Insight into the molecular basis for the kinetic differences between the two insulin receptor isoforms

2011 ◽  
Vol 440 (3) ◽  
pp. 397-403 ◽  
Author(s):  
Louise Knudsen ◽  
Pierre De Meyts ◽  
Vladislav V. Kiselyov
Keyword(s):  
Ligand Binding ◽  
Insulin Receptor ◽  
Dissociation Rate ◽  
Dissociation Kinetics ◽  
Binding Properties ◽  
Receptor Isoforms ◽  
Insulin Receptor Isoforms ◽  
Exon 11

More than 20 years after the description of the two IR (insulin receptor) isoforms, designated IR-A (lacking exon 11) and IR-B (with exon 11), nearly every functional aspect of the alternative splicing both in vitro and in vivo remains controversial. In particular, there is no consensus on the precise ligand-binding properties of the isoforms. Increased affinity and dissociation kinetics have been reported for IR-A in comparison with IR-B, but the opposite results have also been reported. These are not trivial issues considering the reported possible increased mitogenic potency of IR-A, and the reported link between slower dissociation and increased mitogenesis. We have re-examined the ligand-binding properties of the two isoforms using a novel rigorous mathematical analysis based on the concept of a harmonic oscillator. We found that insulin has 1.5-fold higher apparent affinity towards IR-A and a 2-fold higher overall dissociation rate. Analysis based on the model showed increased association (3-fold) and dissociation (2-fold) rate constants for binding site 1 of IR in comparison with IR-B. We also provide a structural interpretation of these findings on the basis of the structure of the IR ectodomain and the proximity of the sequence encoded by exon 11 to the C-terminal peptide that is a critical trans-component of site 1.

scholarly journals Insulin Receptor Isoforms in Cancer

2018 ◽  
Vol 19 (11) ◽  
pp. 3615 ◽  
Author(s):  
Veronica Vella ◽  
Agostino Milluzzo ◽  
Nunzio Scalisi ◽  
Paolo Vigneri ◽  
Laura Sciacca
Keyword(s):  
Insulin Receptor ◽  
Cancer Cells ◽  
Predictive Biomarker ◽  
Point Of View ◽  
Receptor Isoforms ◽  
Insulin Receptor Isoforms ◽  
Target Therapies ◽  
Isoform Expression ◽  
Exon 11 ◽  
Clinical Conditions

The insulin receptor (IR) mediates both metabolic and mitogenic effects especially when overexpressed or in clinical conditions with compensatory hyperinsulinemia, due to the metabolic pathway resistance, as obesity diabetes. In many cancers, IR is overexpressed preferentially as IR-A isoform, derived by alternative splicing of exon 11. The IR-A overexpression, and the increased IR-A:IR-B ratio, are mechanisms that promote the mitogenic response of cancer cells to insulin and IGF-2, which is produced locally by both epithelial and stromal cancer cells. In cancer IR-A, isoform predominance may occur for dysregulation at both mRNA transcription and post-transcription levels, including splicing factors, non-coding RNAs and protein degradation. The mechanisms that regulate IR isoform expression are complex and not fully understood. The IR isoform overexpression may play a role in cancer cell stemness, in tumor progression and in resistance to target therapies. From a clinical point of view, the IR-A overexpression in cancer may be a determinant factor for the resistance to IGF-1R target therapies for this issue. IR isoform expression in cancers may have the meaning of a predictive biomarker and co-targeting IGF-1R and IR-A may represent a new more efficacious treatment strategy.

Differential effect of pp120 on insulin endocytosis by two variant insulin receptor isoforms

1997 ◽  
Vol 273 (4) ◽  
pp. E801-E808 ◽  
Author(s):  
Sergio Li Calzi ◽  
Curtis V. Choice ◽  
Sonia M. Najjar
Keyword(s):  
Insulin Receptor ◽  
3T3 Cells ◽  
Insulin Receptor Tyrosine Kinase ◽  
Α Subunit ◽  
3T3 Fibroblasts ◽  
Receptor Isoforms ◽  
Insulin Receptor Isoforms ◽  
Exon 11 ◽  
Isoform B ◽  
Nih 3T3

The insulin receptor is expressed as two variably spliced isoforms that differ by the absence (isoform A) or presence (isoform B) of a 12-amino acid sequence encoded by exon 11 at the carboxy terminus of the α-subunit. Coexpression of the A isoform and pp120, a substrate of the insulin receptor tyrosine kinase, in NIH 3T3 fibroblasts increased receptor A-mediated insulin endocytosis and degradation by two- to threefold compared with cells expressing receptors alone. Because B is the predominant isoform in the liver and binds insulin with lower affinity than A, we have examined the effect of pp120 on receptor B-mediated endocytosis. In contrast to isoform A, the effect of pp120 on isoform B-mediated insulin internalization and degradation in stably transfected NIH 3T3 cells was minimal.

Receptor-isoform-selective insulin analogues give tissue-preferential effects

2011 ◽  
Vol 440 (3) ◽  
pp. 301-308 ◽  
Author(s):  
Sara G. Vienberg ◽  
Stephan D. Bouman ◽  
Heidi Sørensen ◽  
Carsten E. Stidsen ◽  
Thomas Kjeldsen ◽  
...  
Keyword(s):  
Biological Effects ◽  
Glycogen Synthesis ◽  
Expression Patterns ◽  
Rat Hepatocytes ◽  
Insulin Analogues ◽  
Glycogen Accumulation ◽  
Insulin Receptor Isoforms ◽  
Exon 11

The relative expression patterns of the two IR (insulin receptor) isoforms, +/− exon 11 (IR-B/IR-A respectively), are tissue-dependent. Therefore we have developed insulin analogues with different binding affinities for the two isoforms to test whether tissue-preferential biological effects can be attained. In rats and mice, IR-B is the most prominent isoform in the liver (>95%) and fat (>90%), whereas in muscles IR-A is the dominant isoform (>95%). As a consequence, the insulin analogue INS-A, which has a higher relative affinity for human IR-A, had a higher relative potency [compared with HI (human insulin)] for glycogen synthesis in rat muscle strips (26%) than for glycogen accumulation in rat hepatocytes (5%) and for lipogenesis in rat adipocytes (4%). In contrast, the INS-B analogue, which has an increased affinity for human IR-B, had higher relative potencies (compared with HI) for inducing glycogen accumulation (75%) and lipogenesis (130%) than for affecting muscle (45%). For the same blood-glucose-lowering effect upon acute intravenous dosing of mice, INS-B gave a significantly higher degree of IR phosphorylation in liver than HI. These in vitro and in vivo results indicate that insulin analogues with IR-isoform-preferential binding affinity are able to elicit tissue-selective biological responses, depending on IR-A/IR-B expression.

CarR, a MarR-family regulator from Corynebacterium glutamicum, modulated antibiotic and aromatic compound resistance

2019 ◽  
Vol 476 (21) ◽  
pp. 3141-3159 ◽  
Author(s):  
Meiru Si ◽  
Can Chen ◽  
Zengfan Wei ◽  
Zhijin Gong ◽  
GuiZhi Li ◽  
...  
Keyword(s):  
Stress Response ◽  
Ligand Binding ◽  
Corynebacterium Glutamicum ◽  
Conformational Changes ◽  
Cysteine Oxidation ◽  
Transcriptional Regulatory ◽  
Ligand Free ◽  
Redox Sensing

Abstract MarR (multiple antibiotic resistance regulator) proteins are a family of transcriptional regulators that is prevalent in Corynebacterium glutamicum. Understanding the physiological and biochemical function of MarR homologs in C. glutamicum has focused on cysteine oxidation-based redox-sensing and substrate metabolism-involving regulators. In this study, we characterized the stress-related ligand-binding functions of the C. glutamicum MarR-type regulator CarR (C. glutamicum antibiotic-responding regulator). We demonstrate that CarR negatively regulates the expression of the carR (ncgl2886)–uspA (ncgl2887) operon and the adjacent, oppositely oriented gene ncgl2885, encoding the hypothetical deacylase DecE. We also show that CarR directly activates transcription of the ncgl2882–ncgl2884 operon, encoding the peptidoglycan synthesis operon (PSO) located upstream of carR in the opposite orientation. The addition of stress-associated ligands such as penicillin and streptomycin induced carR, uspA, decE, and PSO expression in vivo, as well as attenuated binding of CarR to operator DNA in vitro. Importantly, stress response-induced up-regulation of carR, uspA, and PSO gene expression correlated with cell resistance to β-lactam antibiotics and aromatic compounds. Six highly conserved residues in CarR were found to strongly influence its ligand binding and transcriptional regulatory properties. Collectively, the results indicate that the ligand binding of CarR induces its dissociation from the carR–uspA promoter to derepress carR and uspA transcription. Ligand-free CarR also activates PSO expression, which in turn contributes to C. glutamicum stress resistance. The outcomes indicate that the stress response mechanism of CarR in C. glutamicum occurs via ligand-induced conformational changes to the protein, not via cysteine oxidation-based thiol modifications.

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