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Weil-Ktorza O, Dhayalan B, Chen YS, Weiss MA, Metanis N. Se-Glargine: Chemical Synthesis of a Basal Insulin Analogue Stabilized by an Internal Diselenide Bridge. Chembiochem 2024; 25:e202300818. [PMID: 38149322 DOI: 10.1002/cbic.202300818] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 12/21/2023] [Accepted: 12/24/2023] [Indexed: 12/28/2023]
Abstract
Insulin has long provided a model for studies of protein folding and stability, enabling enhanced treatment of diabetes mellitus via analogue design. We describe the chemical synthesis of a basal insulin analogue stabilized by substitution of an internal cystine (A6-A11) by a diselenide bridge. The studies focused on insulin glargine (formulated as Lantus® and Toujeo®; Sanofi). Prepared at pH 4 in the presence of zinc ions, glargine exhibits a shifted isoelectric point due to a basic B chain extension (ArgB31 -ArgB32 ). Subcutaneous injection leads to pH-dependent precipitation of a long-lived depot. Pairwise substitution of CysA6 and CysA11 by selenocysteine was effected by solid-phase peptide synthesis; the modified A chain also contained substitution of AsnA21 by Gly, circumventing acid-catalyzed deamidation. Although chain combination of native glargine yielded negligible product, in accordance with previous synthetic studies, the pairwise selenocysteine substitution partially rescued this reaction: substantial product was obtained through repeated combination, yielding a stabilized insulin analogue. This strategy thus exploited both (a) the unique redox properties of selenocysteine in protein folding and (b) favorable packing of an internal diselenide bridge in the native state, once achieved. Such rational optimization of protein folding and stability may be generalizable to diverse disulfide-stabilized proteins of therapeutic interest.
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Affiliation(s)
- Orit Weil-Ktorza
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Balamurugan Dhayalan
- 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
| | - Norman Metanis
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
- Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
- The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
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2
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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: 4] [Impact Index Per Article: 4.0] [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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3
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Crawley EM, Pye S, Forbes BE, Raston CL. Vortex Fluidic Mediated Oxidative Sulfitolysis of Oxytocin. Molecules 2022; 27:1109. [PMID: 35164375 PMCID: PMC8840205 DOI: 10.3390/molecules27031109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 02/03/2022] [Accepted: 02/04/2022] [Indexed: 11/18/2022] Open
Abstract
In peptide production, oxidative sulfitolysis can be used to protect the cysteine residues during purification, and the introduction of a negative charge aids solubility. Subsequent controlled reduction aids in ensuring correct disulfide bridging. In vivo, these problems are overcome through interaction with chaperones. Here, a versatile peptide production process has been developed using an angled vortex fluidic device (VFD), which expands the viable pH range of oxidative sulfitolysis from pH 10.5 under batch conditions, to full conversion within 20 min at pH 9-10.5 utilising the VFD. VFD processing gave 10-fold greater conversion than using traditional batch processing, which has potential in many applications of the sulfitolysis reaction.
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Affiliation(s)
- Emily M. Crawley
- Flinders Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Adelaide, SA 5042, Australia; (E.M.C.); (S.P.)
| | - Scott Pye
- Flinders Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Adelaide, SA 5042, Australia; (E.M.C.); (S.P.)
| | - Briony E. Forbes
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, SA 5042, Australia;
| | - Colin L. Raston
- Flinders Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Adelaide, SA 5042, Australia; (E.M.C.); (S.P.)
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Dhayalan B, Weiss MA. Diabetes-Associated Mutations in Proinsulin Provide a "Molecular Rheostat" of Nascent Foldability. Curr Diab Rep 2022; 22:85-94. [PMID: 35119630 DOI: 10.1007/s11892-022-01447-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/04/2022] [Indexed: 11/28/2022]
Abstract
PURPOSE OF REVIEW Diabetes mellitus (DM) due to toxic misfolding of proinsulin variants provides a monogenic model of endoplasmic reticulum (ER) stress. The mutant proinsulin syndrome (also designated MIDY; Mutant INS-gene-induced Diabetes of Youth or Maturity-onset diabetes of the young 10 (MODY10)) ordinarily presents as permanent neonatal-onset DM, but specific amino-acid substitutions may also present later in childhood or adolescence. This review highlights structural mechanisms of proinsulin folding as inferred from phenotype-genotype relationships. RECENT FINDINGS MIDY mutations most commonly add or remove a cysteine, leading to a variant polypeptide containing an odd number of thiol groups. Such variants are associated with aberrant intermolecular disulfide pairing, ER stress, and neonatal β-cell dysfunction. Non-cysteine-related (NCR) mutations (occurring in both the B and A domains of proinsulin) define distinct determinants of foldability and vary in severity. The range of ages of onset, therefore, reflects a "molecular rheostat" connecting protein biophysics to quality-control ER checkpoints. Because in most mammalian cell lines even wild-type proinsulin exhibits limited folding efficiency, molecular barriers to folding uncovered by NCR MIDY mutations may pertain to β-cell dysfunction in non-syndromic type 2 DM due to INS-gene overexpression in the face of peripheral insulin resistance. Recent studies of MIDY mutations and related NCR variants, combining molecular and cell-based approaches, suggest that proinsulin has evolved at the edge of non-foldability. Chemical protein synthesis promises to enable comparative studies of "non-foldable" proinsulin variants to define key steps in wild-type biosynthesis. Such studies may create opportunities for novel therapeutic approaches to non-syndromic type 2 DM.
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Affiliation(s)
- Balamurugan Dhayalan
- 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.
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA.
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA.
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5
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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: 3] [Impact Index Per Article: 1.0] [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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Rege NK, Liu M, Yang Y, Dhayalan B, Wickramasinghe NP, Chen YS, Rahimi L, Guo H, Haataja L, Sun J, Ismail-Beigi F, Phillips NB, Arvan P, Weiss MA. Evolution of insulin at the edge of foldability and its medical implications. Proc Natl Acad Sci U S A 2020; 117:29618-29628. [PMID: 33154160 PMCID: PMC7703552 DOI: 10.1073/pnas.2010908117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Proteins have evolved to be foldable, and yet determinants of foldability may be inapparent once the native state is reached. Insight has emerged from studies of diseases of protein misfolding, exemplified by monogenic diabetes mellitus due to mutations in proinsulin leading to endoplasmic reticulum stress and β-cell death. Cellular foldability of human proinsulin requires an invariant Phe within a conserved crevice at the receptor-binding surface (position B24). Any substitution, even related aromatic residue TyrB24, impairs insulin biosynthesis and secretion. As a seeming paradox, a monomeric TyrB24 insulin analog exhibits a native-like structure in solution with only a modest decrement in stability. Packing of TyrB24 is similar to that of PheB24, adjoining core cystine B19-A20 to seal the core; the analog also exhibits native self-assembly. Although affinity for the insulin receptor is decreased ∼20-fold, biological activities in cells and rats were within the range of natural variation. Together, our findings suggest that the invariance of PheB24 among vertebrate insulins and insulin-like growth factors reflects an essential role in enabling efficient protein folding, trafficking, and secretion, a function that is inapparent in native structures. In particular, we envision that the para-hydroxyl group of TyrB24 hinders pairing of cystine B19-A20 in an obligatory on-pathway folding intermediate. The absence of genetic variation at B24 and other conserved sites near this disulfide bridge-excluded due to β-cell dysfunction-suggests that insulin has evolved to the edge of foldability. Nonrobustness of a protein's fitness landscape underlies both a rare monogenic syndrome and "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
- Nischay K Rege
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, 300052 Tianjin, China
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Yanwu Yang
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Balamurugan Dhayalan
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | | | - Yen-Shan Chen
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Leili Rahimi
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
- Department of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Faramarz Ismail-Beigi
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
- Department of Medicine, Case Western Reserve University, Cleveland, OH 44106
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
| | - Nelson B Phillips
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106;
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
- Department of Medicine, Case Western Reserve University, Cleveland, OH 44106
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8
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Zheng N, Karra P, VandenBerg MA, Kim JH, Webber MJ, Holland WL, Chou DHC. Synthesis and Characterization of an A6-A11 Methylene Thioacetal Human Insulin Analogue with Enhanced Stability. J Med Chem 2019; 62:11437-11443. [PMID: 31804076 PMCID: PMC7217704 DOI: 10.1021/acs.jmedchem.9b01589] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Insulin has been a life-saving drug for millions of people with diabetes. However, several challenges exist which limit therapeutic benefits and reduce patient convenience. One key challenge is the fibrillation propensity, which necessitates refrigeration for storage. To address this limitation, we chemically synthesized and evaluated a methylene thioacetal human insulin analogue (SCS-Ins). The synthesized SCS-Ins showed enhanced serum stability and aggregation resistance while retaining bioactivity compared with native insulin.
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Affiliation(s)
- Nan Zheng
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112, United States
| | - Prasoona Karra
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT 84112, United States
| | - Michael A. VandenBerg
- Department of Chemical Engineering, University of Notre Dame, Notre Dame, IN 46556, United States
| | - Jin Hwan Kim
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112, United States
| | - Matthew J. Webber
- Department of Chemical Engineering, University of Notre Dame, Notre Dame, IN 46556, United States
| | - William L. Holland
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT 84112, United States
| | - Danny Hung-Chieh Chou
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112, United States
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9
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Moroder L, Musiol H. Amino acid chalcogen analogues as tools in peptide and protein research. J Pept Sci 2019; 26:e3232. [DOI: 10.1002/psc.3232] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/16/2019] [Accepted: 10/21/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Luis Moroder
- Bioorganic ChemistryMax‐Planck Institute of Biochemistry Martinsried Germany
| | - Hans‐Jürgen Musiol
- Bioorganic ChemistryMax‐Planck Institute of Biochemistry Martinsried Germany
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10
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Sharma AK, Khandelwal R, Kumar MJM, Ram NS, Chidananda AH, Raj TA, Sharma Y. Secretagogin Regulates Insulin Signaling by Direct Insulin Binding. iScience 2019; 21:736-753. [PMID: 31734536 PMCID: PMC6864339 DOI: 10.1016/j.isci.2019.10.066] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 09/17/2019] [Accepted: 10/29/2019] [Indexed: 02/07/2023] Open
Abstract
Secretagogin (SCGN) is a β-cell enriched, secretory/cytosolic Ca2+-binding protein with unknown secretory regulation and functions. Recent findings suggest that SCGN deficiency correlates with compromised insulin response and diabetes. However, the (patho)physiological SCGN-insulin nexus remains unexplored. We here report that SCGN is an insulin-interacting protein. The protein-protein interaction between SCGN and insulin regulates insulin stability and increases insulin potency in vitro and in vivo. Mutagenesis studies suggest an indispensable role for N-terminal domain of SCGN in modulating insulin stability and function. SCGN supplementation in diabetogenic-diet-fed mice preserves physiological insulin responsiveness while relieving obesity and cardiovascular risk. SCGN-insulin interaction mediated alleviation of hyperinsulinemia by increased insulin internalization, which translates to reduced body fat and hepatic lipid accumulation, emerges as a plausible mechanism for the preservation of insulin responsiveness. These findings establish SCGN as a functional insulin-binding protein (InsBP) with therapeutic potential against diabetes. SCGN is an insulin-interacting calcium sensor protein SCGN binding protects insulin from aggregation SCGN potentiates insulin action in vivo SCGN administration into HFD-fed animals impedes insulin resistance
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Affiliation(s)
- Anand Kumar Sharma
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Radhika Khandelwal
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi, India
| | - M Jerald Mahesh Kumar
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - N Sai Ram
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Amrutha H Chidananda
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - T Avinash Raj
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Yogendra Sharma
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi, India; Indian Institute of Science Education and Research (IISER), Berhampur, Odisha 760010, India.
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11
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Weil-Ktorza O, Rege N, Lansky S, Shalev DE, Shoham G, Weiss MA, Metanis N. Substitution of an Internal Disulfide Bridge with a Diselenide Enhances both Foldability and Stability of Human Insulin. Chemistry 2019; 25:8513-8521. [PMID: 31012517 PMCID: PMC6861001 DOI: 10.1002/chem.201900892] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 04/12/2019] [Indexed: 11/12/2022]
Abstract
Insulin analogues, mainstays in the modern treatment of diabetes mellitus, exemplify the utility of protein engineering in molecular pharmacology. Whereas chemical syntheses of the individual A and B chains were accomplished in the early 1960s, their combination to form native insulin remains inefficient because of competing disulfide pairing and aggregation. To overcome these limitations, we envisioned an alternative approach: pairwise substitution of cysteine residues with selenocysteine (Sec, U). To this end, CysA6 and CysA11 (which form the internal intrachain A6-A11 disulfide bridge) were each replaced with Sec. The A chain[C6U, C11U] variant was prepared by solid-phase peptide synthesis; while sulfitolysis of biosynthetic human insulin provided wild-type B chain-di-S-sulfonate. The presence of selenium atoms at these sites markedly enhanced the rate and fidelity of chain combination, thus solving a long-standing challenge in chemical insulin synthesis. The affinity of the Se-insulin analogue for the lectin-purified insulin receptor was indistinguishable from that of WT-insulin. Remarkably, the thermodynamic stability of the analogue at 25 °C, as inferred from guanidine denaturation studies, was augmented (ΔΔGu ≈0.8 kcal mol-1 ). In accordance with such enhanced stability, reductive unfolding of the Se-insulin analogue and resistance to enzymatic cleavage by Glu-C protease occurred four times more slowly than that of WT-insulin. 2D-NMR and X-ray crystallographic studies demonstrated a native-like three-dimensional structure in which the diselenide bridge was accommodated in the hydrophobic core without steric clash.
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Affiliation(s)
- Orit Weil-Ktorza
- The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem, 91904, Israel
| | - Nischay Rege
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Shifra Lansky
- The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem, 91904, Israel
| | - Deborah E Shalev
- Wolfson Center for Applied Structural Biology, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem, 91904, Israel
| | - Gil Shoham
- The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem, 91904, Israel
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106, USA
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Norman Metanis
- The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem, 91904, Israel
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12
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Akbarian M, Yousefi R. Human αB-crystallin as fusion protein and molecular chaperone increases the expression and folding efficiency of recombinant insulin. PLoS One 2018; 13:e0206169. [PMID: 30339677 PMCID: PMC6195290 DOI: 10.1371/journal.pone.0206169] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 10/08/2018] [Indexed: 01/19/2023] Open
Abstract
Low expression and instability are significant challenges in the recombinant production of therapeutic peptides. The current study introduces a novel expression and purification system for human insulin production using the molecular chaperone αB-crystallin (αB-Cry) as a fusion partner protein. Insulin is composed of A- and B-chain containing three disulfide bonds (one intarchain and two interchains). We have constructed two plasmids harboring the A- or B-chain of insulin joined with human αB-Cry. This system is suitable for cloning of the genes and for directing the synthesis of large amounts of the fusion proteins αB-Cry/A-chain (αB-AC) and αB-Cry/B-chain (αB-BC). The construction of vectors, their efficient expression in Escherichia coli and simple purification of the fusion proteins and two insulin chains are described. A large amount of the recombinant fusion proteins with high purity was obtained by applying a single step anion exchange chromatography or metal chelate affinity. The insulin A- and B-chain were released from the fusion proteins using cyanogen bromide cleavage. The insulin peptides were obtained with an appreciable yield and high purity using one-step gel filtration chromatography. To increase efficiency of chain combination to produce insulin, αB-Cry was used under oxidative conditions. The purification of natively folded insulin was performed by phenyl sepharose hydrophobic interaction chromatography. Finally, using an insulin tolerance test in mice and various biophysical methods, the structure and function of purified human recombinant insulin was compared with authentic insulin, to verify folding of insulin to its native state. Overall, the novel expression system using αB-Cry is highly demanding for producing human insulin and functional protein. The procedure for αB-Cry-mediated insulin folding could be also applicable for the large-scale production of this highly important therapeutic peptide hormone.
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Affiliation(s)
- Mohsen Akbarian
- Protein Chemistry Laboratory, Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
| | - Reza Yousefi
- Protein Chemistry Laboratory, Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
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13
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Liu M, Weiss MA, Arunagiri A, Yong J, Rege N, Sun J, Haataja L, Kaufman RJ, Arvan P. Biosynthesis, structure, and folding of the insulin precursor protein. Diabetes Obes Metab 2018; 20 Suppl 2:28-50. [PMID: 30230185 PMCID: PMC6463291 DOI: 10.1111/dom.13378] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [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: 05/04/2018] [Accepted: 05/23/2018] [Indexed: 02/06/2023]
Abstract
Insulin synthesis in pancreatic β-cells is initiated as preproinsulin. Prevailing glucose concentrations, which oscillate pre- and postprandially, exert major dynamic variation in preproinsulin biosynthesis. Accompanying upregulated translation of the insulin precursor includes elements of the endoplasmic reticulum (ER) translocation apparatus linked to successful orientation of the signal peptide, translocation and signal peptide cleavage of preproinsulin-all of which are necessary to initiate the pathway of proper proinsulin folding. Evolutionary pressures on the primary structure of proinsulin itself have preserved the efficiency of folding ("foldability"), and remarkably, these evolutionary pressures are distinct from those protecting the ultimate biological activity of insulin. Proinsulin foldability is manifest in the ER, in which the local environment is designed to assist in the overall load of proinsulin folding and to favour its disulphide bond formation (while limiting misfolding), all of which is closely tuned to ER stress response pathways that have complex (beneficial, as well as potentially damaging) effects on pancreatic β-cells. Proinsulin misfolding may occur as a consequence of exuberant proinsulin biosynthetic load in the ER, proinsulin coding sequence mutations, or genetic predispositions that lead to an altered ER folding environment. Proinsulin misfolding is a phenotype that is very much linked to deficient insulin production and diabetes, as is seen in a variety of contexts: rodent models bearing proinsulin-misfolding mutants, human patients with Mutant INS-gene-induced Diabetes of Youth (MIDY), animal models and human patients bearing mutations in critical ER resident proteins, and, quite possibly, in more common variety type 2 diabetes.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202 IN USA
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Jing Yong
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Nischay Rege
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Jinhong Sun
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
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14
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Characterization and optimization of two-chain folding pathways of insulin via native chain assembly. Commun Chem 2018. [DOI: 10.1038/s42004-018-0024-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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15
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van Lierop B, Ong SC, Belgi A, Delaine C, Andrikopoulos S, Haworth NL, Menting JG, Lawrence MC, Robinson AJ, Forbes BE. Insulin in motion: The A6-A11 disulfide bond allosterically modulates structural transitions required for insulin activity. Sci Rep 2017; 7:17239. [PMID: 29222417 PMCID: PMC5722942 DOI: 10.1038/s41598-017-16876-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/17/2017] [Indexed: 01/10/2023] Open
Abstract
The structural transitions required for insulin to activate its receptor and initiate regulation of glucose homeostasis are only partly understood. Here, using ring-closing metathesis, we substitute the A6-A11 disulfide bond of insulin with a rigid, non-reducible dicarba linkage, yielding two distinct stereo-isomers (cis and trans). Remarkably, only the cis isomer displays full insulin potency, rapidly lowering blood glucose in mice (even under insulin-resistant conditions). It also posseses reduced mitogenic activity in vitro. Further biophysical, crystallographic and molecular-dynamics analyses reveal that the A6-A11 bond configuration directly affects the conformational flexibility of insulin A-chain N-terminal helix, dictating insulin’s ability to engage its receptor. We reveal that in native insulin, contraction of the Cα-Cα distance of the flexible A6-A11 cystine allows the A-chain N-terminal helix to unwind to a conformation that allows receptor engagement. This motion is also permitted in the cis isomer, with its shorter Cα-Cα distance, but prevented in the extended trans analogue. These findings thus illuminate for the first time the allosteric role of the A6-A11 bond in mediating the transition of the hormone to an active conformation, significantly advancing our understanding of insulin action and opening up new avenues for the design of improved therapeutic analogues.
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Affiliation(s)
- Bianca van Lierop
- School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia
| | - Shee Chee Ong
- College of Medicine & Public Health, Flinders University of South Australia, Bedford Park, 5042, Australia
| | - Alessia Belgi
- School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia
| | - Carlie Delaine
- College of Medicine & Public Health, Flinders University of South Australia, Bedford Park, 5042, Australia
| | | | - Naomi L Haworth
- School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia.,Research School of Chemistry, Australian National University, Acton, ACT 2601, Australia.,School of Life and Environmental Sciences, Deakin University, Waurn Ponds, Victoria, 3216, Australia
| | - John G Menting
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria, 3052, Australia
| | - 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, Royal Parade, Parkville, Victoria, 3050, Australia
| | - Andrea J Robinson
- School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia.
| | - Briony E Forbes
- College of Medicine & Public Health, Flinders University of South Australia, Bedford Park, 5042, Australia.
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16
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Kent S. Chemical protein synthesis: Inventing synthetic methods to decipher how proteins work. Bioorg Med Chem 2017; 25:4926-4937. [DOI: 10.1016/j.bmc.2017.06.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 06/07/2017] [Accepted: 06/13/2017] [Indexed: 12/15/2022]
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17
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Banerjee A, Ibsen K, Iwao Y, Zakrewsky M, Mitragotri S. Transdermal Protein Delivery Using Choline and Geranate (CAGE) Deep Eutectic Solvent. Adv Healthc Mater 2017; 6. [PMID: 28337858 DOI: 10.1002/adhm.201601411] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 02/21/2017] [Indexed: 12/20/2022]
Abstract
Transdermal delivery of peptides and other biological macromolecules is limited due to skin's inherent low permeability. Here, the authors report the use of a deep eutectic solvent, choline and geranate (CAGE), to enhance topical delivery of proteins such as bovine serum albumin (BSA, molecular weight: ≈66 kDa), ovalbumin (OVA, molecular weight: ≈45 kDa) and insulin (INS, molecular weight: 5.8 kDa). CAGE enhances permeation of BSA, OVA, and insulin into porcine skin ex vivo, penetrating deep into the epidermis and dermis. Studies using tritium-labeled BSA and fluorescein isothiocyanate labeled insulin show significantly enhanced delivery of proteins into and across porcine skin, penetrating the skin in a time-dependent manner. Fourier transform IR spectra of porcine stratum corneum (SC) samples before and after incubation in CAGE show a reduction in peak area attributed to SC lipid content, suggesting lipid extraction from the SC. Circular dichroism confirms that CAGE does not affect insulin's secondary conformation. In vivo studies in rats show that topical application of 10 U insulin dispersed in CAGE (25 U kg-1 insulin dose) leads to a highly significant 40% drop in blood glucose levels in 4 h that is relatively sustained for 12 h. Taken together, these studies demonstrate that CAGE is a promising vehicle for transdermal delivery of therapeutic proteins; specifically, as a noninvasive delivery alternative to injectable insulin for the treatment of diabetes.
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Affiliation(s)
- Amrita Banerjee
- Department of Chemical Engineering and Center for Bioengineering University of California Santa Barbara Santa Barbara CA 93106 USA
| | - Kelly Ibsen
- Department of Chemical Engineering and Center for Bioengineering University of California Santa Barbara Santa Barbara CA 93106 USA
| | - Yasunori Iwao
- Department of Pharmaceutical Engineering School of Pharmaceutical Sciences University of Shizuoka Shizuoka 422‐8526 Japan
| | - Michael Zakrewsky
- Department of Chemical Engineering and Center for Bioengineering University of California Santa Barbara Santa Barbara CA 93106 USA
| | - Samir Mitragotri
- Department of Chemical Engineering and Center for Bioengineering University of California Santa Barbara Santa Barbara CA 93106 USA
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18
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Andrade F, Fonte P, Oliva M, Videira M, Ferreira D, Sarmento B. Solid state formulations composed by amphiphilic polymers for delivery of proteins: characterization and stability. Int J Pharm 2015; 486:195-206. [DOI: 10.1016/j.ijpharm.2015.03.050] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/22/2015] [Accepted: 03/25/2015] [Indexed: 02/08/2023]
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19
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Ksenofontova OI. [Introduction of mutations in insulin molecule: positive and negative mutations]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2014; 60:430-7. [PMID: 25249526 DOI: 10.18097/pbmc20146004430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Introduction of mutations in an insulin molecule is one of the important approaches to drug development for treatment of diabetes mellitus. Generally, usage of mutations is aimed at activation of insulin and insulin receptor interaction. Such mutations can be considered as positive. Mutations that reduce the binding efficacy are negative. There are neutral mutations as well. This article considers both natural mutations that are typical for various members of the insulin superfamily and artificial ones which are introduced to improve the insulin pharmacological characteristics. Data presented here can be useful in developing new effective insulin analogues for treatment of diabetes mellitus.
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20
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Zaykov AN, Mayer JP, Gelfanov VM, DiMarchi RD. Chemical synthesis of insulin analogs through a novel precursor. ACS Chem Biol 2014; 9:683-91. [PMID: 24328449 DOI: 10.1021/cb400792s] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Insulin remains a challenging synthetic target due in large part to its two-chain, disulfide-constrained structure. Biomimetic single chain precursors inspired by proinsulin that utilize short peptides to join the A and B chains can dramatically enhance folding efficiency. Systematic chemical analysis of insulin precursors using an optimized synthetic protocol identified a 49 amino acid peptide named DesDi, which folds with high efficiency by virtue of an optimized structure and could be proteolytically converted to bioactive two-chain insulin. In subsequent applications, we observed that the folding of the DesDi precursor was highly tolerant to amino acid substitution at various insulin residues. The versatility of DesDi as a synthetic insulin precursor was demonstrated through the preparation of several alanine mutants (A10, A16, A18, B12, B15), as well as ValA16, an analog that was unattainable in prior reports. In vitro bioanalysis highlighted the importance of the native, hydrophobic residues at A16 and B15 as part of the core structure of the hormone and revealed the significance of the A18 residue to receptor selectivity. We propose that the DesDi precursor is a versatile synthetic intermediate for the preparation of diverse insulin analogs. It should enable a more comprehensive analysis of function to insulin structure than might not be otherwise possible through conventional approaches.
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Affiliation(s)
- Alexander N. Zaykov
- Indiana University, Department
of Chemistry, Bloomington, Indiana 47405, United States of America
| | - John P. Mayer
- Indiana University, Department
of Chemistry, Bloomington, Indiana 47405, United States of America
| | - Vasily M. Gelfanov
- Indiana University, Department
of Chemistry, Bloomington, Indiana 47405, United States of America
| | - Richard D. DiMarchi
- Indiana University, Department
of Chemistry, Bloomington, Indiana 47405, United States of America
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21
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Ksenofontova OI, Romanovskaya EV, Stefanov VE. Study of conformational mobility of insulin, proinsulin, and insulin-like growth factors. J EVOL BIOCHEM PHYS+ 2014. [DOI: 10.1134/s002209301401006x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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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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23
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Avital-Shmilovici M, Mandal K, Gates ZP, Phillips NB, Weiss MA, Kent SBH. Fully convergent chemical synthesis of ester insulin: determination of the high resolution X-ray structure by racemic protein crystallography. J Am Chem Soc 2013; 135:3173-85. [PMID: 23343390 DOI: 10.1021/ja311408y] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Efficient total synthesis of insulin is important to enable the application of medicinal chemistry to the optimization of the properties of this important protein molecule. Recently we described "ester insulin"--a novel form of insulin in which the function of the 35 residue C-peptide of proinsulin is replaced by a single covalent bond--as a key intermediate for the efficient total synthesis of insulin. Here we describe a fully convergent synthetic route to the ester insulin molecule from three unprotected peptide segments of approximately equal size. The synthetic ester insulin polypeptide chain folded much more rapidly than proinsulin, and at physiological pH. Both the D-protein and L-protein enantiomers of monomeric DKP ester insulin (i.e., [Asp(B10), Lys(B28), Pro(B29)]ester insulin) were prepared by total chemical synthesis. The atomic structure of the synthetic ester insulin molecule was determined by racemic protein X-ray crystallography to a resolution of 1.6 Å. Diffraction quality crystals were readily obtained from the racemic mixture of {D-DKP ester insulin + L-DKP ester insulin}, whereas crystals were not obtained from the L-ester insulin alone even after extensive trials. Both the D-protein and L-protein enantiomers of monomeric DKP ester insulin were assayed for receptor binding and in diabetic rats, before and after conversion by saponification to the corresponding DKP insulin enantiomers. L-DKP ester insulin bound weakly to the insulin receptor, while synthetic L-DKP insulin derived from the L-DKP ester insulin intermediate was fully active in binding to the insulin receptor. The D- and L-DKP ester insulins and D-DKP insulin were inactive in lowering blood glucose in diabetic rats, while synthetic L-DKP insulin was fully active in this biological assay. The structural basis of the lack of biological activity of ester insulin is discussed.
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24
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Liu R, Su R, Yu Y, Qi W, Wang L, He Z. Regeneration of insulin monomers from amyloid fibrils by a NH3/H2O2 two-step method. Biotechnol Lett 2012; 34:1959-64. [PMID: 22714274 DOI: 10.1007/s10529-012-0974-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 05/22/2012] [Indexed: 11/28/2022]
Abstract
We have developed a NH(3)/H(2)O(2) two-step method for the recovery of insulin monomers from amyloid fibrils by modulating the cleavage and regeneration of disulfide bonds. Insulin fibrils were disaggregated into insulin A- and B-chains in 14 M (w/v) NH(4)OH for 2 h at 60 °C. Insulin monomers, with a MW of ~5,882 Da, were then regenerated by oxidation of sulfhydryls with 30 % (w/v) H(2)O(2) (10 M) for 12 h at 25 °C. No two A-chains or two B-chains of insulin formed during the oxidation process. Because of the inconformity of the optimal reduction and oxidation temperature, the NH(3)/H(2)O(2) two-step method is more practical than the NH(3)/H(2)O(2) coupling method.
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Affiliation(s)
- Rui Liu
- State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
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25
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Abstract
Insulin is a hormone that is essential for regulating energy storage and glucose metabolism in the body. Insulin in liver, muscle, and fat tissues stimulates the cell to take up glucose from blood and store it as glycogen in liver and muscle. Failure of insulin control causes diabetes mellitus (DM). Insulin is the unique medicine to treat some forms of DM. The population of diabetics has dramatically increased over the past two decades, due to high absorption of carbohydrates (or fats and proteins), lack of physical exercise, and development of new diagnostic techniques. At present, the two largest developing countries (India and China) and the largest developed country (United States) represent the top three countries in terms of diabetic population. Insulin is a small protein, but contains almost all structural features typical of proteins: α-helix, β-sheet, β-turn, high order assembly, allosteric T®R-transition, and conformational changes in amyloidal fibrillation. More than ten years' efforts on studying insulin disulfide intermediates by NMR have enabled us to decipher the whole picture of insulin folding coupled to disulfide pairing, especially at the initial stage that forms the nascent peptide. Two structural switches are also known to regulate insulin binding to receptors and progress has been made to identify the residues involved in binding. However, resolving the complex structure of insulin and its receptor remains a challenge in insulin research. Nevertheless, the accumulated knowledge of insulin structure has allowed us to specifically design a new ultra-stable and active single-chain insulin analog (SCI-57), and provides a novel way to design super-stable, fast-acting and cheaper insulin formulations for DM patients. Continuing this long journey of insulin study will benefit basic research in proteins and in pharmaceutical therapy.
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Affiliation(s)
- Qingxin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106-4935, USA.
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26
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Ng DT, Sarkar CA. Nisin-inducible secretion of a biologically active single-chain insulin analog by Lactococcus lactis NZ9000. Biotechnol Bioeng 2011; 108:1987-96. [DOI: 10.1002/bit.23130] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 01/25/2011] [Accepted: 03/03/2011] [Indexed: 12/12/2022]
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27
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Sohma Y, Hua QX, Whittaker J, Weiss MA, Kent SBH. Design and folding of [GluA4(ObetaThrB30)]insulin ("ester insulin"): a minimal proinsulin surrogate that can be chemically converted into human insulin. Angew Chem Int Ed Engl 2011; 49:5489-93. [PMID: 20509131 DOI: 10.1002/anie.201001151] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Youhei Sohma
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA.
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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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Liu M, Hodish I, Haataja L, Lara-Lemus R, Rajpal G, Wright J, Arvan P. Proinsulin misfolding and diabetes: mutant INS gene-induced diabetes of youth. Trends Endocrinol Metab 2010; 21:652-9. [PMID: 20724178 PMCID: PMC2967602 DOI: 10.1016/j.tem.2010.07.001] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Revised: 07/07/2010] [Accepted: 07/08/2010] [Indexed: 12/23/2022]
Abstract
Type 1B diabetes (typically with early onset and without islet autoantibodies) has been described in patients bearing small coding sequence mutations in the INS gene. Not all mutations in the INS gene cause the autosomal dominant Mutant INS-gene Induced Diabetes of Youth (MIDY) syndrome, but most missense mutations affecting proinsulin folding produce MIDY. MIDY patients are heterozygotes, with the expressed mutant proinsulins exerting dominant-negative (toxic gain of function) behavior in pancreatic beta cells. Here we focus primarily on proinsulin folding in the endoplasmic reticulum, providing insight into perturbations of this folding pathway in MIDY. Accumulated evidence indicates that, in the molecular pathogenesis of the disease, misfolded proinsulin exerts dominant effects that initially inhibit insulin production, progressing to beta cell demise with diabetes.
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Affiliation(s)
| | | | | | | | | | | | - Peter Arvan
- To whom correspondence may be addressed: Division of Metabolism, Endocrinology & Diabetes University of Michigan, 5560 MSRB2 1150 W. Medical Center Drive Ann Arbor, MI 48109-0678 Telephone: 734-936-5006 FAX: 734-936-6684
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30
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Liu M, Hua QX, Hu SQ, Jia W, Yang Y, Saith SE, Whittaker J, Arvan P, Weiss MA. Deciphering the hidden informational content of protein sequences: foldability of proinsulin hinges on a flexible arm that is dispensable in the mature hormone. J Biol Chem 2010; 285:30989-1001. [PMID: 20663888 PMCID: PMC2945590 DOI: 10.1074/jbc.m110.152645] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 07/21/2010] [Indexed: 01/28/2023] Open
Abstract
Protein sequences encode both structure and foldability. Whereas the interrelationship of sequence and structure has been extensively investigated, the origins of folding efficiency are enigmatic. We demonstrate that the folding of proinsulin requires a flexible N-terminal hydrophobic residue that is dispensable for the structure, activity, and stability of the mature hormone. This residue (Phe(B1) in placental mammals) is variably positioned within crystal structures and exhibits (1)H NMR motional narrowing in solution. Despite such flexibility, its deletion impaired insulin chain combination and led in cell culture to formation of non-native disulfide isomers with impaired secretion of the variant proinsulin. Cellular folding and secretion were maintained by hydrophobic substitutions at B1 but markedly perturbed by polar or charged side chains. We propose that, during folding, a hydrophobic side chain at B1 anchors transient long-range interactions by a flexible N-terminal arm (residues B1-B8) to mediate kinetic or thermodynamic partitioning among disulfide intermediates. Evidence for the overall contribution of the arm to folding was obtained by alanine scanning mutagenesis. Together, our findings demonstrate that efficient folding of proinsulin requires N-terminal sequences that are dispensable in the native state. Such arm-dependent folding can be abrogated by mutations associated with β-cell dysfunction and neonatal diabetes mellitus.
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Affiliation(s)
- Ming Liu
- From the Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109 and
| | - Qing-xin Hua
- the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Shi-Quan Hu
- the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Wenhua Jia
- the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Yanwu Yang
- the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Sunil Evan Saith
- From the Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109 and
| | - Jonathan Whittaker
- the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Peter Arvan
- From the Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109 and
| | - Michael A. Weiss
- the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
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31
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Sohma Y, Hua QX, Whittaker J, Weiss M, Kent S. Design and Folding of [GluA4(OβThrB30)]Insulin (“Ester Insulin”): A Minimal Proinsulin Surrogate that Can Be Chemically Converted into Human Insulin. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201001151] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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Sohma Y, Kent SBH. Biomimetic synthesis of lispro insulin via a chemically synthesized "mini-proinsulin" prepared by oxime-forming ligation. J Am Chem Soc 2010; 131:16313-8. [PMID: 19835355 DOI: 10.1021/ja9052398] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Here we report a proof-of-principle study demonstrating the efficient folding, with concomitant formation of the correct disulfides, of an isolated polypeptide insulin precursor of defined covalent structure. We used oxime-forming chemical ligation to introduce a temporary "chemical tether" to link the N-terminal residue of the insulin A chain to the C-terminal residue of the insulin B chain; the tether enabled us to fold/form disulfides with high efficiency. Enzymatic removal of the temporary chemical tether gave mature, fully active insulin. This chemical tethering principle could form the basis of a practical, high yield total synthesis of insulin and analogues.
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Affiliation(s)
- Youhei Sohma
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA
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33
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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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34
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Liu M, Wan ZL, Chu YC, Aladdin H, Klaproth B, Choquette M, Hua QX, Mackin RB, Rao JS, De Meyts P, Katsoyannis PG, Arvan P, Weiss MA. Crystal structure of a "nonfoldable" insulin: impaired folding efficiency despite native activity. J Biol Chem 2009; 284:35259-72. [PMID: 19850922 DOI: 10.1074/jbc.m109.046888] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Protein evolution is constrained by folding efficiency ("foldability") and the implicit threat of toxic misfolding. A model is provided by proinsulin, whose misfolding is associated with beta-cell dysfunction and diabetes mellitus. An insulin analogue containing a subtle core substitution (Leu(A16) --> Val) is biologically active, and its crystal structure recapitulates that of the wild-type protein. As a seeming paradox, however, Val(A16) blocks both insulin chain combination and the in vitro refolding of proinsulin. Disulfide pairing in mammalian cell culture is likewise inefficient, leading to misfolding, endoplasmic reticular stress, and proteosome-mediated degradation. Val(A16) destabilizes the native state and so presumably perturbs a partial fold that directs initial disulfide pairing. Substitutions elsewhere in the core similarly destabilize the native state but, unlike Val(A16), preserve folding efficiency. We propose that Leu(A16) stabilizes nonlocal interactions between nascent alpha-helices in the A- and B-domains to facilitate initial pairing of Cys(A20) and Cys(B19), thus surmounting their wide separation in sequence. Although Val(A16) is likely to destabilize this proto-core, its structural effects are mitigated once folding is achieved. Classical studies of insulin chain combination in vitro have illuminated the impact of off-pathway reactions on the efficiency of native disulfide pairing. The capability of a polypeptide sequence to fold within the endoplasmic reticulum may likewise be influenced by kinetic or thermodynamic partitioning among on- and off-pathway disulfide intermediates. The properties of [Val(A16)]insulin and [Val(A16)]proinsulin demonstrate that essential contributions of conserved residues to folding may be inapparent once the native state is achieved.
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Affiliation(s)
- Ming Liu
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA
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35
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Abstract
Insulin plays a central role in the regulation of vertebrate metabolism. The hormone, the post-translational product of a single-chain precursor, is a globular protein containing two chains, A (21 residues) and B (30 residues). Recent advances in human genetics have identified dominant mutations in the insulin gene causing permanent neonatal-onset DM(2) (1-4). The mutations are predicted to block folding of the precursor in the ER of pancreatic beta-cells. Although expression of the wild-type allele would in other circumstances be sufficient to maintain homeostasis, studies of a corresponding mouse model (5-7) suggest that the misfolded variant perturbs wild-type biosynthesis (8, 9). Impaired beta-cell secretion is associated with ER stress, distorted organelle architecture, and cell death (10). These findings have renewed interest in insulin biosynthesis (11-13) and the structural basis of disulfide pairing (14-19). Protein evolution is constrained not only by structure and function but also by susceptibility to toxic misfolding.
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Affiliation(s)
- Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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36
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Kuang Z, Yao S, McNeil KA, Forbes BE, Wallace JC, Norton RS. Insulin-like growth factor-I (IGF-I): solution properties and NMR chemical shift assignments near physiological pH. Growth Horm IGF Res 2009; 19:226-231. [PMID: 19056307 DOI: 10.1016/j.ghir.2008.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 10/08/2008] [Accepted: 10/17/2008] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Insulin-like growth factor-I (IGF-I) plays important roles in normal growth and development, as well as in disease states, and its structure and function have been studied extensively using nuclear magnetic resonance (NMR) spectroscopy. However, IGF-I typically gives poor quality NMR spectra containing many broad peaks, because of aggregation at the protein concentrations generally required for NMR experiments as well as the internal dynamics of the molecule. The present study was undertaken to determine a reliable set of assignments under more physiological conditions. DESIGN Several reports of chemical shift assignments have been published previously for IGF-I either bound to a ligand or at relatively low pH (approximately 3-4), but there are many contradictions among them, reflecting the poor behaviour of IGF-I. Low pH conditions are also suboptimal for the analysis of interactions between IGF-I and IGF binding proteins (IGFBP) or IGFBP fragments. Spectra were recorded at low concentrations in order to identify conditions of temperature and pH where all peaks could be observed. RESULTS We show that good quality 2D (1)H-(15)N HSQC spectra of (15)N-labelled IGF-I can be obtained at pH 6 and 37 degrees C, much closer to physiological conditions, by using lower IGF-I concentrations (0.05 mM). Surprisingly, at this concentration and temperature, spectra were of better quality at pH 6 than at pH 4, in contrast to previous observations made at millimolar concentrations of IGF-I. We were then also able to assign the chemical shifts of IGF-I at pH 6 and 37 degrees C using 3D heteronuclear spectra recorded on a 0.7 mM (15)N/(13)C-labelled IGF-I sample. CONCLUSION These results provide a valuable resource for future studies of the structure, dynamics, folding, and binding interactions of IGF-I, as well as analogues thereof, by means of NMR spectroscopy.
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Affiliation(s)
- Zhihe Kuang
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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37
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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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38
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Abstract
Crystal structures of insulin are remarkable for a long-range reorganization among three families of hexamers (designated T(6), T(3)R(3)(f), and R(6)). Although these structures are well characterized at atomic resolution, the biological implications of the TR transition remain the subject of speculation. Recent studies indicate that such allostery reflects a structural switch between distinct folding-competent and active conformations. Stereospecific modulation of this switch by corresponding d- and l-amino-acid substitutions yields reciprocal effects on protein stability and receptor-binding activity. Naturally occurring human mutations at the site of conformational change impair the folding of proinsulin and cause permanent neonatal-onset diabetes mellitus. The repertoire of classical structures thus foreshadows the conformational lifecycle of insulin in vivo. By highlighting the richness of information provided by protein crystallography-even in a biological realm far removed from conditions of crystallization-these findings validate the prescient insights of the late D. C. Hodgkin. Future studies of the receptor-bound structure of insulin may enable design of novel agonists for the treatment of diabetes mellitus.
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39
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Wan ZL, Huang K, Hu SQ, Whittaker J, Weiss MA. The structure of a mutant insulin uncouples receptor binding from protein allostery. An electrostatic block to the TR transition. J Biol Chem 2008; 283:21198-210. [PMID: 18492668 PMCID: PMC2475698 DOI: 10.1074/jbc.m800235200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 05/01/2008] [Indexed: 11/06/2022] Open
Abstract
The zinc insulin hexamer undergoes allosteric reorganization among three conformational states, designated T(6), T(3)R(3)(f), and R(6). Although the free monomer in solution (the active species) resembles the classical T-state, an R-like conformational change is proposed to occur upon receptor binding. Here, we distinguish between the conformational requirements of receptor binding and the crystallographic TR transition by design of an active variant refractory to such reorganization. Our strategy exploits the contrasting environments of His(B5) in wild-type structures: on the T(6) surface but within an intersubunit crevice in R-containing hexamers. The TR transition is associated with a marked reduction in His(B5) pK(a), in turn predicting that a positive charge at this site would destabilize the R-specific crevice. Remarkably, substitution of His(B5) (conserved among eutherian mammals) by Arg (occasionally observed among other vertebrates) blocks the TR transition, as probed in solution by optical spectroscopy. Similarly, crystallization of Arg(B5)-insulin in the presence of phenol (ordinarily a potent inducer of the TR transition) yields T(6) hexamers rather than R(6) as obtained in control studies of wild-type insulin. The variant structure, determined at a resolution of 1.3A, closely resembles the wild-type T(6) hexamer. Whereas Arg(B5) is exposed on the protein surface, its side chain participates in a solvent-stabilized network of contacts similar to those involving His(B5) in wild-type T-states. The substantial receptor-binding activity of Arg(B5)-insulin (40% relative to wild type) demonstrates that the function of an insulin monomer can be uncoupled from its allosteric reorganization within zinc-stabilized hexamers.
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Affiliation(s)
- Zhu-li Wan
- Departments of Biochemistry
and Nutrition, Case Western Reserve
University School of Medicine, Cleveland, Ohio 44106
| | - Kun Huang
- Departments of Biochemistry
and Nutrition, Case Western Reserve
University School of Medicine, Cleveland, Ohio 44106
| | - Shi-Quan Hu
- Departments of Biochemistry
and Nutrition, Case Western Reserve
University School of Medicine, Cleveland, Ohio 44106
| | - Jonathan Whittaker
- Departments of Biochemistry
and Nutrition, Case Western Reserve
University School of Medicine, Cleveland, Ohio 44106
| | - Michael A. Weiss
- Departments of Biochemistry
and Nutrition, Case Western Reserve
University School of Medicine, Cleveland, Ohio 44106
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40
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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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41
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Structural interpretation of reduced insulin activity as seen in the crystal structure of human Arg-insulin. Biochimie 2007; 90:467-73. [PMID: 18029081 DOI: 10.1016/j.biochi.2007.09.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 09/14/2007] [Indexed: 10/22/2022]
Abstract
The N-terminal glycine of the A-chain in insulin is reported to be one of the residues that binds to the insulin receptor. Modifications near this region lead to variations in the biological activity of insulin. One such modification viz., an addition of an arginine at the N-terminal A-chain, was reported to possess two-thirds the activity of native insulin. The crystal structure of 2 zinc human arg (A0) insulin has been elucidated to 2A resolution to understand the mechanism of reduction in insulin activity. A conformational transition from T6 to T3R3(f) and a decrease in the surface accessibility of residues in the so called receptor binding region have been observed. The presence of arginine has also induced distortions in the A chain N-terminal helix. The subtle conformational alterations like decrease in surface accessibility, alterations in the charge surface and changes in the relative orientation of the two helices in the A chain may be responsible for the reduction in activity.
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42
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Abstract
One of the predominant aims of insulin therapy for diabetes is to appropriately mimic physiological insulin secretion levels and their correlation with glucose concentration in healthy individuals. This report outlines current methods and their limitations in glycemic control and their possible relationship to insufficient knowledge about the structure and dynamics of the insulin hormone itself. Based on recent experimental and computational work, a possible approach to less-invasive insulin administration is sketched.
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Affiliation(s)
- Manuela Koch
- Department of Chemistry, University of Basel, Basel, Switzerland
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43
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Hua QX, Mayer JP, Jia W, Zhang J, Weiss MA. The folding nucleus of the insulin superfamily: a flexible peptide model foreshadows the native state. J Biol Chem 2006; 281:28131-42. [PMID: 16864583 DOI: 10.1074/jbc.m602616200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oxidative folding of insulin-like growth factor I (IGF-I) and single-chain insulin analogs proceeds via one- and two-disulfide intermediates. A predominant one-disulfide intermediate in each case contains the canonical A20-B19 disulfide bridge (cystines 18-61 in IGF-I and 19-85 in human proinsulin). Here, we describe a disulfide-linked peptide model of this on-pathway intermediate. One peptide fragment (19 amino acids) spans IGF-I residues 7-25 (canonical positions B8-B26 in the insulin superfamily); the other (18 amino acids) spans IGF-I residues 53-70 (positions A12-A21 and D1-D8). Containing only half of the IGF-I sequence, the disulfide-linked polypeptide (designated IGF-p) is not well ordered. Nascent helical elements corresponding to native alpha-helices are nonetheless observed at 4 degrees C. Furthermore, (13)C-edited nuclear Overhauser effects establish transient formation of a native-like partial core; no non-native nuclear Overhauser effects are observed. Together, these observations suggest that early events in the folding of insulin-related polypeptides are nucleated by a native-like molten subdomain containing Cys(A20) and Cys(B19). We propose that nascent interactions within this subdomain orient the A20 and B19 thiolates for disulfide bond formation and stabilize the one-disulfide intermediate once formed. Substitutions in the corresponding region of insulin are associated with inefficient chain combination and impaired biosynthetic expression. The intrinsic conformational propensities of a flexible disulfide-linked peptide thus define a folding nucleus, foreshadowing the structure of the native state.
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Affiliation(s)
- Qing-xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
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44
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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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45
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Nakagawa SH, Hua QX, Hu SQ, Jia W, Wang S, Katsoyannis PG, Weiss MA. Chiral mutagenesis of insulin. Contribution of the B20-B23 beta-turn to activity and stability. J Biol Chem 2006; 281:22386-22396. [PMID: 16751187 DOI: 10.1074/jbc.m603547200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin contains a beta-turn (residues B20-B23) interposed between two receptor-binding elements, the central alpha-helix of the B chain (B9-B19) and its C-terminal beta-strand (B24-B28). The turn contains conserved glycines at B20 and B23. Although insulin exhibits marked conformational variability among crystal forms, these glycines consistently maintain positive phi dihedral angles within a classic type-I beta-turn. Because the Ramachandran conformations of GlyB20 and GlyB23 are ordinarily forbidden to L-amino acids, turn architecture may contribute to structure or function. Here, we employ "chiral mutagenesis," comparison of corresponding D- and L-Ala substitutions, to investigate this turn. Control substitutions are introduced at GluB21, a neighboring residue exhibiting a conventional (negative) phi angle. The D- and L-Ala substitutions at B23 are associated with a marked stereospecific difference in activity. Whereas the D-AlaB23 analog retains native activity, the L analog exhibits a 20-fold decrease in receptor binding. By contrast, D- and L-AlaB20 analogs each exhibit high activity. Stereospecific differences between the thermodynamic stabilities of the analogs are nonetheless more pronounced at B20 (delta deltaG(u) 2.0 kcal/mole) than at B23 (delta deltaG(u) 0.7 kcal/mole). Control substitutions at B21 are well tolerated without significant stereospecificity. Chiral mutagenesis thus defines the complementary contributions of these conserved glycines to protein stability (GlyB20) or receptor recognition (GlyB23).
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Affiliation(s)
- Satoe H Nakagawa
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Qing-Xin Hua
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Shi-Quan Hu
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Wenhua Jia
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Shuhua Wang
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Panayotis G Katsoyannis
- Department of Pharmacology & Biological Chemistry, Mt. Sinai School of Medicine, New York, New York 10029
| | - Michael A Weiss
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106.
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46
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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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47
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Zoete V, Meuwly M, Karplus M. Study of the insulin dimerization: binding free energy calculations and per-residue free energy decomposition. Proteins 2006; 61:79-93. [PMID: 16080143 DOI: 10.1002/prot.20528] [Citation(s) in RCA: 187] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A calculation of the binding free energy for the dimerization of insulin has been performed using the molecular mechanics-generalized Born surface area approach. The calculated absolute binding free energy is -11.9 kcal/mol, in approximate agreement with the experimental value of -7.2 kcal/mol. The results show that the dimerization is mainly due to nonpolar interactions. The role of the hydrogen bonds between the 2 monomers appears to give the direction of the interactions. A per-atom decomposition of the binding free energy has been performed to identify the residues contributing most to the self association free energy. Residues B24-B26 are found to make the largest favorable contributions to the dimerization. Other residues situated at the interface between the 2 monomers were found to make favorable but smaller contributions to the dimerization: Tyr B16, Val B12, and Pro B28, and to an even lesser extent, Gly B23. The energy decomposition on a per-residue basis is in agreement with experimental alanine scanning data. The results obtained from a single trajectory (i.e., the dimer trajectory is also used for the monomer analysis) and 2 trajectories (i.e., separate trajectories are used for the monomer and dimer) are similar.
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Affiliation(s)
- Vincent Zoete
- Laboratoire de Chimie Biophysique, ISIS/Université Louis Pasteur, Strasbourg Cedex, France
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48
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Huang K, Dong J, Phillips NB, Carey PR, Weiss MA. Proinsulin Is Refractory to Protein Fibrillation. J Biol Chem 2005; 280:42345-55. [PMID: 16239223 DOI: 10.1074/jbc.m507110200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin is susceptible to fibrillation, a misfolding process leading to well ordered cross-beta assembly. Protection from fibrillation in beta cells is provided by sequestration of the susceptible monomer within zinc hexamers. We demonstrate that proinsulin is refractory to fibrillation under conditions that promote the rapid fibrillation of zinc-free insulin. Proinsulin fibrils, as probed by Raman microscopy, are nonetheless similar in structure to insulin fibrils. The connecting peptide, although not well ordered in native proinsulin, participates in a fibril-specific beta-sheet. Native insulin and proinsulin exhibit similar free energies of unfolding as inferred from guanidine denaturation studies: relative amyloidogenicities are thus not correlated with global stability. Strikingly, the susceptibility of proinsulin to fibrillation is increased by scission of the connecting peptide at single sites. We thus propose that the connecting peptide constrains a large scale conformational change in the misfolded protein. A tethering mechanism is proposed based on a model of an insulin protofilament derived from electron-microscopic image reconstruction. The proposed relationship between cross-beta assembly and protein topology is supported by studies of single-chain analogs (mini-proinsulin and insulin-like growth factor I) in which foreshortened connecting peptides further retard fibrillation. In addition to its classic function to facilitate disulfide pairing, the connecting peptide may protect beta cells from toxic protein misfolding in the endoplasmic reticulum.
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Affiliation(s)
- Kun Huang
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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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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Liu M, Li Y, Cavener D, Arvan P. Proinsulin disulfide maturation and misfolding in the endoplasmic reticulum. J Biol Chem 2005; 280:13209-12. [PMID: 15705595 PMCID: PMC2527538 DOI: 10.1074/jbc.c400475200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Upon nonreducing Tris-Tricine-urea-SDS-PAGE, newly synthesized proinsulin from pancreatic islets of normal rodents forms a band fast mobility representing the native disulfide isomer, which is efficiently secreted. In addition at least two slower migrating "isomer 1 and 2" bands are recovered, not discernible under reducing conditions, which represent minor species that exhibit less efficient secretion. Although rats and mice have two proinsulin genes, three distinct migrating species are also produced upon proinsulin expression from a single wild-type human proinsulin cDNA. The "Akita-type" proinsulin mutation, which causes dominant-negative diabetes mellitus due to point mutation C(A7)Y that leaves B7-cysteine without its disulfide pairing partner, is recovered as a form that near quantitatively co-migrates with the aberrant isomer 1 band of proinsulin. Anomalous migration is also demonstrated for several other mutants lacking a single cysteine. In islets from PERK-/- mice, which exhibit premature loss of pancreatic beta cells, hypersynthesis of proinsulin increases the amount of nonnative proinsulin isomers. Such findings appear consistent with an hypothesis that supranormal production of nonnative proinsulin may predispose to pancreatic beta cell toxicity.
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Affiliation(s)
- Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Yulin Li
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Douglas Cavener
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan 48109
- ¶ To whom correspondence should be addressed: Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, MSRB2 Rm. 5560, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0678. Tel.: 734-936-5505; Fax: 734-936-6684; E-mail:
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