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Lipid-protein interactions of growth factor receptor-bound protein 14 in insulin receptor signaling

Raju V S Rajala1, Michael D Chan, Ammaji Rajala

  • 1Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA. raju-rajala@ouhsc.edu

Biochemistry
|November 23, 2005
PubMed

Insights

Researchers identified Grb14 as a novel protein interacting with the insulin receptor in the retina. This interaction, dependent on receptor activity, suggests Grb14 regulates retinal insulin signaling and may impact degenerative diseases.

Area of Science:

  • Retinal Biology
  • Molecular Cell Biology
  • Neuroscience

Background:

  • Retinal degenerative diseases often involve rod and cone cell apoptosis.
  • Insulin receptor tyrosine phosphorylation in the retina activates anti-apoptotic signaling.
  • The regulatory mechanism of the retinal insulin receptor remains unknown.

Purpose of the Study:

  • To identify novel regulators of the insulin receptor in the retina.
  • To characterize the interaction between the insulin receptor and its binding partners.
  • To elucidate the role of Grb14 in retinal insulin signaling pathways.

Main Methods:

  • Yeast two-hybrid screening of a bovine retinal cDNA library using the insulin receptor beta subunit (IRbeta).
  • Co-expression of hybrid proteins in yeast to study protein-protein interactions.
  • Deletion mutagenesis to map interaction domains on Grb14.
  • Nuclear import assays in yeast and subcellular localization studies in isolated retinas.
  • Protein-lipid overlay assays and analysis of stimulated retinal lysates.

Main Results:

  • Grb14, a member of the Grb7 gene family, was identified as an IRbeta-interacting protein.
  • Grb14 specifically binds to the cytoplasmic domain of IRbeta, dependent on receptor tyrosine kinase activity.
  • A novel phosphorylated insulin receptor interacting (PIR) domain in Grb14 mediates IRbeta binding.
  • Grb14 possesses a functional nuclear localization signal and is present in nuclear fractions of retinal tissue.
  • Grb14 binds to phosphoinositides, with differential binding observed under insulin-stimulated and non-stimulated conditions.

Conclusions:

  • Grb14 is a novel binding partner of the insulin receptor in the retina.
  • Grb14's interaction with the insulin receptor is regulated by receptor activity and involves specific domains.
  • Grb14's nuclear localization and phosphoinositide binding suggest a multifaceted role in regulating insulin receptor-mediated pathways in the retina.

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