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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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CFBP is a novel tyrosine-phosphorylated protein that might function as a regulator of CIN85/CD2AP

Hiroaki Konishi1, Kyoko Tashiro, Yasunobu Murata

  • 1Institute for Enzyme Research, University of Tokushima, Tokushima 770-8503, Japan and Harima Institute at SPring-8, RIKEN, Hyogo 679-5148, Japan. konishi@ier.tokushima-u.ac.jp

The Journal of Biological Chemistry
|August 10, 2006
PubMed

Insights

A novel protein, CFBP, binds to CIN85/CD2AP and is phosphorylated upon epidermal growth factor (EGF) stimulation. CFBP plays a key role in EGF receptor down-regulation and internalization.

Area of Science:

  • Cellular signaling pathways
  • Proteomics
  • Receptor biology

Background:

  • The epidermal growth factor (EGF) receptor pathway is crucial for cell growth and differentiation.
  • Understanding the complex network of EGF receptor signaling requires comprehensive proteomic analysis.
  • Novel proteins involved in this pathway are key to deciphering its regulatory mechanisms.

Purpose of the Study:

  • To characterize a newly identified protein, CFBP (CIN85/CD2AP family binding protein), within the EGF receptor signaling network.
  • To elucidate the interaction between CFBP and the CIN85/CD2AP family.
  • To determine CFBP's role in EGF receptor regulation.

Main Methods:

  • Large-scale proteomic analysis of tyrosine-phosphorylated proteins.
  • Identification of protein-protein interactions using biochemical assays.
  • Analysis of protein localization and cellular morphology changes.
  • Investigation of EGF receptor down-regulation mechanisms.

Main Results:

  • CFBP is phosphorylated at tyrosine 204 upon EGF stimulation.
  • CFBP binds to the CIN85/CD2AP family via a proline-rich motif, with binding affinity regulated by CFBP phosphorylation.
  • CFBP and CIN85/CD2AP co-localize in actin-rich structures, and CFBP overexpression alters cell morphology and actin organization.
  • CFBP accelerates EGF receptor down-regulation by mediating Cbl recruitment to the CD2AP/CIN85 complex.
  • Two spliced variants of CFBP exist, with one lacking the binding motif for CIN85/CD2AP.

Conclusions:

  • CFBP is a novel component of the EGF receptor signaling pathway.
  • CFBP's interaction with CIN85/CD2AP and its phosphorylation status are critical for its function.
  • CFBP plays a significant role in the internalization and down-regulation of the EGF receptor following ligand stimulation.

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