1. ¹Department of Dermatology, University Hospital of Regensburg, Regensburg, Germany
2. ²Institute of Clinical Chemistry, University Hospital of Regensburg, Regensburg, Germany

Correspondence: Dr Stefanie Meyer, Department of Dermatology, University of Regensburg, D-93042 Regensburg, Germany. E-mail: stefanie.meyer@klinik.uni-regensburg.de

Received 14 June 2006; Revised 10 December 2006; Accepted 2 January 2007; Published online 22 March 2007.

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-1 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-1 is also preferentially detected in such Lubrol-RAFTs. Accordingly, the presence of ephrin-B2 and integrin-1 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-1 in the plasma membrane. We conclude that Lubrol-RAFTs probably represent the platform for tumor-promoting ephrin-B2–integrin-1 interaction, which could become an interesting target for future antitumoral therapies.