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Ataie-Ashtiani S, Forbes B. A Review of the Biosynthesis and Structural Implications of Insulin Gene Mutations Linked to Human Disease. Cells 2023; 12:cells12071008. [PMID: 37048081 PMCID: PMC10093311 DOI: 10.3390/cells12071008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 03/13/2023] [Accepted: 03/15/2023] [Indexed: 03/29/2023] Open
Abstract
The discovery of the insulin hormone over 100 years ago, and its subsequent therapeutic application, marked a key landmark in the history of medicine and medical research. The many roles insulin plays in cell metabolism and growth have been revealed by extensive investigations into the structure and function of insulin, the insulin tyrosine kinase receptor (IR), as well as the signalling cascades, which occur upon insulin binding to the IR. In this review, the insulin gene mutations identified as causing disease and the structural implications of these mutations will be discussed. Over 100 studies were evaluated by one reviewing author, and over 70 insulin gene mutations were identified. Mutations may impair insulin gene transcription and translation, preproinsulin trafficking and proinsulin sorting, or insulin-IR interactions. A better understanding of insulin gene mutations and the resultant pathophysiology can give essential insight into the molecular mechanisms underlying impaired insulin biosynthesis and insulin-IR interaction.
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2
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Determinants of IGF-II influencing stability, receptor binding and activation. Sci Rep 2022; 12:4695. [PMID: 35304516 PMCID: PMC8933565 DOI: 10.1038/s41598-022-08467-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 02/28/2022] [Indexed: 11/28/2022] Open
Abstract
Insulin like growth factor II (IGF-II) is involved in metabolic and mitogenic signalling in mammalian cells and plays important roles in normal fetal development and postnatal growth. It is structurally similar to insulin and binds not only with high affinity to the type 1 insulin-like growth factor receptor (IGF-1R) but also to the insulin receptor isoform A (IR-A). As IGF-II expression is commonly upregulated in cancer and its signalling promotes cancer cell survival, an antagonist that blocks IGF-II action without perturbing insulin signalling would be invaluable. The high degree of structural homology between the IR and IGF-1R makes selectively targeting either receptor in the treatment of IGF-II-dependent cancers very challenging. However, there are sequence differences between insulin and IGF-II that convey receptor selectivity and influence binding affinity and signalling outcome. Insulin residue YB16 is a key residue involved in maintaining insulin stability, dimer formation and IR binding. Mutation of this residue to glutamine (as found in IGF-II) results in reduced binding affinity. In this study we sought to determine if the equivalent residue Q18 in IGF-II plays a similar role. We show through site-directed mutagenesis of Q18 that this residue contributes to IGF-II structural integrity, selectivity of IGF-1R/IR binding, but surprisingly does not influence IR-A signalling activation. These findings provide insights into a unique IGF-II residue that can influence receptor binding specificity whilst having little influence on signalling outcome.
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Yang Y, Glidden MD, Dhayalan B, Zaykov AN, Chen YS, Wickramasinghe NP, DiMarchi RD, Weiss MA. Peptide Model of the Mutant Proinsulin Syndrome. II. Nascent Structure and Biological Implications. Front Endocrinol (Lausanne) 2022; 13:821091. [PMID: 35299958 PMCID: PMC8922542 DOI: 10.3389/fendo.2022.821091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/21/2022] [Indexed: 11/13/2022] Open
Abstract
Toxic misfolding of proinsulin variants in β-cells defines a monogenic diabetes syndrome, designated mutant INS-gene induced diabetes of the young (MIDY). In our first study (previous article in this issue), we described a one-disulfide peptide model of a proinsulin folding intermediate and its use to study such variants. The mutations (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser) probe residues conserved among vertebrate insulins. In this companion study, we describe 1H and 1H-13C NMR studies of the peptides; key NMR resonance assignments were verified by synthetic 13C-labeling. Parent spectra retain nativelike features in the neighborhood of the single disulfide bridge (cystine B19-A20), including secondary NMR chemical shifts and nonlocal nuclear Overhauser effects. This partial fold engages wild-type side chains LeuB15, LeuA16 and PheB24 at the nexus of nativelike α-helices α1 and α3 (as defined in native proinsulin) and flanking β-strand (residues B24-B26). The variant peptides exhibit successive structural perturbations in order: parent (most organized) > SerB24 >> ProA16 > ProB15 (least organized). The same order pertains to (a) overall α-helix content as probed by circular dichroism, (b) synthetic yields of corresponding three-disulfide insulin analogs, and (c) ER stress induced in cell culture by corresponding mutant proinsulins. These findings suggest that this and related peptide models will provide a general platform for classification of MIDY mutations based on molecular mechanisms by which nascent disulfide pairing is impaired. We propose that the syndrome's variable phenotypic spectrum-onsets ranging from the neonatal period to later in childhood or adolescence-reflects structural features of respective folding intermediates.
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Affiliation(s)
- Yanwu Yang
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Michael D. Glidden
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, United States
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | | | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Nalinda P. Wickramasinghe
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
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Jarosinski MA, Dhayalan B, Chen YS, Chatterjee D, Varas N, Weiss MA. Structural principles of insulin formulation and analog design: A century of innovation. Mol Metab 2021; 52:101325. [PMID: 34428558 PMCID: PMC8513154 DOI: 10.1016/j.molmet.2021.101325] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 08/12/2021] [Accepted: 08/17/2021] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The discovery of insulin in 1921 and its near-immediate clinical use initiated a century of innovation. Advances extended across a broad front, from the stabilization of animal insulin formulations to the frontiers of synthetic peptide chemistry, and in turn, from the advent of recombinant DNA manufacturing to structure-based protein analog design. In each case, a creative interplay was observed between pharmaceutical applications and then-emerging principles of protein science; indeed, translational objectives contributed to a growing molecular understanding of protein structure, aggregation and misfolding. SCOPE OF REVIEW Pioneering crystallographic analyses-beginning with Hodgkin's solving of the 2-Zn insulin hexamer-elucidated general features of protein self-assembly, including zinc coordination and the allosteric transmission of conformational change. Crystallization of insulin was exploited both as a step in manufacturing and as a means of obtaining protracted action. Forty years ago, the confluence of recombinant human insulin with techniques for site-directed mutagenesis initiated the present era of insulin analogs. Variant or modified insulins were developed that exhibit improved prandial or basal pharmacokinetic (PK) properties. Encouraged by clinical trials demonstrating the long-term importance of glycemic control, regimens based on such analogs sought to resemble daily patterns of endogenous β-cell secretion more closely, ideally with reduced risk of hypoglycemia. MAJOR CONCLUSIONS Next-generation insulin analog design seeks to explore new frontiers, including glucose-responsive insulins, organ-selective analogs and biased agonists tailored to address yet-unmet clinical needs. In the coming decade, we envision ever more powerful scientific synergies at the interface of structural biology, molecular physiology and therapeutics.
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Affiliation(s)
- Mark A Jarosinski
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, 46202, IN, USA
| | - Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, 46202, IN, USA
| | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, 46202, IN, USA
| | - Deepak Chatterjee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, 46202, IN, USA
| | - Nicolás Varas
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, 46202, IN, USA
| | - Michael A Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, 46202, IN, USA; Department of Chemistry, Indiana University, Bloomington, 47405, IN, USA; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, 47907, IN, USA.
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Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Structural Lessons From the Mutant Proinsulin Syndrome. Front Endocrinol (Lausanne) 2021; 12:754693. [PMID: 34659132 PMCID: PMC8514764 DOI: 10.3389/fendo.2021.754693] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 09/13/2021] [Indexed: 12/30/2022] Open
Abstract
Insight into folding mechanisms of proinsulin has been provided by analysis of dominant diabetes-associated mutations in the human insulin gene (INS). Such mutations cause pancreatic β-cell dysfunction due to toxic misfolding of a mutant proinsulin and impairment in trans of wild-type insulin secretion. Anticipated by the "Akita" mouse (a classical model of monogenic diabetes mellitus; DM), this syndrome illustrates the paradigm endoreticulum (ER) stress leading to intracellular proteotoxicity. Diverse clinical mutations directly or indirectly perturb native disulfide pairing leading to protein misfolding and aberrant aggregation. Although most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships, but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of non-syndromic Type 2 DM. Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of non-foldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
| | | | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
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6
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Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Diabetes mellitus due to toxic misfolding of proinsulin variants. Mol Metab 2021:101229. [PMID: 33823319 DOI: 10.1016/j.molmet.2021.101229] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/10/2021] [Accepted: 03/29/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Dominant mutations in the human insulin gene (INS) lead to pancreatic β-cell dysfunction and diabetes mellitus (DM) due to toxic misfolding of a mutant proinsulin. Analogous to a classical mouse model of monogenic DM ("Akita"), this syndrome highlights the susceptibility of β-cells to endoreticulum (ER) stress due to protein misfolding and aberrant aggregation. SCOPE OF REVIEW Diverse clinical mutations directly or indirectly perturb native disulfide pairing. Whereas most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of nonsyndromic Type 2 DM. MAJOR CONCLUSIONS Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of nonfoldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
- Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Deepak Chatterjee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Michael A Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Characterization of viral insulins reveals white adipose tissue-specific effects in mice. Mol Metab 2020; 44:101121. [PMID: 33220491 PMCID: PMC7770979 DOI: 10.1016/j.molmet.2020.101121] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/05/2020] [Accepted: 11/16/2020] [Indexed: 12/11/2022] Open
Abstract
Objective Members of the insulin/insulin-like growth factor (IGF) superfamily are well conserved across the evolutionary tree. We recently showed that four viruses in the Iridoviridae family possess genes that encode proteins highly homologous to human insulin/IGF-1. Using chemically synthesized single-chain (sc), i.e., IGF-1-like, forms of the viral insulin/IGF-1-like peptides (VILPs), we previously showed that they can stimulate human receptors. Because these peptides possess potential cleavage sites to form double chain (dc), i.e., more insulin-like, VILPs, in this study, we have characterized dc forms of VILPs for Grouper iridovirus (GIV), Singapore grouper iridovirus (SGIV) and Lymphocystis disease virus-1 (LCDV-1) for the first time. Methods The dcVILPs were chemically synthesized. Using murine fibroblast cell lines overexpressing insulin receptor (IR-A or IR-B) or IGF1R, we first determined the binding affinity of dcVILPs to the receptors and characterized post-receptor signaling. Further, we used C57BL/6J mice to study the effect of dcVILPs on lowering blood glucose. We designed a 3-h dcVILP in vivo infusion experiment to determine the glucose uptake in different tissues. Results GIV and SGIV dcVILPs bind to both isoforms of human insulin receptor (IR-A and IR-B) and to the IGF1R, and for the latter, show higher affinity than human insulin. These dcVILPs stimulate IR and IGF1R phosphorylation and post-receptor signaling in vitro and in vivo. Both GIV and SGIV dcVILPs stimulate glucose uptake in mice. In vivo infusion experiments revealed that while insulin (0.015 nmol/kg/min) and GIV dcVILP (0.75 nmol/kg/min) stimulated a comparable glucose uptake in heart and skeletal muscle and brown adipose tissue, GIV dcVILP stimulated 2-fold higher glucose uptake in white adipose tissue (WAT) compared to insulin. This was associated with increased Akt phosphorylation and glucose transporter type 4 (GLUT4) gene expression compared to insulin in WAT. Conclusions Our results show that GIV and SGIV dcVILPs are active members of the insulin superfamily with unique characteristics. Elucidating the mechanism of tissue specificity for GIV dcVILP will help us to better understand insulin action, design new analogs that specifically target the tissues and provide new insights into their potential role in disease. Viral insulin/IGF1-like peptides (VILPs) are microbial members of the insulin superfamily. VILPs bind to human IR and IGF1R and stimulate post-receptor signaling. Grouper iridovirus (GIV) VILP has white adipose tissue (WAT)-specific characteristics. GIV VILP stimulates increased glucose uptake in WAT via increased GLUT4 expression.
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Xu Y, Kirk NS, Venugopal H, Margetts MB, Croll TI, Sandow JJ, Webb AI, Delaine CA, Forbes BE, Lawrence MC. How IGF-II Binds to the Human Type 1 Insulin-like Growth Factor Receptor. Structure 2020; 28:786-798.e6. [PMID: 32459985 PMCID: PMC7343240 DOI: 10.1016/j.str.2020.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/23/2020] [Accepted: 05/05/2020] [Indexed: 02/06/2023]
Abstract
Human type 1 insulin-like growth factor receptor (IGF-1R) signals chiefly in response to the binding of insulin-like growth factor I. Relatively little is known about the role of insulin-like growth factor II signaling via IGF-1R, despite the affinity of insulin-like growth factor II for IGF-1R being within an order of magnitude of that of insulin-like growth factor I. Here, we describe the cryoelectron microscopy structure of insulin-like growth factor II bound to a leucine-zipper-stabilized IGF-1R ectodomain, determined in two conformations to a maximum average resolution of 3.2 Å. The two conformations differ in the relative separation of their respective points of membrane entry, and comparison with the structure of insulin-like growth factor I bound to IGF-1R reveals long-suspected differences in the way in which the critical C domain of the respective growth factors interact with IGF-1R.
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Affiliation(s)
- Yibin Xu
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC 3050, Australia
| | - Nicholas S Kirk
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC 3050, Australia
| | - Hariprasad Venugopal
- Ramaciotti Centre for Cryo-Electron Microscopy, Monash University, Clayton, VIC 3800, Australia
| | - Mai B Margetts
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
| | - Tristan I Croll
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge CB2 0XY, UK
| | - Jarrod J Sandow
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC 3050, Australia
| | - Andrew I Webb
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC 3050, Australia
| | - Carlie A Delaine
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University of South Australia, Bedford Park, SA 5042, Australia
| | - Briony E Forbes
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University of South Australia, Bedford Park, SA 5042, Australia
| | - Michael C Lawrence
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC 3050, Australia.
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A structurally minimized yet fully active insulin based on cone-snail venom insulin principles. Nat Struct Mol Biol 2020; 27:615-624. [PMID: 32483339 PMCID: PMC7374640 DOI: 10.1038/s41594-020-0430-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 04/07/2020] [Indexed: 12/26/2022]
Abstract
Human insulin and its current therapeutic analogs all show propensity, albeit varyingly, to self-associate into dimers and hexamers, which delays their onset of action and makes blood glucose management difficult for people with diabetes. Recently, we described a monomeric, insulin-like peptide in cone-snail venom with moderate human insulin-like bioactivity. Here, with insights from structural biology studies, we report the development of mini-Ins-a human des-octapeptide insulin analog-as a structurally minimal, full-potency insulin. Mini-Ins is monomeric and, despite the lack of the canonical B-chain C-terminal octapeptide, has similar receptor binding affinity to human insulin. Four mutations compensate for the lack of contacts normally made by the octapeptide. Mini-Ins also has similar in vitro insulin signaling and in vivo bioactivities to human insulin. The full bioactivity of mini-Ins demonstrates the dispensability of the PheB24-PheB25-TyrB26 aromatic triplet and opens a new direction for therapeutic insulin development.
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10
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Ahorukomeye P, Disotuar MM, Gajewiak J, Karanth S, Watkins M, Robinson SD, Flórez Salcedo P, Smith NA, Smith BJ, Schlegel A, Forbes BE, Olivera B, Hung-Chieh Chou D, Safavi-Hemami H. Fish-hunting cone snail venoms are a rich source of minimized ligands of the vertebrate insulin receptor. eLife 2019; 8:41574. [PMID: 30747102 PMCID: PMC6372279 DOI: 10.7554/elife.41574] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 12/30/2018] [Indexed: 12/27/2022] Open
Abstract
The fish-hunting marine cone snail Conus geographus uses a specialized venom insulin to induce hypoglycemic shock in its prey. We recently showed that this venom insulin, Con-Ins G1, has unique characteristics relevant to the design of new insulin therapeutics. Here, we show that fish-hunting cone snails provide a rich source of minimized ligands of the vertebrate insulin receptor. Insulins from C. geographus, Conus tulipa and Conus kinoshitai exhibit diverse sequences, yet all bind to and activate the human insulin receptor. Molecular dynamics reveal unique modes of action that are distinct from any other insulins known in nature. When tested in zebrafish and mice, venom insulins significantly lower blood glucose in the streptozotocin-induced model of diabetes. Our findings suggest that cone snails have evolved diverse strategies to activate the vertebrate insulin receptor and provide unique insight into the design of novel drugs for the treatment of diabetes. Insulin is a hormone critical for maintaining healthy blood sugar levels in humans. When the insulin system becomes faulty, blood sugar levels become too high, which can lead to diabetes. At the moment, the only effective treatment for one of the major types of diabetes are daily insulin injections. However, designing fast-acting insulin drugs has remained a challenge. Insulin molecules form clusters (so-called hexamers) that first have to dissolve in the body to activate the insulin receptor, which plays a key role in regulating the blood sugar levels throughout the body. This can take time and can therefore delay the blood-sugar control. In 2015, researchers discovered that the fish-hunting cone snail Conus geographus uses a specific type of insulin to capture its prey – fish. The cone snail releases insulin into the surrounding water and then engulfs its victim with its mouth. This induces dangerously low blood sugar levels in the fish and so makes them an easy target. Unlike the human version, the snail insulin does not cluster, and despite structural differences, can bind to the human insulin receptor. Now, Ahorukomeye, Disotuar et al. – including some of the authors involved in the previous study – wanted to find out whether other fish-hunting cone snails also make insulins and if they differed from the one previously discovered in C. geographus. The insulin molecules were extracted and analyzed, and the results showed that the three cone snail species had different versions of insulin – but none of them formed clusters. Ahorukomeye, Disotuar et al. further revealed that the snail insulins could bind to the human insulin receptors and could also reverse high blood sugar levels in fish and mouse models of the disease. This research may help guide future studies looking into developing fast-acting insulin drugs for diabetic patients. A next step will be to fully understand how snail insulins can be active at the human receptor without forming clusters. Cone snails solved this problem millions of years ago and by understanding how they have done this, researchers are hoping to redesign current diabetic therapeutics. Since the snail insulins do not form clusters and should act faster than currently available insulin drugs, they may lead to better or new diabetes treatments.
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Affiliation(s)
- Peter Ahorukomeye
- Department of Biology, University of Utah School of Medicine, Salt Lake City, United States
| | - Maria M Disotuar
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States
| | - Joanna Gajewiak
- Department of Biology, University of Utah School of Medicine, Salt Lake City, United States
| | - Santhosh Karanth
- Molecular Medicine Program, University of Utah, Salt Lake City, United States.,Department of Internal Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Utah School of Medicine, Salt Lake City, United States.,Department of Nutrition and Integrative Physiology, College of Health, University of Utah, Salt Lake City, United States
| | - Maren Watkins
- Department of Biology, University of Utah School of Medicine, Salt Lake City, United States
| | - Samuel D Robinson
- Department of Biology, University of Utah School of Medicine, Salt Lake City, United States
| | - Paula Flórez Salcedo
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States
| | - Nicholas A Smith
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Brian J Smith
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Amnon Schlegel
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States.,Molecular Medicine Program, University of Utah, Salt Lake City, United States.,Department of Internal Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Utah School of Medicine, Salt Lake City, United States.,Department of Nutrition and Integrative Physiology, College of Health, University of Utah, Salt Lake City, United States
| | - Briony E Forbes
- Department of Medical Biochemistry, Flinders University, Bedford Park, Australia
| | - Baldomero Olivera
- Department of Biology, University of Utah School of Medicine, Salt Lake City, United States
| | - Danny Hung-Chieh Chou
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States
| | - Helena Safavi-Hemami
- Department of Biology, University of Utah School of Medicine, Salt Lake City, United States.,Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States
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Abstract
There have been many advances in insulin with a realistic possibility of mimicking nature to improve insulin replacement, with a view to achieving improved metabolic control. Lessons can be learnt from the evolution of insulin, insulin development, and new advances in technology. This may lead to fewer side effects of therapy resulting in a lower risk of hypoglycaemia and less weight gain, which could in turn could reduce long-term complications for people with diabetes.
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Affiliation(s)
- R Herring
- Royal Surrey County NHS Foundation Hospital, Guildford, UK
- University of Surrey, Guildford, Surrey, UK
| | - D D L Russell-Jones
- Royal Surrey County NHS Foundation Hospital, Guildford, UK
- University of Surrey, Guildford, Surrey, UK
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12
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Weiss MA, Lawrence MC. A thing of beauty: Structure and function of insulin's "aromatic triplet". Diabetes Obes Metab 2018; 20 Suppl 2:51-63. [PMID: 30230175 PMCID: PMC6159917 DOI: 10.1111/dom.13402] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/25/2018] [Accepted: 05/31/2018] [Indexed: 12/30/2022]
Abstract
The classical crystal structure of insulin was determined in 1969 by D.C. Hodgkin et al. following a 35-year program of research. This structure depicted a hexamer remarkable for its self-assembly as a zinc-coordinated trimer of dimer. Prominent at the dimer interface was an "aromatic triplet" of conserved residues at consecutive positions in the B chain: PheB24 , PheB25 and TyrB26 . The elegance of this interface inspired the Oxford team to poetry: "A thing of beauty is a joy forever" (John Keats as quoted by Blundell, T.L., et al. Advances in Protein Chemistry 26:279-286 [1972]). Here, we revisit this aromatic triplet in light of recent advances in the structural biology of insulin bound as a monomer to fragments of the insulin receptor. Such co-crystal structures have defined how these side chains pack at the primary hormone-binding surface of the receptor ectodomain. On receptor binding, the B-chain β-strand (residues B24-B28) containing the aromatic triplet detaches from the α-helical core of the hormone. Whereas TyrB26 lies at the periphery of the receptor interface and may functionally be replaced by a diverse set of substitutions, PheB24 and PheB25 engage invariant elements of receptor domains L1 and αCT. These critical contacts were anticipated by the discovery of diabetes-associated mutations at these positions by Donald Steiner et al. at the University of Chicago. Conservation of PheB24 , PheB25 and TyrB26 among vertebrate insulins reflects the striking confluence of structure-based evolutionary constraints: foldability, protective self-assembly and hormonal activity.
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Affiliation(s)
- Michael A. Weiss
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202 USA
| | - Michael C. Lawrence
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, AUSTRALIA
- Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, AUSTRALIA
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13
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Selivanova OM, Grishin SY, Glyakina AV, Sadgyan AS, Ushakova NI, Galzitskaya OV. Analysis of Insulin Analogs and the Strategy of Their Further Development. BIOCHEMISTRY (MOSCOW) 2018; 83:S146-S162. [DOI: 10.1134/s0006297918140122] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 07/09/2017] [Indexed: 08/30/2023]
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14
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Yang Y, Chan L. Monogenic Diabetes: What It Teaches Us on the Common Forms of Type 1 and Type 2 Diabetes. Endocr Rev 2016; 37:190-222. [PMID: 27035557 PMCID: PMC4890265 DOI: 10.1210/er.2015-1116] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To date, more than 30 genes have been linked to monogenic diabetes. Candidate gene and genome-wide association studies have identified > 50 susceptibility loci for common type 1 diabetes (T1D) and approximately 100 susceptibility loci for type 2 diabetes (T2D). About 1-5% of all cases of diabetes result from single-gene mutations and are called monogenic diabetes. Here, we review the pathophysiological basis of the role of monogenic diabetes genes that have also been found to be associated with common T1D and/or T2D. Variants of approximately one-third of monogenic diabetes genes are associated with T2D, but not T1D. Two of the T2D-associated monogenic diabetes genes-potassium inward-rectifying channel, subfamily J, member 11 (KCNJ11), which controls glucose-stimulated insulin secretion in the β-cell; and peroxisome proliferator-activated receptor γ (PPARG), which impacts multiple tissue targets in relation to inflammation and insulin sensitivity-have been developed as major antidiabetic drug targets. Another monogenic diabetes gene, the preproinsulin gene (INS), is unique in that INS mutations can cause hyperinsulinemia, hyperproinsulinemia, neonatal diabetes mellitus, one type of maturity-onset diabetes of the young (MODY10), and autoantibody-negative T1D. Dominant heterozygous INS mutations are the second most common cause of permanent neonatal diabetes. Moreover, INS gene variants are strongly associated with common T1D (type 1a), but inconsistently with T2D. Variants of the monogenic diabetes gene Gli-similar 3 (GLIS3) are associated with both T1D and T2D. GLIS3 is a key transcription factor in insulin production and β-cell differentiation during embryonic development, which perturbation forms the basis of monogenic diabetes as well as its association with T1D. GLIS3 is also required for compensatory β-cell proliferation in adults; impairment of this function predisposes to T2D. Thus, monogenic forms of diabetes are invaluable "human models" that have contributed to our understanding of the pathophysiological basis of common T1D and T2D.
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Affiliation(s)
- Yisheng Yang
- Division of Endocrinology (Y.Y.), Department of Medicine, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio 44109; and Diabetes and Endocrinology Research Center (L.C.), Division of Diabetes, Endocrinology and Metabolism, Departments of Medicine, Molecular and Cellular Biology, Biochemistry and Molecular Biology, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
| | - Lawrence Chan
- Division of Endocrinology (Y.Y.), Department of Medicine, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio 44109; and Diabetes and Endocrinology Research Center (L.C.), Division of Diabetes, Endocrinology and Metabolism, Departments of Medicine, Molecular and Cellular Biology, Biochemistry and Molecular Biology, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
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15
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Lundby A, Bolvig P, Hegelund AC, Hansen BF, Worm J, Lützen A, Billestrup N, Bonnesen C, Oleksiewicz MB. Surface-expressed insulin receptors as well as IGF-I receptors both contribute to the mitogenic effects of human insulin and its analogues. J Appl Toxicol 2014; 35:842-50. [DOI: 10.1002/jat.3082] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 09/13/2014] [Accepted: 09/15/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Anders Lundby
- Department of Biomedical Sciences; University of Copenhagen; Blegdamsvej 3 2200 Copenhagen N Denmark
| | - Pernille Bolvig
- Diabetes Research Unit, Novo Nordisk A/S; Novo Nordisk Park 2760 Maaloev Denmark
| | | | - Bo F. Hansen
- Diabetes Research Unit, Novo Nordisk A/S; Novo Nordisk Park 2760 Maaloev Denmark
| | - Jesper Worm
- Diabetes Research Unit, Novo Nordisk A/S; Novo Nordisk Park 2760 Maaloev Denmark
| | - Anne Lützen
- Diabetes Research Unit, Novo Nordisk A/S; Novo Nordisk Park 2760 Maaloev Denmark
| | - Nils Billestrup
- Department of Biomedical Sciences; University of Copenhagen; Blegdamsvej 3 2200 Copenhagen N Denmark
| | - Christine Bonnesen
- Diabetes Research Unit, Novo Nordisk A/S; Novo Nordisk Park 2760 Maaloev Denmark
| | - Martin B. Oleksiewicz
- Centre for Biosecurity and Biopreparedness; Statens Serum Institute; Artillerivej 5 2300 Copenhagen S Denmark
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16
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Diabetes mellitus due to the toxic misfolding of proinsulin variants. FEBS Lett 2013; 587:1942-50. [PMID: 23669362 DOI: 10.1016/j.febslet.2013.04.044] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 02/06/2023]
Abstract
Dominant mutations in the human insulin gene can lead to pancreatic β-cell dysfunction and diabetes mellitus due to toxic folding of a mutant proinsulin. Analogous to a classical mouse model (the Akita mouse), this monogenic syndrome highlights the susceptibility of human β-cells to endoreticular stress due to protein misfolding and aberrant aggregation. The clinical mutations directly or indirectly perturb native disulfide pairing. Whereas the majority of mutations introduce or remove a cysteine (leading in either case to an unpaired residue), non-cysteine-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the evolution of insulin has been constrained not only by its structure and function, but also by the susceptibility of its single-chain precursor to impaired foldability.
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Rowzee AM, Perez-Riveros PJ, Zheng C, Krygowski S, Baum BJ, Cawley NX. Expression and secretion of human proinsulin-B10 from mouse salivary glands: implications for the treatment of type I diabetes mellitus. PLoS One 2013; 8:e59222. [PMID: 23554999 PMCID: PMC3598661 DOI: 10.1371/journal.pone.0059222] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 02/12/2013] [Indexed: 12/29/2022] Open
Abstract
Adenovirus (Ad) mediated expression of therapeutic proteins from salivary glands can result in the delivery of biologically active proteins into the circulation where they impart their physiological function. In recent years, Ad vector delivery to salivary glands (SGs) has emerged as a viable option for gene therapy. Here, we engineered a variant of human proinsulin (hProinsulin-B10) into an Ad vector and demonstrated its ability to transduce cell lines, and express a bioactive protein that induces the phosphorylation of AKT, a key insulin signaling molecule. We also examined its expression in mice following delivery of the vector to the parotid gland (PTG), the submandibular gland (SMG) or to the liver via the tail vein and assessed transgenic protein expression and vector containment for each delivery method. In all cases, hProinsulin-B10 was expressed and secreted into the circulation. Lower levels of circulating hProinsulin-B10 were obtained from the PTG while higher levels were obtained from the tail vein and the SMG; however, vector particle containment was best when delivered to the SMG. Expression of hProinsulin-B10 in the SMG of chemically induced diabetic mice prevented excessive hyperglycemia observed in untreated mice. These results demonstrate that hProinsulin-B10 can be expressed and secreted into the circulation from SGs and can function physiologically in vivo. The ability to remediate a diabetic phenotype in a model of type 1 diabetes mellitus is the first step in an effort that may lead to a possible therapy for diabetes.
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Affiliation(s)
- Anne M. Rowzee
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Paola J. Perez-Riveros
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Changyu Zheng
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sarah Krygowski
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bruce J. Baum
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Niamh X. Cawley
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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18
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Preliminary Structure–Function Relationship Studies on Insulin-Like Peptide 5 (INSL5). Int J Pept Res Ther 2013. [DOI: 10.1007/s10989-013-9341-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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19
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Abstract
Pancreatic β-cell dysfunction plays an important role in the pathogenesis of both type 1 and type 2 diabetes. Insulin, which is produced in β-cells, is a critical regulator of metabolism. Insulin is synthesized as preproinsulin and processed to proinsulin. Proinsulin is then converted to insulin and C-peptide and stored in secretary granules awaiting release on demand. Insulin synthesis is regulated at both the transcriptional and translational level. The cis-acting sequences within the 5' flanking region and trans-activators including paired box gene 6 (PAX6), pancreatic and duodenal homeobox- 1(PDX-1), MafA, and β-2/Neurogenic differentiation 1 (NeuroD1) regulate insulin transcription, while the stability of preproinsulin mRNA and its untranslated regions control protein translation. Insulin secretion involves a sequence of events in β-cells that lead to fusion of secretory granules with the plasma membrane. Insulin is secreted primarily in response to glucose, while other nutrients such as free fatty acids and amino acids can augment glucose-induced insulin secretion. In addition, various hormones, such as melatonin, estrogen, leptin, growth hormone, and glucagon like peptide-1 also regulate insulin secretion. Thus, the β-cell is a metabolic hub in the body, connecting nutrient metabolism and the endocrine system. Although an increase in intracellular [Ca2+] is the primary insulin secretary signal, cAMP signaling- dependent mechanisms are also critical in the regulation of insulin secretion. This article reviews current knowledge on how β-cells synthesize and secrete insulin. In addition, this review presents evidence that genetic and environmental factors can lead to hyperglycemia, dyslipidemia, inflammation, and autoimmunity, resulting in β-cell dysfunction, thereby triggering the pathogenesis of diabetes.
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Affiliation(s)
- Zhuo Fu
- Department of Human Nutrition, Foods and Exercise, Virginia Tech, Blacksburg, VA 24061, USA
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20
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Fu Z, Gilbert ER, Liu D. Regulation of insulin synthesis and secretion and pancreatic Beta-cell dysfunction in diabetes. Curr Diabetes Rev 2013; 9:25-53. [PMID: 22974359 PMCID: PMC3934755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 09/11/2012] [Accepted: 09/11/2012] [Indexed: 11/11/2023]
Abstract
Pancreatic β-cell dysfunction plays an important role in the pathogenesis of both type 1 and type 2 diabetes. Insulin, which is produced in β-cells, is a critical regulator of metabolism. Insulin is synthesized as preproinsulin and processed to proinsulin. Proinsulin is then converted to insulin and C-peptide and stored in secretary granules awaiting release on demand. Insulin synthesis is regulated at both the transcriptional and translational level. The cis-acting sequences within the 5' flanking region and trans-activators including paired box gene 6 (PAX6), pancreatic and duodenal homeobox- 1(PDX-1), MafA, and β-2/Neurogenic differentiation 1 (NeuroD1) regulate insulin transcription, while the stability of preproinsulin mRNA and its untranslated regions control protein translation. Insulin secretion involves a sequence of events in β-cells that lead to fusion of secretory granules with the plasma membrane. Insulin is secreted primarily in response to glucose, while other nutrients such as free fatty acids and amino acids can augment glucose-induced insulin secretion. In addition, various hormones, such as melatonin, estrogen, leptin, growth hormone, and glucagon like peptide-1 also regulate insulin secretion. Thus, the β-cell is a metabolic hub in the body, connecting nutrient metabolism and the endocrine system. Although an increase in intracellular [Ca2+] is the primary insulin secretary signal, cAMP signaling- dependent mechanisms are also critical in the regulation of insulin secretion. This article reviews current knowledge on how β-cells synthesize and secrete insulin. In addition, this review presents evidence that genetic and environmental factors can lead to hyperglycemia, dyslipidemia, inflammation, and autoimmunity, resulting in β-cell dysfunction, thereby triggering the pathogenesis of diabetes.
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Affiliation(s)
- Zhuo Fu
- Department of Human Nutrition, Foods and Exercise, Virginia Tech, Blacksburg, VA 24061, USA
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21
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Phillips NB, Whittaker J, Ismail-Beigi F, Weiss MA. Insulin fibrillation and protein design: topological resistance of single-chain analogs to thermal degradation with application to a pump reservoir. J Diabetes Sci Technol 2012; 6:277-88. [PMID: 22538136 PMCID: PMC3380768 DOI: 10.1177/193229681200600210] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Insulin is susceptible to thermal fibrillation, a misfolding process that leads to nonnative cross-β assembly analogous to pathological amyloid deposition. Pharmaceutical formulations are ordinarily protected from such degradation by sequestration of the susceptible monomer within native protein assemblies. With respect to the safety and efficacy of insulin pumps, however, this strategy imposes an intrinsic trade-off between pharmacokinetic goals (rapid absorption and clearance) and the requisite physical properties of a formulation (prolonged shelf life and stability within the reservoir). Available rapid-acting formulations are suboptimal in both respects; susceptibility to fibrillation is exacerbated even as absorption is delayed relative to the ideal specifications of a closed-loop system. To circumvent this molecular trade-off, we exploited structural models of insulin fibrils and amyloidogenic intermediates to define an alternative protective mechanism. Single-chain insulin (SCI) analogs were shown to be refractory to thermal fibrillation with maintenance of biological activity for more than 3 months under conditions that promote the rapid fibrillation and inactivation of insulin. The essential idea exploits an intrinsic incompatibility between SCI topology and the geometry of cross-β assembly. A peptide tether was thus interposed between the A- and B-chains whose length was (a) sufficiently long to provide the "play" needed for induced fit of the hormone on receptor binding and yet (b) sufficiently short to impose a topological barrier to fibrillation. Our findings suggest that ultrastable monomeric SCI analogs may be formulated without protective self-assembly and so permit simultaneous optimization of pharmacokinetics and reservoir life.
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Affiliation(s)
- Nelson B. Phillips
- Department of Biochemistry, Case Western Reserve University School of MedicineCleveland, Ohio
| | - Jonathan Whittaker
- Department of Biochemistry, Case Western Reserve University School of MedicineCleveland, Ohio
| | - Faramarz Ismail-Beigi
- Department of Medicine, Case Western Reserve University School of MedicineCleveland, Ohio
| | - Michael A. Weiss
- Department of Biochemistry, Case Western Reserve University School of MedicineCleveland, Ohio
- Department of Medicine, Case Western Reserve University School of MedicineCleveland, Ohio
- Biomedical Engineering, Case Western Reserve University School of MedicineCleveland, Ohio
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22
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Glendorf T, Knudsen L, Stidsen CE, Hansen BF, Hegelund AC, Sørensen AR, Nishimura E, Kjeldsen T. Systematic evaluation of the metabolic to mitogenic potency ratio for B10-substituted insulin analogues. PLoS One 2012; 7:e29198. [PMID: 22383948 PMCID: PMC3285154 DOI: 10.1371/journal.pone.0029198] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Accepted: 11/22/2011] [Indexed: 12/14/2022] Open
Abstract
Background Insulin analogues comprising acidic amino acid substitutions at position B10 have previously been shown to display increased mitogenic potencies compared to human insulin and the underlying molecular mechanisms have been subject to much scrutiny and debate. However, B10 is still an attractive position for amino acid substitutions given its important role in hexamer formation. The aim of this study was to investigate the relationships between the receptor binding properties as well as the metabolic and mitogenic potencies of a series of insulin analogues with different amino acid substitutions at position B10 and to identify a B10-substituted insulin analogue without an increased mitogenic to metabolic potency ratio. Methodology/Principal Findings A panel of ten singly-substituted B10 insulin analogues with different amino acid side chain characteristics were prepared and insulin receptor (both isoforms) and IGF-I receptor binding affinities using purified receptors, insulin receptor dissociation rates using BHK cells over-expressing the human insulin receptor, metabolic potencies by lipogenesis in isolated rat adipocytes, and mitogenic potencies using two different cell types predominantly expressing either the insulin or the IGF-I receptor were systematically investigated. Only analogues B10D and B10E with significantly increased insulin and IGF-I receptor affinities as well as decreased insulin receptor dissociation rates displayed enhanced mitogenic potencies in both cell types employed. For the remaining analogues with less pronounced changes in receptor affinities and insulin receptor dissociation rates, no apparent correlation between insulin receptor occupancy time and mitogenicity was observed. Conclusions/Significance Several B10-substituted insulin analogues devoid of disproportionate increases in mitogenic compared to metabolic potencies were identified. In the present study, receptor binding affinity rather than insulin receptor off-rate appears to be the major determinant of both metabolic and mitogenic potency. Our results also suggest that the increased mitogenic potency is attributable to both insulin and IGF-I receptor activation.
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Affiliation(s)
- Tine Glendorf
- Diabetes Research Unit, Novo Nordisk A/S, Maaloev, Denmark.
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23
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Kulahin N, Sanni SJ, Slaaby R, Nøhr J, Gammeltoft S, Hansen JL, Jorgensen R. A BRET assay for monitoring insulin receptor interactions and ligand pharmacology. J Recept Signal Transduct Res 2012; 32:57-64. [PMID: 22272819 DOI: 10.3109/10799893.2011.647351] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The insulin receptor (IR) belongs to the receptor tyrosine kinase super family and plays an important role in glucose homeostasis. The receptor interacts with several large docking proteins that mediate signaling from the receptor, including the insulin receptor substrate (IRS) family and Src homology-2-containing proteins (Src). Here, we applied the bioluminescence resonance energy transfer 2 (BRET2) technique to study the IR signaling pathways. The interaction between the IR and the substrates IRS1, IRS4 and Shc was examined in response to ligands with different signaling properties. The association between IR and the interacting partners could successfully be monitored when co-expressing green fluorescent protein 2 (GFP2) tagged substrates with Renilla reniformis luciferase 8 (Rluc8) tagged IR. Through additional optimization steps, we developed a stable and flexible BRET2 assay for monitoring the interactions between the IR and its substrates. Furthermore, the insulin analogue X10 was characterized in the BRET2 assay and was found to be 10 times more potent with respect to IRS1, IRS4 and Shc recruitment compared to human insulin. This study demonstrates that the BRET2 technique can be applied to study IR signaling pathways, and that this assay can be used as a platform for screening and characterization of IR ligands.
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Affiliation(s)
- Nikolaj Kulahin
- Incretin Biology, Hagedorn Research Institute, Gentofte, Denmark
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24
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Alvino CL, Ong SC, McNeil KA, Delaine C, Booker GW, Wallace JC, Forbes BE. Understanding the mechanism of insulin and insulin-like growth factor (IGF) receptor activation by IGF-II. PLoS One 2011; 6:e27488. [PMID: 22140443 PMCID: PMC3227035 DOI: 10.1371/journal.pone.0027488] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 10/18/2011] [Indexed: 12/29/2022] Open
Abstract
Background Insulin-like growth factor-II (IGF-II) promotes cell proliferation and survival and plays an important role in normal fetal development and placental function. IGF-II binds both the insulin-like growth factor receptor (IGF-1R) and insulin receptor isoform A (IR-A) with high affinity. Interestingly both IGF-II and the IR-A are often upregulated in cancer and IGF-II acts via both receptors to promote cancer proliferation. There is relatively little known about the mechanism of ligand induced activation of the insulin (IR) and IGF-1R. The recently solved IR structure reveals a folded over dimer with two potential ligand binding pockets arising from residues on each receptor half. Site-directed mutagenesis has mapped receptor residues important for ligand binding to two separate sites within the ligand binding pocket and we have recently shown that the IGFs have two separate binding surfaces which interact with the receptor sites 1 and 2. Methodology/Principal Findings In this study we describe a series of partial IGF-1R and IR agonists generated by mutating Glu12 of IGF-II. By comparing receptor binding affinities, abilities to induce negative cooperativity and potencies in receptor activation, we provide evidence that residue Glu12 bridges the two receptor halves leading to receptor activation. Conclusions/Significance This study provides novel insight into the mechanism of receptor binding and activation by IGF-II, which may be important for the future development of inhibitors of its action for the treatment of cancer.
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Affiliation(s)
- Clair L. Alvino
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
| | - Shee Chee Ong
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
| | - Kerrie A. McNeil
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
| | - Carlie Delaine
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
| | - Grant W. Booker
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
| | - John C. Wallace
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
| | - Briony E. Forbes
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia
- * E-mail:
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25
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Hansen BF, Kurtzhals P, Jensen AB, Dejgaard A, Russell-Jones D. Insulin X10 revisited: a super-mitogenic insulin analogue. Diabetologia 2011; 54:2226-31. [PMID: 21633908 DOI: 10.1007/s00125-011-2203-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 04/06/2011] [Indexed: 12/13/2022]
Abstract
The molecular safety of insulin analogues has received a great deal of attention over the last year. In particular, attention has been directed to the mitogenic properties of insulin analogues as compared with human insulin. Understanding the mechanisms implicated in mediating mitogenic effects of insulin is therefore of particular interest. In this review we detail the story of the rapid-acting insulin analogue known as X10, which was the first insulin analogue in clinical development, but ended up being discontinued at an early clinical development stage following findings of mammary tumours in female Sprague-Dawley rats. The molecular characteristics of insulin X10, along with its interaction at both the IGF-1 receptor and the insulin receptor, have provided us with important insights into mechanisms implicated in metabolic and mitogenic signalling of insulin analogues.
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26
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Abstract
Some mutations of the insulin gene cause hyperinsulinemia or hyperproinsulinemia. Replacement of biologically important amino acid leads to defective receptor binding, longer half-life and hyperinsulinemia. Three mutant insulins have been identified: (i) insulin Chicago (F49L or PheB25Leu); (ii) insulin Los Angeles (F48S or PheB24Ser); (iii) and insulin Wakayama (V92L or ValA3Leu). Replacement of amino acid is necessary for proinsulin processing results in hyperproinsulinemia. Four types have been identified: (i) proinsulin Providence (H34D); (ii) proinsulin Tokyo (R89H); (iii) proinsulin Kyoto (R89L); and (iv) proinsulin Oxford (R89P). Three of these are processing site mutations. The mutation of proinsulin Providence, in contrast, is thought to cause sorting abnormality. Compared with normal proinsulin, a significant amount of proinsulin Providence enters the constitutive pathway where processing does not occur. These insulin gene mutations with hyper(pro)insulinemia were very rare, showed only mild diabetes or glucose intolerance, and hyper(pro)insulinemia was the key for their diagnosis. However, this situation changed dramatically after the identification of insulin gene mutations as a cause of neonatal diabetes. This class of insulin gene mutations does not show hyper(pro)insulinemia. Mutations at the cysteine residue or creating a new cysteine will disturb the correct disulfide bonding and proper conformation, and finally will lead to misfolded proinsulin accumulation, endoplasmic reticulum stress and apoptosis of pancreatic β-cells. Maturity-onset diabetes of the young (MODY) or an autoantibody-negative type 1-like phenotype has also been reported. Very recently, recessive mutations with reduced insulin biosynthesis have been reported. The importance of insulin gene mutation in the pathogenesis of diabetes will increase a great deal and give us a new understanding of β-cell biology and diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00100.x, 2011).
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Affiliation(s)
- Masahiro Nishi
- Department of Metabolism and Clinical Nutrition, Wakayama Medical University
| | - Kishio Nanjo
- Research Center of Rural Medicine, Nachi‐Katsuura Spa Hospital, Wakayama, Japan
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27
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Abstract
The insulin-like growth factor (IGF) system plays essential role in the regulation of cell growth, proliferation and survival and affects nearly every organ system in the body. IGF-I, which has a high structural similarity to insulin, exerts growth-promoting effects, influences glucose metabolism and has neuroprotective and cardioprotective effects, partly because of its cell-proliferative and antiapoptotic properties. Aberrations in the IGF system may associate with various pathological conditions, including cancer. Insulin and its synthetic analogs are known to possess IGF-IR binding affinity, and concern has been raised about their mitogenic potential in humans. The present review summarizes the main aspects of the IGF system biology and the interactions among IGF-I, insulin, insulin analogs and their receptors.
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Affiliation(s)
- Marta Annunziata
- Division of Endocrinology, Diabetology and Metabolism, Department of Internal Medicine, University of Turin, Corso Dogliotti 14, Turin, Italy
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28
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Abstract
We have exploited a prandial insulin analog to elucidate the underlying structure and dynamics of insulin as a monomer in solution. A model was provided by insulin lispro (the active component of Humalog(®); Eli Lilly and Co.). Whereas NMR-based modeling recapitulated structural relationships of insulin crystals (T-state protomers), dynamic anomalies were revealed by amide-proton exchange kinetics in D(2)O. Surprisingly, the majority of hydrogen bonds observed in crystal structures are only transiently maintained in solution, including key T-state-specific inter-chain contacts. Long-lived hydrogen bonds (as defined by global exchange kinetics) exist only at a subset of four α-helical sites (two per chain) flanking an internal disulfide bridge (cystine A20-B19); these sites map within the proposed folding nucleus of proinsulin. The anomalous flexibility of insulin otherwise spans its active surface and may facilitate receptor binding. Because conformational fluctuations promote the degradation of pharmaceutical formulations, we envisage that "dynamic re-engineering" of insulin may enable design of ultra-stable formulations for humanitarian use in the developing world.
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Affiliation(s)
- Qing-Xin Hua
- Department of Biochemistry, School of Medicine, Case Western Reserve UniversityCleveland, OH, USA
| | - Wenhua Jia
- Department of Biochemistry, School of Medicine, Case Western Reserve UniversityCleveland, OH, USA
| | - Michael A. Weiss
- Department of Biochemistry, School of Medicine, Case Western Reserve UniversityCleveland, OH, USA
- *Correspondence: Michael A. Weiss, Department of Biochemistry, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue – Wood W436, Cleveland, OH 44106-4935, USA. e-mail:
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29
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Oleksiewicz MB, Bonnesen C, Hegelund AC, Lundby A, Holm GMN, Jensen MB, Krabbe JS. Comparison of intracellular signalling by insulin and the hypermitogenic AspB10 analogue in MCF-7 breast adenocarcinoma cells. J Appl Toxicol 2010; 31:329-41. [DOI: 10.1002/jat.1590] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 08/16/2010] [Accepted: 08/16/2010] [Indexed: 12/17/2022]
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30
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Sajid W, Holst PA, Kiselyov VV, Andersen AS, Conlon JM, Kristensen C, Kjeldsen T, Whittaker J, Chan SJ, De Meyts P. Structural basis of the aberrant receptor binding properties of hagfish and lamprey insulins. Biochemistry 2009; 48:11283-95. [PMID: 19863112 PMCID: PMC2781304 DOI: 10.1021/bi901269j] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
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The insulin from the Atlantic hagfish (Myxine glutinosa) has been one of the most studied insulins from both a structural and a biological viewpoint; however, some aspects of its biology remain controversial, and there has been no satisfying structural explanation for its low biological potency. We have re-examined the receptor binding kinetics, as well as the metabolic and mitogenic properties, of this phylogenetically ancient insulin, as well as that from another extant representative of the ancient chordates, the river lamprey (Lampetra fluviatilis). Both insulins share unusual binding kinetics and biological properties with insulin analogues that have single mutations at residues that contribute to the hexamerization surface. We propose and demonstrate by reciprocal amino acid substitutions between hagfish and human insulins that the reduced biological activity of hagfish insulin results from unfavorable substitutions, namely, A10 (Ile to Arg), B4 (Glu to Gly), B13 (Glu to Asn), and B21 (Glu to Val). We likewise suggest that the altered biological activity of lamprey insulin may reflect substitutions at A10 (Ile to Lys), B4 (Glu to Thr), and B17 (Leu to Val). The substitution of Asp at residue B10 in hagfish insulin and of His at residue A8 in both hagfish and lamprey insulins may help compensate for unfavorable changes in other regions of the molecules. The data support the concept that the set of unusual properties of insulins bearing certain mutations in the hexamerization surface may reflect those of the insulins evolutionarily closer to the ancestral insulin gene product.
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Affiliation(s)
- Waseem Sajid
- Receptor Systems Biology Laboratory, Hagedorn Research Institute, Gentofte, Denmark.
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31
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Sohma Y, Hua QX, Liu M, Phillips NB, Hu SQ, Whittaker J, Whittaker LJ, Ng A, Roberts CT, Arvan P, Kent SBH, Weiss MA. Contribution of residue B5 to the folding and function of insulin and IGF-I: constraints and fine-tuning in the evolution of a protein family. J Biol Chem 2009; 285:5040-55. [PMID: 19959476 DOI: 10.1074/jbc.m109.062992] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proinsulin exhibits a single structure, whereas insulin-like growth factors refold as two disulfide isomers in equilibrium. Native insulin-related growth factor (IGF)-I has canonical cystines (A6-A11, A7-B7, and A20-B19) maintained by IGF-binding proteins; IGF-swap has alternative pairing (A7-A11, A6-B7, and A20-B19) and impaired activity. Studies of mini-domain models suggest that residue B5 (His in insulin and Thr in IGFs) governs the ambiguity or uniqueness of disulfide pairing. Residue B5, a site of mutation in proinsulin causing neonatal diabetes, is thus of broad biophysical interest. Here, we characterize reciprocal B5 substitutions in the two proteins. In insulin, His(B5) --> Thr markedly destabilizes the hormone (DeltaDeltaG(u) 2.0 +/- 0.2 kcal/mol), impairs chain combination, and blocks cellular secretion of proinsulin. The reciprocal IGF-I substitution Thr(B5) --> His (residue 4) specifies a unique structure with native (1)H NMR signature. Chemical shifts and nuclear Overhauser effects are similar to those of native IGF-I. Whereas wild-type IGF-I undergoes thiol-catalyzed disulfide exchange to yield IGF-swap, His(B5)-IGF-I retains canonical pairing. Chemical denaturation studies indicate that His(B5) does not significantly enhance thermodynamic stability (DeltaDeltaG(u) 0.2 +/- 0.2 kcal/mol), implying that the substitution favors canonical pairing by destabilizing competing folds. Whereas the activity of Thr(B5)-insulin is decreased 5-fold, His(B5)-IGF-I exhibits 2-fold increased affinity for the IGF receptor and augmented post-receptor signaling. We propose that conservation of Thr(B5) in IGF-I, rescued from structural ambiguity by IGF-binding proteins, reflects fine-tuning of signal transduction. In contrast, the conservation of His(B5) in insulin highlights its critical role in insulin biosynthesis.
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Affiliation(s)
- Youhei Sohma
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637, USA
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Bonnesen C, Nelander GM, Hansen BF, Jensen P, Krabbe JS, Jensen MB, Hegelund AC, Svendsen JE, Oleksiewicz MB. Synchronization in G0/G1 enhances the mitogenic response of cells overexpressing the human insulin receptor A isoform to insulin. Cell Biol Toxicol 2009; 26:293-307. [PMID: 19898946 PMCID: PMC2896650 DOI: 10.1007/s10565-009-9142-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Accepted: 10/22/2009] [Indexed: 01/01/2023]
Abstract
Evaluating mitogenic signaling specifically through the human insulin receptor (IR) is relevant for the preclinical safety assessment of developmental insulin analogs. It is known that overexpression of IR sensitizes cells to the mitogenic effects of insulin, but it is essentially unknown how mitogenic responses can be optimized to allow practical use of such recombinant cell lines for preclinical safety testing. We constitutively overexpressed the short isoform of the human insulin receptor (hIR-A, exon 11-negative) in L6 rat skeletal myoblasts. Because the mitogenic effect of growth factors such as insulin is expected to act in G0/G1, promoting S-phase entry, we developed a combined topoinhibition + serum deprivation strategy to explore the effect of G0/G1 synchronization as an independent parameter in the context of serum deprivation, the latter being routinely used to reduce background in mitogenicity assays. G0/G1 synchronization significantly improved the mitogenic responses of L6-hIR cells to insulin, measured by 3H-thymidine incorporation. Comparison with the parental L6 cells using phospho-mitogen-activated protein kinase, phospho-AKT, as well as 3H-thymidine incorporation end points supported that the majority of the mitogenic effect of insulin in L6-hIR cells was mediated by the overexpressed hIR-A. Using the optimized L6-hIR assay, we found that the X-10 insulin analog was more mitogenic than native human insulin, supporting that X-10 exhibits increased mitogenic signaling through the hIR-A. In summary, this study provides the first demonstration that serum deprivation may not be sufficient, and G0/G1 synchronization may be required to obtain optimal responsiveness of hIR-overexpressing cell lines for preclinical safety testing.
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Zhao M, Wan ZL, Whittaker L, Xu B, Phillips NB, Katsoyannis PG, Ismail-Beigi F, Whittaker J, Weiss MA. Design of an insulin analog with enhanced receptor binding selectivity: rationale, structure, and therapeutic implications. J Biol Chem 2009; 284:32178-87. [PMID: 19773552 DOI: 10.1074/jbc.m109.028399] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Insulin binds with high affinity to the insulin receptor (IR) and with low affinity to the type 1 insulin-like growth factor (IGF) receptor (IGFR). Such cross-binding, which reflects homologies within the insulin-IGF signaling system, is of clinical interest in relation to the association between hyperinsulinemia and colorectal cancer. Here, we employ nonstandard mutagenesis to design an insulin analog with enhanced affinity for the IR but reduced affinity for the IGFR. Unnatural amino acids were introduced by chemical synthesis at the N- and C-capping positions of a recognition alpha-helix (residues A1 and A8). These sites adjoin the hormone-receptor interface as indicated by photocross-linking studies. Specificity is enhanced more than 3-fold on the following: (i) substitution of Gly(A1) by D-Ala or D-Leu, and (ii) substitution of Thr(A8) by diaminobutyric acid (Dab). The crystal structure of [D-Ala(A1),Dab(A8)]insulin, as determined within a T(6) zinc hexamer to a resolution of 1.35 A, is essentially identical to that of human insulin. The nonstandard side chains project into solvent at the edge of a conserved receptor-binding surface shared by insulin and IGF-I. Our results demonstrate that modifications at this edge discriminate between IR and IGFR. Because hyperinsulinemia is typically characterized by a 3-fold increase in integrated postprandial insulin concentrations, we envisage that such insulin analogs may facilitate studies of the initiation and progression of cancer in animal models. Future development of clinical analogs lacking significant IGFR cross-binding may enhance the safety of insulin replacement therapy in patients with type 2 diabetes mellitus at increased risk of colorectal cancer.
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Affiliation(s)
- Ming Zhao
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Xu B, Huang K, Chu YC, Hu SQ, Nakagawa S, Wang S, Wang RY, Whittaker J, Katsoyannis PG, Weiss MA. Decoding the cryptic active conformation of a protein by synthetic photoscanning: insulin inserts a detachable arm between receptor domains. J Biol Chem 2009; 284:14597-608. [PMID: 19321435 PMCID: PMC2682907 DOI: 10.1074/jbc.m900087200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 03/20/2009] [Indexed: 12/15/2022] Open
Abstract
Proteins evolve in a fitness landscape encompassing a complex network of biological constraints. Because of the interrelation of folding, function, and regulation, the ground-state structure of a protein may be inactive. A model is provided by insulin, a vertebrate hormone central to the control of metabolism. Whereas native assembly mediates storage within pancreatic beta-cells, the active conformation of insulin and its mode of receptor binding remain elusive. Here, functional surfaces of insulin were probed by photocross-linking of an extensive set of azido derivatives constructed by chemical synthesis. Contacts are circumferential, suggesting that insulin is encaged within its receptor. Mapping of photoproducts to the hormone-binding domains of the insulin receptor demonstrated alternating contacts by the B-chain beta-strand (residues B24-B28). Whereas even-numbered probes (at positions B24 and B26) contact the N-terminal L1 domain of the alpha-subunit, odd-numbered probes (at positions B25 and B27) contact its C-terminal insert domain. This alternation corresponds to the canonical structure of abeta-strand (wherein successive residues project in opposite directions) and so suggests that the B-chain inserts between receptor domains. Detachment of a receptor-binding arm enables photo engagement of surfaces otherwise hidden in the free hormone. The arm and associated surfaces contain sites also required for nascent folding and self-assembly of storage hexamers. The marked compression of structural information within a short polypeptide sequence rationalizes the diversity of diabetes-associated mutations in the insulin gene. Our studies demonstrate that photoscanning mutagenesis can decode the active conformation of a protein and so illuminate cryptic constraints underlying its evolution.
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Affiliation(s)
- Bin Xu
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Hua QX, Xu B, Huang K, Hu SQ, Nakagawa S, Jia W, Wang S, Whittaker J, Katsoyannis PG, Weiss MA. Enhancing the activity of a protein by stereospecific unfolding: conformational life cycle of insulin and its evolutionary origins. J Biol Chem 2009; 284:14586-96. [PMID: 19321436 DOI: 10.1074/jbc.m900085200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A central tenet of molecular biology holds that the function of a protein is mediated by its structure. An inactive ground-state conformation may nonetheless be enjoined by the interplay of competing biological constraints. A model is provided by insulin, well characterized at atomic resolution by x-ray crystallography. Here, we demonstrate that the activity of the hormone is enhanced by stereospecific unfolding of a conserved structural element. A bifunctional beta-strand mediates both self-assembly (within beta-cell storage vesicles) and receptor binding (in the bloodstream). This strand is anchored by an invariant side chain (Phe(B24)); its substitution by Ala leads to an unstable but native-like analog of low activity. Substitution by d-Ala is equally destabilizing, and yet the protein diastereomer exhibits enhanced activity with segmental unfolding of the beta-strand. Corresponding photoactivable derivatives (containing l- or d-para-azido-Phe) cross-link to the insulin receptor with higher d-specific efficiency. Aberrant exposure of hydrophobic surfaces in the analogs is associated with accelerated fibrillation, a form of aggregation-coupled misfolding associated with cellular toxicity. Conservation of Phe(B24), enforced by its dual role in native self-assembly and induced fit, thus highlights the implicit role of misfolding as an evolutionary constraint. Whereas classical crystal structures of insulin depict its storage form, signaling requires engagement of a detachable arm at an extended receptor interface. Because this active conformation resembles an amyloidogenic intermediate, we envisage that induced fit and self-assembly represent complementary molecular adaptations to potential proteotoxicity. The cryptic threat of misfolding poses a universal constraint in the evolution of polypeptide sequences.
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Affiliation(s)
- Qing-xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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36
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Alvino CL, McNeil KA, Ong SC, Delaine C, Booker GW, Wallace JC, Whittaker J, Forbes BE. A novel approach to identify two distinct receptor binding surfaces of insulin-like growth factor II. J Biol Chem 2009; 284:7656-64. [PMID: 19139090 DOI: 10.1074/jbc.m808061200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Very little is known about the residues important for the interaction of insulin-like growth factor II (IGF-II) with the type 1 IGF receptor (IGF-1R) and the insulin receptor (IR). Insulin, to which IGF-II is homologous, is proposed to cross-link opposite halves of the IR dimer through two receptor binding surfaces, site 1 and site 2. In the present study we have analyzed the contribution of IGF-II residues equivalent to insulin's two binding surfaces toward the interaction of IGF-II with the IGF-1R and IR. Four "site 1" and six "site 2" analogues were produced and analyzed in terms of IGF-1R and IR binding and activation. The results show that Val(43), Phe(28), and Val(14) (equivalent to site 1) are critical to IGF-1R and IR binding, whereas mutation to alanine of Gln(18) affects only IGF-1R and not IR binding. Alanine substitutions at Glu(12), Asp(15), Phe(19), Leu(53), and Glu(57) analogues resulted in significant (>2-fold) decreases in affinity for both the IGF-1R and IR. Furthermore, taking a novel approach using a monomeric, single-chain minimized IGF-1R we have defined a distinct second binding surface formed by Glu(12), Phe(19), Leu(53), and Glu(57) that potentially engages the IGF-1R at one or more of the FnIII domains.
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Affiliation(s)
- Clair L Alvino
- School of Molecular and Biomedical Science, The University of Adelaide, Gate 8, Victoria Drive, Adelaide, South Australia 5005, Australia
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Ishikawa T, Chatake T, Morimoto Y, Maeda M, Kurihara K, Tanaka I, Niimura N. An abnormal pK(a) value of internal histidine of the insulin molecule revealed by neutron crystallographic analysis. Biochem Biophys Res Commun 2008; 376:32-5. [PMID: 18725203 DOI: 10.1016/j.bbrc.2008.08.071] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Accepted: 08/11/2008] [Indexed: 12/01/2022]
Abstract
Insulin is stored in pancreatic beta-cell as hexameric form with Zn2+ ions, while the hormonally active form is monomer. The hexamer requires the coordination of Zn2+ ions to the HisB10. In order to reveal the mechanism of the hexamerization of insulin, we investigated the Zn2+ free insulin at pD6.6 and pD9 by neutron crystallographic analyses. HisB10 is doubly protonated not only at pD6.6 but also at pD9, indicating an abnormal pK(a) of this histidine. It is suggested that HisB10 acts on a strong cation capture and contributes to the high stability of the hexameric form in pancreas.
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Affiliation(s)
- Takuya Ishikawa
- Kyoto University Research Reactor, Asashironishi 2, Kumatori, Osaka 590-0494, Japan
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38
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Tian J, Lei P, Laychock SG, Andreadis ST. Regulated Insulin Delivery From Human Epidermal Cells Reverses Hyperglycemia. Mol Ther 2008; 16:1146-53. [DOI: 10.1038/mt.2008.79] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Bara H, Sambanis A. Insulin-secreting L-cells for the treatment of insulin-dependent diabetes. Biochem Biophys Res Commun 2008; 371:39-43. [PMID: 18406351 DOI: 10.1016/j.bbrc.2008.03.154] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Accepted: 03/27/2008] [Indexed: 11/24/2022]
Abstract
Cell-based treatments for insulin-dependent diabetes (IDD) may provide more physiologic regulation of blood glucose levels than daily insulin injections, thereby reducing the occurrence of secondary complications associated with diabetes. An autologous cell source is especially attractive for regulatory and ethical reasons in addition to eliminating the need for immunosuppression. This study uses non-beta-cells, genetically modified for physiologic insulin secretion. Enteroendocrine L-cells, exhibit regulated secretion in response to physiologic stimuli and their endogenous products are fully compatible with prandial metabolism. Murine GLUTag L-cells were transfected with a plasmid co-expressing human insulin and neomycin resistance and the stable cell line, GLUTag-INS, was established. Secretion properties of GLUTag-INS cells were investigated in vitro through induced secretion tests using meat hydrolysate or 3-isobutyl-1-methylxanthine and forskolin as secretagogues. GLUTag-INS cells rapidly co-secreted recombinant insulin and endogenous glucagon-like peptide in response to metabolic cues from the surrounding medium and demonstrated efficient processing of proinsulin to insulin.
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Affiliation(s)
- Heather Bara
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 315 Ferst Drive, IBB Building, Room 1306, Atlanta, GA 30332, USA
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40
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Glendorf T, Sørensen AR, Nishimura E, Pettersson I, Kjeldsen T. Importance of the solvent-exposed residues of the insulin B chain alpha-helix for receptor binding. Biochemistry 2008; 47:4743-51. [PMID: 18376848 DOI: 10.1021/bi800054z] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Conjointly, the solvent-exposed residues of the central alpha-helix of the B chain form a well-defined ridge, which is flanked and partly overlapped by the two described insulin receptor binding surfaces on either side of the insulin molecule. To evaluate the importance of this interface in insulin receptor binding, we developed a new powerful method that allows us to introduce all the naturally occurring amino acids into a given position and subsequently determine the receptor binding affinities of the resulting insulin analogues. The total amino acid scanning mutagenesis was performed at positions B9, B10, B12, B13, B16, and B17, and the vast majority of the insulin analogue precursors were expressed and secreted in amounts close to that of the wild-type (human insulin) precursor. The analogue binding data revealed that positions B12 and B16 were the two positions most affected by the amino acid substitutions. Interestingly, the receptor binding affinities of the B13 analogues were also markedly affected by the amino acid substitutions, suggesting that GluB13 indeed is a part of insulin's binding surface. The B10 library screen generated analogues covering a wide range of (20-340%) of relative binding affinities, and the results indicated that a structural stabilization of the central alpha-helix and thereby a more rigid presentation of the binding epitope at the insulin receptor is important for receptor recognition. In conclusion, systematic amino acid scanning mutagenesis allowed us to confirm the importance of the B chain alpha-helix as a central recognition element serving as a linker of a continual binding surface.
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Affiliation(s)
- Tine Glendorf
- Diabetes Protein Engineering, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Måløv, Denmark.
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41
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Hua QX, Nakagawa SH, Jia W, Huang K, Phillips NB, Hu SQ, Weiss MA. Design of an active ultrastable single-chain insulin analog: synthesis, structure, and therapeutic implications. J Biol Chem 2008; 283:14703-16. [PMID: 18332129 DOI: 10.1074/jbc.m800313200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Single-chain insulin (SCI) analogs provide insight into the inter-relation of hormone structure, function, and dynamics. Although compatible with wild-type structure, short connecting segments (<3 residues) prevent induced fit upon receptor binding and so are essentially without biological activity. Substantial but incomplete activity can be regained with increasing linker length. Here, we describe the design, structure, and function of a single-chain insulin analog (SCI-57) containing a 6-residue linker (GGGPRR). Native receptor-binding affinity (130 +/- 8% relative to the wild type) is achieved as hindrance by the linker is offset by favorable substitutions in the insulin moiety. The thermodynamic stability of SCI-57 is markedly increased (DeltaDeltaG(u) = 0.7 +/- 0.1 kcal/mol relative to the corresponding two-chain analog and 1.9 +/- 0.1 kcal/mol relative to wild-type insulin). Analysis of inter-residue nuclear Overhauser effects demonstrates that a native-like fold is maintained in solution. Surprisingly, the glycine-rich connecting segment folds against the insulin moiety: its central Pro contacts Val(A3) at the edge of the hydrophobic core, whereas the final Arg extends the A1-A8 alpha-helix. Comparison between SCI-57 and its parent two-chain analog reveals striking enhancement of multiple native-like nuclear Overhauser effects within the tethered protein. These contacts are consistent with wild-type crystal structures but are ordinarily attenuated in NMR spectra of two-chain analogs, presumably due to conformational fluctuations. Linker-specific damping of fluctuations provides evidence for the intrinsic flexibility of an insulin monomer. In addition to their biophysical interest, ultrastable SCIs may enhance the safety and efficacy of insulin replacement therapy in the developing world.
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Affiliation(s)
- Qing-xin Hua
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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Abstract
Throughout much of the last century insulin served a central role in the advancement of peptide chemistry, pharmacology, cell signaling and structural biology. These discoveries have provided a steadily improved quantity and quality of life for those afflicted with diabetes. The collective work serves as a foundation for the development of insulin analogs and mimetics capable of providing more tailored therapy. Advancements in patient care have been paced by breakthroughs in core technologies, such as semisynthesis, high performance chromatography, rDNA-biosynthesis and formulation sciences. How the structural and conformational dynamics of this endocrine hormone elicit its biological response remains a vigorous area of study. Numerous insulin analogs have served to coordinate structural biology and biochemical signaling to provide a first level understanding of insulin action. The introduction of broad chemical diversity to the study of insulin has been limited by the inefficiency in total chemical synthesis, and the inherent limitations in rDNA-biosynthesis and semisynthetic approaches. The goals of continued investigation remain the delivery of insulin therapy where glycemic control is more precise and hypoglycemic liability is minimized. Additional objectives for medicinal chemists are the identification of superagonists and insulins more suitable for non-injectable delivery. The historical advancements in the synthesis of insulin analogs by multiple methods is reviewed with the specific structural elements of critical importance being highlighted. The functional refinement of this hormone as directed to improved patient care with insulin analogs of more precise pharmacology is reported.
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Affiliation(s)
- John P Mayer
- Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA
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Lei P, Ogunade A, Kirkwood KL, Laychock SG, Andreadis ST. Efficient Production of Bioactive Insulin from Human Epidermal Keratinocytes and Tissue-Engineered Skin Substitutes: Implications for Treatment of Diabetes. ACTA ACUST UNITED AC 2007; 13:2119-31. [PMID: 17518716 DOI: 10.1089/ten.2006.0210] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Despite many years of research, daily insulin injections remain the gold standard for diabetes treatment. Gene therapy may provide an alternative strategy by imparting the ability to secrete insulin from an ectopic site. The epidermis is a self-renewing tissue that is easily accessible and can provide large numbers of autologous cells to generate insulin-secreting skin substitutes. Here we used a recombinant retrovirus to modify human epidermal keratinocytes with a gene encoding for human proinsulin containing the furin recognition sequences at the A-C and B-C junctions. Keratinocytes were able to process proinsulin and secrete active insulin that promoted glucose uptake. Primary epidermal cells produced higher amounts of insulin than cell lines, suggesting that insulin secretion may depend on the physiological state of the producer cells. Modified cells maintained the ability to stratify into 3-dimensional skin equivalents that expressed insulin at the basal and suprabasal layers. Modifications at the furin recognition sites did not improve proinsulin processing, but a single amino acid substitution in the proinsulin B chain enhanced C-peptide secretion from cultured cells and bioengineered skin substitutes 10- and 28-fold, respectively. These results suggest that gene-modified bioengineered skin may provide an alternative means of insulin delivery for treatment of diabetes.
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Affiliation(s)
- Pedro Lei
- Bioengineering Laboratory, Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Amherst, New York 14260, USA
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44
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Abstract
Insulin analogues were developed to modify the structure of the human insulin molecule in order to more accurately approximate the endogenous secretion of insulin. With the help of recombinant technology and site-directed mutagenesis, the insulin molecule can be modified to either delay or shorten absorption time, providing better insulin treatment options and facilitating the achievement of glycaemic goals. Changing the structure of the insulin molecule, however, may significantly alter both its metabolic and mitogenic activity. Multiple factors such as residence time on the receptor, dissociation rate, rate of receptor internalization and the degree of phosphorylation of signalling proteins can affect the mitogenic potencies of insulin analogues. Changes in the structure of the insulin have raised concern about the safety of the insulin analogues. For example, questions have emerged about the relationship between the use of insulin lispro and insulin glargine and the progression of diabetic retinopathy. Two studies have shown progression of retinopathy with the use of insulin lispro. However, others have not confirmed these results, and causality could not be proven as progression of retinopathy can occur with rapid improvement in glycaemic control, and methods of assessments among studies were not consistent. Therefore, we examine the metabolic and mitogenic characteristics of the three insulin analogues, insulin lispro, insulin aspart and insulin glargine, that are currently on the market, as well as the two insulin analogues, insulin glulisine and insulin detemir, that are soon going to be available for clinical use.
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Affiliation(s)
- Ivana Zib
- Department on Internal Medicine, Division of Endocrinology and Metabolism, University of Texas Southwestern Medical Center, Dallas, TX 75390-8858, USA
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Bhatnagar S, Srivastava D, Jayadev MSK, Dubey AK. Molecular variants and derivatives of insulin for improved glycemic control in diabetes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2006; 91:199-228. [PMID: 16061274 DOI: 10.1016/j.pbiomolbio.2005.05.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin is a historic molecule. It presents many first instances, such as the first protein to be fully sequenced, one of the first proteins to be crystallized in pure form, one among the early proteins whose structure was investigated using X-ray crystallography, the first protein to be chemically synthesized and the first Biotech drug. Therefore, the development of insulin in the early years is intricately intertwined with the progress in molecular and structural biology. In recent years, development of a range of insulin analogs has led to better control of glucose levels, thus preventing secondary complications and improving the quality of life in diabetic patients. Such analogs were obtained by modification of the native insulin sequence. They vary with regard to their pharmacokinetic profile, stability, tissue specificity and mode of administration. In addition, alterations involving incorporation of various chemical moieties in insulin and its co-crystallization with insoluble derivatives are used to modulate the time-action profile of the drug. This article traces the development of molecular variants and derivatives of insulin. It discusses future directions for further improvement in their properties to produce still better insulin therapeutics for tight glycemic control.
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Affiliation(s)
- Sonika Bhatnagar
- Division of Biotechnology, School of Applied Science, Netaji Subhas Institute of Technology, Dwarka, New Delhi, India
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46
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Hua QX, Nakagawa S, Hu SQ, Jia W, Wang S, Weiss MA. Toward the active conformation of insulin: stereospecific modulation of a structural switch in the B chain. J Biol Chem 2006; 281:24900-9. [PMID: 16762918 DOI: 10.1074/jbc.m602691200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
How insulin binds to the insulin receptor has long been a subject of speculation. Although the structure of the free hormone has been extensively characterized, a variety of evidence suggests that a conformational change occurs upon receptor binding. Here, we employ chiral mutagenesis, comparison of corresponding d and l amino acid substitutions, to investigate a possible switch in the B-chain. To investigate the interrelation of structure, function, and stability, isomeric analogs have been synthesized in which an invariant glycine in a beta-turn (Gly(B8)) is replaced by d- or l-Ser. The d substitution enhances stability (DeltaDeltaG(u) 0.9 kcal/mol) but impairs receptor binding by 100-fold; by contrast, the l substitution markedly impairs stability (DeltaDeltaG(u) -3.0 kcal/mol) with only 2-fold reduction in receptor binding. Although the isomeric structures each retain a native-like overall fold, the l-Ser(B8) analog exhibits fewer helix-related and long range nuclear Overhauser effects than does the d-Ser(B8) analog or native monomer. Evidence for enhanced conformational fluctuations in the unstable analog is provided by its attenuated CD spectrum. The inverse relationship between stereospecific stabilization and receptor binding strongly suggests that the B7-B10 beta-turn changes conformation on receptor binding.
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Affiliation(s)
- Qing-Xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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47
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Hua QX, Liu M, Hu SQ, Jia W, Arvan P, Weiss MA. A conserved histidine in insulin is required for the foldability of human proinsulin: structure and function of an ALAB5 analog. J Biol Chem 2006; 281:24889-99. [PMID: 16728398 DOI: 10.1074/jbc.m602617200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The insulins of eutherian mammals contain histidines at positions B5 and B10. The role of His(B10) is well defined: although not required in the mature hormone for receptor binding, in the islet beta cell this side chain functions in targeting proinsulin to glucose-regulated secretory granules and provides axial zincbinding sites in storage hexamers. In contrast, the role of His(B5) is less well understood. Here, we demonstrate that its substitution with Ala markedly impairs insulin chain combination in vitro and blocks the folding and secretion of human proinsulin in a transfected mammalian cell line. The structure and stability of an Ala(B5)-insulin analog were investigated in an engineered monomer (DKP-insulin). Despite its impaired foldability, the structure of the Ala(B5) analog retains a native-like T-state conformation. At the site of substitution, interchain nuclear Overhauser effects are observed between the methyl resonance of Ala(B5) and side chains in the A chain; these nuclear Overhauser effects resemble those characteristic of His(B5) in native insulin. Substantial receptor binding activity is retained (80 +/- 10% relative to the parent monomer). Although the thermodynamic stability of the Ala(B5) analog is decreased (DeltaDeltaG(u) = 1.7 +/- 0.1 kcal/mol), consistent with loss of His(B5)-related interchain packing and hydrogen bonds, control studies suggest that this decrement cannot account for its impaired foldability. We propose that nascent long-range interactions by His(B5) facilitate alignment of Cys(A7) and Cys(B7) in protein-folding intermediates; its conservation thus reflects mechanisms of oxidative folding rather than structure-function relationships in the native state.
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Affiliation(s)
- Qing-Xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
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48
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Hennige AM, Strack V, Metzinger E, Seipke G, Häring HU, Kellerer M. Effects of new insulin analogues HMR1964 (insulin glulisine) and HMR1423 on insulin receptors. Diabetologia 2005; 48:1891-7. [PMID: 16052329 DOI: 10.1007/s00125-005-1870-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Accepted: 03/10/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS New insulin analogues have been created by amino-acid exchange to provide an improved pharmacokinetic profile. However, safety issues have been raised regarding their use, as amino-acid exchange of insulin may induce altered metabolic and mitogenic effects. For example, the insulin analogue Asp(B10) causes breast cancer in rodents. The aim of this study was to compare two new insulin analogues HMR1964 (Lys[B3],Glu[B29]) (insulin glulisine) and HMR1423 (Gly[A21],His[B31],His[B32]) with regular insulin and the mitogenic analogue Asp(B10). MATERIALS AND METHODS We analysed insulin receptor binding characteristics and dissociation kinetics, as well as insulin-induced receptor auto- and dephosphorylation kinetics, in rat-1 fibroblasts overexpressing the human insulin receptor isoform B. Mitogenic activity was tested in the non-malignant cell line MCF10. RESULTS Regular insulin, HMR1964 and HMR1423 showed no significant differences in receptor association, dissociation and receptor binding affinity, while Asp(B10) displayed markedly increased insulin receptor affinity. All of the analogues induced rapid insulin receptor autophosphorylation, reaching a maximum 10 min after stimulation (10(-9) mmol/l insulin). In contrast, Asp(B10) induced a prolonged phosphorylation and dephosphorylation state of the 95 kDa insulin receptor beta-subunit. With respect to [3H]thymidine incorporation, the new analogues had similar (HMR1423) or even lower (HMR1964) effects than regular insulin in the mammary epithelial cell line MCF10, while Asp(B10) showed increased [3H]thymidine incorporation. CONCLUSIONS/INTERPRETATION HMR1964 and HMR1423 displayed the same association, dissociation and insulin receptor affinity kinetics as regular insulin, and might therefore be useful for the treatment of diabetes.
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Affiliation(s)
- A M Hennige
- Department of Internal Medicine IV, University of Tübingen, Otfried-Müller-Str. 10, 72076 Tübingen, Germany
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49
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Chen NKF, Sivalingam J, Tan SY, Kon OL. Plasmid-electroporated primary hepatocytes acquire quasi-physiological secretion of human insulin and restore euglycemia in diabetic mice. Gene Ther 2005; 12:655-67. [PMID: 15703765 DOI: 10.1038/sj.gt.3302446] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We describe the durable correction of streptozotocin-induced murine diabetes by in vivo implantation of primary mouse hepatocytes electroporated ex vivo with a human proinsulin cDNA plasmid construct controlled by glucose and zinc regulatory elements. Transfected hepatocytes increased insulin transgene transcription and secretion within 10-20 min of exposure to 25 mM glucose or 60 microM zinc. Insulin release did not occur from secretory granules. Electroporated Rosa26 hepatocytes ( approximately 8 x 10(5) viable cells) were implanted in C57BL/6J diabetic mice in one of three sites: unresected liver, regenerating liver or mesentery. Control diabetic mice were implanted with untransfected hepatocytes. At 30 days after implantation, 8/15 control mice were alive, while 19/19 treated mice were alive. The ratio of body weight on day 30/nadir body weight was significantly higher for all treated groups compared with controls. All eight surviving control mice were hyperglycemic 30 days post-implantation, while 16/19 treated diabetic mice remained normoglycemic. Treated mice had lower mean glucose values (P< or =0.001) without fasting hypoglycemia and better glucose tolerance (P< or =0.0003) than untreated controls. All (6/6) diabetic mice implanted in regenerating liver and 71% (5/7) implanted in unresected liver were alive 77 days after implantation. Engrafted hepatocytes were identified, mainly around central veins, by staining for beta-galactosidase activity and with anti-human insulin antibody.
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Affiliation(s)
- N K F Chen
- Division of Medical Sciences, National Cancer Centre, Singapore, Republic of Singapore
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50
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Nakagawa SH, Zhao M, Hua QX, Hu SQ, Wan ZL, Jia W, Weiss MA. Chiral mutagenesis of insulin. Foldability and function are inversely regulated by a stereospecific switch in the B chain. Biochemistry 2005; 44:4984-99. [PMID: 15794637 PMCID: PMC3845378 DOI: 10.1021/bi048025o] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
How insulin binds to its receptor is unknown despite decades of investigation. Here, we employ chiral mutagenesis-comparison of corresponding d and l amino acid substitutions in the hormone-to define a structural switch between folding-competent and active conformations. Our strategy is motivated by the T --> R transition, an allosteric feature of zinc-hexamer assembly in which an invariant glycine in the B chain changes conformations. In the classical T state, Gly(B8) lies within a beta-turn and exhibits a positive phi angle (like a d amino acid); in the alternative R state, Gly(B8) is part of an alpha-helix and exhibits a negative phi angle (like an l amino acid). Respective B chain libraries containing mixtures of d or l substitutions at B8 exhibit a stereospecific perturbation of insulin chain combination: l amino acids impede native disulfide pairing, whereas diverse d substitutions are well-tolerated. Strikingly, d substitutions at B8 enhance both synthetic yield and thermodynamic stability but markedly impair biological activity. The NMR structure of such an inactive analogue (as an engineered T-like monomer) is essentially identical to that of native insulin. By contrast, l analogues exhibit impaired folding and stability. Although synthetic yields are very low, such analogues can be highly active. Despite the profound differences between the foldabilities of d and l analogues, crystallization trials suggest that on protein assembly substitutions of either class can be accommodated within classical T or R states. Comparison between such diastereomeric analogues thus implies that the T state represents an inactive but folding-competent conformation. We propose that within folding intermediates the sign of the B8 phi angle exerts kinetic control in a rugged landscape to distinguish between trajectories associated with productive disulfide pairing (positive T-like values) or off-pathway events (negative R-like values). We further propose that the crystallographic T -->R transition in part recapitulates how the conformation of an insulin monomer changes on receptor binding. At the very least the ostensibly unrelated processes of disulfide pairing, allosteric assembly, and receptor binding appear to utilize the same residue as a structural switch; an "ambidextrous" glycine unhindered by the chiral restrictions of the Ramachandran plane. We speculate that this switch operates to protect insulin-and the beta-cell-from protein misfolding.
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Affiliation(s)
- Satoe H. Nakagawa
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Ming Zhao
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Qing-xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
| | - Shi-Quan Hu
- Department of Pharmacology and Biological Chemistry, Mt. Sinai School of Medicine of New York University, New York, New York 10029
| | - Zhu-li Wan
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
| | - Wenhua Jia
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
| | - Michael A. Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935
- To whom correspondence should be addressed. ; telephone: (216) 368-5991; fax: (216) 368-3419
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