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OBJECTIVE: The HIV-1 transactivating factor (Tat) possesses features typical of both cell-adhesive and angiogenic growth factor (AGF) proteins, inducing endothelial cell (EC) adhesion and proangiogenic activation. Tat was exploited to investigate the events triggered by EC adhesion to substrate-bound AGF that lead to proangiogenic activation. METHODS AND RESULTS: Immobilized Tat induces actin cytoskeleton organization, formation of α(v)β(3) integrin(+)focal adhesion plaques, and recruitment of vascular endothelial growth factor receptor-2 (VEGFR2) in the ventral plasma membrane of adherent ECs. Also, acceptor photobleaching fluorescence resonance energy transfer demonstrated that VEGFR2/α(v)β(3) coupling occurs at the basal aspect of Tat-adherent ECs. Cell membrane fractionation showed that a limited fraction of α(v)β(3) integrin and VEGFR2 does colocalize in lipid rafts at the basal aspect of Tat-adherent ECs. VEGFR2 undergoes phosphorylation and triggers pp60src/ERK(1/2) activation. The use of lipid raft disrupting agents and second messenger inhibitors demonstrated that intact lipid rafts and the VEGFR2/pp60src/ERK(1/2) pathway are both required for cytoskeleton organization and proangiogenic activation of Tat-adherent ECs. CONCLUSIONS: Substrate-immobilized Tat causes VEGFR2/α(v)β(3) complex formation and polarization at the basal aspect of adherent ECs, VEGFR2/pp60src/ERK(1/2) phosphorylation, cytoskeleton organization, and proangiogenic activation. These results provide novel insights in the AGF/tyrosine kinase receptor/integrin cross-talk.

Original publication




Journal article


Arteriosclerosis, thrombosis, and vascular biology

Publication Date





e25 - e34


Section of General Pathology and Immunology, Department of Biomedical Sciences and Biotechnology, University of Brescia, Italy.


Endothelium, Vascular, Cells, Cultured, Focal Adhesions, Endothelial Cells, Humans, HIV-1, Vascular Endothelial Growth Factor Receptor-2, Integrin alphaVbeta3, Signal Transduction, Cell Movement, tat Gene Products, Human Immunodeficiency Virus