Structural Basis for the Lower Affinity of the Insulin-like Growth Factors for the Insulin Receptor

Gauguin, Lisbeth; Klaproth, Birgit; Sajid, Waseem; Andersen, Asser S.; McNeil, Kerrie A.; Forbes, Briony E.; Meyts, Pierre De

doi:10.1074/jbc.m709220200

Cited by 57 publications

(61 citation statements)

References 51 publications

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“…The [PheB26]-insulin analogue was included in this study to examine the importance of the Tyr-B26 hydroxyl group for insulin affinity, as the next analogue studied here, [NMePheB26]-insulin, featured two combined modifications: the loss of phenolic character of the B26 side chain with N-methylation of the B26NH. The [PheB26]-insulin showed 46% binding affinity that was in full agreement with data (47%) already reported for this analogue (39), clearly indicating that the loss of Tyr-B26 hydroxyl group is responsible for the reduced binding affinity of this analogue. Therefore, an even more drastic (actually to 4%) loss of affinity of the [NMePheB26]-insulin was expected, as it results from a double (side and main chain) modification of the hormone at this position.…”

Section: Impact Of Modifications On Binding Affinity Of Analogues-supporting

confidence: 79%

“…The N-methylation of the B24 amide also had a highly negative effect on the binding affinity of the respective analogue (3%). In contrast, the B26 position was much more tolerant to the modifications, with [PheB26]-insulin displaying only moderate reduction of the affinity (45.9%) (very similar to its binding affinity (47.6%), determined using an IM-9 cells binding assay (39)). N-Methylation of Tyr-B26 reduces the binding affinity of the analogue to 20.7%, and the combination of both N-methylation and the substitution of Phe for Tyr at B26 results in a very weak binding of this insulin analogue (4.2%).…”

Section: Resultsmentioning

confidence: 99%

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Non-equivalent Role of Inter- and Intramolecular Hydrogen Bonds in the Insulin Dimer Interface

Antolíková

Žáková

Turkenburg

et al. 2011

Journal of Biological Chemistry

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Apart from its role in insulin receptor (IR) activation, the C terminus of the B-chain of insulin is also responsible for the formation of insulin dimers. The dimerization of insulin plays an important role in the endogenous delivery of the hormone and in the administration of insulin to patients. Here, we investigated insulin analogues with selective N-methylations of peptide bond amides at positions B24, B25, or B26 to delineate their structural and functional contribution to the dimer interface. All N-methylated analogues showed impaired binding affinities to IR, which suggests a direct IR-interacting role for the respective amide hydrogens. The dimerization capabilities of analogues were investigated by isothermal microcalorimetry. Insulin is an important polypeptide hormone that controls a wide range of cellular processes such as the regulation of blood glucose uptake and has a large impact on protein and lipid metabolism. However, despite decades of intensive research, many questions about the structure of insulin and its mechanism of action remain. The solid state-based structural insight into the insulin molecule is limited to inactive dimeric or hexameric storage forms (1-3), whereas the insulin monomer represents the active form of the hormone when binding to the insulin receptor (IR).3 It is also widely accepted that insulin undergoes a profound structural change during this process (4 -6), a hypothesis supported by a plethora of highly dynamic hormone conformers identified by NMR studies (7-13). Attempts to determine the structure of the insulin-IR complex have been unsuccessful so far. However, the regions of the insulin molecule responsible for the interaction with the IR (3, 14) or for its dimerization and hexamerization (15, 16) have been functionally and structurally identified in a number of insulin analogues.The insulin molecule consists of two peptide chains, a 21-amino acid A-chain and a 30-amino acid B-chain, interconnected by two interchain and one intrachain disulfide bridges. The C terminus of the B-chain of insulin, particularly residues B24 -B26, plays a substantial role in the initial contact with the receptor. It is believed that the C terminus of the B-chain of insulin must be detached away from the central B-chain ␣-helix of insulin (2, 6). One of the main signatures of this so-called "active form" of insulin should be the exposure of the previously hidden amino acids Gly-A1, Ile-A2, and Val-A3, which are important for the interaction with IR (3). Recently, we described crystal structures of several shortened and full-length insulin analogues with modifications at the B26 position (17). The structural convergence of some of these highly active analogues (200 -400%) enabled us to postulate that the active form of human insulin is characterized by a formation of a new type II ␤-turn at positions B24 -B26.Besides its role in IR activation and IR negative cooperativity (18,19), the C terminus of the B-chain is also responsible for the formation and stabilization of the insulin dimers t...

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Section: Impact Of Modifications On Binding Affinity Of Analogues-supporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Non-equivalent Role of Inter- and Intramolecular Hydrogen Bonds in the Insulin Dimer Interface

Antolíková

Žáková

Turkenburg

et al. 2011

Journal of Biological Chemistry

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“…Although positive charges are well tolerated at this site in insulin (42,43), IGF-I contains Phe A8 (by contrast a large aromatic side chain); this position has recently been shown to contribute to specificity (19). Accordingly, we predicted that Dab A8 -insulin would exhibit native IR binding but decreased IGFR binding.…”

Section: Resultsmentioning

confidence: 99%

“…We chose to focus on two solvent-exposed sites of salient difference between these ␣-helices, A8 and A1. Thr A8 (insulin) and Phe A8 (IGF-I) differ in size, shape, and polarity as emphasized in the studies of De Meyts and co-workers (19). Although Gly A1 is conserved within the insulin-related family, we reasoned that its difference in charge, i.e.…”

mentioning

confidence: 99%

“…Such cross-binding reflects the structural homology between insulin and IGF-I (17) and between IR and IGFR (18). The structural basis for receptor discrimination by insulin and IGF-I has been described recently (19). As a first step toward dissecting the molecular mechanism of insulin-dependent proliferation of colonic epithelia cells and their neoplastic transformation, we have therefore sought to design an insulin analog with more stringent receptor binding selectivity, i.e.…”

mentioning

confidence: 99%

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Design of an Insulin Analog with Enhanced Receptor Binding Selectivity

Zhao

Wan

Whittaker

et al. 2009

Journal of Biological Chemistry

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Insulin binds with high affinity to the insulin receptor (IR) and with low affinity to the type 1 insulin-like growth factor (IGF) receptor (IGFR). Such cross-binding, which reflects homologies within the insulin-IGF signaling system, is of clinical interest in relation to the association between hyperinsulinemia and colorectal cancer. Here, we employ nonstandard mutagenesis to design an insulin analog with enhanced affinity for the IR but reduced affinity for the IGFR. Unnatural amino acids were introduced by chemical synthesis at the N-and C-capping positions of a recognition ␣-helix (residues A1 and A8). These sites adjoin the hormone-receptor interface as indicated by photocross-linking studies. Specificity is enhanced more than 3-fold on the following: Epidemiological studies have demonstrated an association between the metabolic syndrome and type 2 diabetes mellitus (DM) 4 with enhanced risk of colorectal cancer (CRC) (1-3). Animal models suggest that this risk is due to hyperinsulinemia (4, 5). An increased risk of CRC is conferred by treated-derived hyperinsulinemia, either as a direct consequence of insulin replacement therapy or as an indirect response to sulfonylurea secretagogues (6 -9). A reduced CRC risk is by contrast associated with metformin treatment, which results in lower circulating insulin concentrations (7). Because of the global epidemic of type 2 DM (10, 11), it would be of interest to develop a form of insulin therapy that does not elevate CRC risk in this clinical setting.A variety of evidence suggests that the association between hyperinsulinemia and CRC is due to aberrant activation of the type 1 IGF receptor (IGFR) (for review see Refs. 5,12). Although underlying molecular mechanisms are incompletely understood, two models have been proposed (5, 12). The first posits cross-binding of insulin to IGFR in colonic epithelia and neoplastic clones, driving proliferation and tumorigenesis; the second proposes indirect IGFR activation through perturbation of the IGF-I axis (including expression of the IGF-binding proteins) (13,14). Whereas consistent changes in bioactive IGF-I have been difficult to document (4), evidence favoring the direct model is provided by studies of epithelial proliferation in rats (15). Exogenous administration of insulin with a euglycemic clamp causes an acute dose-dependent increase in the proliferation rate of colonic epithelia despite decreased IGF-I expression. Such increased proliferation was not observed as a consequence of hyperglycemia or following infusion of a triglyceride emulsion (15).Insulin binds with high affinity (K d ϳ0.05 nM) to the insulin receptor (IR) and with low but significant affinity (K d Ј ϳ9.0 nM) to IGFR (16). Such cross-binding reflects the structural homology between insulin and IGF-I (17) and between IR and IGFR (18). The structural basis for receptor discrimination by insulin and IGF-I has been described recently (19). As a first step toward dissecting the molecular mechanism of insulin-dependent proliferation of colonic epithelia c...

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Ligand‐induced activation of the insulin receptor: a multi‐step process involving structural changes in both the ligand and the receptor

2009

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Current models of insulin binding to the insulin receptor (IR) propose (i) that there are two binding sites on the surface of insulin which engage with two binding sites on the receptor and (ii) that ligand binding involves structural changes in both the ligand and the receptor. Many of the features of insulin binding to its receptor, namely B-chain helix interactions with the leucine-rich repeat domain and A-chain residue interactions with peptide loops from another part of the receptor, are also seen in models of relaxin and insulin-like peptide 3 binding to their receptors. We show that these principles can likely be extended to the group of mimetic peptides described by Schäffer and coworkers, which are reported to have no sequence identity with insulin. This review summarizes our current understanding of ligand-induced activation of the IR and highlights the key issues that remain to be addressed.

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Structural Basis for the Lower Affinity of the Insulin-like Growth Factors for the Insulin Receptor

Cited by 57 publications

References 51 publications

Non-equivalent Role of Inter- and Intramolecular Hydrogen Bonds in the Insulin Dimer Interface

Non-equivalent Role of Inter- and Intramolecular Hydrogen Bonds in the Insulin Dimer Interface

Design of an Insulin Analog with Enhanced Receptor Binding Selectivity

Ligand‐induced activation of the insulin receptor: a multi‐step process involving structural changes in both the ligand and the receptor

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