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RhoC GTPase Activation Assay
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The R-Ras/RIN2/Rab5 complex controls endothelial cell adhesion and morphogenesis via active integrin endocytosis and

Chiara Sandri1, Francesca Caccavari, Donatella Valdembri

  • 1Laboratory of Cell Adhesion Dynamics, Institute for Cancer Research and Treatment (IRCC), Candiolo (TO), Italy.

Cell Research
|July 25, 2012
PubMed

Insights

Ras and Rab5 interacting protein 2 (RIN2) mediates R-Ras-induced cell adhesion during blood vessel formation. R-Ras-GTP binding to RIN2 triggers integrin endocytosis and Rac1 activation, promoting angiogenesis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Angiogenesis Research

Background:

  • Semaphorins regulate blood vessel navigation via plexin receptors, inhibiting R-Ras GTPases.
  • R-Ras, expressed in vascular cells, promotes extracellular matrix (ECM) adhesion through poorly understood mechanisms.

Purpose of the Study:

  • To identify the effector mediating R-Ras's pro-adhesive and pro-angiogenic activity in endothelial cells.
  • To elucidate the molecular mechanism by which R-Ras controls cell adhesion.

Main Methods:

  • Co-immunoprecipitation and localization studies to identify protein interactions.
  • Analysis of protein complex formation and subcellular localization (e.g., early endosomes, lamellipodia).
  • Guanine nucleotide exchange factor (GEF) assays and functional assays assessing integrin endocytosis and Rac1 activation.

Main Results:

  • Ras and Rab5 interacting protein 2 (RIN2) was identified as a key effector of R-Ras.
  • R-Ras-GTP and RIN2 co-localize at nascent ECM adhesion sites.
  • GTP-bound R-Ras converts RIN2 from a GEF to an adaptor, promoting β1 integrin endocytosis and R-Ras translocation to early endosomes.
  • The R-Ras/RIN2/Rab5 module activates Rac1 via TIAM1 on early endosomes, leading to cell adhesion.

Conclusions:

  • R-Ras-GTP binding to RIN2 triggers a signaling cascade involving β1 integrin endocytosis and Rac1 activation.
  • This mechanism explains how R-Ras promotes cell adhesion and angiogenesis.
  • RIN2 acts as a crucial adaptor converting R-Ras signaling from a GEF-dependent to an adaptor-mediated pathway.

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