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Dimerize RACK1 upon transformation with oncogenic ras

Ling-Yun Chu1, Yu-Hsun Chen, Nin-Nin Chuang

  • 1Institute of Zoology, National Taiwan University, Taipei, Taiwan.

Biochemical and Biophysical Research Communications
|March 31, 2005
PubMed

Insights

Oncogenic Ras transformation disrupts RACK1 binding to syndecan-2 by promoting RACK1 dimerization with GTP-Ras. This mechanism depletes RACK1, allowing Src kinase activity and cell transformation.

Area of Science:

  • Molecular Cell Biology
  • Oncogenesis
  • Signal Transduction

Background:

  • Previous studies identified the syndecan-2/p120-GAP complex as a docking site for Src tyrosine kinase activity during oncogenic Ras transformation.
  • RACK1 protein normally interacts with syndecan-2 to maintain Src inactivation, but this interaction is disrupted by Ras overexpression.

Purpose of the Study:

  • To characterize the specific interaction between RACK1 protein and Ras.
  • To elucidate the mechanism by which oncogenic Ras disrupts the RACK1-syndecan-2 interaction.

Main Methods:

  • Isolation of RACK1 from BALB/3T3 cells transfected with oncogenic Ras plasmids.
  • Confirmation of RACK1 interaction with GTP-bound Ras (GTP-K(B)-Ras(Q61K)) using various RACK1 sources (shrimp, human, mouse).
  • Analysis of RACK1 dimerization and its interaction with p120-GAP using Src tyrosine kinase phosphorylation assays.

Main Results:

  • RACK1 selectively binds to GTP-bound Ras, not GDP-bound Ras.
  • RACK1 dimerizes upon binding to GTP-Ras, 14-3-3beta, and geranylgeranyl pyrophosphate.
  • The RACK1/GTP-Ras complex interacts with p120-GAP, leading to RACK1 monomerization and subsequent competition for syndecan-2 binding.

Conclusions:

  • Oncogenic Ras transformation induces RACK1 dimerization with GTP-Ras, effectively sequestering RACK1 and preventing its interaction with syndecan-2.
  • This RACK1 sequestration mechanism allows for sustained Src tyrosine kinase activity, promoting cell transformation.
  • The RACK1/GTP-Ras complex facilitates interaction with p120-GAP, potentially recycling monomeric RACK1 to syndecan-2.

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