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The insulin-like growth factor I receptor-induced interaction of insulin receptor substrate-4 and Crk-II

M Karas1, A P Koval, Y Zick

  • 1Clinical Endocrinology Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-1758, USA.

Endocrinology
|April 24, 2001
PubMed

Insights

Insulin receptor substrate-4 (IRS-4) interacts with Crk-II proteins upon insulin-like growth factor (IGF)-I receptor activation. This interaction is mediated by a specific region on IRS-4 containing four tyrosine residues, suggesting a novel binding mechanism.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Biochemistry

Background:

  • Insulin receptor substrate (IRS) proteins are key mediators of insulin and insulin-like growth factor (IGF)-I receptor signaling pathways.
  • IRS-4, a newly identified member of the IRS family, has been shown to interact with Crk proteins following IGF-I receptor stimulation.

Purpose of the Study:

  • To elucidate the molecular basis of the interaction between IRS-4 and Crk family proteins.
  • To identify the specific regions and residues within IRS-4 responsible for mediating Crk-II binding upon IGF-I receptor activation.

Main Methods:

  • Truncation analysis of IRS-4 to pinpoint the interacting region with Crk-II.
  • Site-directed mutagenesis of specific tyrosine residues within the identified IRS-4 region.
  • Assessment of IRS-4 and Crk-II interaction following IGF-I receptor stimulation in 293 HEK cells.

Main Results:

  • A specific region on IRS-4, between amino acids 678 and 800, was identified as crucial for Crk-II interaction.
  • This region contains a cluster of four tyrosine residues (Y700, Y717, Y743, Y779) hypothesized to be involved in binding.
  • Mutational analysis revealed that while individual tyrosine mutations did not abolish the interaction, simultaneous mutation of all four tyrosines to phenylalanine completely abrogated IGF-I induced IRS-4 and Crk-II binding.

Conclusions:

  • The interaction between IRS-4 and Crk-II is dependent on the phosphorylation of specific tyrosine residues within a defined region of IRS-4.
  • These findings suggest a novel mechanism for Crk-II binding to tyrosine-phosphorylated proteins, involving a cluster of tyrosines rather than a single residue.
  • This study provides critical insights into the molecular intricacies of IGF-I signaling pathways mediated by IRS proteins.

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