An arginine to cysteine(252) mutation in insulin receptors from a patient with severe insulin resistance inhibits receptor internalisation but preserves signalling events.

Abstract

AIMS/HYPOTHESIS:

We examined the properties of a mutant insulin receptor (IR) with an Arg(252) to Cys (IR(R252C)) substitution in the alpha-subunit originally identified in a patient with extreme insulin resistance and acanthosis nigricans.

METHODS:

We studied IR cell biology and signalling pathways in Chinese Hamster Ovary cells overexpressing this IR(R252C).

RESULTS:

Our investigation showed an impairment in insulin binding to IR(R252C) related mostly to a reduced affinity of the receptor for insulin and to a reduced rate of IR(R252C) maturation; an inhibition of IR(R252C)-mediated endocytosis resulting in a decreased insulin degradation and insulin-induced receptor down-regulation; a maintenance of IR(R252C) on microvilli even in the presence of insulin; a similar autophosphorylation of mutant IR(R252C) followed by IRS 1/IRS 2 phosphorylation, p85 association with IRS 1 and IRS 2 and Akt phosphorylation similar to those observed in cells expressing wild type IR (IRwt); and finally, a reduced insulin-induced Shc phosphorylation accompanied by decreased ERK1/2 phosphorylation and activity and of thymidine incorporation into DNA in cells expressing IR(R252C) as compared to cells expressing IRwt.

CONCLUSION/INTERPRETATION:

These observations suggest that: parameters other than tyrosine kinase activation participate in or control the first steps of IR internalisation or both; IR-mediated IRS 1/2 phosphorylation can be achieved from the cell surface and microvilli in particular; Shc phosphorylation and its subsequent signalling pathway might require IR internalisation; defective IR endocytosis correlates with an enhancement of some biological responses to insulin and attenuation of others.

• Authors: I Hamer, M Foti, R Emkey, M Cordier-Bussat, J Philippe, P De Meyts, C Maeder, C R Kahn, J-L Carpentier
• Journal: Diabetologia (Diabetologia) Vol. 45 Issue 5 Pg. 657-67 (May 2002) ISSN: 0012-186X [Print] Germany
• PMID: 12107746 (Publication Type: Case Reports, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Insulin
• Protein Subunits
• Recombinant Proteins
• DNA
• Arginine
• Receptor, Insulin
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3
• Mitogen-Activated Protein Kinases
• Cysteine
• Thymidine

Topics

• Acanthosis Nigricans (genetics)
• Adult
• Amino Acid Substitution
• Animals
• Arginine
• CHO Cells
• Cricetinae
• Cysteine
• DNA (biosynthesis)
• Humans
• Insulin (metabolism)
• Insulin Resistance (genetics)
• Male
• Mitogen-Activated Protein Kinase 1 (metabolism)
• Mitogen-Activated Protein Kinase 3
• Mitogen-Activated Protein Kinases (metabolism)
• Mutation
• Phosphorylation
• Protein Subunits
• Protein Transport
• Receptor, Insulin (genetics, metabolism, physiology)
• Recombinant Proteins (metabolism)
• Signal Transduction (physiology)
• Thymidine (metabolism)
• Transfection