Extracellular matrix regulates endothelial functions through interaction of VEGFR-3 and integrin alpha5beta1.

Endothelium extracellular matrix (ECM) interactions can provide distinct spatial and molecular signals which control cellular proliferation, migration, and differentiation. Here, we investigated the role of fibronectin (FN), a major ECM protein, on the functions of lymphatic endothelial cells (LEC). We observed that FN, the ligand for integrin alpha5beta1, selectively promoted the growth of LEC as compared with vitronectin (VN) in the presence of the ligand for vascular endothelial growth factor receptor 3 [VEGFR-3 (VEGF-C156S)]. Upon investigating the mechanisms whereby ECM components regulate VEGFR-3 signaling, we found that FN transactivated VEGFR-3 and significantly enhanced the phosphorylation of VEGFR-3 induced by VEGF-C156S as compared to VN. An enhanced association of the integrin subunit alpha5 or beta1 with VEGFR-3, after stimulation with VEGF-C156S, was observed by co-immunoprecipitation. While blockade of integrin alpha5beta1 inhibited the VEGF-C156S-induced phosphorylation of VEGFR-3, no similar effect was obtained by blocking integrin alphavbeta3. FN also protected the endothelial cells from serum deprivation-induced apoptosis. Moreover, while the specific PI3 kinase inhibitor, LY294002, abolished this FN-mediated cell survival, the MAPK kinase inhibitor, PD98059, had no significant effect. Furthermore, a dominant-negative mutant of VEGFR-3 (G857R) reduced VEGF-C156S or FN-mediated cell survival, as well as the activities of PI3 kinase/Akt. Our results indicate that integrin alpha5beta1 participates in the activation of both VEGFR-3 and its downstream PI3 kinase/Akt signaling pathway, which is essential for FN-mediated lymphatic endothelial cell survival and proliferation.

Zhang X ，Groopman JE ，Wang JF 《JOURNAL OF CELLULAR PHYSIOLOGY》

Fibronectin and vitronectin induce AP-1-mediated matrix metalloproteinase-9 expression through integrin α(5)β(1)/α(v)β(3)-dependent Akt, ERK and JNK signaling pathways in human umbilical vein endothelial cells.

The activity of matrix metalloproteinases (MMPs), which selectively degrades the extracellular matrix (ECM), is critical in angiogenesis. Conversely, changes in ECM composition/structure alter the expression and activity of MMPs in various cell types. In the present study, we examined whether changes in ECM composition affect MMPs expression/activity of endothelial cells and thereby alter the surrounding ECM structure. Among the ECM molecules examined, fibronectin (FN) and vitronectin (VN) increased the expression and activity of MMP-9 in human umbilical vein endothelial cells (HUVECs). Both α(5)β(1) and α(v)β(3) integrins were involved in FN-induced MMP-9 expression. Also, FN-induced MMP-9 expression was found to be mediated by AP-1 transcription factors, including c-Jun, JunB, and JunD. Inhibitors or siRNAs specific to AP-1 activating signal transducers, including FAK-Src, PI3K/Akt, ERK, and JNK, abolished both FN-induced AP-1 activation and MMP-9 expression. VN-induced AP-1 activation and MMP-9 expression were also mediated by these AP-1 activating signal transducers in addition to p38 MAPK. Moreover, treatment with FN or VN resulted in increased degradation of collagen on HUVEC culture plates. Taken together, our data suggest that both fibronectin and vitronectin induce MMP-9 expression via the AP-1-activating signaling pathways in endothelial cells, and thereby stimulate degradation of surrounding collagen, leading to alterations in ECM structure and potentially the promotion of angiogenesis.

Jin YJ ，Park I ，Hong IK ，Byun HJ ，Choi J ，Kim YM ，Lee H ... -  《-》

The tyrosine kinase inhibitor cediranib blocks ligand-induced vascular endothelial growth factor receptor-3 activity and lymphangiogenesis.

Heckman CA ，Holopainen T ，Wirzenius M ，Keskitalo S ，Jeltsch M ，Ylä-Herttuala S ，Wedge SR ，Jürgensmeier JM ，Alitalo K ... -  《-》

Endothelial cell adhesion to the extracellular matrix induces c-Src-dependent VEGFR-3 phosphorylation without the activation of the receptor intrinsic kinase activity.

Galvagni F ，Pennacchini S ，Salameh A ，Rocchigiani M ，Neri F ，Orlandini M ，Petraglia F ，Gotta S ，Sardone GL ，Matteucci G ，Terstappen GC ，Oliviero S ... -  《-》

Fibronectin promotes VEGF-induced CD34 cell differentiation into endothelial cells.

Wijelath ES ，Rahman S ，Murray J ，Patel Y ，Savidge G ，Sobel M ... -  《JOURNAL OF VASCULAR SURGERY》