Lubrol-RAFTs in melanoma cells: a molecular platform for tumor-promoting ephrin-B2-integrin-beta1 interaction

J Invest Dermatol. 2007 Jul;127(7):1615-21. doi: 10.1038/sj.jid.5700778. Epub 2007 Mar 22.

Abstract

Ephrins control cell motility and matrix adhesion. These functions play a pivotal role in cancer progression, for example, in malignant melanomas. We have previously shown that the ephrin-B2-tumor-promoting action is partly mediated by integrin-beta1 interaction. However, the subcellular prerequisites for molecular interaction like molecular proximity and co-compartmentalization have not been elucidated yet. Specific cholesterol-rich microdomains, termed lipid rafts (RAFTs), are known to be essential for functional ephrin-B2 signalling and integrin-mediated effects. Therefore, we addressed the question whether RAFT co-compartmentalization of both molecules could provide the molecular platform for their tumor-promoting interaction. In this study, we show that overexpressed ephrin-B2 is not only compartmentalized to classical Triton X-100 RAFTs in B16 melanoma cells, but also to the recently defined Lubrol-RAFTs. Interestingly, in the melanoma cells investigated, integrin-beta1 is also preferentially detected in such Lubrol-RAFTs. Accordingly, the presence of ephrin-B2 and integrin-beta1 in RAFTs and their function in cell migration and matrix attachment are highly sensitive to RAFT disruption by cholesterol depletion. Confocal fluorescence microscopy analyses also support the concept of a close molecular proximity and functional interplay of ephrin-B2 and integrin-beta1 in the plasma membrane. We conclude that Lubrol-RAFTs probably represent the platform for tumor-promoting ephrin-B2-integrin-beta1 interaction, which could become an interesting target for future antitumoral therapies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Adhesion / physiology
  • Cell Line, Tumor
  • Cell Movement / physiology
  • Cell Transformation, Neoplastic
  • Cholesterol / physiology
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / physiopathology
  • Ephrin-B2 / genetics
  • Ephrin-B2 / metabolism*
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Integrin beta1 / metabolism*
  • Melanoma / genetics
  • Melanoma / metabolism
  • Melanoma / physiopathology*
  • Membrane Microdomains / physiology*
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Polyethylene Glycols*
  • Protein Interaction Mapping / methods*
  • Skin Neoplasms / genetics
  • Skin Neoplasms / metabolism
  • Skin Neoplasms / physiopathology*

Substances

  • Ephrin-B2
  • Integrin beta1
  • Polyethylene Glycols
  • lubrol
  • Cholesterol