propyl cis-trans isomerase). We conclude that IDE protease binds to the 73-kDa gE precursor and that this event occurs in the cytosol but not as a receptor/ligand interaction.
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11
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Hulse RE, Ralat LA, Wei-Jen T. Structure, function, and regulation of insulin-degrading enzyme. VITAMINS AND HORMONES 2009; 80:635-48. [PMID: 19251053 DOI: 10.1016/s0083-6729(08)00622-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The short half-life of insulin in the human body (4-6 min) prompted the search and discovery of insulin-degrading enzyme (IDE), a 110-kDa metalloprotease that can rapidly degrade insulin into inactive fragments. Genetic and biochemical evidence accumulated in the last sixty years has implicated IDE as an important physiological contributor in the maintenance of insulin levels. Recent structural and biochemical analyses reveal the molecular basis of how IDE uses size and charge distribution of the catalytic chamber and structural flexibility of substrates to selectively recognize and degrade insulin, as well as the regulatory mechanisms of this enzyme. These studies provide a path for potential therapeutics in the control of insulin metabolism by the degradation of insulin.
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Affiliation(s)
- Raymond E Hulse
- Committee on Neurobiology, The University of Chicago, Chicago, Illinois 60637, USA
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12
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Reed B, Bidlack JM, Chait BT, Kreek MJ. Extracellular biotransformation of beta-endorphin in rat striatum and cerebrospinal fluid. J Neuroendocrinol 2008; 20:606-16. [PMID: 18363801 PMCID: PMC2682726 DOI: 10.1111/j.1365-2826.2008.01705.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Numerous studies have investigated the behavioural effects of beta-endorphin, both endogenous and exogenously applied. However, the potential for biotransformation of beta-endorphin in the extracellular space of the brain has not been previously directly addressed in vivo. Utilising microinfusion/microdialysis and matrix-assisted laser desorption/ionisation mass spectrometry, we investigated beta-endorphin biotransformation in the striatum of rats. We infused 1.0 nmol beta-endorphin into the striatum of adult male Fischer rats and observed rapid cleavage resulting in beta-endorphin 1-18, as well as several fragments resulting from further N-terminal degradation. In vitro studies with incubation of full-length beta-endorphin, with and without protease inhibitors, in the incubation fluid of isolated striatal slices indicate that beta-endorphin is initially cleaved predominantly at the Phe(18)-Lys(19), position, as well as at the Leu(17)-Phe(18) position. Investigations of cerebrospinal fluid revealed similar enzymatic cleavage of beta-endorphin. The observed pattern of cleavage sites (Phe(18)-Lys(19) and Leu(17)-Phe(18)) is consistent with published in vitro studies of purified insulin-degrading enzyme cleavage of beta-endorphin. The binding affinities of full-length beta-endorphin, as well as previously identified beta-endorphin fragments alpha-endorphin (beta-endorphin 1-16) and gamma-endorphin (beta-endorphin 1-17), and the fragment identified in the present study, beta-endorphin 1-18, at heterologously expressed mu, delta and kappa-opioid receptors, respectively, were determined; the affinity of the truncation fragments is reduced at each of the receptors compared to the affinity of full length beta-endorphin.
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Affiliation(s)
- B Reed
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY 10021, USA.
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13
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Regulation of protein degradation by insulin-degrading enzyme: Analysis by small interfering RNA-mediated gene silencing. Arch Biochem Biophys 2007; 468:128-33. [DOI: 10.1016/j.abb.2007.09.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2007] [Revised: 09/22/2007] [Accepted: 09/25/2007] [Indexed: 11/19/2022]
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14
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Cole AR, Astell A, Green C, Sutherland C. Molecular connexions between dementia and diabetes. Neurosci Biobehav Rev 2007; 31:1046-63. [PMID: 17544131 DOI: 10.1016/j.neubiorev.2007.04.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 03/27/2007] [Accepted: 04/11/2007] [Indexed: 12/29/2022]
Abstract
Recent evidence suggests that the molecular defects associated with the development of diabetes also contribute to an increased risk of all types of dementia, including Alzheimer's disease, vascular dementia and Pick's disease. Indeed, the presence of type II diabetes mellitus results in a two to three fold higher risk of developing dementia [Fontbonne et al., 2001. Changes in cognitive abilities over a 4-year period are unfavourably affected in elderly diabetic subjects: results of the Epidemiology of Vascular Aging Study. Diabetes Care 24, 366-370; Gregg et al., 2000. Is diabetes associated with cognitive impairment and cognitive decline among older women? Study of Osteoporotic Fractures Research Group. Archives of Internal Medicine 160, 174-180; Peila et al., 2002. Type 2 diabetes, APOE gene, and the risk for dementia and related pathologies: The Honolulu-Asia Aging Study. Diabetes 51, 1256-1262]. There are currently 250 million people worldwide (>2 million in the UK) diagnosed with diabetes, and this number is predicted to double within the next 20 years, therefore the associated risk translates into a potential explosion in the appearance of dementia in the population. This review primarily focuses on the proposed molecular links between insulin action, Diabetes and Alzheimer's disease, while discussing the potential for therapeutic intervention to alleviate these disorders. In particular, we will review the regulation of glycogen synthase kinase-3 (GSK-3) and its neuronal substrates.
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Affiliation(s)
- Adam R Cole
- Division of Pathology and Neurosciences, University of Dundee, Ninewells Hospital, Dundee, Scotland, UK
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Shaw E. Cysteinyl proteinases and their selective inactivation. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 63:271-347. [PMID: 2407065 DOI: 10.1002/9780470123096.ch5] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The affinity-labeling of cysteinyl proteinases may now be carried out with a number of peptide-derived reagents with selectivity, particularly for reactions carried out in vitro. These reagents have been described with emphasis on their selectivity for cysteine proteinases and lack of action on serine proteinases, the most likely source of side reactions among proteinases. Perhaps a crucial feature of this selectivity is an enzyme-promoted activation due to initial formation of a hemiketal, which may destabilize the reagent. Prominent among the reagent types that have this class selectivity are the peptidyl diazomethyl ketones, the acyloxymethyl ketones, the peptidylmethyl sulfonium salts, and peptidyl oxides analogous to E-64. The need for specific inhibitors capable of inactivating the target enzyme in intact cells and animals is inevitably pushing the biochemical application of these inhibitors into more complex molecular environments where the possibilities of competing reactions are greatly increased. In dealing with the current state and potential developments for the in vivo use of affinity-labeling reagents of cysteine proteinases, the presently known variety of cysteinyl proteinases had to be considered. Therefore this chapter has, at the same time, attempted to survey these proteinases with respect to specificity and gene family. The continual discovery of new proteinases will increase the complexity of this picture. At present the lysosomal cysteine proteinases cathepsins B and L and the cytoplasmic calcium-dependent proteinases are reasonable goals for a fairly complete metabolic clarification. The ability of investigators to inactivate individual members of this family in vivo, possibly without complications due to concurrent inactivation of serine proteinases by improvements in reagent specificity, is increasing. Among the cysteine proteinases, at least those of the papain super family, hydrophobic interactions in the S2 and S3 subsites are important and some specificity has been achieved by taking advantage of topographical differences among members of this group. Some of this has probably involved surface differences removed from the regions involved in proteolytic action. The emerging cysteine proteinases include some which, in contrast to the papain family, have a pronounced specificity in S1 for the binding of basic side chains, familiar in the trypsin family of serine proteinases. At least a potential conflict with serine proteinases can be avoided by choice of a covalent bonding mechanism. The departing group region, has not been exploited. As a sole contributor to binding, this region may be rather limited as a source of specificity.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- E Shaw
- Friedrich Miescher-Institut, Basel, Switzerland
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16
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Bennett RG, Hamel FG, Duckworth WC. An insulin-degrading enzyme inhibitor decreases amylin degradation, increases amylin-induced cytotoxicity, and increases amyloid formation in insulinoma cell cultures. Diabetes 2003; 52:2315-20. [PMID: 12941771 DOI: 10.2337/diabetes.52.9.2315] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Amylin (islet amyloid polypeptide) is the chief component of the islet amyloid found in type 2 diabetes, and amylin fibril precursors may be cytotoxic to pancreatic beta-cells. Little is known about the prevention of amylin aggregation. We investigated the role of insulin-degrading enzyme (IDE) in amylin degradation, amyloid deposition, and cytotoxicity in RIN-m5F insulinoma cells. Human (125)I-labeled amylin degradation was inhibited by 46 and 65% with the addition of 100 nmol/l human amylin or insulin, respectively. (125)I-labeled insulin degradation was inhibited with 100 nmol/l human amylin, rat amylin, and insulin (by 50, 50, and 73%, respectively). The IDE inhibitor bacitracin inhibited amylin degradation by 78% and insulin degradation by 100%. Amyloid staining by Congo red fluorescence was detectable at 100 nmol/l amylin and was pronounced at 1,000 nmol/l amylin treatment for 48 h. Bacitracin treatment markedly increased staining at all amylin concentrations. Bacitracin with amylin caused a dramatic decrease in cell viability compared with amylin alone (68 and 25%, respectively, at 10 nmol/l amylin). In summary, RIN-m5F cells degraded both amylin and insulin through a common proteolytic pathway. IDE inhibition by bacitracin impaired amylin degradation, increased amyloid formation, and increased amylin-induced cytotoxicity, suggesting a role for IDE in amylin clearance and the prevention of amylin aggregation.
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Affiliation(s)
- Robert G Bennett
- Department of Internal Medicine, University of Nebraska Medical Center, and Veterans Affairs Medical Center, Omaha, Nebraska 68105, USA.
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17
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Abstract
An emerging body of evidence suggests that an increased prevalence of insulin abnormalities and insulin resistance in Alzheimer's disease may contribute to the disease pathophysiology and clinical symptoms. It has long been known that insulin is essential for energy metabolism in the periphery. In the past 2 decades, convergent findings have begun to demonstrate that insulin also plays a role in energy metabolism and other aspects of CNS function. Investigators reported 20 years ago that insulin and insulin receptors were densely but selectively expressed in the brain, including the medial temporal regions that support the formation of memory. It has recently been demonstrated that insulin-sensitive glucose transporters are localised to the same regions supporting memory and that insulin plays a role in memory functions. Collectively, these findings suggest that insulin may contribute to normal cognitive functioning and that insulin abnormalities may exacerbate cognitive impairments, such as those associated with Alzheimer's disease. Insulin may also play a role in regulating the amyloid precursor protein and its derivative beta-amyloid (Abeta), which is associated with senile plaques, a neuropathological hallmark of Alzheimer's disease. It has been proposed that insulin can accelerate the intracellular trafficking of Abeta and interfere with its degradation. These findings are consistent with the notion that insulin abnormalities may potentially influence levels of Abeta in the brains of patients with Alzheimer's disease. The increased occurrence of insulin resistance in Alzheimer's disease and the numerous mechanisms through which insulin may affect clinical and pathological aspects of the disease suggest that improving insulin effectiveness may have therapeutic benefit for patients with Alzheimer's disease. The thiazolidinedione rosiglitazone has been shown to have a potent insulin-sensitising action that appears to be mediated through the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). PPAR-gamma agonists, such as rosiglitazone, also have anti-inflammatory effects that may be of therapeutic benefit in patients with Alzheimer's disease. This review presents evidence suggesting that insulin resistance plays a role in the pathophysiology and clinical symptoms of Alzheimer's disease. Based on this evidence, we propose that treatment of insulin resistance may reduce the risk or retard the development of Alzheimer's disease.
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Affiliation(s)
- G Stennis Watson
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, Washington, USA
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18
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Cook DG, Leverenz JB, McMillan PJ, Kulstad JJ, Ericksen S, Roth RA, Schellenberg GD, Jin LW, Kovacina KS, Craft S. Reduced hippocampal insulin-degrading enzyme in late-onset Alzheimer's disease is associated with the apolipoprotein E-epsilon4 allele. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 162:313-9. [PMID: 12507914 PMCID: PMC1851126 DOI: 10.1016/s0002-9440(10)63822-9] [Citation(s) in RCA: 251] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Abeta is the major component of amyloid plaques characterizing Alzheimer's disease (AD). Abeta accumulation can be affected by numerous factors including increased rates of production and/or impaired clearance. Insulin-degrading enzyme (IDE) has been implicated as a candidate enzyme responsible for the degradation and clearance of Abeta in the brain. We have previously shown that AD patients exhibit abnormalities in insulin metabolism that are associated with apoliprotein E (APOE) status. The possible association of IDE with AD, as well as the link between APOE status and insulin metabolism, led us to examine the expression of IDE in AD. We report that hippocampal IDE protein is reduced by approximately 50% in epsilon4+ AD patients compared to epsilon4- patients and controls. The allele-specific decrease of IDE in epsilon4+ AD patients is not associated with neuronal loss since neuron-specific enolase levels were comparable between the AD groups, regardless of APOE status. Hippocampal IDE mRNA levels were also reduced in AD patients with the epsilon4 allele compared to AD and normal subjects without the epsilon4 allele. These findings show that reduced IDE expression is associated with a significant risk factor for AD and suggest that IDE may interact with APOE status to affect Abeta metabolism.
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Affiliation(s)
- David G Cook
- Geriatric Research, Education, and Clinical Center, Veteran Affairs Puget Sound Health Care System, Seattle, Washington 98108, USA
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19
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Edbauer D, Willem M, Lammich S, Steiner H, Haass C. Insulin-degrading enzyme rapidly removes the beta-amyloid precursor protein intracellular domain (AICD). J Biol Chem 2002; 277:13389-93. [PMID: 11809755 DOI: 10.1074/jbc.m111571200] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The intramembranous gamma-secretase cleavage of the beta-amyloid precursor protein (APP) is dependent on biologically active presenilins (PS). Notch also undergoes a similar PS-dependent gamma-secretase-like cleavage, resulting in the liberation of the Notch intracellular domain (NICD), which is critically required for developmental signal transduction. gamma-Secretase processing of APP results in the production of a similar fragment called AICD (APP intracellular domain), which may function in nuclear signaling as well. AICD, like NICD, is rapidly removed. By using a battery of protease inhibitors we demonstrate that AICD, in contrast to NICD, is degraded by a cytoplasmic metalloprotease. In vitro degradation of AICD can be reconstituted with cytoplasmic fractions obtained from neuronal and non-neuronal cells. Taking into account the inhibition profile and the cytoplasmic localization, we identified three candidate enzymes (neurolysin, thimet oligopeptidase, and insulin-degrading enzyme (IDE), also known as insulysin), which all are involved in the degradation of bioactive peptides in the brain. When insulin, a well characterized substrate of IDE, was added to the in vitro degradation assay, removal of AICD was efficiently blocked. Moreover, overexpression of IDE resulted in enhanced degradation of AICD, whereas overexpression of the inactive IDE E111Q mutant did not affect AICD degradation. Finally, immunodepletion of IDE significantly reduced the AICD degrading activity. Therefore our data demonstrate that IDE, which is one of the proteases implicated in the removal of extracellular Abeta, also removes the cytoplasmic product of gamma-secretase cleaved APP.
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Affiliation(s)
- Dieter Edbauer
- Department of Biochemistry, Laboratory for Alzheimer's and Parkinson's Disease Research, Adolf-Butenandt-Institute, Ludwig-Maximilians-University, Schillerstrasse 44, 80336 Munich, Germany
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20
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Authier F, Metioui M, Fabrega S, Kouach M, Briand G. Endosomal proteolysis of internalized insulin at the C-terminal region of the B chain by cathepsin D. J Biol Chem 2002; 277:9437-46. [PMID: 11779865 DOI: 10.1074/jbc.m110188200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The endosomal compartment of hepatic parenchymal cells contains an acidic endopeptidase, endosomal acidic insulinase, which hydrolyzes internalized insulin and generates the major primary end product A(1--21)-B(1--24) insulin resulting from a major cleavage at residues Phe(B24)-Phe(B25). This study addresses the nature of the relevant endopeptidase activity in rat liver that is responsible for most receptor-mediated insulin degradation in vivo. The endosomal activity was shown to be aspartic acid protease cathepsin D (CD), based on biochemical similarities to purified CD in 1) the rate and site of substrate cleavage, 2) pH optimum, 3) sensitivity to pepstatin A, and 4) binding to pepstatin A-agarose. The identity of the protease was immunologically confirmed by removal of greater than 90% of the insulin-degrading activity associated with an endosomal lysate using polyclonal antibodies to CD. Moreover, the elution profile of the endosomal acidic insulinase activity on a gel-filtration TSK-GEL G3000 SW(XL) high performance liquid chromatography column corresponded exactly with the elution profile of the immunoreactive 45-kDa mature form of endosomal CD. Using nondenaturating immunoprecipitation and immunoblotting procedures, other endosomal aspartic acid proteases such as cathepsin E and beta-site amyloid precursor protein-cleaving enzyme (BACE) were ruled out as candidate enzymes for the endosomal degradation of internalized insulin. Immunofluorescence studies showed a largely vesicular staining pattern for internalized insulin in rat hepatocytes that colocalized partially with CD. In vivo pepstatin A treatment was without any observable effect on the insulin receptor content of endosomes but augmented the phosphotyrosine content of the endosomal insulin receptor after insulin injection. These results suggest that CD is the endosomal acidic insulinase activity which catalyzes the rate-limiting step of the in vivo cleavage at the Phe(B24)-Phe(B25) bond, generating the inactive A(1--21)-B(1--24) insulin intermediate.
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Affiliation(s)
- Francois Authier
- INSERM U510, Faculté de Pharmacie Paris XI, 92296 Châtenay-Malabry, France.
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21
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Stimulation of beta-amyloid precursor protein trafficking by insulin reduces intraneuronal beta-amyloid and requires mitogen-activated protein kinase signaling. J Neurosci 2001. [PMID: 11306609 DOI: 10.1523/jneurosci.21-08-02561.2001] [Citation(s) in RCA: 315] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's Disease (AD) is characterized by cerebral accumulation of beta-amyloid peptides (Abeta), which are proteolytically derived from beta-amyloid precursor protein (betaAPP). betaAPP metabolism is highly regulated via various signal transduction systems, e.g., several serine/threonine kinases and phosphatases. Several growth factors known to act via receptor tyrosine kinases also have been demonstrated to regulate sbetaAPP secretion. Among these receptors, insulin and insulin-like growth factor-1 receptors are highly expressed in brain, especially in hippocampus and cortex. Emerging evidence indicates that insulin has important functions in brain regions involved in learning and memory. Here we present evidence that insulin significantly reduces intracellular accumulation of Abeta and that it does so by accelerating betaAPP/Abeta trafficking from the trans-Golgi network, a major cellular site for Abeta generation, to the plasma membrane. Furthermore, insulin increases the extracellular level of Abeta both by promoting its secretion and by inhibiting its degradation via insulin-degrading enzyme. The action of insulin on betaAPP metabolism is mediated via a receptor tyrosine kinase/mitogen-activated protein (MAP) kinase kinase pathway. The results suggest cell biological and signal transduction mechanisms by which insulin modulates betaAPP and Abeta trafficking in neuronal cultures.
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22
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Camberos MC, Pérez AA, Udrisar DP, Wanderley MI, Cresto JC. ATP inhibits insulin-degrading enzyme activity. Exp Biol Med (Maywood) 2001; 226:334-41. [PMID: 11368426 DOI: 10.1177/153537020122600411] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We studied the ability of ATP to inhibit in vitro the degrading activity of insulin-degrading enzyme. The enzyme was purified from rat skeletal muscle by successive chromatographic steps. The last purification step showed two bands at 110 and 60 kDa in polyacrylamide gel. The enzyme was characterized by its insulin degradation activity, the substrate competition of unlabeled to labeled insulin, the profile of enzyme inhibitors, and the recognition by a specific antibody. One to 5 mM ATP induced a dose-dependent inhibition of insulin degradation (determined by trichloroacetic acid precipitation and insulin antibody binding). Inhibition by 3 mM adenosine 5'-diphosphate, adenosine 5'-monophosphate, guanosine 5'-triphosphate, pyrophosphate, beta-gamma-methyleneadenosine 5'-triphosphate, adenosine 5'-O-(3 thiotriphosphate), and dibutiryl cyclic adenosine 5'-monophosphate was 74%, 4%, 38%, 46%, 65%, 36%, and 0%, respectively, of that produced by 3 mM ATP. Kinetic analysis of ATP inhibition suggested an allosteric effect as the plot of 1/v (insulin degradation) versus ATP concentration was not linear and the Hill coefficient was more than 1 (1.51 and 2.44). The binding constant for allosteric inhibition was KiT = 1.5 x 10(-7) M showing a decrease of enzyme affinity induced by ATP. We conclude that ATP has an inhibitory effect on the insulin degradation activity of the enzyme.
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Affiliation(s)
- M C Camberos
- CEDIE-Endocrinology, Htal. de Niños R. Gutiérrez, Buenos Aires, Argentina
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23
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Gasparini L, Gouras GK, Wang R, Gross RS, Beal MF, Greengard P, Xu H. Stimulation of beta-amyloid precursor protein trafficking by insulin reduces intraneuronal beta-amyloid and requires mitogen-activated protein kinase signaling. J Neurosci 2001; 21:2561-70. [PMID: 11306609 PMCID: PMC6762523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023] Open
Abstract
Alzheimer's Disease (AD) is characterized by cerebral accumulation of beta-amyloid peptides (Abeta), which are proteolytically derived from beta-amyloid precursor protein (betaAPP). betaAPP metabolism is highly regulated via various signal transduction systems, e.g., several serine/threonine kinases and phosphatases. Several growth factors known to act via receptor tyrosine kinases also have been demonstrated to regulate sbetaAPP secretion. Among these receptors, insulin and insulin-like growth factor-1 receptors are highly expressed in brain, especially in hippocampus and cortex. Emerging evidence indicates that insulin has important functions in brain regions involved in learning and memory. Here we present evidence that insulin significantly reduces intracellular accumulation of Abeta and that it does so by accelerating betaAPP/Abeta trafficking from the trans-Golgi network, a major cellular site for Abeta generation, to the plasma membrane. Furthermore, insulin increases the extracellular level of Abeta both by promoting its secretion and by inhibiting its degradation via insulin-degrading enzyme. The action of insulin on betaAPP metabolism is mediated via a receptor tyrosine kinase/mitogen-activated protein (MAP) kinase kinase pathway. The results suggest cell biological and signal transduction mechanisms by which insulin modulates betaAPP and Abeta trafficking in neuronal cultures.
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Affiliation(s)
- L Gasparini
- Laboratory of Molecular and Cellular Neuroscience, Fisher Center for Research on Alzheimer Disease, and Laboratory for Mass Spectrometry, The Rockefeller University, New York, New York 10021, USA
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24
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Chesneau V, Vekrellis K, Rosner MR, Selkoe DJ. Purified recombinant insulin-degrading enzyme degrades amyloid beta-protein but does not promote its oligomerization. Biochem J 2000; 351 Pt 2:509-16. [PMID: 11023838 PMCID: PMC1221388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Amyloid beta-protein (Abeta) has been implicated as an early and essential factor in the pathogenesis of Alzheimer's disease. Although its cellular production has been studied extensively, little is known about Abeta clearance. Recently, insulin-degrading enzyme (IDE), a 110-kDa metalloendopeptidase, was found to degrade both endogenously secreted and synthetic Abeta peptides. Surprisingly, IDE-mediated proteolysis of [(125)I]Abeta(1-40) in microglial cell-culture media was accompanied by the formation of (125)I-labelled peptides with higher apparent molecular masses, raising the possibility that the degradation products act as 'seeds' for Abeta oligomerization. To directly address the role of IDE in Abeta degradation and oligomerization, we investigated the action of purified recombinant wild-type and catalytically inactive IDEs. Our data demonstrate that (i) IDE alone is sufficient to cleave purified Abeta that is either unlabelled, iodinated or (35)S-labelled; (ii) the initial cleavage sites are His(14)-Gln(15), Phe(19)-Phe(20) and Phe(20)-Ala(21); and (iii) incubation of IDE with [(125)I]Abeta, but not with [(35)S]-Abeta, leads to the formation of slower migrating species on gels. Since iodination labels N-terminal fragments of Abeta, and (35)S labels C-terminal products, we analysed unlabelled synthetic fragments of Abeta and determined that only the N-terminal fragments migrate with anomalously high molecular mass. These results indicate that IDE alone is sufficient to degrade Abeta at specific sites, and that its degradation products do not promote oligomerization of the intact Abeta peptide.
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Affiliation(s)
- V Chesneau
- Ben May Institute for Cancer Research, University of Chicago, 5841 S. Maryland Avenue, MC 6027, Chicago, IL 60637, USA
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25
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Bennett RG, Hamel FG, Duckworth WC. Insulin inhibits the ubiquitin-dependent degrading activity of the 26S proteasome. Endocrinology 2000; 141:2508-17. [PMID: 10875252 DOI: 10.1210/endo.141.7.7575] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A major metabolic effect of insulin is inhibition of cellular proteolysis, but the proteolytic systems involved are unclear. Tissues have multiple proteolytic systems, including the ATP- and ubiquitin-dependent proteasome pathway. The effect of insulin on this pathway was examined in vitro and in cultured cells. Insulin inhibited ATP- and ubiquitin-dependent lysozyme degradation more than 90% by reticulocyte extract, in a dose-dependent manner (IC50 approximately 50 nM). Insulin did not reduce the conjugation of ubiquitin to lysozyme and was not itself ubiquitin-conjugated. In HepG2 cells, insulin increased ubiquitin-conjugate accumulation 80%. The association between the 26S proteasome and an intracellular protease, the insulin-degrading enzyme (IDE), was examined by a purification scheme designed to enrich for the 26S proteasome. Copurification of IDE activity and immunoreactivity with the proteasome were detected through several chromatographic steps. Glycerol gradient analysis revealed cosedimentation of IDE with the 20S proteasome and possibly with the 26S proteasome. The proteasome-associated IDE was displaced when the samples were treated with insulin. These results suggest that insulin regulates protein catabolism, at least in part, by decreasing ubiquitin-mediated proteasomal activity, and provides a new target for insulin action. The displacement of IDE from the proteasome provides a mechanism for this insulin action.
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Affiliation(s)
- R G Bennett
- Veterans Affairs Medical Center, and the Department of Internal Medicine, University of Nebraska Medical Center, Omaha 68198-3020, USA.
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26
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Chesneau V, Rosner MR. Functional human insulin-degrading enzyme can be expressed in bacteria. Protein Expr Purif 2000; 19:91-8. [PMID: 10833395 DOI: 10.1006/prep.2000.1217] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin-degrading enzyme (IDE) has been shown to degrade a number of biologically important peptides, including insulin and the amyloid-beta protein implicated in Alzheimer's disease. However, lack of a facile method to generate purified enzyme and related mutants has made it difficult to study the precise role of IDE in the clearance of these peptides. Therefore, we determined whether recombinant wild-type and mutant human IDEs can be overexpressed as functional enzymes in bacteria. Three vectors carrying cDNAs encoding N-terminally polyhistidine-tagged recombinant IDEs were constructed, and the proteins expressed in Escherichia coli were purified by metal affinity chromatography (final yield approximately 8 mg per liter of culture). The recombinant IDEs, like the endogenous mammalian enzyme, migrate with 110-kDa apparent molecular masses in SDS-polyacrylamide gels and as a approximately 200-kDa species in gel filtration. Further analysis by native PAGE indicates that IDE can form multimers of different complexities. The wild-type recombinant endopeptidase degrades insulin with an efficiency similar to that of the enzyme purified from mammalian tissues. Purified IDEs are stable at 4 degrees C for at least 1 month. Purified recombinant protein was used to raise specific polyclonal antibodies that can immunoprecipitate native mammalian IDE. Thus, the procedure described allows the rapid production of large amounts of purified IDE and demonstrates that IDE can be produced in an active form in the absence of other potential interacting mammalian proteins.
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Affiliation(s)
- V Chesneau
- Ben May Institute for Cancer Research, University of Chicago, Illinois 60637, USA
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27
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Abstract
Insulin (Ins) and various other hormones and growth factors have been shown to be rapidly internalized and translocated to the cell nucleus. This review summarizes the mechanisms that are involved in the translocation of Ins to the nucleus, and discusses its possible role in Ins action, based on observations by the authors and others. Ins is internalized to endosomes by both receptor-mediated and fluid-phase endocytosis, the latter occurring only at high Ins concentrations. The authors recently demonstrated the caveolae are the primary cell membrane locations responsible for initiating the signal transduction cascade induced by Ins. Once Ins is internalized, Ins dissociates from the Ins receptor in the endosome, and is translocated to the cytoplasm, where most Ins is degraded by Ins-degrading enzyme (IDE), although how the polypeptides cross the lipid bilayer is unknown. Some Ins escapes the degradation and binds to cytosolic Ins-binding proteins (CIBPs), in addition to IDE. IDE and some CIBPs are known to be binding proteins for other hormones or their receptors, and are involved in gene regulation, suggesting physiological relevance of CIBPs in the signaling of Ins and other hormones. Ins is eventually translocated through the nuclear pore to the nucleus, where Ins tightly associates with nuclear matrix. The role of Ins internalization and translocation to the nucleus is still controversial, although there is substantial evidence to support its role in cellular responses caused by Ins. Many studies indicate that nuclear translocation of various growth factors and hormones plays an important role in cell proliferation or DNA synthesis. It would be reasonable to suggest that Ins internalization, its association with CIBPs, and its translocation to the nucleus may be essential for the regulation of nuclear events by Ins.
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Affiliation(s)
- S Harada
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
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28
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Authier F, Métioui M, Bell AW, Mort JS. Negative regulation of epidermal growth factor signaling by selective proteolytic mechanisms in the endosome mediated by cathepsin B. J Biol Chem 1999; 274:33723-31. [PMID: 10559264 DOI: 10.1074/jbc.274.47.33723] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We have investigated the relevant protease activity in rat liver, which is responsible for most of the receptor-mediated epidermal growth factor (EGF) degradation in vivo. EGF was sequentially cleaved by endosomal proteases at a limited number of sites, which were identified by high performance liquid chromatography and mass spectrometry. EGF proteolysis is initiated by hydrolysis at the C-terminal Glu(51)-Leu(52) bond. Three additional minor cleavage sites were identified at positions Arg(48)-Trp(49), Trp(49)-Trp(50), and Trp(50)-Glu(51) after prolonged incubation. Using nondenaturating immunoprecipitation and cross-linking procedures, the major proteolytic activity was identified as that of the cysteine protease cathepsin-B. The effect of injected EGF on subsequent endosomal EGF receptor (EGFR) proteolysis was further evaluated by immunoblotting. Using endosomal fractions prepared from EGF-injected rats and incubated in vitro, the EGFR was lost with a time course superimposable with the loss of phosphotyrosine content. The cathepsin-B proinhibitor CA074-Me inhibited both in vivo and in vitro the endosomal degradation of the EGFR and increased the tyrosine phosphorylation states of the EGFR protein and the molecule SHC within endosomes. The data, therefore, describe a unique pathway for the endosomal processing of internalized EGF receptor complexes, which involves the sequential function of cathepsin-B through selective degradation of both the ligand and receptor.
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Affiliation(s)
- F Authier
- INSERM U510, Faculté de Pharmacie Paris XI, 5 rue Jean-Baptiste Clément, 92296 Châtenay-Malabry, France.
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29
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Nishiuma T, Hara K, Tsujishita Y, Kaneko K, Shii K, Yonezawa K. Characterization of the phosphoproteins and protein kinase activity in mTOR immunoprecipitates. Biochem Biophys Res Commun 1998; 252:440-4. [PMID: 9826548 DOI: 10.1006/bbrc.1998.9671] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mammalian target of rapamycin, mTOR, has been shown to be an upstream regulator of translational effectors. In the present study, in order to detect potential molecules involved in the mTOR signaling, an in vitro phosphorylation assay using mTOR immunoprecipitates from HEK293 cells was carried out. In addition to the autophosphorylation of mTOR, 32P incorporation into 80-kDa (pp80) and 175-kDa (pp175) bands was observed in mTOR immunoprecipitates. The protein kinase activity toward the recombinant eIF-4E binding protein 1 (4E-BP1) was also detected as previously described. When mTOR immunoprecipitates from HEK293 cells were prepared in the presence of a detergent, Nonidet P-40, the 4E-BP1 kinase activity and 32P incorporation into pp175 dramatically diminished, while the phosphorylation of mTOR and 32P incorporation into pp80 did not change. These results raised a possibility that mTOR may associate with protein cofactors, some of which may be involved in the regulation of kinase activities associated with mTOR.
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Affiliation(s)
- T Nishiuma
- Biosignal Research Center, Kobe University, 1-1 Rokkodai-cho, Kobe, Nada-ku, 657-8501, Japan
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30
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Abstract
Insulin degradation is a regulated process that plays a role in controlling insulin action by removing and inactivating the hormone. Abnormalities in insulin clearance and degradation are present in various pathological conditions including type 2 diabetes and obesity and may be important in producing clinical problems. The uptake, processing, and degradation of insulin by cells is a complex process with multiple intracellular pathways. Most evidence supports IDE as the primary degradative mechanism, but other systems (PDI, lysosomes, and other enzymes) undoubtedly contribute to insulin metabolism. Recent studies support a multifunctional role for IDE, as an intracellular binding, regulatory, and degradative protein. IDE increases proteasome and steroid hormone receptor activity, and this activation is reversed by insulin. This raises the possibility of a direct intracellular interaction of insulin with IDE that could modulate protein and fat metabolism. The recent findings would place intracellular insulin-IDE interaction into the insulin signal transduction pathway for mediating the intermediate effects of insulin on fat and protein turnover.
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Affiliation(s)
- W C Duckworth
- Veterans Affairs Medical Center, Omaha, Nebraska 68105, USA
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Thiele DL, Sarada B, Dang T, Safavi A, Hersh LB, Cottam GL. Regulated expression of an endopeptidase that hydrolyses beta-endorphin during differentiation of macrophages and T cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 437:291-300. [PMID: 9666282 DOI: 10.1007/978-1-4615-5347-2_32] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- D L Thiele
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-9038, USA
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Authier F, Di Guglielmo GM, Danielsen GM, Bergeron JJ. Uptake and metabolic fate of [HisA8,HisB4,GluB10,HisB27]insulin in rat liver in vivo. Biochem J 1998; 332 ( Pt 2):421-30. [PMID: 9601071 PMCID: PMC1219497 DOI: 10.1042/bj3320421] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Receptor-mediated endocytosis and subsequent endosomal proteolysis of [125I]TyrA14-[HisA8,HisB4,GluB10,HisB27]in sulin ([125I]TyrA14-H2 analogue), an insulin analogue exhibiting a high affinity for the insulin receptor, has been studied in liver parenchymal cells by quantitative subcellular fractionation and compared with that of wild-type [125I]TyrA14-insulin. Whereas the kinetics of uptake of the H2 analogue by liver was not different from that of insulin, the H2 analogue radioactivity after the 2 min peak declined significantly more slowly. A significant retention of the H2 analogue compared with insulin in both plasma membrane and endosomal fractions was observed and corresponded to decreased processing and dissociation of the H2 analogue. Cell-free endosomes preloaded in vivo with radiolabelled ligands and incubated in vitro processed insulin and extraluminally released insulin intermediates at a 2-3-fold higher rate than the H2 analogue. In vitro proteolysis of both non-radiolabelled and monoiodinated molecules by endosomal lysates showed a decreased response to the endosomal proteolytic machinery for the H2 analogue. However, in cross-linking and competition studies the H2 analogue exhibited an affinity for insulin-degrading enzyme identical with that of wild-type insulin. Brij-35-permeabilized endosomes revealed a 2-fold higher rate of dissociation of insulin from internalized receptors compared with the H2 analogue. After the administration of a saturating dose of both ligands, a rapid and reversible ligand-induced translocation of insulin receptor was observed, but without receptor loss. The H2 analogue induced a higher receptor concentration and tyrosine autophosphorylation of the receptor beta subunit in endosomes. Moreover, a prolonged temporal interaction of the in vivo injected H2 analogue with receptor was observed by direct binding assays performed on freshly prepared subcellular fractions. These results indicate that endosomal proteolysis for the H2 analogue is slowed as a result of an increased residence time of the analogue on the insulin receptor and a low affinity of endosomal acidic insulinase for the dissociated H2 molecule.
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Affiliation(s)
- F Authier
- Institut National de la Santé et de la Recherche Médicale U30, Hôpital Necker des Enfants Malades, 75015 Paris, France
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Hsu MC, Bai JP. Investigation into the presence of insulin-degrading enzyme in cultured type II alveolar cells and the effects of enzyme inhibitors on pulmonary bioavailability of insulin in rats. J Pharm Pharmacol 1998; 50:507-14. [PMID: 9643444 DOI: 10.1111/j.2042-7158.1998.tb06192.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The purpose of this study was to investigate the role of insulin-degrading enzyme (IDE, EC 3.4.22.11) in insulin degradation in alveolar epithelium. The primary culture of isolated rat type-II pneumocytes was used for the in-vitro characterization of IDE. Insulin was then administered intratracheally with various inhibitors to assess the improvement in its pulmonary bioavailability. In cultured type-II pneumocytes, the cytosolic insulin-degrading activity contributed 81% of total insulin degradation, reached a maximum at pH 7.5 and had an apparent Michaelis-Menten constant (Km) of 135 nM. N-Ethylmaleimide, p-chloromercuribenzoic acid and 1,10-phenanthroline inhibited insulin-degrading activity almost completely in both crude homogenate and cytosol. An immunoprecipitation study showed that IDE contributed 74% of cytosolic insulin-degrading activity. Western blot analysis showing a single band of 110 kDa on reduced SDS (sodium dodecylsulphate) gels confirmed the presence of IDE in cultured type-II cells. When given intratracheally with insulin, inhibitors including N-ethylmaleimide, p-chloromercuribenzoic acid, and 1,10-phenanthroline significantly enhanced the absolute bioavailability of insulin and the compound's hypoglycaemic effects. These results suggest that IDE is present in alveolar epithelium and might be involved in limiting insulin absorption in the lung.
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Affiliation(s)
- M C Hsu
- Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis 55455, USA
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Sarada B, Thiele D, Dang T, Lee J, Safavia A, Hersh LB, Cottam GL. Anti-CD3 activation of human CD4+ T cells increases expression of the intracellular beta-endorphin endopeptidase (IDE/gamma-EpGE). J Neuroimmunol 1998; 85:59-68. [PMID: 9626998 DOI: 10.1016/s0165-5728(97)00268-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this study, increased expression of an endopeptidase hydrolyzing beta-endorphin (beta-Ep) to gamma-endorphin (gamma-Ep, beta-Ep1-17) was observed upon immobilized anti-CD3 stimulated activation of human peripheral blood CD4+ T cells (hCD4+ T cells). Although freshly isolated hCD4+ T cells are devoid of significant beta-Ep endopeptidase activity ( < 0.1 nmol h(-1) 10(6) cells (-1)), activation of these cells with immobilized anti-CD3 results in a time dependent appearance of beta-Ep endopeptidase activity which reaches a maximal value of 17.4+/-0.48 nmol h(-1) 10(6) cells(-1) after 48 h of culture. Significant up-regulation of both mRNA encoding IDE/gamma-EpGE and immunoreactive protein are observed in anti-CD3 stimulated hCD4+ T cells, indicating transcription and translation of IDE/gamma-EpGE may be elevated. No significant hydrolysis of exogenous beta-Ep is observed with intact hCD4+ T cells whether quiescent or activated or from preparations of hCD4+ T cell membranes. Therefore, this activity appears to be intracellular. Immunoreactive IDE/gamma-EpGE is detected inside activated hCD4+ T cells. Analysis of metabolites generated upon hydrolysis of beta-Ep with lysed activated hCD4+ T cell preparations identified the presence of: beta-Ep1-18, beta-Ep2-18, beta-Ep1-17, beta-Ep2-17, beta-Ep18-31, beta-Ep19-31, beta-Ep1-13, beta-Ep2-13, beta-Ep18-26, and beta-Ep20-31 as major metabolites and the majority of these are consistent with beta-Ep hydrolytic activity attributable to IDE/gamma-EpGE.
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Affiliation(s)
- B Sarada
- Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, 75235-9038, USA
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Chesneau V, Perlman RK, Li W, Keller GA, Rosner MR. Insulin-degrading enzyme does not require peroxisomal localization for insulin degradation. Endocrinology 1997; 138:3444-51. [PMID: 9231799 DOI: 10.1210/endo.138.8.5344] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Although considerable evidence implicates insulin-degrading enzyme (IDE) in the cellular metabolism of insulin in many cell types, its mechanism and site of action are not clear. In this study, we have examined the relationship between insulin-degrading enzyme's peroxisomal location and its ability to degrade insulin by mutation of its peroxisomal targeting signal (PTS), the carboxy terminal A/S-K-L tripeptide. Site-directed mutagenesis was used to destroy the peroxisomal targeting signal of human insulin-degrading enzyme by changing alanine to leucine (AL.pts), leucine to valine (LV.pts), or by deleting the entire tripeptide (DEL.pts). The alanine or leucine mutants, when expressed in COS cells, were indistinguishable from wild-type insulin-degrading enzyme with respect to size (110 kDa), amount of immunoreactive material, ability to bind insulin, in vitro activity, and cellular degradation of insulin. In contrast, the deletion mutant was shorter in size (approximately 0 kDa) and unable to bind the hormone. Thus, although the tripeptide at insulin-degrading enzyme's carboxy terminus appeared to confer enzyme stability, the conserved sequence was not required for insulin degradation. Finally, an immunocytofluorescence study showed that, whereas a significant amount of the wild-type protein was localized in peroxisomes, none of the peroxisomal targeting mutants could be detected in these organelles. These findings indicate that insulin-degrading enzyme does not require peroxisomal localization for insulin degradation and suggest that this enzyme has multiple cellular functions.
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Affiliation(s)
- V Chesneau
- Ben May Institute for Cancer Research, The University of Chicago, Illinois 60637, USA
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Seta KA, Roth RA. Overexpression of insulin degrading enzyme: cellular localization and effects on insulin signaling. Biochem Biophys Res Commun 1997; 231:167-71. [PMID: 9070242 DOI: 10.1006/bbrc.1997.6066] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
To investigate the role of insulin degrading enzyme (insulysin, EC 3.4.24.56) in insulin signaling, Chinese hamster ovary cells overexpressing the human insulin receptor were genetically engineered to also stably overexpress the rat insulin degrading enzyme. In comparison to the parental cells, these cells expressed 2.7-fold elevated levels of enzyme and insulin degradation was also increased 2-fold. These cells also exhibited a more rapid decrease in receptor tyrosine phosphorylation after removal of insulin. Moreover, low concentrations of insulin were less effective at stimulating proliferation of the cells overexpressing the enzyme. Finally, a fraction of the overexpressed enzyme as well a fraction of the endogenous enzyme could be detected on the plasma membrane surface of these cells. These results support the hypothesis that this enzyme may function in insulin signaling by degrading the insulin molecule.
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Affiliation(s)
- K A Seta
- Department of Molecular Pharmacology, Stanford University School of Medicine, California 94305, USA
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Smith RM, Harada S, Jarett L. Insulin internalization and other signaling pathways in the pleiotropic effects of insulin. INTERNATIONAL REVIEW OF CYTOLOGY 1997; 173:243-80. [PMID: 9127955 DOI: 10.1016/s0074-7696(08)62479-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Insulin is the major anabolic hormone in humans and affects multiple cellular processes. Insulin rapidly regulates short-term effects on carbohydrate, lipid, and protein metabolism and is also a potent growth factor controlling cell proliferation and differentiation. The metabolic and growth-related effects require insulin binding to its receptor and receptor phosphorylation. Evidence suggests these events result in subsequent substrate phosphorylation and activation of multiple signaling pathways involving Src homology domain-containing proteins and the internalization of the insulin:receptor complex. The role of insulin internalization in insulin action is largely speculative. For more than two decades, extensive investigation has been carried out by numerous laboratories of the mechanisms by which insulin causes its pleiotropic responses and the cellular processing of insulin receptors. This chapter reviews our current knowledge of the phosphorylation signaling pathways activated by insulin and presents evidence that substrates other than insulin receptor substrate-1 are involved in insulin's regulation of immediate-early gene expression. We also review the mechanisms involved in insulin internalization and present evidence that internalization may play a key role in insulin action through both signal transduction processes and translocation of insulin to the cell cytoplasm and nucleus.
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Affiliation(s)
- R M Smith
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia 19104, USA
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38
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Bai JP, Hong HJ, Rothenberger DA, Wong WD, Buls JG. The presence of insulin-degrading enzyme in human ileal and colonic mucosal cells. J Pharm Pharmacol 1996; 48:1180-4. [PMID: 8961169 DOI: 10.1111/j.2042-7158.1996.tb03917.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The aim of this research is to characterize the presence of insulin-degrading enzyme in human colon and ileal mucosal cells. Biochemical studies, including the activity-pH profiles, the effects of enzyme inhibitors, immunoprecipitation and western blots, were conducted. The majority of insulin-degrading activity in colon mucosal cells was localized in the cytosol. In both colon and ileum, cytosolic insulin-degrading activities had a pH optimum at pH 7.5, and were extensively inhibited by each of N-ethylmaleimide, p-chloromercuribenzoate, and 1,10-phenanthroline, but were very weakly affected by each of leupeptin, chymostatin, diisopropyl phosphofluoridate and soybean trypsin inhibitor. In the colon and ileum, more than 93% and 96%, respectively, of cytosolic insulin-degrading activities were removed by the mouse monoclonal antibody to human RBC insulin-degrading enzyme, as compared with less than 20% by the normal mouse IgG for both tissues. Further, a western blot analysis revealed that a cytosolic protein of 110 kD, in both human colon and ileum, reacted with the monoclonal antibody to insulin-degrading enzyme. It is concluded that insulin-degrading enzyme is present in the cytosol of human colon and ileal mucosal cells.
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Affiliation(s)
- J P Bai
- College of Pharmacy, University of Minnesota, Minneapolis 55455, USA
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Authier F, Cameron PH, Taupin V. Association of insulin-degrading enzyme with a 70 kDa cytosolic protein in hepatoma cells. Biochem J 1996; 319 ( Pt 1):149-58. [PMID: 8870662 PMCID: PMC1217748 DOI: 10.1042/bj3190149] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have investigated the biosynthesis, subcellular location and expression of insulin-degrading enzyme (IDE). a type-I peroxisomal protease, in semi-permeabilized hepatoma cells using pulse-chase experiments, non-denaturing immunoprecipitation protocols and Northern-blot analyses. In HcpG2 cell lysates prepared from cells radiolabelled with Tran[35S]-label, immunoprecipitated IDE was observed immediately after a 5 min pulse and subsequently declined during chase with t1/2 of approx. 33 h. In addition to the 110 kDa IDE protein, a protein of 70 kDa (p70) was identified in radiolabelled immunoprecipitates when using a monoclonal anti-IDE antibody 9B12 under non-denaturing conditions. This same antibody did not recognize p70 on Western blots of whole-cell lysates nor in sequential immunoprecipitates of immunocomplex-bead eluates from anti-IDE immunoprecipitations. Likewise, cross-linking studies performed on intact HepG2 and H35 hepatoma cells in vivo revealed the existence of a hetero-oligomeric complex of 180 kDa in which IDE and p70 were physically associated. Digitonin-permeabilization studies in normal and 35S-labelled HepG2 cells have defined a predominant association of IDE and its associated protein p70 with cytosol (supernatant); only a minor amount of the protein IDE was detected in peroxisomes (cellular pellet). Immunoprecipitation of IDE from 35S-labelled cell lysates of normal and stably transfected Chinese hamster ovary cells overexpressing IDE failed to detect p70. Treatment of HepG2 cells with clofibrate, a peroxisome proliferator, resulted in a dose-dependent increase of the two human IDE transcripts of 3.6 and 3.2 kb. This effect was not accompanied by a similar change at the protein level, nor by a change in the subcellular location of the proteins IDE and p70. Based on these findings we propose that in hepatoma cells: (1) IDE mainly exists in a stable cytoplasmic pool that is unchanged in cells undergoing peroxisomal proliferation; and (2) p70 binding to IDE may serve to maintain the dual cytosolic and peroxisomal pools of IDE in a stable equilibrium.
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Affiliation(s)
- F Authier
- Institut National de la Santé et de la Recherche Médicale U30, Hôpital des Enfants Malades, Paris, France
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40
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Bai JP, Chang LL. Transepithelial transport of insulin: I. Insulin degradation by insulin-degrading enzyme in small intestinal epithelium. Pharm Res 1995; 12:1171-5. [PMID: 7494830 DOI: 10.1023/a:1016263926946] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PURPOSE The purpose of this study was to determine the existence of insulin-degrading enzyme (EC 3.4.22.11) (IDE) in rat intestinal enterocytes. METHODS Subcellular fractionation, biochemical characterization, immunoprecipitation, and western blots were employed. RESULTS Insulin-degrading activity was localized in the cytosol, constituting 92% of total insulin-degrading activity. Cytosolic insulin-degrading activity had a pH optimum of 7.5, was almost completely inhibited by IDE inhibitors (N-ethylmaleimide, 1,10-phenanthroline, EDTA, p-chloromercuribenzoate, bacitracin), but was not or only weakly inhibited by others (aprotinin, chymostatin, leupeptin, and diisopropyl phosphofluoridate.) Further, cytosolic insulin-degrading activity had a Km of 78 nM, sharing a similar Km value with insulin-degrading enzyme in non-purified forms. Approximately, 87 +/- 1.7% of cytosolic insulin-degrading activity was removed by the monoclonal antibody to IDE. On the SDS gel, the molecular weight of cytosolic IDE was 110 KD which is the same as that of human IDE. CONCLUSIONS IDE is the major enzyme which degrades insulin in enterocytes.
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Affiliation(s)
- J P Bai
- Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis 55455, USA
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Bai JP, Hsu MJ, Shier WT. Insulin-degrading enzyme in a human colon adenocarcinoma cell line (Caco-2). Pharm Res 1995; 12:513-7. [PMID: 7596985 DOI: 10.1023/a:1016241610649] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The activity of insulin-degrading enzyme (IDE), a thiol metalloprotease degrading insulin in many insulin target cells, was determined in human colon adenocarcinoma (Caco-2) cells. Insulin-degrading activity was localized in the cytosol of Caco-2 cells, accounting for 88% of total activity. Western blots and immunoprecipitation showed that IDE was present in the cytosol of Caco-2 cells and contributed to more than 93% cytosolic insulin-degrading activity. Cytosolic insulin degradation was strongly inhibited by IDE inhibitors, including N-ethylmaleimide, 1,10-phenanthroline, p-chloromericuribenzoate, and EDTA, but was not significantly or not as extensively inhibited by strong inhibitors of proteasome, i.e., chymostatin, soybean trypsin inhibitor, leupeptin, and Dip-F. These results suggest that IDE is present in Caco-2 cells, that Caco-2 IDE has properties similar to those of its counterparts in insulin-target tissues, and that it significantly contributes to intracellular insulin degradation.
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Affiliation(s)
- J P Bai
- Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis 55455, USA
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Harada S, Smith RM, Smith JA, Shah N, Jarett L. Demonstration of specific insulin binding to cytosolic proteins in H35 hepatoma cells, rat liver and skeletal muscle. Biochem J 1995; 306 ( Pt 1):21-8. [PMID: 7864812 PMCID: PMC1136476 DOI: 10.1042/bj3060021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We previously demonstrated that internalized insulin enters the cytoplasm before accumulating in nuclei of H35 rat hepatoma cells. This finding raises the possibility that insulin may interact with cytosolic proteins in addition to insulin-degrading enzyme (IDE). In the present study, cytosol from H35 hepatoma cells, rat liver or muscle was incubated with A14- or B26-125I-insulin at 4 degrees C for 5-120 min in the absence or presence of 25 micrograms/ml unlabelled insulin. 125I-insulin was cross-linked to cytosolic proteins by disuccinimidyl suberate and analysed by reducing or non-reducing SDS/PAGE and autoradiography. Our results demonstrate the presence of both tissue-specific and common cytosolic proteins which specifically bind insulin. In muscle cytosol, only two proteins of 27 and 110 kDa were specifically labelled with B26-125I-insulin. Seven major bands, of 27, 45, 55, 60, 76, 82 and 110 kDa, were labelled in rat liver cytosol. Detection of cytosolic insulin-binding proteins in H35-cell cytosol was dependent on cell-culture conditions. Labelling in cytosol from serum-deprived cells was decreased or absent compared with cytosol prepared from serum-fed or serum-deprived cells treated with 100 ng/ml insulin for 1 h before preparation of the cytosol, in which six bands, of 32, 41, 45, 55, 82 and 110 kDa, were specifically labelled with B26-125I-insulin. This result suggests that the concentration or binding activity of some cytosolic insulin-binding proteins is rapidly regulated. Labelling of both rat liver and H35 cytosolic insulin-binding proteins was time-dependent, and decreased or disappeared at 120 min in parallel with the degradation of labelled insulin. Fewer bands were specifically labelled with A14-125I-insulin than with B26-125I-insulin. The number of labelled bands observed under reducing and non-reducing conditions was not different in any of the cytosols. The 110 kDa band in all cytosols was identified as IDE by Western-blot analysis; the other proteins did not react with anti-IDE antibody and remain unidentified. 1,10-Phenanthroline (2 mM) increased IDE labelling, but decreased the labelling of 82 and 27 kDa bands. The marked difference in the number of cytosolic insulin-binding proteins in muscle and either H35 cells or liver suggests both that the labelling is specific and that these proteins serve a function and may be involved in some heretofore unknown mechanism of the signalling pathway by which insulin regulates cell growth or differentiation.
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Affiliation(s)
- S Harada
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104
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45
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Werlen RC, Offord RE, Rose K. Preparation and characterization of novel substrates of insulin proteinase (EC 3.4.99.45). Biochem J 1994; 302 ( Pt 3):907-11. [PMID: 7945219 PMCID: PMC1137316 DOI: 10.1042/bj3020907] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The specificity of insulin proteinase (EC 3.4.99.45) has been difficult to categorize using only its natural substrates. By exploiting the fact that two substrates competing for the same enzyme inhibit one another, we have found some new substrates of the insulin proteinase from porcine muscle. Two of these substrates, a tryptic fragment of BSA and a fragment of cytochrome c, have been shown to be cleaved at a single site. The albumin fragment, as well as another fragment of cytochrome c., have susceptibilities (Vmax/Km) comparable with that of insulin. In a second aspect of the study, the porcine-muscle enzyme was shown to be related to other members of its superfamily in that it was immunoprecipitated by a monoclonal antibody raised against the insulin-degrading enzyme from human red blood cells and has the same cleavage sites on insulin as has the rat skeletal-muscle insulin proteinase. We note, however, a possible discrepancy between our results and those of another group regarding the subunit size (110 kDa) of the immunoprecipitated material.
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Affiliation(s)
- R C Werlen
- Département de Biochimie Médicale, C.M.U., Geneva, Switzerland
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46
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Kuo W, Gehm B, Rosner M, Li W, Keller G. Inducible expression and cellular localization of insulin-degrading enzyme in a stably transfected cell line. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31688-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Kurochkin IV, Goto S. Alzheimer's beta-amyloid peptide specifically interacts with and is degraded by insulin degrading enzyme. FEBS Lett 1994; 345:33-7. [PMID: 8194595 DOI: 10.1016/0014-5793(94)00387-4] [Citation(s) in RCA: 297] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cerebral deposition of beta-amyloid peptide (beta A) is a hallmark of Alzheimer's disease. Concentration of beta A could play a critical role in the rate of amyloid deposition. It is therefore of considerable importance to identify proteases involved in processing of beta A. 125I-labeled synthetic beta A specifically cross-linked to a single protein with M(r) = 110,000 in cytosol fractions from rat brain and liver. This protein was identified as insulin degrading enzyme (IDE) since the labeling of the 110 kDa protein was completely blocked by an excess of insulin, and anti-IDE monoclonal antibodies precipitated the labeled protein. Purified rat IDE effectively degraded beta A.
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Affiliation(s)
- I V Kurochkin
- Department of Biochemistry, School of Pharmaceutical Sciences, Toho University, Chiba, Japan
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Harada S, Smith RM, Jarett L. 1,10-Phenanthroline increases nuclear accumulation of insulin in response to inhibiting insulin degradation but has a biphasic effect on insulin's ability to increase mRNA levels. DNA Cell Biol 1994; 13:487-93. [PMID: 8024692 DOI: 10.1089/dna.1994.13.487] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Previous reports demonstrated that insulin is translocated through the cytoplasm to the nucleus of H35 hepatoma cells and suggested that nuclear insulin may be involved in stimulating transcription of immediate-early genes. In a recent study, inhibition of insulin-degrading enzyme with 1,10-phenanthroline, a Zn2+ chelator, caused a significant increase in the nuclear accumulation of insulin. The present study characterized the effects of 1,10-phenanthroline and its nonchelating isomer, 1,7-phenanthroline, on insulin degradation, nuclear accumulation, and stimulation of immediate-early gene expression. 1,10- but not 1,7-phenanthroline inhibited insulin degradation and increased nuclear accumulation of insulin in a dose-dependent manner. 1,7-phenanthroline caused a dose-dependent decrease in the expression of insulin-stimulated immediate-early genes, but had no significant effect on alpha-tubulin mRNA levels. In the presence of insulin, Northern analysis revealed that 1,10-phenanthroline at all concentrations tested increased alpha-tubulin mRNA levels, but had a biphasic effect on insulin-stimulated immediate-early gene expression. At low concentrations (5-200 microM), 1,10-phenanthroline increased the expression of insulin-stimulated g33, c-fos, and Egr-1 mRNA. At concentrations greater than 1 mM, insulin-stimulated immediate-early gene expression was decreased similar to the effect seen with 1,7-phenanthroline. Nuclear run-on analysis demonstrated that high concentrations of 1,10-phenanthroline decreased insulin-stimulated immediate-early gene transcription but had no effect on transcription of alpha-tubulin. However, low concentrations of 1,10-phenanthroline did not increase transcription of any genes.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Harada
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104
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50
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Hosomi Y, Shii K, Ogawa W, Matsuba H, Yoshida M, Okada Y, Yokono K, Kasuga M, Baba S, Roth R. Characterization of a 60-kilodalton substrate of the insulin receptor kinase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)78151-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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