Absence of functional insulin receptor substrate-3 (IRS-3) gene in humans

• Published in: Diabetologia 2002-12, Vol.45 (12), p.1697-1702
• Main Authors: BJÖRNHOLM, M, HE, A. R, ATTERSAND, A, LAKE, S, LIU, S. C. H, LIENHARD, G. E, TAYLOR, S, ARNER, P, ZIERATH, J. R
• Format: Article
• Language: English
• Subjects: Adipocytes; Adipocytes - metabolism; Adult; Amino Acid Sequence - genetics; Animals; Bioinformatics; Biological and medical sciences; Body fat; Cloning; Cloning, Molecular; Computational Biology; Diabetes; Diabetes. Impaired glucose tolerance; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Female; Gene Deletion; Gene Library; Genes; Genome, Human; Genomes; Hospitals; Humans; Insulin Receptor Substrate Proteins; Insulin resistance; Kinases; Male; Medical sciences; Metabolism; Mice; Middle Aged; Molecular Sequence Data; Musculoskeletal system; Phosphoproteins - deficiency; Phosphoproteins - genetics; Phosphoproteins - physiology; Phosphorylation; Physiology; Proteins; Rats; Reverse Transcriptase Polymerase Chain Reaction; Signal transduction; Tyrosine - metabolism
• ISSN: 0012-186X; 1432-0428
• DOI: 10.1007/s00125-002-0945-z

Insulin receptor substrate (IRS) proteins play important roles in insulin action and pancreatic beta-cell function. At least four mammalian IRS molecules have been identified. Although genes and cDNAs encoding human IRS-1, IRS-2, and IRS-4 have been cloned, IRS-3 has been identified only in rodents. Thus, we have attempted to clone the human IRS-3 gene. Insulin-stimulated rat or human adipocytes were subjected to Western blot analysis to assess IRS-3 tyrosine phosphorylation. Human liver and adipose cDNA libraries were screened in an effort to clone IRS-3 cDNA. A PCR-based approach was designed to amplify IRS-3 cDNA. Reverse transcription PCR was carried out using mRNA from adipose tissue, liver, and skeletal muscle as templates in combination with an in silico screen using mouse IRS-1, IRS-2 and IRS-3 in a tblastn search of the draft public human genome. In human adipocytes we did not detect a M(r) 60 000 phosphoprotein corresponding to IRS-3, whereas in rat adipocytes IRS-3 protein and insulin-stimulated tyrosine phosphorylation was readily observed. None of the molecular approaches provided evidence for a functional IRS-3gene in human tissue. Two deletions in human IRS-3 gene were identified using bioinformatics. The human IRS-3 gene product is predicted to lack a phosphotyrosine binding domain and also the sequence corresponding amino acid 353-407 of murine IRS-3. The contiguous sequence of genomic DNA between these two homologous regions does not have the coding information for human IRS-3. In silico screening of the human IRS-3 genome region, combined with further biological and molecular validation, provides evidence against a functional IRS-3 in humans.