Urokinase-Type Plasminogen Activator Receptor (uPAR, CD87) Regulates Integrin Redistribution in Endothelial Cells Via Interaction with Low Density Lipoprotein Receptor- (LDLR-) Like Proteins

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 5315-5315
Author(s):  
Gerald Prager ◽  
Rene Novotny ◽  
Matthias Unseld ◽  
Marina Poettler ◽  
Waclawa Kalinowska ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Protein Interaction ◽  
Conflicts Of Interest ◽  
Focal Adhesions ◽  
Matrix Proteins ◽  
Endothelial Cell Migration ◽  
Binding Motif ◽  
Wild Type

Abstract Abstract 5315 angiogenesis by degradation of extracellular matrix proteins as well as induction of intracellular signal transduction. We recently could demonstrate that in VEGF-stimulated endothelial cells pro-uPA becomes activated, which leads to uPAR-complex formation, it's internalization and redistribution of uPAR to newly formed focal adhesions ad the leading edge of migrating endothelial cells. Thereby, uPAR surface expression is tightly transcriptional regulated via the Density Enhanced Phosphatase-1 (DEP-1), but also via the LDLR-family members, which regulate subcellular uPAR distribution. Here, we describe a mechanisms by which uPAR-internalization regulates integrin redistribution. We have characterized a novel binding motif on uPAR domain 3 for LDLR-protein interaction by using affinity chromatography as well as co-immunoprecipitation experiments. To proof a functional relevance of a direct uPAR/LDLR protein interaction, we reconstituted either uPAR mutants (mutL3/uPAR), lacking the binding site for LDLR-proteins, or wild type uPAR into endothelial cells derived from uPAR−/− mice. Reconstitution of mutL3/uPAR was incapable to redistribute uPAR as well as integrins during VEGF-induced endothelial cell migration when compared to wild type uPAR reconstitutes. The functional importance of uPAR / LDLR interaction was further reflected by the use of an inhibitory peptide (P1) interfering with uPAR/LDLR-protein interaction, which functionally reverted full length uPAR reconstitution, or the chaperon Receptor Associated Protein (RAP), a high affinity ligand for LDLR-proteins, which prevents uPAR/LDLR interactions. Thus, interfering with uPAR/LDLR-protein interaction at different levels led to an impaired endothelial cell spreading behavior on integrin-adhesive matrix proteins as well as a reduced pY576 FAK phosphorylation upon endothelial cell adhesion, leading to an reduced migratory response towards VEGF. These data suggest a central role of uPAR/LDLR-protein interaction in VEGF-induced endothelial cell migration via induction of integrin redistribution. Thus, uPAR/LDLR interaction might represent a novel therapeutic target in angiogenesis-related diseases. Disclosures: No relevant conflicts of interest to declare.

Urokinase Receptor (uPAR)-Dependent Integrin Redistribution Represents a Central Mechanism for Growth Factor Induced Endothelial Cell Migration

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2119-2119 ◽  
Author(s):  
Rene Novotny ◽  
Matthias Unseld ◽  
Marina Poettler ◽  
Christoph Zielinski ◽  
Bernd Binder ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Growth Factors ◽  
Endothelial Cell ◽  
Growth Factor ◽  
Binding Site ◽  
Protein Interaction ◽  
Conflicts Of Interest ◽  
Endothelial Cell Migration ◽  
Angiogenic Growth Factors

Abstract Abstract 2119 Tumor angiogenesis is induced when the net balance of pro- and antiangiogenic molecules is tipped in favor of angiogenesis, the so called ‘angiogenic switch’. Recently, we described a mechanism how VEGF induces pro-urokinase (pro-uPA) activation, which led to uPAR-complex formation and internalization of beta-1 integrins into the endosomal compartment via LDLR-proteins such as ApoER2 or VLDLR. Thereby, uPAR plays a central role for VEGF-induced endothelial cell migration. Here, we describe that uPAR-induced integrin internalization and redistribution to the leading edge is not only limited to VEGF-induced endothelial cell migration, but plays a central role for others angiogenic growth factors such as fibroblast growth factor-2 (FGF-2), hepatocyte growth factor (HGF) as well as epidermal growth factor (EGF). Furthermore, we found that a hitherto undescribed binding site on domain 3 of uPAR for direct LDLR-protein interaction is required and sufficient for uPAR-dependent integrin redistribution. Interference with the uPAR/integrin internalization either by the Receptor Associated Protein (RAP) or a specific LDLR-binding site mimicking peptide (P1), the migratory response of endothelial cells towards the growth factors VEGF, HGF, FGF-2, or EGF was almost blocked (20.24% ± 4.56%). Consistently, expression of a mutated uPAR lacking interaction site for LDLR-proteins in uPAR-/- endothelial cells via a retroviral construct led to reduced invasive response towards angiogenic growth factors in vitro as well as in a Matrigel plug in vivo assay. From these data we conclude that uPAR/LDLR-protein interaction represents a central molecule in growth factor-induced endothelial cell behavior, which might open a new avenue for therapeutic intervention. Disclosures: No relevant conflicts of interest to declare.

PECAM-1 isoform-specific regulation of kidney endothelial cell migration and capillary morphogenesis

2007 ◽  
Vol 292 (6) ◽  
pp. C2070-C2083 ◽  
Author(s):  
Shuji Kondo ◽  
Elizabeth A. Scheef ◽  
Nader Sheibani ◽  
Christine M. Sorenson
Keyword(s):  
Cell Migration ◽  
Cell Adhesion ◽  
Endothelial Cell ◽  
Vascular Development ◽  
Focal Adhesions ◽  
Endothelial Cell Migration ◽  
Extracellular Matrix Protein ◽  
Wild Type ◽  
Renal Vasculature ◽  
Capillary Morphogenesis

Platelet endothelial cell adhesion molecule-1 (PECAM-1) has been implicated in angiogenesis through its involvement in endothelial cell-cell and cell-matrix interactions and signal transduction. Recent studies indicate that the cytoplasmic domain of PECAM-1 plays an important role in its cell adhesive and signaling properties. However, the role PECAM-1 isoforms play during angiogenic events such as cell adhesion and migration requires further delineation. To gain insight into the role PECAM-1 plays during vascular development and angiogenesis, we examined the expression pattern of PECAM-1 isoforms during kidney vascularization. We show that multiple isoforms of PECAM-1 are expressed during renal vascular development with different frequencies. The PECAM-1 that lacks exons 14 and 15 (Δ14&15) was the predominant isoform detected in the renal vasculature. To further study PECAM-1 isoform-specific functions we isolated kidney endothelial cells (EC) from wild-type and PECAM-1-deficient (PECAM-1−/−) mice with B4-lectin-coated magnetic beads. PECAM-1−/− kidney EC showed reduced migration, inability to undergo capillary morphogenesis in Matrigel, dense peripheral focal adhesions, and peripheral cortical actin distribution compared with wild-type cells. PECAM-1−/− kidney EC secreted increased amounts of fibronectin and decreased amounts of tenascin-C and thrombospondin-1. Reexpression of Δ14&15, but not full-length, PECAM-1 in PECAM-1−/− kidney EC restored cell migration and capillary morphogenesis defects. Thus PECAM-1 may regulate the adhesive and migratory properties of kidney EC in an isoform-specific fashion through modulation of integrin activity and extracellular matrix protein expression. Our results indicate that regulated expression of specific PECAM-1 isoforms may enable EC to accommodate the different stages of angiogenesis.

Vascular Endothelial Growth Factor (VEGF)-Induced Endothelial Cell Migration Requires Urokinase Receptor (uPAR) for Integrin Redistribution.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 846-846
Author(s):  
Gerald W. Prager ◽  
Johannes M. Breuss4 ◽  
Patrick Brunner4 ◽  
Bernd R. Binder4
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Focal Adhesions ◽  
Specific Inhibitor ◽  
Leading Edge ◽  
Urokinase Receptor ◽  
Endothelial Cell Migration ◽  
Spatial Proximity

Abstract VEGF activates endothelial cells to migrate and invade surrounding tissues, an initial event in the angiogenic process. For invasion, the coordinated localized formation of a proteolytic repertoir is necessary. Focusing the urokinase receptor towards the leading edge of migrating cells provides such armor and inhibition of uPA binding to its receptor inhibits invasion of endothelial cells. In addition integrins continuously have to form focal contacts at the leading edge. Thus the spatial proximity between the localized proteases and the matrix seems to be essential for matrix degradation. In order to allow cell locomotion integrins have to release their ligands when they reach the trailing end and are subsequently endocytosed and redistributed to newly formed focal adhesions in a repetitive process. We here describe a new role of uPAR in regulating integrin redistribution. We have previously reported that stimulation of human endothelial cells by VEGF (50ng/ml) via its receptor flk-1 induces pro-uPA activation, when bound to uPAR. Subsequently a uPA/PAI-1/uPAR-complex is formed, which thereafter is endocytosed via a LDL-R family member. We now show that by this process beta-1 integrins are co-internalized in clathrin coated vesicles via a uPAR dependent mechanism. Subsequently, endocytosed uPAR recycles to focal adhesions where it co-localizes with integrin alpha-v/beta-3. Disrupting this chain of events, either by (1) RAP - a specific inhibitor of the LDL-R family - or by (2) uPAR depletion (using uPAR−/− cells or cleaving the GPI-anchor of uPAR by PI-PLC), beta-1 integrins are no longer internalized after VEGF stimulation. Under the same circumstances the migratory response of endothelial cells toward VEGF is impaired in vitro as shown by video-based migration assays and in vivo as demonstrated by matrigel angiogenesis assays. Next, we generated synthetic peptides interfering with uPAR/integrin interaction, which inhibit not only VEGF-induced integrin redistribution, but also diminish VEGF-induced endothelial cell migration, significantly. These data suggest that in VEGF-induced cell migration uPAR plays a central role not only in focusing proteolytic activity, but also in initial integrin redistribution. Interference with this process could be a therapeutic target for diseases depending on VEGF-induced angiogenesis.

Microtopography and flow modulate the direction of endothelial cell migration

2008 ◽  
Vol 294 (2) ◽  
pp. H1027-H1035 ◽  
Author(s):  
P. Uttayarat ◽  
M. Chen ◽  
M. Li ◽  
F. D. Allen ◽  
R. J. Composto ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Fluid Shear Stress ◽  
Focal Adhesions ◽  
Endothelial Cell Migration ◽  
High Shear ◽  
High Shear Stress ◽  
Initial Exposure

The migration of vascular endothelial cells under flow can be modulated by the addition of chemical or mechanical stimuli. The aim of this study was to investigate how topographic cues derived from a substrate containing three-dimensional microtopography interact with fluid shear stress in directing endothelial cell migration. Subconfluent bovine aortic endothelial cells were seeded on fibronectin-coated poly(dimethylsiloxane) substrates patterned with a combinatorial array of parallel and orthogonal microgrooves ranging from 2 to 5 μm in width at a constant depth of 1 μm. During a 4-h time-lapse observation in the absence of flow, the majority of the prealigned cells migrated parallel to the grooves with the distribution of their focal adhesions (FAs) depending on the groove width. No change in this migratory pattern was observed after the cells were exposed to moderate shear stress (13.5 dyn/cm2), irrespective of groove direction with respect to flow. After 4-h exposure to high shear stress (58 dyn/cm2) parallel to the grooves, the cells continued to migrate in the direction of both grooves and flow. By contrast, when microgrooves were oriented perpendicular to flow, most cells migrated orthogonal to the grooves and downstream with flow. Despite the change in the migration direction of the cells under high shear stress, most FAs and actin microfilaments maintained their original alignment parallel to the grooves, suggesting that topographic cues were more effective than those derived from shear stress in guiding the orientation of cytoskeletal and adhesion proteins during the initial exposure to flow.

scholarly journals VEGF binding to NRP1 is essential for VEGF stimulation of endothelial cell migration, complex formation between NRP1 and VEGFR2, and signaling via FAK Tyr407 phosphorylation

2011 ◽  
Vol 22 (15) ◽  
pp. 2766-2776 ◽  
Author(s):  
Birger Herzog ◽  
Caroline Pellet-Many ◽  
Gary Britton ◽  
Basil Hartzoulakis ◽  
Ian C. Zachary
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Complex Formation ◽  
Rational Design ◽  
Cell Model ◽  
Umbilical Vein ◽  
Focal Adhesions ◽  
Dominant Negative ◽  
Endothelial Cell Migration

In endothelial cells, neuropilin-1 (NRP1) binds vascular endothelial growth factor (VEGF)-A and is thought to act as a coreceptor for kinase insert domain-containing receptor (KDR) by associating with KDR and enhancing VEGF signaling. Here we report mutations in the NRP1 b1 domain (Y297A and D320A), which result in complete loss of VEGF binding. Overexpression of Y297A and D320A NRP1 in human umbilical vein endothelial cells reduced high-affinity VEGF binding and migration toward a VEGF gradient, and markedly inhibited VEGF-induced angiogenesis in a coculture cell model. The Y297A NRP1 mutant also disrupted complexation between NRP1 and KDR and decreased VEGF-dependent phosphorylation of focal adhesion kinase at Tyr407, but had little effect on other signaling pathways. Y297A NRP1, however, heterodimerized with wild-type NRP1 and NRP2 indicating that nonbinding NRP1 mutants can act in a dominant-negative manner through formation of NRP1 dimers with reduced binding affinity for VEGF. These findings indicate that VEGF binding to NRP1 has specific effects on endothelial cell signaling and is important for endothelial cell migration and angiogenesis mediated via complex formation between NRP1 and KDR and increased signaling to focal adhesions. Identification of key residues essential for VEGF binding and biological functions provides the basis for a rational design of antagonists of VEGF binding to NRP1.

Reactive oxygen species mediate Rac-induced loss of cell-cell adhesion in primary human endothelial cells

2002 ◽  
Vol 115 (9) ◽  
pp. 1837-1846 ◽  
Author(s):  
Sandra van Wetering ◽  
Jaap D. van Buul ◽  
Safira Quik ◽  
Frederik P. J. Mul ◽  
Eloise C. Anthony ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Endothelial Cells ◽  
Cell Migration ◽  
Cell Adhesion ◽  
Endothelial Cell ◽  
Reactive Oxygen ◽  
Small Gtpases ◽  
Endothelial Cell Migration ◽  
Oxygen Species ◽  
Cell Cell

The integrity of the endothelium is dependent on cell-cell adhesion, which is mediated by vascular-endothelial (VE)-cadherin. Proper VE-cadherin-mediated homotypic adhesion is, in turn, dependent on the connection between VE-cadherin and the cortical actin cytoskeleton. Rho-like small GTPases are key molecular switches that control cytoskeletal dynamics and cadherin function in epithelial as well as endothelial cells. We show here that a cell-penetrating, constitutively active form of Rac (Tat-RacV12) induces a rapid loss of VE-cadherin-mediated cell-cell adhesion in endothelial cells from primary human umbilical veins (pHUVEC). This effect is accompanied by the formation of actin stress fibers and is dependent on Rho activity. However,transduction of pHUVEC with Tat-RhoV14, which induces pronounced stress fiber and focal adhesion formation, did not result in a redistribution of VE-cadherin or an overall loss of cell-cell adhesion. In line with this observation, endothelial permeability was more efficiently increased by Tat-RacV12 than by Tat-RhoV14. The loss of cell-cell adhesion, which is induced by Tat-RacV12, occurred in parallel to and was dependent upon the intracellular production of reactive oxygen species (ROS). Moreover, Tat-RacV12 induced an increase in tyrosine phosphorylation of a component the VE-cadherin-catenin complex, which was identified as α-catenin. The functional relevance of this signaling pathway was further underscored by the observation that endothelial cell migration, which requires a transient reduction of cell-cell adhesion, was blocked when signaling through ROS was inhibited. In conclusion, Rac-mediated production of ROS represents a previously unrecognized means of regulating VE-cadherin function and may play an important role in the (patho)physiology associated with inflammation and endothelial damage as well as with endothelial cell migration and angiogenesis.

scholarly journals CRIF1 deficiency suppresses endothelial cell migration via upregulation of RhoGDI2

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256646
Author(s):  
Harsha Nagar ◽  
Seonhee Kim ◽  
Ikjun Lee ◽  
Su-Jeong Choi ◽  
Shuyu Piao ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Signaling Pathway ◽  
Umbilical Vein ◽  
Vascular Endothelial Cell ◽  
Cellular Migration ◽  
Endothelial Cell Migration ◽  
Migration And Invasion ◽  
Mitochondrial Functions

Rho GDP-dissociation inhibitor (RhoGDI), a downregulator of Rho family GTPases, prevents nucleotide exchange and membrane association. It is responsible for the activation of Rho GTPases, which regulate a variety of cellular processes, such as migration. Although RhoGDI2 has been identified as a tumor suppressor gene involved in cellular migration and invasion, little is known about its role in vascular endothelial cell (EC) migration. CR6-interacting factor 1 (CRIF1) is a CR6/GADD45-interacting protein with important mitochondrial functions and regulation of cell growth. We examined the expression of RhoGDI2 in CRIF1-deficient human umbilical vein endothelial cells (HUVECs) and its role in cell migration. Expression of RhoGDI2 was found to be considerably higher in CRIF1-deficient HUVECs along with suppression of cell migration. Moreover, the phosphorylation levels of Akt and CREB were decreased in CRIF1-silenced cells. The Akt-CREB signaling pathway was implicated in the changes in endothelial cell migration caused by CRIF1 downregulation. In addition to RhoGDI2, we identified another factor that promotes migration and invasion of ECs. Adrenomedullin2 (ADM2) is an autocrine/paracrine factor that regulates vascular tone and other vascular functions. Endogenous ADM2 levels were elevated in CRIF1-silenced HUVECs with no effect on cell migration. However, siRNA-mediated depletion of RhoGDI2 or exogenous ADM2 administration significantly restored cell migration via the Akt-CREB signaling pathway. In conclusion, RhoGDI2 and ADM2 play important roles in the migration of CRIF1-deficient endothelial cells.

scholarly journals Skeletal muscle-endothelial cell cross talk through angiotensin II

2010 ◽  
Vol 299 (6) ◽  
pp. C1402-C1408 ◽  
Author(s):  
Leeann M. Bellamy ◽  
Adam P. W. Johnston ◽  
Michael De Lisio ◽  
Gianni Parise
Keyword(s):  
Skeletal Muscle ◽  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Angiotensin Ii ◽  
Branch Point ◽  
Endothelial Cell Migration ◽  
Tube Length ◽  
Ang Ii

The role of angiotensin II (ANG II) in postnatal vasculogenesis and angiogenesis during skeletal muscle (SKM) regeneration is unknown. We examined the capacity of ANG II to stimulate capillary formation and growth during cardiotoxin-induced muscle regeneration in ACE inhibitor-treated ANG II type 1a receptor knockout (AT1a−/−) and C57Bl/6 control mice. Analysis of tibialis anterior (TA) cross-sections revealed 17% and 23% reductions in capillarization in AT1a−/− and captopril treated mice, respectively, when compared with controls, 21 days postinjury. Conversely, no differences in capillarization were detected at early time points (7 and 10 days). These results identify ANG II as a regulator of angiogenesis but not vasculogenesis in vivo. In vitro angiogenesis assays of human umbilical vein endothelial cells (HUVECs) further confirmed ANG II as proangiogeneic as 71% and 124% increases in tube length and branch point number were observed following ANG II treatment. Importantly, treatment of HUVECs with conditioned media from differentiated muscle cells resulted in an 84% and 203% increase in tube length and branch point number compared with controls, which was abolished following pretreatment of the cells with an angiotensin-converting enzyme inhibitor. The pro-angiogenic effect of ANG II can be attributed to an enhanced endothelial cell migration because both transwell and under agarose migration assays revealed a 37% and 101% increase in cell motility, respectively. Collectively, these data highlight ANG II as a proangiogenic regulator during SKM regeneration in vivo and more importantly demonstrates that ANG II released from SKM can signal endothelial cells and regulate angiogenesis through the induction of endothelial cell migration.

Vascular endothelial growth factor (VEGF) in cartilage neovascularization and chondrocyte differentiation: auto-paracrine role during endochondral bone formation

2000 ◽  
Vol 113 (1) ◽  
pp. 59-69 ◽  
Author(s):  
M.F. Carlevaro ◽  
S. Cermelli ◽  
R. Cancedda ◽  
F. Descalzi Cancedda
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Hypertrophic Chondrocytes ◽  
Endothelial Cell Migration ◽  
Vegf Receptor ◽  
Hypertrophic Cartilage ◽  
Endothelial Growth Factor

Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) induces endothelial cell migration and proliferation in culture and is strongly angiogenic in vivo. VEGF synthesis has been shown to occur in both normal and transformed cells. The receptors for the factor have been shown to be localized mainly in endothelial cells, however, the presence of VEGF synthesis and the VEGF receptor in cells other than endothelial cells has been demonstrated. Neoangiogenesis in cartilage growth plate plays a fundamental role in endochondral ossification. We have shown that, in an avian in vitro system for chondrocyte differentiation, VEGF was produced and localized in cell clusters totally resembling in vivo cartilage. The factor was synthesized by hypertrophic chondrocytes and was released into their conditioned medium, which is highly chemotactic for endothelial cells. Antibodies against VEGF inhibited endothelial cell migration induced by chondrocyte conditioned media. Similarly, endothelial cell migration was inhibited also by antibodies directed against the VEGF receptor 2/Flk1 (VEGFR2). In avian and mammalian embryo long bones, immediately before vascular invasion, VEGF was distinctly localized in growth plate hypertrophic chondrocytes. In contrast, VEGF was not observed in quiescent and proliferating chondrocytes earlier in development. VEGF receptor 2 colocalized with the factor both in hypertrophic cartilage in vivo and hypertrophic cartilage engineered in vitro, suggesting an autocrine loop in chondrocytes at the time of their maturation to hypertrophic cells and of cartilage erosion. Regardless of cell exposure to exogenous VEGF, VEGFR-2 phosphorylation was recognized in cultured hypertrophic chondrocytes, supporting the idea of an autocrine functional activation of signal transduction in this non-endothelial cell type as a consequence of the endogenous VEGF production. In summary we propose that VEGF is actively responsible for hypertrophic cartilage neovascularization through a paracrine release by chondrocytes, with invading endothelial cells as a target. Furthermore, VEGF receptor localization and signal transduction in chondrocytes strongly support the hypothesis of a VEGF autocrine activity also in morphogenesis and differentiation of a mesoderm derived cell.

Tissue factor pathway inhibitor (TFPI) interferes with endothelial cell migration by inhibition of both the Erk pathway and focal adhesion proteins

2008 ◽  
Vol 99 (03) ◽  
pp. 576-585 ◽  
Author(s):  
Mathieu Provençal ◽  
Marisol Michaud ◽  
Édith Beaulieu ◽  
David Ratel ◽  
Georges-Étienne Rivard ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Tissue Factor ◽  
Focal Adhesion ◽  
Tissue Factor Pathway Inhibitor ◽  
Endothelial Cell Migration ◽  
Cell Functions ◽  
Tissue Factor Pathway

SummaryTissue factor pathway inhibitor (TFPI) is a plasma Kunitz-type serine protease inhibitor that is mainly known for its inhibition of tissue factor-mediated coagulation. In addition to its anticoagulant properties, emerging data show that TFPI may also regulate endothelial cell functions via a non-haemostatic pathway. In this work we demonstrate that at concentrations within the physiological range,TFPI inhibits both endothelial cell migration and their differentiation into capillary-like structures in vitro. These effects were specific to endothelial cells since no inhibitory effect was observed on the migration of tumor (glio- blastoma) cells. Inhibition of endothelial cell migration was correlated with a concomitant loss in cell adhesion,suggesting an alteration of focal adhesion complex integrity. Accordingly,we observed thatTFPI inhibited the phosphorylation of focal adhesion kinase and paxillin,two key proteins involved in the scaffolding of these complexes, and that this effect was specific to endothelial cells. These results suggest that TFPI influences the angiogenic process via a non-haemostatic pathway, by downregulating the migratory mechanisms of endothelial cells.

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