Mechanisms of Integrin–Vascular Endothelial Growth Factor Receptor Cross-Activation in Angiogenesis

Abstract

Abstract-The functional responses of endothelial cells are dependent on signaling from peptide growth factors and the cellular adhesion receptors, integrins. These include cell adhesion, migration, and proliferation, which, in turn, are essential for more complex processes such as formation of the endothelial tube network during angiogenesis. This study identifies the molecular requirements for the cross-activation between ␤ 3 integrin and tyrosine kinase receptor 2 for vascular endothelial growth factor (VEGF) receptor (VEGFR-2) on endothelium. The relationship between VEGFR-2 and ␤ 3 integrin appears to be synergistic, because VEGFR-2 activation induces ␤ 3 integrin tyrosine phosphorylation, which, in turn, is crucial for VEGF-induced tyrosine phosphorylation of VEGFR-2. We demonstrate here that adhesionand growth factor-induced ␤ 3 integrin tyrosine phosphorylation are directly mediated by c-Src. VEGF-stimulated recruitment and activation of c-Src and subsequent ␤ 3 integrin tyrosine phosphorylation are critical for interaction between VEGFR-2 and ␤ 3 integrin. Moreover, c-Src mediates growth factor-induced ␤ 3 integrin activation, ligand binding, ␤ 3 integrin-dependent cell adhesion, directional migration of endothelial cells, and initiation of angiogenic programming in endothelial cells. Thus, the present study determines the molecular mechanisms and consequences of the synergism between 2 cell surface receptor systems, growth factor receptor and integrins, and opens new avenues for the development of pro-and antiangiogenic strategies. Key Words: angiogenesis Ⅲ endothelial cell Ⅲ ␤ 3 integrin signaling Ⅲ vascular endothelial growth factor receptor Ⅲ extracellular matrix proteins A ngiogenesis, the process of new blood vessel formation from preexisting vasculature, plays critical roles in tissue regeneration, postischemic tissue repair on myocardial infarction and stroke, and in the pathogenesis of cancer, rheumatoid arthritis, and diabetic microvascular disease. 1 Angiogenesis is triggered by angiogenic growth factors and their receptors in coordination with extracellular matrix (ECM) receptors known as integrins. 2 On integrin engagement, ECM triggers activation of numerous intracellular signaling pathways essential for endothelial cell (EC) survival, proliferation, migration, morphogenesis, and organization of ECs into blood vessels. 3 There are several manifestations of a tightly collaborative relationship between integrins and receptors for growth factors. 4,5 On ECs, engagement of ␣ v ␤ 3 integrin promotes phosphorylation and activation of vascular endothelial growth factor (VEGF) receptor (VEGFR)-2, thereby augmenting the mitogenic activity of VEGFs. 6 Among several integrins on ECs, ␣ v ␤ 3 is the most abundant and influential receptor regulating angiogenesis. 7 The upregulation of ␣ v ␤ 3 during angiogenesis suggests that this integrin might play a crucial role during this process. Indeed, antagonists of ␣ v ␤ 3 , including blocking monoclonal antibody (LM609) and RGD cyclic peptides, were shown ...

UPARANT: A Urokinase Receptor–Derived Peptide Inhibitor of VEGF-Driven Angiogenesis with Enhanced Stability and In Vitro and In Vivo Potency

“…Although we have not investigated UPARANT/FPR association and disassociation process, we found that an excess of UPARANT prevents fMLF binding to FPR, suggesting that fMLF and UPARANT share the same binding site. The pivotal role of avb3 in mediating VEGF-dependent proangiogenic stimulus is well established (35). The involvement of avb3 integrin in the UPARANT inhibitory effect is supported by the findings that cell adhesion to vitronectin is greatly reduced in the presence of UPARANT.…”

“…It is known that avb3 integrin has a prominent role in the activity of VEGF. In response to VEGF, b3 integrin regulates integrin-dependent actin reorganization, thus leading avb3-VEGFR2 complexes to localize at new formed focal adhesions (35). UPARANT caused disappearance of avb3 at focal adhesions and the appearance of thin, avb3-positive linings at the cell edge, similar to untreated cells, whereas the addition of 10 nmol/L ERFR did not modify VEGF-dependent integrin redistribution.…”

Tetraspanin CD63 Promotes Vascular Endothelial Growth Factor Receptor 2-β1 Integrin Complex Formation, Thereby Regulating Activation and Downstream Signaling in Endothelial Cells in Vitro and in Vivo

“…Thus, VEGF receptor-mediated activation of FAK via c-Src allows formation of FAK-␣v␤5 integrin signaling complexes (46). Furthermore, VEGF induces ␣3 integrin tyrosine phosphorylation via c-Src, regulating adhesion and migration of endothelial cells (47).…”

Interplay between αvβ3 Integrin and Nucleolin Regulates Human Endothelial and Glioma Cell Migration

“…Among several integrins, ␣ v ␤ 3 is the most abundant and influential receptor regulating angiogenesis, and its tumor cell expression is correlated with disease progression in various tumor types (19). Growing evidence supports a central role for cooperative signaling between ␣ v ␤ 3 integrin and growth factor receptors, such as ErbB-2 (20), platelet-derived growth factor receptor ␤ (21,22), and vascular endothelial growth factor receptor 2 (21,23), mediating tumor cell adhesion, migration, invasion, and survival, as well as endothelial cell activation (19). In the same line, we have previously shown interaction of ␣ v ␤ 3 with the PTN receptor protein-tyrosine phosphatase ␤/ (RPTP␤/), which is required for PTN-induced endothelial cell migration (24).…”