Genotype–Phenotype Correlations and Structural Basis of INSR and IGF1R Mutations Causing Severe Insulin/IGF-1 Resistance

Abstract

Mutations of the insulin receptor (INSR) gene cause severe insulin resistance, resulting in several syndromes with various abnormal phenotypes associated with variable severity of INSR dysfunction. As a member of the insulin receptor family, the IGF-I receptor (IGF1R) shows the same domain structure as INSR containing the fibronectin type III (FnIII) domains where there are an α-β cleavage site and a part of the ligand binding site. Mutations of IGF1R can cause intrauterine and postnatal growth retardation. We compiled 3 mutations of the FnIII-2 and FnIII-3 domains in IGF1R registered in HGMD, ClinVar and UniProt databases as causing growth retardation as well as the SNP with >1% allele frequency in IGF1R from the 1000 Genomes Project data, ESP6500, HGVD and 3.5KJPN, a reference panel of Japanese individuals. We conducted in silico structural analysis of the mutations of the FnIII domains in IGF1R which revealed that the pathogenic mutations were predicted to severely impair stability of the FnIII domains and hydrophobic core formation or affect processing site, while the SNP was predicted not to affect folding of the domains. In addition, IGF-1 proreceptor processing was impaired in cells expressing mutations of FnIII compared to cells expressing WT form. Previously, we performed structural analysis of mutations of the FnIII domains in INSR, which revealed that missense mutations causing the most severe Donohue syndrome were predicted to severely impair hydrophobic core formation and stability of the FnIII domains, while those causing less severe Rabson-Mendenhall syndrome were predicted to lead to localized destabilization and not to affect folding of the FnIII domains. Genotype-structure-phenotype correlations of variants of the FnIII domains in INSR and IGF1R identified in these analyses will enable early diagnosis of pathogenic mutations in INSR and IGF1R and provide a valuable insight into the molecular mechanism of severe insulin or IGF-1 resistance. Disclosure J. Hosoe: None. H. Kadowaki: None. F. Miya: None. M. Takakura: None. T. Tsunoda: None. N. Shojima: None. T. Yamauchi: Research Support; Self; Novo Nordisk Inc., Daiichi Sankyo Company, Limited, Sanofi, Takeda, Tanabe-Mitsubishi. T. Kadowaki: Consultant; Self; Novo Nordisk A/S, AstraZeneca, Merck Sharp & Dohme Corp.. Research Support; Self; Kissei Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Sanofi, Kyowa Hakko Kirin Co., Ltd., Novo Nordisk A/S, Astellas Pharma, Daiichi Sankyo Company, Limited, Takeda, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Merck Sharp & Dohme Corp., Nippon Boehringer Ingelheim Co. Ltd.. Speaker's Bureau; Self; Astellas Pharma, AstraZeneca, Merck Sharp & Dohme Corp., Ono Pharmaceutical Co., Ltd., Takeda, Eli Lilly and Company, Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk A/S.