Two naturally occurring mutations in the kinase domain of insulin receptor accelerate degradation of the insulin receptor and impair the kinase activity

Takeshi Imamura, Yasumitsu Takata, Toshiyasu Sasaoka, Yoshihisa Takada, Hisao Morioka, Tetsuro Haruta, Tasuku Sawa, Masanori Iwanishi, Yang Guan Hu, Yoshimi Suzuki, Junzou Hamada, Masashi Kobayashi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

We identified two novel heterozygous missense mutations of the insulin receptor gene: the Asp1179 mutation in one family and the Leu1193 mutation in two unrelated families with extreme insulin resistance. In these patients, the number of insulin receptors on the cell surface was found to be markedly decreased by insulin binding and surface labeling studies in transformed lymphocytes. Insulin binding to the transfected COS 7 cells and Rat-1 cells with both mutant cDNAs was also decreased to 5-31% of normal, and the mutant insulin receptors showed a markedly decreased kinase activity. Although biosynthetic labeling studies revealed that both mutant receptors were synthesized as 190-kDa proreceptors, the degradation of the mutant proreceptors was 2-fold faster than that of the wild type proreceptors. However, the degradation rate of the mutant receptors on the cell surface was comparable to that of wild type insulin receptor. These results suggest that the Asp1179 and Leu1193 mutations in the kinase domain are unique in causing decreased insulin receptor number on the cell surface by accelerated intracellular degradation, and that insulin resistance in these patients is mainly due to the decreased receptor number rather than impaired kinase activity.

Original languageEnglish
Pages (from-to)31019-31027
Number of pages9
JournalJournal of Biological Chemistry
Volume269
Issue number49
StatePublished - 1994/12/09

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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