401
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Laursen LS, Oxvig C. Real-time measurement in living cells of insulin-like growth factor activity using bioluminescence resonance energy transfer. Biochem Pharmacol 2005; 69:1723-32. [PMID: 15935147 DOI: 10.1016/j.bcp.2005.04.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 04/11/2005] [Accepted: 04/11/2005] [Indexed: 01/21/2023]
Abstract
Insulin-like growth factor (IGF)-I and -II function in normal physiology to control growth, development, and differentiation, but are also important in pathophysiological conditions, particularly in cancer. The biological effects of the IGFs are mediated by the IGF-I receptor (IGFR), a covalent homodimer composed of two alpha and two beta chains, similar in structure to the insulin receptor (IR). To allow measurement of the stimulation of IGFR in living cells, we developed an assay based on bioluminescence resonance energy transfer (BRET) between a donor molecule, Renilla luciferase, and an acceptor fluorophore, enhanced yellow fluorescent protein (EYFP). Initial attempts based on fusion of the luciferase to IGFR, and EYFP to IGFR, or to downstream signaling molecules, insulin receptor substrate-1 (IRS1) or protein tyrosine phosphatases-1B (PTP-1B), failed. However, similar experiments with IR, carried our in parallel, proved successful. We therefore, constructed assays based on chimeric IGFR/IR proteins, in which the ligand binding site was derived from IGFR. With the most efficient assay, in which the luciferase is fused to a chimeric receptor with the entire intracellular portion derived from IR, and EYFP fused to PTP-1B, IGF activity was measured specifically with sensitivity similar to the corresponding assay for insulin, based on IR. The established system allows efficient evaluation of candidate ligand- or receptor-directed molecules for the modulation of IGF activities. Furthermore, we demonstrate that a set of inhibitory IGF binding proteins (IGFBPs) or activating IGFBP-specific proteinases, unique to the IGF system, may serve as potential targets. In addition to screening, real-time measurement of IGFR stimulation may be important in efforts to understand the kinetics of receptor stimulation, in particular differences between IGFR and IR.
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Affiliation(s)
- Lisbeth S Laursen
- Department of Molecular Biology, Science Park, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
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402
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Whittaker J, Whittaker L. Characterization of the Functional Insulin Binding Epitopes of the Full-length Insulin Receptor. J Biol Chem 2005; 280:20932-6. [PMID: 15799978 DOI: 10.1074/jbc.m411320200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mutational analyses of the secreted recombinant insulin receptor extracellular domain have identified a ligand binding site composed of residues located in the L1 domain (amino acids 1-470) and at the C terminus of the alpha subunit (amino acids 705-715). To evaluate the physiological significance of this ligand binding site, we have transiently expressed cDNAs encoding full-length receptors with alanine mutations of the residues forming the functional epitopes of this binding site and determined their insulin binding properties. Insulin bound to wild-type receptors with complex kinetics, which were fitted to a two-component sequential model; the Kd of the high affinity component was 0.03 nM and that of the low affinity component was 0.4 nM. Mutations of Arg14, Phe64, Phe705, Glu706, Tyr708, Asn711, and Val715 inactivated the receptor. Alanine mutation of Asn15 resulted in a 20-fold decrease in affinity, whereas mutations of Asp12, Gln34, Leu36, Leu37, Leu87, Phe89, Tyr91, Lys121, Leu709, and Phe714 all resulted in 4-10-fold decreases. When the effects of the mutations were compared with those of the same mutations of the secreted recombinant receptor, significant differences were observed for Asn15, Leu37, Asp707, Leu709, Tyr708, Asn711, Phe714, and Val715, suggesting that the molecular basis for the interaction of each form of the receptor with insulin differs. We also examined the effects of alanine mutations of Asn15, Gln34, and Phe89 on insulin-induced receptor autophosphorylation. They had no effect on the maximal response to insulin but produced an increase in the EC50 commensurate with their effect on the affinity of the receptor for insulin.
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Affiliation(s)
- Jonathan Whittaker
- Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106-4906, USA.
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403
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Borisov NM, Markevich NI, Hoek JB, Kholodenko BN. Signaling through receptors and scaffolds: independent interactions reduce combinatorial complexity. Biophys J 2005; 89:951-66. [PMID: 15923229 PMCID: PMC1366644 DOI: 10.1529/biophysj.105.060533] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
After activation, many receptors and their adaptor proteins act as scaffolds displaying numerous docking sites and engaging multiple targets. The consequent assemblage of a variety of protein complexes results in a combinatorial increase in the number of feasible molecular species presenting different states of a receptor-scaffold signaling module. Tens of thousands of such microstates emerge even for the initial signal propagation events, greatly impeding a quantitative analysis of networks. Here, we demonstrate that the assumption of independence of molecular events occurring at distinct sites enables us to approximate a mechanistic picture of all possible microstates by a macrodescription of states of separate domains, i.e., macrostates that correspond to experimentally verifiable variables. This analysis dissects a highly branched network into interacting pathways originated by protein complexes assembled on different sites of receptors and scaffolds. We specify when the temporal dynamics of any given microstate can be expressed using the product of the relative concentrations of individual sites. The methods presented here are equally applicable to deterministic and stochastic calculations of the temporal dynamics. Our domain-oriented approach drastically reduces the number of states, processes, and kinetic parameters to be considered for quantification of complex signaling networks that propagate distinct physiological responses.
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Affiliation(s)
- Nikolay M Borisov
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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404
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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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405
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Urizar E, Montanelli L, Loy T, Bonomi M, Swillens S, Gales C, Bouvier M, Smits G, Vassart G, Costagliola S. Glycoprotein hormone receptors: link between receptor homodimerization and negative cooperativity. EMBO J 2005; 24:1954-64. [PMID: 15889138 PMCID: PMC1142614 DOI: 10.1038/sj.emboj.7600686] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Accepted: 04/27/2005] [Indexed: 11/09/2022] Open
Abstract
The monomeric model of rhodopsin-like G protein-coupled receptors (GPCRs) has progressively yielded the floor to the concept of GPCRs being oligo(di)mers, but the functional correlates of dimerization remain unclear. In this report, dimers of glycoprotein hormone receptors were demonstrated in living cells, with a combination of biophysical (bioluminescence resonance energy transfer and homogenous time resolved fluorescence/fluorescence resonance energy transfer), functional and biochemical approaches. Thyrotropin (TSHr) and lutropin (LH/CGr) receptors form homo- and heterodimers, via interactions involving primarily their heptahelical domains. The large hormone-binding ectodomains were dispensable for dimerization but modulated protomer interaction. Dimerization was not affected by agonist binding. Observed functional complementation indicates that TSHr dimers may function as a single functional unit. Finally, heterologous binding-competition studies, performed with heterodimers between TSHr and LH/CG-TSHr chimeras, demonstrated the unsuspected existence of strong negative cooperativity of hormone binding. Tracer desorption experiments indicated an allosteric behavior in TSHr and, to a lesser extent, in LH/CGr and FSHr homodimers. This study is the first report of homodimerization associated with negative cooperativity in rhodopsin-like GPCRs. As such, it may warrant revisitation of allosterism in the whole GPCR family.
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Affiliation(s)
- Eneko Urizar
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
- Departamento de Neurofarmacología, Facultad de Farmacia, Universidad del País Vasco, Vitoria-Gasteiz, Spain
| | - Lucia Montanelli
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
| | - Tiffany Loy
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
| | - Marco Bonomi
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
- Institute of Endocrine Sciences, Istituto Auxologico Italiano IRCCS and Ospedale Maggiore di Milano IRCCS, Italy
| | - Stéphane Swillens
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
| | - Céline Gales
- Department of Biochemistry, Université de Montréal, succursale Centre-Ville, Montréal, Québec, Canada
| | - Michel Bouvier
- Department of Biochemistry, Université de Montréal, succursale Centre-Ville, Montréal, Québec, Canada
| | - Guillaume Smits
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
- Service de Génétique Médicale, Hôpital Erasme, Brussels, Belgium
| | - Gilbert Vassart
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
- Service de Génétique Médicale, Hôpital Erasme, Brussels, Belgium
| | - Sabine Costagliola
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, Brussels, Belgium
- IRIBHM, Université Libre de Bruxelles, Campus Erasme, 808 Route de Lennik, 1070 Bruxelles, Belgium. Tel.: +32 2 555 4169; Fax: +32 2 555 4212; E-mail:
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406
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Chakravarty A, Hinrichsen J, Whittaker L, Whittaker J. Rescue of ligand binding of a mutant IGF-I receptor by complementation. Biochem Biophys Res Commun 2005; 331:74-7. [PMID: 15845360 DOI: 10.1016/j.bbrc.2005.03.122] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Indexed: 11/26/2022]
Abstract
The IGF-I receptor binds IGF-I with complex kinetics characterized by a curvilinear Scatchard plot, suggesting receptor heterogeneity and apparent negative cooperativity. To explore the molecular mechanisms underlying these properties, we have characterized the binding of a hybrid receptor formed from a wild-type receptor monomer and a mutant receptor monomer devoid of binding activity. Receptor hybrids were generated by transient co-transfection of cDNAs encoding wild-type and mutant receptors with unique epitope tags. Hybrid receptors were purified from transfected cells by sequential immuno-affinity chromatography and their ligand-binding properties were determined. Complementation produced a hybrid with near wild-type affinity. Dissociation studies demonstrated that the hybrid did not exhibit negative cooperativity.
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Affiliation(s)
- Anders Chakravarty
- Receptor Biology Laboratory, Novo Nordisk A/S, Hagedorn Research Institute, DK-2820 Gentofte, Denmark
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407
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Wan ZL, Huang K, Xu B, Hu SQ, Wang S, Chu YC, Katsoyannis PG, Weiss MA. Diabetes-Associated Mutations in Human Insulin: Crystal Structure and Photo-Cross-Linking Studies of A-Chain Variant InsulinWakayama†,‡. Biochemistry 2005; 44:5000-16. [PMID: 15794638 DOI: 10.1021/bi047585k] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Naturally occurring mutations in insulin associated with diabetes mellitus identify critical determinants of its biological activity. Here, we describe the crystal structure of insulin Wakayama, a clinical variant in which a conserved valine in the A chain (residue A3) is substituted by leucine. The substitution occurs within a crevice adjoining the classical receptor-binding surface and impairs receptor binding by 500-fold, an unusually severe decrement among mutant insulins. To resolve whether such decreased activity is directly or indirectly mediated by the variant side chain, we have determined the crystal structure of Leu(A3)-insulin and investigated the photo-cross-linking properties of an A3 analogue containing p-azidophenylalanine. The structure, characterized in a novel crystal form as an R(6) zinc hexamer at 2.3 A resolution, is essentially identical to that of the wild-type R(6) hexamer. The variant side chain remains buried in a nativelike crevice with small adjustments in surrounding side chains. The corresponding photoactivatable analogue, although of low affinity, exhibits efficient cross-linking to the insulin receptor. The site of photo-cross-linking lies within a 14 kDa C-terminal domain of the alpha-subunit. This domain, unrelated in sequence to the major insulin-binding region in the N-terminal L1 beta-helix, is also contacted by photoactivatable probes at positions A8 and B25. Packing of Val(A3) at this interface may require a conformational change in the B chain to expose the A3-related crevice. The structure of insulin Wakayama thus evokes the reasoning of Sherlock Holmes in "the curious incident of the dog in the night": the apparent absence of structural perturbations (like the dog that did not bark) provides a critical clue to the function of a hidden receptor-binding surface.
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Affiliation(s)
- Zhu-li Wan
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4935, USA
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408
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Opazo JC, Palma RE, Melo F, Lessa EP. Adaptive evolution of the insulin gene in caviomorph rodents. Mol Biol Evol 2005; 22:1290-8. [PMID: 15728738 DOI: 10.1093/molbev/msi117] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Insulin is a conservative molecule among mammals, maintaining both its structure and function. Rodents that belong to the Suborder Hystricognathi represent an exception, having a very divergent molecule with unusual physiological properties. In this work, we analyzed the evolutionary pattern of the insulin gene in caviomorph rodents (South American hystricomorph rodents). We found that these rodents have higher rates of nonsynonymous:synonymous substitutions (d(N)/d(S)) than nonhystricomorph rodents and that values are heterogeneous inside the group. We estimated codons under positive selection, specifically the second binding site (A13 and B17) and others related with hexamerization (B18, B20, and B22). In the monomer structure, all selected sites formed a single patch around the second binding site. In the hexamer structure, these amino acids were grouped into three major patches. In this structure, contacts between B chains involved all selected sites (except B18), and between faces in the center of the molecule, all contacts were among selected sites. While there is no clear hypothesis regarding the cause of this drastic change, experimental evidence does show that this group of rodents has some peculiarities in growth function, and, whether coincidental or not, these changes appeared together with important changes in life-history traits.
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Affiliation(s)
- Juan C Opazo
- Center for Advanced Studies in Ecology and Biodiversity, Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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409
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Abstract
I present here a personal perspective on more than three decades of research into the structural biology of the insulin-receptor interaction. The solution of the three-dimensional structure of insulin in 1969 provided a detailed understanding of the insulin surfaces involved in self-assembly. In subsequent years, hundreds of insulin analogues were prepared by insulin chemists and molecular biologists, with the goal of relating the structure to the biological function of the molecule. The design of methods for direct receptor-binding studies in the 1970s, and the cloning of the receptor in the mid 1980s, provided the required tools for detailed structure-function studies. In the absence of a full three-dimensional structure of the insulin-receptor complex, I attempt to assemble the existing pieces of the puzzle generated by our and other laboratories, in order to generate a plausible mechanistic model of the insulin-receptor interaction that explains its kinetics and negative cooperativity.
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Affiliation(s)
- Pierre De Meyts
- Receptor Biology Laboratory, Hagedorn Research Institute, Niels Steensens Vej 6, DK-2820 Gentofte, Denmark.
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410
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Mazitschek R, Giannis A. Inhibitors of angiogenesis and cancer-related receptor tyrosine kinases. Curr Opin Chem Biol 2005; 8:432-41. [PMID: 15288254 DOI: 10.1016/j.cbpa.2004.06.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inhibition of tumor angiogenesis is an attractive target in cancer therapy. In this context, receptor tyrosine kinases play a pivotal role. Extensive efforts have been made to identify and develop small-molecule inhibitors of these central signaling proteins. Some of these compounds have already passed or are currently in clinical trials to investigate their applicability as anti-cancer drugs. However, the high expectations that are set in antiangiogenic therapy have not yet been accomplished. But there are also new and exciting opportunities for cancer treatment by combining antiangiogenic molecules with newly emerging therapeutics.
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Affiliation(s)
- Ralph Mazitschek
- Institute for Chemistry and Cell Biology, Harvard Medical School, 250 Longwood Avenue, Boston, Massachusetts 02115, USA.
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411
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Wan Z, Xu B, Huang K, Chu YC, Li B, Nakagawa SH, Qu Y, Hu SQ, Katsoyannis PG, Weiss MA. Enhancing the Activity of Insulin at the Receptor Interface: Crystal Structure and Photo-Cross-Linking of A8 Analogues. Biochemistry 2004; 43:16119-33. [PMID: 15610006 DOI: 10.1021/bi048223f] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The receptor-binding surface of insulin is broadly conserved, reflecting its evolutionary optimization. Neighboring positions nevertheless offer an opportunity to enhance activity, through either transmitted structural changes or introduction of novel contacts. Nonconserved residue A8 is of particular interest as Thr(A8) --> His substitution (a species variant in birds and fish) augments the potency of human insulin. Diverse A8 substitutions are well tolerated, suggesting that the hormone-receptor interface is not tightly packed at this site. To resolve whether enhanced activity is directly or indirectly mediated by the variant A8 side chain, we have determined the crystal structure of His(A8)-insulin and investigated the photo-cross-linking properties of an A8 analogue containing p-azidophenylalanine. The structure, characterized as a T(3)R(3)(f) zinc hexamer at 1.8 A resolution, is essentially identical to that of native insulin. The photoactivatable analogue exhibits efficient cross-linking to the insulin receptor. The site of cross-linking lies within a 14 kDa C-terminal domain of the alpha-subunit. This contact, to our knowledge the first to be demonstrated from the A chain, is inconsistent with a recent model of the hormone-receptor complex derived from electron microscopy. Optimizing the binding interaction of a nonconserved side chain on the surface of insulin may thus enhance its activity.
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Affiliation(s)
- Zhuli Wan
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4935, USA
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412
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de Jong KP, Hoedemakers RMJ, Fidler V, Bijzet J, Limburg PC, Peeters PMJG, de Vries EGE, Slooff MJH. Portal and systemic serum growth factor and acute-phase response after laparotomy or partial hepatectomy in patients with colorectal liver metastases: a prognostic role for C-reactive protein and hepatocyte growth factor. Scand J Gastroenterol 2004; 39:1141-8. [PMID: 15545174 DOI: 10.1080/00365520410009609] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Growth factors play a role in wound healing and tumour growth. The aim of this study was to compare the effect of partial hepatectomy (PH) and laparotomy on serum levels of growth factors and acute-phase proteins in patients with colorectal liver metastases and to correlate these levels with prognosis after PH. METHODS Epidermal growth factor (EGF), hepatocyte growth factor (HGF), insulin like growth factor-I (IGF-I), insulin, interleukin-6 (IL-6), C-reactive protein (CRP) and serum amyloid-A (SAA) were determined in portal and systemic serum in 24 PH patients and 9 laparotomy patients. RESULTS No differences were found in the clinicopathological characteristics of PH and laparotomy patients with the exception of the number of metastases, blood loss and operation time. The response of SAA, CRP and IGF-I was lower in PH patients than in laparotomy patients (P < 0.02). PH was associated with a higher IL-6 (P = 0.02) and HGF (P = 0.055) response than laparotomy. A higher HGF and CRP response was associated with a poorer prognosis. Total IGF-I was negatively correlated with the resected liver volume (r = -0.48, P < 0.05). CONCLUSIONS PH is associated with a lower acute-phase and total IGF-I response and a higher HGF and IL-6 response compared with laparotomy. HGF and CRP responses had an influence on the prognosis.
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Affiliation(s)
- K P de Jong
- Department of Surgery, Division of Hepato-Pancreato-Biliary Surgery & Liver Transplantation, University Hospital and Medical Faculty of the University of Groningen, 9700 RB Groningen, The Netherlands.
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413
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Mattson MP, Maudsley S, Martin B. A neural signaling triumvirate that influences ageing and age-related disease: insulin/IGF-1, BDNF and serotonin. Ageing Res Rev 2004; 3:445-64. [PMID: 15541711 DOI: 10.1016/j.arr.2004.08.001] [Citation(s) in RCA: 216] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Accepted: 08/06/2004] [Indexed: 12/24/2022]
Abstract
The ageing process and its associated diseases all involve perturbed energy metabolism, oxidative damage, and an impaired ability of the organism and its cells to cope with adversity. We propose that some specific signaling pathways in the brain may be important determinants of health during ageing. Among such specific signaling modalities are those activated in neurons by insulin-like growth factors (IGFs), brain-derived neurotrophic factor (BDNF) and serotonin. This triumvirate may be particularly important because of their cooperative influence on energy metabolism, food intake, stress responses and cardiovascular function. The health benefits to the periphery and central nervous system of dietary restriction and exercise may be mediated by this triumvirate of signals in the brain. At the molecular level, BDNF, serotonin and IGFs can all stimulate the production of proteins involved in cellular stress adaptation, growth and repair, neurogenesis, learning and memory and cell survival. The importance of this triumvirate is emphasized when it is seen that their general roles in energy metabolism, stress adaptation and disease resistance are conserved among diverse organisms consistent with important roles in the ageing process.
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Affiliation(s)
- Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, USA.
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414
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Sato M, Furuike T, Sadamoto R, Fujitani N, Nakahara T, Niikura K, Monde K, Kondo H, Nishimura SI. Glycoinsulins: Dendritic Sialyloligosaccharide-Displaying Insulins Showing a Prolonged Blood-Sugar-Lowering Activity. J Am Chem Soc 2004; 126:14013-22. [PMID: 15506764 DOI: 10.1021/ja046426l] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mono-, di-, and trisialyloligosaccharides were introduced to mutant insulins through enzymatic reactions. Sugar chains were sialylated by alpha2,6-sialyltransferase (alpha2,6-SiaT) via an accessible glutamine residue at the N-terminus of the B-chain attached by transglutaminase (TGase). Sia2,6-di-LacNAc-Ins(B-F1Q) and Sia2,6-tri-LacNAc-Ins(B-F1Q), displaying two and three sialyl-N-acetyllactosamines, respectively, were administered to hyperglycemic mice. Both branched glycoinsulins showed prolonged glucose-lowering effects compared to native or lactose-carrying insulins, showing that sialic acid is important in obtaining a prolonged effect. Sia2,6-tri-LacNAc-Ins(B-F1Q), in particular, induced a significant delay in the recovery of glucose levels.
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Affiliation(s)
- Masaaki Sato
- Division of Biological Sciences, Graduate School of Science, Frontier Research Center for Post-Genomic Science and Technology, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan
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415
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Denley A, Bonython ER, Booker GW, Cosgrove LJ, Forbes BE, Ward CW, Wallace JC. Structural determinants for high-affinity binding of insulin-like growth factor II to insulin receptor (IR)-A, the exon 11 minus isoform of the IR. Mol Endocrinol 2004; 18:2502-12. [PMID: 15205474 DOI: 10.1210/me.2004-0183] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The insulin receptor (IR) lacking the alternatively spliced exon 11 (IR-A) is preferentially expressed in fetal and cancer cells. The IR-A has been identified as a high-affinity receptor for insulin and IGF-II but not IGF-I, which it binds with substantially lower affinity. Several cancer cell types that express the IR-A also overexpress IGF-II, suggesting a possible autocrine proliferative loop. To determine the regions of IGF-I and IGF-II responsible for this differential affinity, chimeras were made where the C and D domains were exchanged between IGF-I and IGF-II either singly or together. The abilities of these chimeras to bind to, and activate, the IR-A were investigated. We also investigated the ability of these chimeras to bind and activate the IR exon 11+ isoform (IR-B) and as a positive control, the IGF-I receptor (IGF-1R). We show that the C domain and, to a lesser extent, the D domains represent the principal determinants of the binding differences between IGF-I and IGF-II to IR-A. The C and D domains of IGF-II promote higher affinity binding to the IR-A than the equivalent domains of IGF-I, resulting in an affinity close to that of insulin for the IR-A. The C and D domains also regulate the IR-B binding specificity of the IGFs in a similar manner, although the level of binding for all IGF ligands to IR-B is lower than to IR-A. In contrast, the C and D domains of IGF-I allow higher affinity binding to the IGF-1R than the analogous domains of IGF-II. Activation of IGF-1R by the chimeras reflected their binding affinities whereas the phosphorylation of the two IR isoforms was more complex.
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Affiliation(s)
- Adam Denley
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide 5005, Australia
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416
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Frystyk J. Free insulin-like growth factors -- measurements and relationships to growth hormone secretion and glucose homeostasis. Growth Horm IGF Res 2004; 14:337-375. [PMID: 15336229 DOI: 10.1016/j.ghir.2004.06.001] [Citation(s) in RCA: 241] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
IGF-I is a multipotent growth factor with important actions on normal tissue growth and regeneration. In addition, IGF-I has been suggested to have beneficial effects on glucose homeostasis due to its glucose lowering and insulin sensitizing actions. However, not all effects of IGF-I are considered to be favorable; thus, epidemiological studies suggest that IGF-I is also involved in the development of common cancers, atherosclerosis and type 2 diabetes. The biological actions of IGF-I are modulated by at least six IGF-binding proteins, which bind approximately 99% of the circulating IGF-I pool. So far, most in vivo studies have used serum or plasma total (extractable IGF-I) as an estimate of the bioactivity of IGF-I in vivo. However, within the last decade, validated assays for measurement of free IGF-I have been described. This review aims to discuss the current assays for free IGF-I and their advances in relation to the traditional measurement of total IGF-I. The literature overview will focus on the role of circulating free versus total IGF-I in the feedback regulation of GH release, and the possible involvement of the circulating IGF-system in glucose homeostasis.
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Affiliation(s)
- Jan Frystyk
- Medical Research Laboratories and Medical Department M, Aarhus University Hospital, Norrebrogade, Aarhus, Denmark.
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417
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Xu B, Hu SQ, Chu YC, Huang K, Nakagawa SH, Whittaker J, Katsoyannis PG, Weiss MA. Diabetes-associated mutations in insulin: consecutive residues in the B chain contact distinct domains of the insulin receptor. Biochemistry 2004; 43:8356-72. [PMID: 15222748 DOI: 10.1021/bi0497796] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
How insulin binds to and activates the insulin receptor has long been the subject of speculation. Of particular interest are invariant phenylalanine residues at consecutive positions in the B chain (residues B24 and B25). Sites of mutation causing diabetes mellitus, these residues occupy opposite structural environments: Phe(B25) projects from the surface of insulin, whereas Phe(B24) packs against the core. Despite these differences, site-specific cross-linking suggests that each contacts the insulin receptor. Photoactivatable derivatives of insulin containing respective p-azidophenylalanine substitutions at positions B24 and B25 were synthesized in an engineered monomer (DKP-insulin). On ultraviolet irradiation each derivative cross-links efficiently to the receptor. Packing of Phe(B24) at the receptor interface (rather than against the core of the hormone) may require a conformational change in the B chain. Sites of cross-linking in the receptor were mapped to domains by Western blot. Remarkably, whereas B25 cross-links to the C-terminal domain of the alpha subunit in accord with previous studies (Kurose, T., et al. (1994) J. Biol. Chem. 269, 29190-29197), the probe at B24 cross-links to its N-terminal domain (the L1 beta-helix). Our results demonstrate that consecutive residues in insulin contact widely separated sequences in the receptor and in turn suggest a revised interpretation of electron-microscopic images of the complex. By tethering the N- and C-terminal domains of the extracellular alpha subunit, insulin is proposed to stabilize an active conformation of the disulfide-linked transmembrane tyrosine kinase.
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Affiliation(s)
- Bin Xu
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4935, USA
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418
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Santolaya-Forgas J, De Leon JA, Cullen Hopkins R, Castracane VD, Kauffman RP, Sifuentes GA. Low Pregnancy-Associated Plasma Protein-A at 10 +1 to 14 +6 Weeks of Gestation and a Possible Mechanism Leading to Miscarriage. Fetal Diagn Ther 2004; 19:456-61. [PMID: 15305104 DOI: 10.1159/000079000] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2003] [Accepted: 10/05/2003] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To compare pregnancy-associated plasma protein-A (PAPP-A) serum levels at 10(+1) to 14(+6) weeks gestation in groups of patients with different obstetrical outcomes. PATIENTS AND METHODS The medical records of women who had consented to donate blood for biochemical research purposes while their pregnancies were uncomplicated were reviewed to define the clinical groups. After the clinical groups were defined, the donated maternal serum samples were thawed and PAPP-A measured by ELISA. ANOVA was used to compare mean values within groups. RESULT All groups had similar gestational ages at blood donation (overall mean 12.5 weeks; no difference in gestational age was found within groups, p = 0.18). The overall PAPP-A serum level was 2.01 mIU/ml with only the spontaneous abortion group having a statistical different PAPP-A level (0.09 mIU/ml; p < 0.001). CONCLUSION These data suggest that those women who experienced spontaneous abortions had significantly different mean PAPP-A serum levels at 10(+1) to 14(+6) weeks gestation. Several lines of evidence suggest that downregulation of insulin-like growth factor-II availability due to a decreased PAPP-A serum level may be the cause of spontaneous abortion in these women.
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Affiliation(s)
- J Santolaya-Forgas
- Division of Reproductive Genetics, Fetal Medicine and Ultrasound, Department of Obstetrics and Gynecology, Amarillo Women's Health Research Institute, Texas Tech University Health Sciences Center, Amarillo, Tex., USA.
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419
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Huang K, Xu B, Hu SQ, Chu YC, Hua QX, Qu Y, Li B, Wang S, Wang RY, Nakagawa SH, Theede AM, Whittaker J, De Meyts P, Katsoyannis PG, Weiss MA. How Insulin Binds: the B-Chain α-Helix Contacts the L1 β-Helix of the Insulin Receptor. J Mol Biol 2004; 341:529-50. [PMID: 15276842 DOI: 10.1016/j.jmb.2004.05.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2004] [Revised: 05/11/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
Binding of insulin to the insulin receptor plays a central role in the hormonal control of metabolism. Here, we investigate possible contact sites between the receptor and the conserved non-polar surface of the B-chain. Evidence is presented that two contiguous sites in an alpha-helix, Val(B12) and Tyr(B16), contact the receptor. Chemical synthesis is exploited to obtain non-standard substitutions in an engineered monomer (DKP-insulin). Substitution of Tyr(B16) by an isosteric photo-activatable derivative (para-azido-phenylalanine) enables efficient cross-linking to the receptor. Such cross-linking is specific and maps to the L1 beta-helix of the alpha-subunit. Because substitution of Val(B12) by larger side-chains markedly impairs receptor binding, cross-linking studies at B12 were not undertaken. Structure-function relationships are instead probed by side-chains of similar or smaller volume: respective substitution of Val(B12) by alanine, threonine, and alpha-aminobutyric acid leads to activities of 1(+/-0.1)%, 13(+/-6)%, and 14(+/-5)% (relative to DKP-insulin) without disproportionate changes in negative cooperativity. NMR structures are essentially identical with native insulin. The absence of transmitted structural changes suggests that the low activities of B12 analogues reflect local perturbation of a "high-affinity" hormone-receptor contact. By contrast, because position B16 tolerates alanine substitution (relative activity 34(+/-10)%), the contribution of this neighboring interaction is smaller. Together, our results support a model in which the B-chain alpha-helix, functioning as an essential recognition element, docks against the L1 beta-helix of the insulin receptor.
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Affiliation(s)
- Kun Huang
- Department of Biochemistry, Case Western Reserve School of Medicine, Cleveland OH 44106-4935, USA
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420
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Affiliation(s)
- Michael N Pollak
- Department of Oncology, McGill University and Lady Davis Research Institute, 3999 Rue Côte Sainte Catherine, Montreal, Quebec H3T 1E2, Canada.
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421
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De Ceuninck F, Caliez A, Dassencourt L, Anract P, Renard P. Pharmacological disruption of insulin-like growth factor 1 binding to IGF-binding proteins restores anabolic responses in human osteoarthritic chondrocytes. Arthritis Res Ther 2004; 6:R393-403. [PMID: 15380039 PMCID: PMC546277 DOI: 10.1186/ar1201] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Revised: 05/05/2004] [Accepted: 05/19/2004] [Indexed: 12/20/2022] Open
Abstract
Insulin-like growth factor 1 (IGF-1) has poor anabolic efficacy in cartilage in osteoarthritis (OA), partly because of its sequestration by abnormally high levels of extracellular IGF-binding proteins (IGFBPs). We studied the effect of NBI-31772, a small molecule that inhibits the binding of IGF-1 to IGFBPs, on the restoration of proteoglycan synthesis by human OA chondrocytes. IGFBPs secreted by human OA cartilage or cultured chondrocytes were analyzed by western ligand blot. The ability of NBI-31772 to displace IGF-1 from IGFBPs was measured by radiobinding assay. Anabolic responses in primary cultured chondrocytes were assessed by measuring the synthesis of proteoglycans in cetylpyridinium-chloride-precipitable fractions of cell-associated and secreted 35S-labeled macromolecules. The penetration of NBI-31772 into cartilage was measured by its ability to displace 125I-labeled IGF-1 from cartilage IGFBPs. We found that IGFBP-3 was the major IGFBP secreted by OA cartilage explants and cultured chondrocytes. NBI-31772 inhibited the binding of 125I-labeled IGF-1 to IGFBP-3 at nanomolar concentrations. It antagonized the inhibitory effect of IGFBP-3 on IGF-1-dependent proteoglycan synthesis by rabbit chondrocytes. The addition of NBI-31772 to human OA chondrocytes resulted in the restoration or potentiation of IGF-1-dependent proteoglycan synthesis, depending on the IGF-1 concentrations. However, NBI-31772 did not penetrate into cartilage explants. This study shows that a new pharmacological approach that uses a small molecule inhibiting IGF-1/IGFBP interaction could restore or potentiate proteoglycan synthesis in OA chondrocytes, thereby opening exciting possibilities for the treatment of OA and, potentially, of other joint-related diseases.
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422
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Abstract
Possible insulin binding sites for D-glucose have been investigated theoretically by docking and molecular dynamics (MD) simulations. Two different docking programs for small molecules were used; Multiple Copy Simultaneous Search (MCSS) and Solvation Energy for Exhaustive Docking (SEED) programs. The configurations resulting from the MCSS search were evaluated with a scoring function developed to estimate the binding free energy. SEED calculations were performed using various values for the dielectric constant of the solute. It is found that scores emphasizing non-polar interactions gave a preferential binding site in agreement with that inferred from recent fluorescence and NMR NOESY experiments. The calculated binding affinity of -1.4 to -3.5 kcal/mol is within the measured range of -2.0 +/- 0.5 kcal/mol. The validity of the binding site is suggested by the dynamical stability of the bound glucose when examined with MD simulations with explicit solvent. Alternative binding sites were found in the simulations and their relative stabilities were estimated. The motions of the bound glucose during molecular dynamics simulations are correlated with the motions of the insulin side chains that are in contact with it and with larger scale insulin motions. These results raise the question of whether glucose binding to insulin could play a role in its activity. The results establish the complementarity of molecular dynamics simulations and normal mode analyses with the search for binding sites proposed with small molecule docking programs.
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Affiliation(s)
- Vincent Zoete
- Laboratoire de Chimie Biophysique, ISIS/Université Louis Pasteur, Strasbourg Cedex, France
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423
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Xu B, Hu SQ, Chu YC, Wang S, Wang RY, Nakagawa SH, Katsoyannis PG, Weiss MA. Diabetes-associated mutations in insulin identify invariant receptor contacts. Diabetes 2004; 53:1599-602. [PMID: 15161767 DOI: 10.2337/diabetes.53.6.1599] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in human insulin cause an autosomal-dominant syndrome of diabetes and fasting hyperinsulinemia. We demonstrate by residue-specific photo cross-linking that diabetes-associated mutations occur at receptor-binding sites. The studies use para-azido-phenylalanine, introduced at five sites by total protein synthesis. Because two such sites (Val(A3) and Phe(B24)) are largely buried in crystal structures of the free hormone, their participation in receptor binding is likely to require a conformational change to expose a hidden functional surface. Our results demonstrate that this surface spans both chains of the insulin molecule and includes sites of rare human mutations that cause diabetes.
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Affiliation(s)
- Bin Xu
- Case Western Reserve University, Department of Biochemistry, 10900 Euclid Ave., SOM Room W427, Cleveland, OH 44106-4935, USA
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424
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Samani AA, Chevet E, Fallavollita L, Galipeau J, Brodt P. Loss of Tumorigenicity and Metastatic Potential in Carcinoma Cells Expressing the Extracellular Domain of the Type 1 Insulin-Like Growth Factor Receptor. Cancer Res 2004; 64:3380-5. [PMID: 15150088 DOI: 10.1158/0008-5472.can-03-3780] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The receptor for the type 1 insulin-like growth factor (IGF-IR) was identified as a major regulator of the malignant phenotype and a target for cancer therapy. In the present study, a novel IGF-IR mutant consisting of the entire extracellular domain of the receptor (IGFIR(933)) was genetically engineered and expressed in highly metastatic H-59 murine lung carcinoma cells. We show here that the cells expressed a truncated heterotetramer (beta(m)-alpha-alpha-beta(m)) that was secreted into the medium and could neutralize the effects of exogenous IGF-I, thus diminishing IGF-I-induced signaling and blocking IGF-I-mediated cellular functions such as cell proliferation, invasion, and survival. In vivo, tumor incidence and growth rate were markedly reduced in mice inoculated s.c. with H-59/IGFIR(933) cells. Moreover, after the intrasplenic/portal inoculation of these cells, there was a 90% reduction in the incidence of hepatic metastases and a significant increase in the long-term, disease-free survival of the mice compared with controls. Our results identify the IGFIR(933) as a potent antitumorigenic and antimetastatic agent with potential applications for cancer gene therapy.
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Affiliation(s)
- Amir Abbas Samani
- Department of Medicine, McGill University Health Center, McGill University, Montreal, Quebec, Canada
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425
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Bennasroune A, Gardin A, Aunis D, Crémel G, Hubert P. Tyrosine kinase receptors as attractive targets of cancer therapy. Crit Rev Oncol Hematol 2004; 50:23-38. [PMID: 15094157 DOI: 10.1016/j.critrevonc.2003.08.004] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2003] [Indexed: 12/24/2022] Open
Abstract
Receptor tyrosine kinases (RTKs) are the main mediators of the signaling network that transmit extracellular signals into the cell, and control cellular differentiation and proliferation. Recent and rapid advances in our understanding of cellular signaling by receptor tyrosine kinases, in normal and malignant cells, have brought to light the potential of RTKs as selective anti-cancer targets. Their activity is normally tightly controlled and regulated. Overexpression of RTK proteins or functional alterations caused by mutations in the corresponding genes or abnormal stimulation by autocrine growth factor loops contribute to constitutive RTK signaling, resulting in dysregulated cell growth and cancer. The mechanisms of uncontrolled RTK signaling that leads to cancer has provided the rationale for anti-RTK drug development. Herceptin, Gleevec, and Iressa are the first examples of drugs which have successfully translated basic research on oncogenes into cancer therapeutics. RTKs can be viewed as multifunctional targets, and strategies towards the prevention and inhibition of RTK signaling include antibodies, antagonist ligands, small molecule inhibitors of protein kinase activity, and inhibitors of protein-protein interactions. Progresses in the field of rational drug design and computational chemistry will vastly benefit from the availability of increasing structural knowledge of both the kinase domains and the ligand-binding sites of these receptors.
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Affiliation(s)
- Amar Bennasroune
- INSERM Unit 575, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France
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426
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Watson RT, Kanzaki M, Pessin JE. Regulated membrane trafficking of the insulin-responsive glucose transporter 4 in adipocytes. Endocr Rev 2004; 25:177-204. [PMID: 15082519 DOI: 10.1210/er.2003-0011] [Citation(s) in RCA: 309] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Since the discovery of insulin roughly 80 yr ago, much has been learned about how target cells receive, interpret, and respond to this peptide hormone. For example, we now know that insulin activates the tyrosine kinase activity of its cell surface receptor, thereby triggering intracellular signaling cascades that regulate many cellular processes. With respect to glucose homeostasis, these include the function of insulin to suppress hepatic glucose production and to increase glucose uptake in muscle and adipose tissues, the latter resulting from the translocation of the glucose transporter 4 (GLUT4) to the cell surface membrane. Although simple in broad outline, elucidating the molecular intricacies of these receptor-signaling pathways and membrane-trafficking processes continues to challenge the creative ingenuity of scientists, and many questions remain unresolved, or even perhaps unasked. The identification and functional characterization of specific molecules required for both insulin signaling and GLUT4 vesicle trafficking remain key issues in our pursuit of developing specific therapeutic agents to treat and/or prevent this debilitating disease process. To this end, the combined efforts of numerous research groups employing a range of experimental approaches has led to a clearer molecular picture of how insulin regulates the membrane trafficking of GLUT4.
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Affiliation(s)
- Robert T Watson
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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427
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Surmacz E. Growth factor receptors as therapeutic targets: strategies to inhibit the insulin-like growth factor I receptor. Oncogene 2003; 22:6589-97. [PMID: 14528284 DOI: 10.1038/sj.onc.1206772] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Neoplastic transformation is often related to abnormal activation of growth factor receptors and their signaling pathways. The concept of targeting specific tumorigenic receptors and/or signaling molecules has been validated by the development and successful clinical application of drugs acting against the epidermal growth factor receptor 2 (HER2/neu, Erb2), the epidermal growth factor receptor 1 (EGFR, HER1), the Brc-Abl kinase, the platelet-derived growth factor receptor, and c-kit. This review will focus on the next promising therapeutic target, the insulin-like growth factor I receptor (IGF-IR). IGF-IR has been implicated in a number of neoplastic diseases, including several common carcinomas. From a pharmaceutical standpoint, of particular importance is that IGF-IR appears to be required for many transforming agents (genetic, viral, chemical) to act, but is not obligatory for the function of normal adult cells. The tumorigenic potential of IGF-IR is mediated through its antiapoptotic and transforming signaling, and in some cases through induction of prometastatic pathways. Preclinical studies demonstrated that downregulation of IGF-IR reversed the neoplastic phenotype and sensitized cells to antitumor treatments. The strategies to block IGF-IR function employed anti-IGF-IR antibodies, small-molecule inhibitors of the IGF-IR tyrosine kinase, antisense oligodeoxynucleotides and antisense RNA, small inhibitory RNA, triple helix, dominant-negative mutants, and various compounds reducing ligand availability. The experience with these strategies combined with the knowledge gained with current anti-growth factor receptor drugs should streamline the development of anti-IGF-IR therapeutics.
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Affiliation(s)
- Eva Surmacz
- Kimmel Cancer Center, Thomas Jefferson University, 233 S 10th St., BLSB 631, Philadelphia, PA 19107, USA.
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428
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Ben-Shlomo I, Yu Hsu S, Rauch R, Kowalski HW, Hsueh AJW. Signaling receptome: a genomic and evolutionary perspective of plasma membrane receptors involved in signal transduction. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2003; 2003:RE9. [PMID: 12815191 DOI: 10.1126/stke.2003.187.re9] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Intercellular communication in multicellular organisms requires the relay of extracellular signals by cell surface proteins to the interiors of cells. The availability of genome sequences from humans and several model organisms has facilitated the identification of several human plasma membrane receptor families and allowed the analysis of their phylogeny. This review provides a global categorization of most known signal transduction-associated receptors as enzymes, recruiters, and latent transcription factors. The evolution of known families of human plasma membrane signaling receptors was traced in current literature and validated by sequence relatedness. This global analysis reveals themes that recur during receptor evolution and allows the formulation of hypotheses for the origins of receptors. The human receptor families involved in signaling (with the exception of channels) are presented in the Human Plasma Membrane Receptome database.
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Affiliation(s)
- Izhar Ben-Shlomo
- Division of Reproductive Biology, Department of Obstetrics and Gynecology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305-5317, USA
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429
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Ben-Shlomo I, Yu Hsu S, Rauch R, Kowalski HW, Hsueh AJW. Signaling Receptome: A Genomic and Evolutionary Perspective of Plasma Membrane Receptors Involved in Signal Transduction. Sci Signal 2003. [DOI: 10.1126/scisignal.1872003re9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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430
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Abstract
The insulin-like growth factor (IGF) family of ligands, binding proteins and receptors is an important growth factor system involved in both the development of the organism and the maintenance of normal function of many cells of the body. The system also has powerful anti-apoptotic effects. More recently, evidence has accrued to demonstrate that the IGFs play an important role in cancer. Individuals with serum IGF-II levels in the upper quartile of the normal range (and IGF binding protein-3 levels in the lower quartiles) have a relative risk for developing breast, prostate, colon and lung cancer. IGF-II is commonly expressed by tumor cells and may act as an autocrine growth factor; occasionally even reaching target tissues and causing tumor-induced hypoglycemia. The IGF-I receptor is commonly (though not always) overexpressed in many cancers, and many recent studies have identified new signaling pathways emanating from the IGF-I receptor that affect cancer cell proliferation, adhesion, migration and cell death; functions that are critical for cancer cell survival and metastases. In this review, many aspects of the IGF system and its relationship to cancer will be discussed.
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Affiliation(s)
- Derek LeRoith
- Diabetes Branch, Room 8D12, Building 10, National Institutes of Health MSC 1758, Bethesda, MD 20892-1758, USA.
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431
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Cole PA, Courtney AD, Shen K, Zhang Z, Qiao Y, Lu W, Williams DM. Chemical approaches to reversible protein phosphorylation. Acc Chem Res 2003; 36:444-52. [PMID: 12809531 DOI: 10.1021/ar0201254] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein phosphorylation catalyzed by protein kinases plays a critical role in cellular signaling. Here we review several chemical approaches to understanding protein kinases and the consequences of protein phosphorylation. We discuss the design of bisubstrate analogue inhibitors based on a dissociative transition state, the development of reagents for cross-linking protein kinases with their substrates, the chemical rescue of mutant protein tyrosine kinases, and the application of expressed protein ligation to understanding protein phosphorylation.
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Affiliation(s)
- Philip A Cole
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205, USA.
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432
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Hua QX, Nakagawa SH, Wilken J, Ramos RR, Jia W, Bass J, Weiss MA. A divergent INS protein in Caenorhabditis elegans structurally resembles human insulin and activates the human insulin receptor. Genes Dev 2003; 17:826-31. [PMID: 12654724 PMCID: PMC196032 DOI: 10.1101/gad.1058003] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Caenorhabditis elegans contains a family of putative insulin-like genes proposed to regulate dauer arrest and senescence. These sequences often lack characteristic sequence features of human insulin essential for its folding, structure, and function. Here, we describe the structure and receptor-binding properties of INS-6, a single-chain polypeptide expressed in specific neurons. Despite multiple nonconservative changes in sequence, INS-6 recapitulates an insulin-like fold. Although lacking classical receptor-binding determinants, INS-6 binds to and activates the human insulin receptor. Its activity is greater than that of an analogous single-chain human insulin analog.
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Affiliation(s)
- Qing-Xin Hua
- Department of Biochemistry, Case Western Reserve School of Medicine, Cleveland, OH 44106, USA
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