Cancer-associated VEGFR2R1032Q sustains receptor activation also by promoting ligand-independent hetero-dimerization with co-expressed wild-type VEGFR2 and translocation into lipid rafts

The substitution R1032Q is the most frequent non-synonymous mutation of the vascular endothelial growth factor receptor 2 (VEGFR2) in cancer patients, classified as a loss-of-function variant. Here we characterize the molecular bases of its role in cancer, demonstrating that it lacks significant activity and pro-oncogenic effects in VEGFR2-negative tumor cells, while being able to sustain the tumorigenic potential of VEGFR2-positive cancer cells. By implementing a cell model that allows expression of either VEGFR2^R1032Q alone or in combination with VEGFR2^WT, we showed that the effects of mutated VEGFR2 are at least in part due to the ability of VEGFR2^R1032Q to form functional heterodimers with co-expressed VEGFR2^WT that result in increased kinase activity and receptor phosphorylation. This was associated with reduced mobility of the receptor on the membrane, linked to its translocation into detergent-resistant membrane (DRM) domains (e.g. lipid rafts), which showed alterations in lipid compositions and structure. These data shed light on a novel oncogenic mechanism of activation of VEGFR2, clarifying the paradoxical loss-of-function nature of the substitution R1032Q of VEGFR2.