Colocalization of proteins involved in VEGF redox signalling in caveolae/lipid rafts of leukaemia cells

Caveolae/lipid rafts are membrane-rich cholesterol domains endowed with several functions in signal transduction, and Cav-1 has been reported to be implicated in regulating multiple cancer-associated processes, ranging from cellular transformation, tumor growth and metastasis, to multidrug resistance and angiogenesis. Vascular endothelial growth factor receptor-2 (VEGFR-2) and caveolin-1 (Cav-1) are frequently colocalized, suggesting an important role played by this colocalization on cancer cell survival, migration and proliferation. Thus, our attention was directed to a human leukaemia cell line (B1647) that constitutively produces VEGF and expresses the tyrosine-kinase receptor VEGFR-2. As the dissociation of VEGFR-2 from caveolae has been shown to be essential for receptor autophosphorylation and activation of downstream signalling events, we investigated the presence and the role of VEGFR-2 in caveolae/lipid rafts, focusing our attention on the correlation between reactive oxygen species (ROS) production and glucose transport modulation by VEGF. Results showed that the disassembly of caveolae/lipid rafts by methyl-cyclodextrin induces an increase in intracellular ROS levels, glucose uptake and VEGFR-2 phosphorylation. In order to better understand the involvement of VEGF/VEGFR-2 in the redox signal transduction pathway, we evaluated the effect of different compounds able to inhibit VEGF interaction with its receptor by different mechanisms. To deeply analyse the role of caveolae/lipid rafts in redox signaling promoted by VEGF, the effect of Cav-1 scaffolding domain peptide was studied. By means of immunoprecipitation and fluorescence techniques, we corroborate the hypothesis of the importance of a colocalization of the membrane proteins under study to modulate B1647 cells proliferation, suggesting different potential anti-leukaemia targets.