Congenital insulin resistance associated with a conformational alteration in a conserved β-sheet in the insulin receptor L1 domain

Mathias Rouard, Joseph Bass*, Florin Grigorescu, Thomas P J Garrett, Colin W. Ward, Gregory Lipkind, Claude Jaffiole, Donald F. Steiner, Graeme I. Bell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The hormone binding site of members of the insulin receptor family is contained within a highly conserved extracellular region of the receptor. Recent crystallization of the N-terminal region of the binding site revealed two large domains (L1, L2), each organized as a single-stranded right-handed β-helix, connected by a rod-shaped cysteine-rich domain. Here, we analyze two new naturally occurring mutations in a single β-sheet within L1, D59G and L62P, that we previously identified in a young woman with classic congenital insulin resistance (type A). Substitution of D59G, a β-sheet connecting loop residue, caused decreased hormone binding but did not disrupt overall folding, assembly, or movement to the cell surface. In contrast, replacement of the adjacent residue L62P, which is located within the β- sheet, and positioned in a hormone binding surface, completely disrupted intracellular folding, oligomerization, and trafficking and resulted in aberrant proteolytic degradation. Immunohistochemistry in combination with biosynthetic studies showed that misfolded receptors were retained in an incorrect cellular location and that they colocalized with the resident endoplasmic reticulum chaperone calnexin. This study, together with other mutagenesis data, shows that formation of β-sheet elements within the L1 β- helix are critical for the folding of the entire extracellular domain of the receptor and that the hormone contact site is composed in part by residues in this domain.

Original languageEnglish (US)
Pages (from-to)18487-18491
Number of pages5
JournalJournal of Biological Chemistry
Volume274
Issue number26
DOIs
StatePublished - Jun 25 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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