Integrin-mediated Signaling Events in Human Endothelial Cells

Abstract

Vascular endothelial cells are important in a variety of physiological and pathophysiological processes. The growth and functions of vascular endothelial cells are regulated both by soluble mitogenic and differentiation factors and by interactions with the extracellular matrix; however, relatively little is known about the role of the matrix. In the present study, we investigate whether integrin-mediated anchorage to a substratum coated with the extracellular matrix protein fibronectin regulates growth factor signaling events in human endothelial cells. We show that cell adhesion to fibronectin and growth factor stimulation trigger distinct initial tyrosine phosphorylation events in endothelial cells. Thus, integrin-dependent adhesion of endothelial cells leads to tyrosine phosphorylation of both focal adhesion kinase and paxillin, but not of several growth factor receptors. Conversely, EGF stimulation causes receptor autophosphorylation, with no effect on focal adhesion kinase or paxillin tyrosine phosphorylation. Adhesion to fibronectin, in the absence of growth factors, leads to activation of MAPK. In addition, adhesion to fibronectin also potentiates growth factor signaling to MAPK. Thus, polypeptide growth factor activation of MAPK in anchored cells is far more effective than in cells maintained in suspension. Other agonists known to activate MAPK were also examined for their ability to activate MAPK in an anchorage-dependent manner. The neuropeptide bombesin, the bioactive lipid lysophosphatidic acid (LPA), and the cytokine tumor necrosis factor α, which signal through diverse mechanisms, were all able to activate MAPK to a much greater degree in fibronectin-adherent cells than in suspended cells. In addition, tumor necrosis factor α activation of c-Jun kinase (JNK) was also much more robust in anchored cells. Together, these data suggest a cooperation between integrins and soluble mitogens in efficient propagation of signals to downstream kinases. This cooperation may contribute to anchorage dependence of mitogenic cell cycle progression.

αvβ3 Integrins Mediate Flow-Induced NF-κB Activation, Proinflammatory Gene Expression, and Early Atherogenic Inflammation

“…Therefore, we first sought to determine how individual transitional matrix integrins contribute to endothelial cell activation by acute onset of flow. Consistent with previous reports, 21 qPCR analysis of HAECs indicated the expression of multiple transitional matrix-binding integrins, including the binding partners a5b1, avb3, and avb5 (Supplemental Figure S1). To test which of these transitional matrix-binding integrins mediate flowinduced endothelial cell activation, we used specific smallmolecule inhibitors or competitive peptides to block integrin signaling.…”

Conjugated Platinum(IV)−Peptide Complexes for Targeting Angiogenic Tumor Vasculature

“…Lysate preparation and Western analysis were performed as described previously (35). mAbs against integrin subunits included: anti-β 1 (clone B3B11, Chemicon International), anti-β 3 (R&D Systems), anti-α v (Chemicon).…”

Adhesion of B Cell Lines to Endothelial Cells from Human Lymphoid Tissue Modulates Tyrosine Phosphorylation and Endothelial Cell Activation

“…It is likely that pp125 FAK autophosphorylates and, in turn, phosphorylates paxillin (13). On the other hand, it has been shown that there is a cooperative interaction between ligation of integrins and growth factors in the activation of MAPKs (19). This may explain our finding that phosphorylation of ERK2 is delayed compared with phosphorylation of pp125 FAK and paxillin in B cell adhesion-induced tyrosine phosphorylation.…”

“…These as well as other studies have demonstrated the importance of ␤ 1 integrin in the activation and differentiation of T and B cells (10,14) as well as in other cell types, such as NK cells (15,16) and monocytes (17). Additionally, studies performed on regular endothelium show that some of these signals induce endothelial cell activation, which, coupled to cytokine and chemokine secretion, affects cytoskeletal reorganization, inducing changes in cell shape (18,19) that ultimately may affect lymphocyte transmigration.…”

“…However, few communications deal with the mechanism leading to the specific structural and functional properties characterizing the endothelium from lymphoid tissue or with the potential signaling events that may arise in high endothelial venules as a consequence of lymphocyte contact (37)(38)(39). These signaling events may be specially relevant in view of increasing evidence indicating that cell-cell interactions activate signal transduction cascades associated with the production and secretion of cytokines and chemokines (30,40,41), as well as with cell attachment (42) and changes in cell shape (19), activities clearly related to lymphocyte transmigration.…”