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Am J Physiol Cell Physiol 295: C600-C610, 2008. First published June 18, 2008; doi:10.1152/ajpcell.00460.2007
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VASCULAR BIOLOGY

Cdc42 and RhoA have opposing roles in regulating membrane type 1-matrix metalloproteinase localization and matrix metalloproteinase-2 activation

Eric Ispanovic, Damiano Serio, and Tara L. Haas

School of Kinesiology and Health Sciences, York University, Toronto, Ontario, Canada M3J 1P3

Submitted 3 October 2007 ; accepted in final form 12 June 2008


    ABSTRACT
 TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Proteolysis of the basement membrane and interstitial matrix occurs early in the angiogenic process and requires matrix metalloproteinase (MMP) activity. Skeletal muscle microvascular endothelial cells exhibit robust actin stress fibers, low levels of membrane type 1 (MT1)-MMP expression, and minimal MMP-2 activation. Depolymerization of the actin cytoskeleton increases MT1-MMP expression and MMP-2 activation. Rho family GTPases are regulators of actin cytoskeleton dynamics, and their activity can be modulated in response to angiogenic stimuli such as vascular endothelial growth factor (VEGF). Therefore, we investigated their roles in MMP-2 and MT1-MMP production. Endothelial cells treated with H1152 [an inhibitor of Rho kinase (ROCK)] induced stress fiber depolymerization and an increase in cortical actin. Both MMP-2 and MT1-MMP mRNA increased, which translated into greater MMP-2 protein production and activation. ROCK inhibition rapidly increased cell surface localization of MT1-MMP and increased PI3K activity, which was required for MMP-2 activation. Constitutively active Cdc42 increased cortical actin polymerization, phosphatidylinositol 3-kinase activity, MT1-MMP cell surface localization, and MMP-2 activation similarly to inhibition of ROCK. Activation of Cdc42 was sufficient to decrease RhoA activity. Capillary sprout formation in a three-dimensional collagen matrix was increased in cultures treated with RhoAN19 or Cdc42QL and, conversely, decreased in cultures treated with dominant negative Cdc42N17. VEGF stimulation also induced activation of Cdc42 while inhibiting RhoA activity. Furthermore, VEGF-dependent activation of MMP-2 was reduced by inhibition of Cdc42. These results suggest that Cdc42 and RhoA have opposing roles in regulating cell surface localization of MT1-MMP and MMP-2 activation.

vascular endothelia growth factor; phosphatidylinositol 3-kinase; Rho-GTPase; cytoskeleton; endothelium; angiogenesis


ANGIOGENESIS is the growth of new capillaries from preexisting mature ones. It occurs through a cascade of events in which disruption of the endothelial adherens junctions, by way of actin cytoskeleton reorganization, and proteolysis of the basement membrane and interstitial matrix are critical steps. Matrix metalloproteinases (MMPs), a family of zinc- and calcium-dependent enzymes (6, 56), are key participants in several steps of the angiogenic response, including regulation of endothelial cell permeability, migration, invasion, and tubule formation (13, 22). MMP-2 and membrane type 1 (MT1)-MMP are produced by endothelial cells and can degrade types I and IV collagen (2, 37). MMP-2-deficient mice have reduced tumor, corneal, and retinal angiogenesis (25, 27, 41), whereas MT1-MMP-deficient mice fail to gain weight, have deficient connective tissue metabolism, and die 3–4 wk after birth (23, 62). Combined MMP-2 and MT1-MMP deficiency causes embryonic lethality (due to respiratory failure, abnormal blood vessels, and immature muscle fibers), highlighting the synergistic potential of these MMPs as key targets in controlling angiogenesis (40).

We, and others (24, 50, 59), have shown that the MMPs, specifically MMP-2 and MT1-MMP, are upregulated in response to reorganization of the actin cytoskeleton. The Rho-GTPases are known regulators of the actin cytoskeleton (39) and contribute to the transformation of extracellular stimuli into angiogenic responses (9). Angiogenic factors such as vascular endothelial growth factor (VEGF) and thrombin recruit downstream pathways, including the mitogen-activated protein kinases (MAPKs), phosphatidylinositol 3-kinase (PI3K), and various transcription factors through Rho-GTPase activation (28, 3234, 54).

RhoA induces stress fiber formation and is required for VEGF-induced increases in endothelial cell permeability, migration, and stabilization of capillary tubes (1, 12, 38). Shear stress increases RhoA activity (46, 57) and stress fiber formation (7) and results in increased focal adhesion and junctional complex formation (45).

Rac1 controls lamellipodia and is linked with angiogenic signaling cascades. It is responsible for endothelial branching morphogenesis and capillary assembly in Matrigel overlay assays (11) through its contributions to endothelial migration (3) and MMP-2 activation (63). Downstream targets of Rac1 include the MAPKs and the AP-1 family of transcription factors, which in turn regulate MMP production (34, 54).

Cdc42 activation occurs with VEGF activation (31) and triggers the formation of filopodia and regulates cell polarization through microtubule organization. Activation of Cdc42 induces lumen and vacuole formation in endothelial cells and confers an invasive phenotype to T-lymphocytes (36, 48). Nobes and Hall (39) proposed that a hierarchy of cross talk occurs in which Cdc42 lies upstream of Rac1 and RhoA and that Cdc42 activates Rac1 while suppressing RhoA activity.

We hypothesized that manipulation of Rho-GTPase activity would result in changes in MMP-2 and MT1-MMP expression and activity in microvascular endothelial cells. We show that RhoA suppresses MMP-2 expression while limiting the amount of cell surface MT1-MMP and, thereby, MMP-2 activation. Conversely, Cdc42 activation promotes angiogenesis and increases the amount of cell surface MT1-MMP, thereby increasing MMP-2 activation. Furthermore, we demonstrate that these pathways contribute to VEGF-dependent activation of MMP-2.


    MATERIALS AND METHODS
 TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Cell culture. Rat microvascular endothelial cells (SMEC) were isolated from extensor digitorum longus muscles and cultured as previously described (21). Cells were used for experiments between passages 4 and 11 and plated on type I collagen (12.5 µg collagen/ml coating buffer)-coated culture dishes. For inhibitor studies, SMEC were pretreated for 3 h with 10 µM LY-294002 or 50 µM SP-600125 and then treated with 10 µM H1152, 10 µM GGTI-298, or 1 µM cytochalasin D for 24 h. All inhibitors were purchased from Calbiochem. VEGF (recombinant human, Invitrogen) treatments were 25 ng/ml for varying times.

Three-dimensional collagen culture. SMEC were embedded in a three-dimensional type I collagen matrix (2.5 mg/ml Vitrogen) as previously described (8). SMEC were cultured in the presence or absence of 10 µM LY-294002 for 24 h at 37°C.

Gelatin zymography. Cells were lysed using 120 mM Tris·HCl (pH 8.7), 0.1% Triton X-100, and 5% glycerol supplemented with protease inhibitors (Sigma, catalog no. P8340) and 100 mM sodium orthovandate (lysis buffer). Whole cell protein extracts (10 µg) were analyzed by gelatin zymography as previously described (20). Gels were visualized and imaged using the Fluorchem gel doc system and analyzed using Alphaease (Alpha Innotech) software. Images were inverted for publication for ease of visualization. Total MMP-2 protein was calculated as the sum of the latent (72 kDa) and active (62 kDa) bands and was expressed as fold increase verses control. Active MMP-2 (62 kDa) was expressed as fold increase versus control.

Northern blot analysis. Total RNA was isolated and analyzed by Northern blot analysis using conventional techniques as described previously (20). Films were scanned and densitometry was performed using Alphaease (AlphaInnotech) software. Loading was normalized to the 28S rRNA band.

Transient transfection and promoter assays. Cells were plated on type I collagen-coated, 12-well dishes at a density of 50,000 cells/well, and 18 h later transient transfections were performed using LipofectAMINE 2000 (Invitrogen) reagent as per manufacturer's instructions. Cells were transfected with 0.5 µg of full-length MMP-2 promoter (21) and 0.05 µg of pRenilla (Promega). Twenty four hours posttransfection, cell were treated with either H1152 or GGTI-298 for 24 h. Forty-eight hours after transfection, cells were lysed with 1x passive lysis reagent (Promega), and reporter assays were performed using the Dual-Glo Luciferase Assay system (Promega). Firefly luciferase values were normalized to Renilla luciferase values. Normalized MMP-2 luciferase values from conditions that were treated with H1152 or GGTI-298 were then compared relative with those control untreated conditions.

Western blot analysis. Whole cell extracts were analyzed by Western blot analysis as described previously (24). Primary antibodies were the following: MT1-MMP (1:1,000, Novus), AKT (1:1,000), and Phospho-AKT (1:1,000, Cell Signaling). Films were scanned and densitometry was performed using Alphaease (AlphaInnotech) software. Phospho-AKT values were normalized to total-AKT values to account for variability in loading.

Immunofluorescence staining. Cells were plated on type I collagen-coated glass coverslips, incubated overnight at 37°C, and then treated with 10 µM H1152 for varying time points. Cells were fixed with 3.75% paraformaldehyde and then blocked and permeabilized in PBS + 5% normal goat serum + 0.05% Triton-X 100. Cells were incubated with primary phospho-c-Jun NH2-terminal kinase (JNK) antibody (1:300, Upstate), followed by secondary goat anti-rabbit Alexa-568 (1:400, Molecular Probes). Actin was visualized with fluorescein isothiocyanate (FITC)-phalloidin (4 µM, Sigma), and nuclei were counterstained with 4',6'-diaminodino-2-phenylindole (DAPI, 1:1,500, Molecular Probes). Cells were visualized by fluorescence microscopy (Zeiss Axiovert 200M). Images were captured using a cooled digital CCD Camera (Quantix 57) and imaging software (Metamorph, Universal Imaging).

TAT-Rho-GTPase fusion protein creation and transduction. Rho-GTPase DNA plasmids (RhoAN19, RhoAQL, Rac1N17, Rac1QL, Cdc42N17, and Cdc42QL were gifts from Dr. Ken Yamada) were subcloned into the psecTAG-TAT vector (amino acids 47–57 of the HIV-Tat, a gift from Dr. Tibor Barka) (5). Cos7 cells (provided Dr. Imogen Coe, York University) were transfected with 6 µl of TransPassD1 (New England Biolabs) and 5 µg TAG-TAT-Rho-GTPase or TAT-TAT plasmid DNA in OptiMEM for 3 h, as per manufacturer's instructions. OptiMEM was replaced with cDMEM and cells were maintained at 37°C overnight after which media was replaced with fresh OptiMEM for 3 h. The Cos7-conditioned OptiMEM, containing the secreted TAT or TAT-Rho-GTPase proteins, was collected and spun down, and the supernatant was stored at –20°C. SMECs were incubated with equal volumes of the OptiMEM containing mutant Rho-GTPase protein after which the cells were lysed as described above. Because the TAT peptide is known to elicit changes in endothelial cell cytoskeleton organization (58) and signaling (4), experimental conditions utilizing the TAT-Rho-GTPase fusion proteins were compared with TAT peptide-treated controls. In some experiments, cyclohexamide (20 µg/ml, Sigma) was added during the OptiMEM incubation to eliminate the effects of mRNA translation on MMP-2 protein levels.

Cell surface immunofluorescence staining. Cells were plated on type I collagen-coated glass coverslips and incubated overnight at 37°C and then treated with 10 µM H1152 or TAT-Cdc42QL-containing media for 2 h. Cells were kept on ice and washed with physiological saline solution (PSS, in mM: 130 NaCl, 1.18 KH2PO4, 1.17 MgSO4·7H2O, 14.9 NaHCO3, pH = 7.3, 5.5 dextrose, 0.026 CaNa2EDTA, and 1.6 CaCl2), blocked for 1 h with 5% BSA in PSS, and incubated with MT1-MMP antibody (1:300, Chemicon, Ab815) in PSS for 1.5 h. After three washes with PSS, cells were fixed with 3.75% paraformaldehyde and then permeabilized in PSS + 0.05% Triton-X 100. Cells were then incubated with secondary goat anti-rabbit Alexa-568 (1:400 dilution, Molecular Probes). Actin was stained with FITC-phalloidin (4 µM, Sigma). Cells were visualized by confocal microscopy (Olympus Fluoview 300 with Argon laser, 488 nm, and HeNe laser, 543 nm, pinhole aperture = 2) using Fluoview software (Olympus). Z-sections were captured (0.1 µm, 10 slices), and complete Z-stacks were used for actin staining images. For cell surface MT1-MMP images, only the first three slices of the Z-section were included in the final Z-stack.

Surface biotinylation. SMEC were cultured on type I collagen for 24 h, pretreated with 50 µM LY-294002, and then stimulated with 25 ng/ml VEGF or 10 µM H1152 for 60 min or treated with TAT-Cdc42QL-containing media for 2 h. Cells were washed with ice-cold PBS and incubated with 1 mg/ml sulfo-NHS-biotin in PBS for 30 min on ice. The reaction was terminated by washing the cells with 100 mM glycine for 20 min. Cells were lysed as described above, and 75 µg of protein from total cell lysates were incubated overnight at 4°C with Streptavidin-Agarose beads (Pierce) with gentle rocking. Beads were collected by centrifugation and the pellet was washed several times with PBS containing 0.1% NP-40. Fifty microliters of 1x loading buffer were added, the samples were boiled, and the proteins were separated by 10% SDS-PAGE followed by MT1-MMP Western blot analysis as previously described above. Blots were then stripped and reprobed for β1-integrin (Cell Signaling) as a loading control.

Capillary sprout formation assay. Capillary segments were isolated from the rat epididymal fat pad and cultured within a three-dimensional type I collagen matrix (Vitrogen) as previously described (20). Fragments were cultured overnight at 37°C after which time culture media was replaced with Opti-MEM (Invitrogen) containing constitutively active or dominant negative TAT-Rho-GTPase proteins or a TAT peptide control for 3 h. Opti-MEM was then replaced with cDMEM, and the fragments were cultured for an additional 48 h. Phase-contrast images were taken, and sprout length was measured using Metamorph imaging software (Universal Imaging).

RhoGTPase activity assays. SMEC were lysed with IP lysis buffer (50 mM Tris, pH 7.5, 10 mM MgCl2, 0.3 M NaCl, and 2% NP-40), and 100 µg of protein were incubated with Rhotekin-GST or PAK-GST protein beads (Cytoskeleton) for 2 h at 4°C with gentle rocking for RhoA or Rac1 and Cdc42 activity measurements respectively. Beads were collected by centrifugation and the pellet was washed 3x with wash buffer (25 mM Tris, pH 7.5, 30 mM MgCl2, 40 mM NaCl). Fifty microliters of 1x reducing loading buffer were added, the samples were boiled, and the proteins were separated by SDS-PAGE through a 15% acrylamide gel followed by Western blot analysis for RhoA, Rac1, or Cdc42 (1:1,000, Cell Signaling).

Statistics. Data were normalized to control and are presented as fold change ± SE versus control. Student's t-test or one-way ANOVA followed by Tukey post hoc tests, were applied to determine statistical significance (P < 0.05).


    RESULTS
 TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Inhibition of RhoA/ROCK induces MMP-2 activation. We previously demonstrated that depolymerization of the actin cytoskeleton with cytochalasin D induces MMP-2 and MT1-MMP mRNA expression (24). To further investigate the signaling pathways involved in this response, we treated SMEC with the nonspecific Rho-GTPases inhibitor GGTI-298 (an inhibitor of geranylgeranyl-transferase-1 that decreases activity of all Rho-GTPases). Pretreatment of SMEC with GGTI-298 abolished the cytochalasin D-induced increase in MMP-2 and MT1-MMP mRNA (Fig. 1A). In contrast, inhibition of Rho kinase (ROCK), a RhoA effector responsible for actin cytoskeleton organization, increased basal levels of both MMP-2 and MT1-MMP mRNA. Cotreatment with the ROCK inhibitor H1152 and cytochalasin D did not result in a greater increase in MMP-2 or MT1-MMP mRNA than seen with either treatment on its own (Fig. 1B). To test whether the increase in MMP-2 mRNA in response to H1152 treatment was due to increased mRNA synthesis, we assayed MMP-2 promoter activity. Promoter activity increased significantly following ROCK inhibition, whereas treatment with GGTI-298 had no effect (Fig. 1C).


Figure 1
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Fig. 1. Long-term inhibition of RhoA/Rho kinase (ROCK) signaling induces MMP-2 production and activation. Endothelial cells pretreated with 10 µM GGTI-298 (A) or 10 µM H1152 (B) were treated with 1 µM cytochalasin D (CD) for 24 h. Matrix metalloproteinase-2 (MMP-2, open bars) and membrane type-1 (MT1)-MMP (solid bars) mRNA were quantified using Northern blot analysis and expressed relative to 18S rRNA. C: normalized MMP-2 promoter activity in cells treated with H1152 or GGTI-298 for 24 h. D: cells were treated with 1 µM CD or 10 µM H1152 for 24 h, and MMP-2 production (72 kDa + 62 kDa bands, open bars) and activation (62 kDa band only, solid bars) were assessed by gelatin zymography. Values are means ± SE. *P < 0.05 vs. control. #P < 0.05 vs. CD; n = 3. E: cells were treated with TAT-RhoAN19 or TAT peptide alone for 4 h and MMP-2 production (open bars) and activation (solid bars) was measured by gelatin zymography. Values are means ± SE. *P < 0.05 vs. TAT; n = 3.

 
These changes in mRNA were translated into increases in MMP-2 protein production and activation. Treatment of endothelial cells with H1152 increased MMP-2 protein production and activation as evidenced by gelatin zymography (Fig. 1D). Treatment of endothelial cells with a dominant-negative RhoA (RhoAN19) coupled to the 11 amino acid cell entry domain of the HIV-Tat peptide (TAT) demonstrated that inhibition of RhoA was sufficient to induce MMP-2 activation (Fig. 1E). Together, these results suggest that Rac1/Cdc42 are required for MMP-2 and MT1-MMP mRNA expression while RhoA activity suppresses their expression.

JNK regulates MMP-2 and MT1-MMP mRNA expression following ROCK inhibition. From our previous findings that JNK regulates MMP-2 and MT1-MMP mRNA expression in endothelial cells (24), we tested whether JNK contributes to the increase in mRNA expression following ROCK inhibition. Inhibition of ROCK with H1152 caused depolymerization of actin stress fibers and an increase in cortical actin (Fig. 2B, arrows). H1152 treatment caused nuclear translocation of phospho-JNK (Fig. 2B, arrowheads). Correlating with this response, we observed that the H1152-induced increase in MMP-2 mRNA expression was attenuated partially by JNK inhibition, whereas the increase in MT1-MMP was blocked completely by pretreatment with SP-600125 (Fig. 2C).


Figure 2
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Fig. 2. Inhibition of ROCK induces MMP-2 and MT1-MMP mRNA expression in a c-Jun NH2-terminal kinase (JNK)-dependent pathway. A: endothelial cells in the absence (top) or presence (bottom) of 10 µM H1152 were stained for phospho-JNK (red), F-actin (green), and DAPI (blue, nuclei). Arrows, cortical actin; arrowheads, nuclear P-JNK. Scale bar = 20 µm. B: cells pretreated with 100 µM SP-600125 were treated with 10 µM H1152 for 24 h. MMP-2 (open bars) and MT1-MMP (solid bars) mRNA was measured by Northern blot analysis and expressed relative to 18S rRNA. Values are means ± SE. *P < 0.05 vs. control. #P < 0.05 vs. H1152; n = 3.

 
Reorganization of the actin cytoskeleton induces MT1-MMP cell surface localization. Because activation of MMP-2 is dependent critically on the amount of MT1-MMP on the cell surface (42), we examined the amount of cell surface MT1-MMP following ROCK inhibition. Endothelial cells treated for 2 h with H1152 were incubated with anti-MT1-MMP antibody before permeabilization to specifically visualize cell surface MT1-MMP. Increased cell surface MT1-MMP was detectable following H1152 treatment, and MT1-MMP localized to areas of actin staining (Fig. 3A). Cell surface biotinylation followed by Western blot analysis confirmed that ROCK inhibition increased cell surface MT1-MMP in the absence of a change in total cellular MT1-MMP (Fig. 3B). Cell surface levels of β1-integrin levels were assessed to confirm equal loading of the surface biotinylated samples (data not shown). These results further suggest that high levels of RhoA activity are inhibitory to MT1-MMP cell surface localization.


Figure 3
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Fig. 3. Short-term inhibition of ROCK induces increased cell surface MT1-MMP. A: cells were treated for 2 h with 10 µM H1152 and then immunostained for MT1-MMP before permeablization (right), followed by F-actin (left). Scale bar = 20 µm. B: cell surface and total cellular MT1-MMP following 2-h treatment of cells with 10 µM H1152 was measured by cell surface biotinylation and Western blot analysis for MT1-MMP. Values are means ± SE. *P < 0.05 vs. control; n = 3.

 
PI3K activity is required for MMP-2 activation. We have shown that MMP-2 protein production and activation can be modified by PI3K signaling (24). We found that P-AKT levels increased as early as 30 min post-ROCK inhibition and remained elevated for 2 h (Fig. 4A). This time course of P-AKT levels corresponds to the timing of increased cortical actin polymerization as demonstrated in Fig. 2B.


Figure 4
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Fig. 4. Phosphatidylinositol 3-kinase (PI3K) is required for MMP-2 activation and capillary sprout formation. A: endothelial cells were treated with 10 µM H1152 for varying time points, and P-AKT, measured by Western blot analysis, was normalized to total AKT. Values are means ± SE. *P < 0.05 vs. control; n = 3. B: cells were pretreated with 10 µM LY-294002 (2 h) and then treated for 2 h with 10 µM H1152 to inhibit ROCK. MMP-2 production and activation were measured by gelatin zymography. Values are means ± SE. *P < 0.05 vs. control, #P < 0.05 vs. H1152; n = 3. C: capillary segments were cultured within a three-dimensional type I collagen matrix in the presence or absence of 10 µM LY-294002. Asterisks denote original capillary segment, whereas arrows denote sprouting cells. D: average sprout length was quantified using Metamorph software. Values are means ± SE. *P < 0.05 vs. control; n = 3. E: endothelial cells were pretreated with 10 µM LY-294002 for 3 h and then cultured within a three-dimensional type I collagen matrix for 24 h. MMP-2 production and activation were measured by gelatin zymography. Values are means ± SE. *P < 0.05 vs. control; n = 3.

 
Endothelial cells were pretreated with LY-294009 (10 µM) for 2 h followed by ROCK inhibition with H1152 to determine whether the changes in MMP-2 activity were dependent on PI3K. H1152 treatment was brief (2 h) to minimize the contribution of de novo synthesized MMP-2. Gelatin zymography demonstrated that PI3K is required for the activation of MMP-2 observed following ROCK inhibition (Fig. 4B). A small, but nonsignificant, increase in total MMP-2 protein was observed between control and H1152-treated cells. Interestingly, inhibition of PI3K failed to attenuate the increase in MT1-MMP cell surface localization following ROCK inhibition (H1152 = 1.8 ± 0.24-fold increase over control vs. H1152 + LY-294009 = 1.6 ± 0.21-fold increase over control, P = 0.48, n = 3). At the dose used, LY-294009 effectively inhibited the H1152-induced increase in P-AKT levels as verified by Western blot analysis (data not shown). It has been suggested that cell surface localization of MT1-MMP is not the critical step for its activation, but, rather, that MT1-MMP clustering on the cell surface is more important (15). This may explain why inhibition of PI3K was sufficient to inhibit MMP-2 activation following H1152 treatment without inhibiting cell surface localization of MT1-MMP.

To test whether PI3K modulates endothelial cell sprouting, we isolated capillary segments and cultured them within a three-dimensional type I collagen matrix in the absence or presence of LY-294009 (Fig. 4C). The typical formation of endothelial cell sprouts from the preexisting capillaries was significant in those treated with the PI3K inhibitor (Fig. 4D). Correspondingly, the increase in total MMP-2 protein observed in endothelial cells following 24 h in three-dimensional culture was attenuated partially by PI3K inhibition (3.3 ± 0.4-fold vs. two-dimensional control, P < 0.05, and 2.3 ± 0.4-fold vs. two-dimensional control, P > 0.05, respectively). Notably, MMP-2 protein activation was significantly reduced by pretreatment with LY-294009 compared with control three-dimensional cultures (Fig. 4E).

Overexpression of Cdc42 increases activation of MMP-2. To further define the roles of individual Rho-GTPase members in MMP-2 activation, we utilized Rho-GTPase fusion proteins of both the dominant negative and constitutively active forms of RhoA, Rac1, and Cdc42, coupled to the 11 amino acid cell entry domain of the HIV-Tat peptide (TAT). Western blot analysis verified the function of the TAT-Rho-GTPase fusion proteins. Activation of Cdc42 and Rac1 by treatment with TAT-Cdc42QL and TAT-Rac1QL, respectively, are shown as representative experiments (Fig. 5A).


Figure 5
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Fig. 5. Overexpression of Cdc42 increases MMP-2 activity and capillary sprouting. A: endothelial cells were treated with TAT-fusion protein of the Rho-GTPases or HIV-Tat (TAT) peptide control. Functional activity of the TAT-fusion proteins was verified by measuring Cdc42 and Rac1 activity in cells treated with TAT-CdcQL and TAT-Rac1QL, respectively, for 4 h by immunoprecipitation using PAK-GST-coated beads and Western blot analysis. B: capillary segments were cultured within a three-dimensional type I collagen matrix in the presence of TAT-RhoAN19/QL, TAT-Rac1N17/QL, TAT-Cdc42N17/QL, or TAT peptide control, and the average sprout length was quantified using Metamorph software. C: endothelial cells were treated with TAT-RhoAQL, TAT-Rac1QL, or TAT-Cdc42QL for 4 h, and MMP-2 production (open bars) and activation (solid bars) were measured by gelatin zymography. Endothelial cells were treated with TAT-Cdc42QL, and P-AKT was detected by Western blot analysis and normalized to total-AKT (D). Values are means ± SE. *P < 0.05 vs. TAT; n = 3.

 
Capillary segment cultures were used to observe the effects of the Rho-GTPases on capillary sprouting. TAT-RhoAN19-, TAT-Rac1QL-, and TAT-Cdc42QL-treated cultures had a greater average sprout length, whereas treatment with TAT-Cdc42N17 significantly decreased average sprout length compared with TAT control (Fig. 5B). TAT-RhoAQL and TAT-Rac1N17 treatments showed a trend toward decreased de novo sprout formation.

Transduction of endothelial cells with TAT-Cdc42QL for 4 h resulted in a significant increase in MMP-2 protein activation (Fig. 5C) without a concurrent increase in total MMP-2 protein. This increase in active MMP-2 was not attenuated in Cdc42QL-transduced cells treated with the translational inhibitor cycloheximide (1.66 ± 0.1-fold above TAT-only in untreated vs. 1.50 ± 0.2-fold above TAT-only in cyclohexmide-treated cells; n = 6–7). There was a trend toward increased MMP-2 activation in SMEC treated with TAT-Rac1QL, but no change in MMP-2 activation was seen in cells treated with TAT-RhoAQL. Increased levels of P-AKT also were observed following transduction of cells with Cdc42QL (Fig. 5D), similar to that observed in response to inhibition of the RhoA effector ROCK (Fig. 4A).

Given the effect of Cdc42QL on MMP-2 activation, we examined MT1-MMP localization. Treatment of endothelial cells with TAT-Cdc42QL caused cell retraction, formation of filopodia-like protrusions, and an increase in cortical actin (Fig. 6A). Cell surface MT1-MMP localization also increased as evidenced by immunostaining (Fig. 6A) and cell surface biotinylation (Fig. 6B).


Figure 6
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Fig. 6. Overexpression of Cdc42 increases cell surface localization of MT1-MMP. A: endothelial cells were treated for 4 h with TAT-Cdc42QL and then immunostained for MT1-MMP before permeablization (right) and F-actin (left). Scale bar = 20 µm. B: cell surface MT1-MMP following 4 h TAT-CdcQL treatment was measured by cell surface biotinylation and Western blot analysis. Values are means ± SE. *P < 0.05 vs. TAT; n = 3.

 
Cdc42 activation inhibits RhoA activity. The results of the above experiments suggest that RhoA and Cdc42 oppose each other in the regulation of MMP-2 production and activation. As cross talk between the Rho-GTPases has been reported, we investigated whether a signaling hierarchy exists in our system. Inhibition of RhoA signaling using H1152 failed to increase Cdc42 activity (data not shown). Conversely, activation of Cdc42 with TAT-Cdc42QL significantly decreased RhoA activity (Fig. 7A).


Figure 7
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Fig. 7. Overexpression of Cdc42 decreases RhoA activity. RhoA activity in endothelial cells treated with TAT-RhoAN19 or TAT-CdcQL for 4 h was measured by immunoprecipitation using Rhotekin-GST protein beads and Western blot analysis. n = 3.

 
VEGF induces activation of MMP-2 via Cdc42. VEGF is reported to induce reorganization of the actin cytoskeleton, dependent on the activity of Rho-GTPases. Here, we confirm that 1 h VEGF stimulation causes reorganization of the actin cytoskeleton to form peripheral regions of cortical actin and induces filopodia-like cellular protrusions (Fig. 8A, top). Similar changes in actin cytoskeleton reorganization followed Cdc42 activation (Fig. 8A, bottom). VEGF stimulation of endothelial cells caused an increase in Cdc42 activity (Fig. 8B, top). Concurrently, RhoA activity was decreased following VEGF stimulation (Fig. 8B, bottom). VEGF-dependent changes in actin organization and Rho-GTPase activity were accompanied by MMP-2 activation (Fig. 8C). Finally, inhibition of Cdc42 activity using TAT-Cdc42N17 was sufficient to decrease MMP-2 activation following VEGF stimulation (Fig. 8D).


Figure 8
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Fig. 8. Vascular endothelial growth factor (VEGF) induces cytoskeletal reorganization and MMP-2 activation via Cdc42GTPase. A: cells were treated with 25 ng/ml VEGF or with TAT-Cdc42QL for 4 h and stained for F actin. Arrows indicate peripheral actin; scale bar = 20 µm. B: cells were treated with 25 ng/ml VEGF for varying time points, and Cdc42 and RhoA activity were measured by immunoprecipitation using PAK-GST or Rhotekin-GST-coated beads, respectively, and Western blot analysis. C: cells were treated with 25 ng/ml VEGF for 1 h, and MMP-2 activation was measured by gelatin zymography. D: cells were pretreated with TAT or TAT-Cdc42N17 and then treated with 25 ng/ml VEGF for 1 h. MMP-2 activation was measured by gelatin zymography. Values are means ± SE. *P < 0.05 vs. control. #P < 0.05 vs. TAT; n = 3.

 

    DISCUSSION
 TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
This study provides evidence that Cdc42 is a positive modulator of the angiogenic response in endothelial cells through its effects on MMP-2 and MT1-MMP. Activation of Cdc42 increased MMP-2 protein production and induced its activation by increasing cell surface MT1-MMP. Conversely, RhoA plays an inhibitory role by suppressing MMP-2 and MT1-MMP mRNA expression and limiting MT1-MMP surface expression. These opposing changes in GTPase activity also can be observed following stimulation with VEGF. Furthermore, VEGF-induced activation of MMP-2 was reduced significantly by inhibition of Cdc42. Reorganization of the actin cytoskeleton participates in the initiation of angiogenesis. We previously reported that reorganization of the actin cytoskeleton modulates both MMP-2 and MT1-MMP production through signal pathways involving JNK and PI3K (24). We extend these findings in the current study by elucidating the involvement of specific Rho-GTPases in these events. In our study, strong stress fiber formation and low levels of MMP-2 expression and activation were characteristic of endothelial cells plated on type I collagen. Our results point to two temporally regulated mechanisms by which inhibition of RhoA signaling increases MMP-2 activation. First, depolymerization of stress fibers rapidly increases the amount of MT1-MMP on the cell surface and facilitates activation of MMP-2. Inhibition of ROCK, a target of RhoA signaling also mobilizes P-JNK to the nucleus and increases MMP-2 and MT1-MMP mRNA expression, which provides sustained MMP-2 and MT1-MMP protein production and further activation of MMP-2.

The level of RhoA activity has been linked previously to MMP-2 activity as Matsumoto et al. (35) showed that in lysophosphatidic acid-stimulated cells, low levels of RhoA activity increased MMP-2 activity but increased RhoA activity-inhibited MMP-2 activity. Similarly, confluent nonmigratory human umbilical vein endothelial cells exhibit high levels of RhoA activity, and RhoA inhibition increases MT1-MMP activity (16). However, mechanisms linking theses effects were not established by these studies. Zucker et al. (64) showed that actin depolymerization increases the number of cell surface receptors for tissue inhibitor of metalloproteinase-2 (TIMP-2) (i.e., MT1-MMP) without altering the binding affinity for TIMP-2. MT1-MMP is internalized by both clathrin-dependent (26, 43) and clathrin-independent (through caveolae) (16, 43) endocytosis, both of which rely on actin scaffolding. Disruption of the actin cytoskeleton may affect normal internalization of MT1-MMP (17), quickly increasing MT1-MMP molecules on the cell surface. These observations suggest that high levels of RhoA and stress fiber formation contribute to a stabilized, nonproteolytic endothelial phenotype.

Increasing Cdc42 activity caused the same effect on MMP-2 activation as inhibition of RhoA/ROCK activity. Overexpression of Cdc42 induced an increase in MT1-MMP on the cell surface and increased angiogenesis in three-dimensional type I collagen. Previous studies indicated a significant permissive role for Cdc42 in tumor cell migration and invasion (19, 30, 55). Our results extend these findings by providing a mechanism by which these events may be mediated, namely Cdc42-dependent MMP-2 activation via increased cell surface MT1-MMP. It is possible that in addition to inhibition of MT1-MMP internalization, activation of Cdc42 may increase MT1-MMP cell surface localization by increasing exocytosis of MT1-MMP from intracellular stores to the plasma membrane. For example, Cdc42 activation plays a positive role in exocytosis of von Willebrand factor in endothelial cells (29, 51) and the second phase of insulin secretion in pancreatic β-cells (53).

The Rho family of GTPases signal to one another in the process of coordinating the appropriate intracellular responses to extracellular signals. We demonstrated that Cdc42 activation suppressed basal RhoA activity. This is in agreement with the hierarchy of Rho-GTPase signaling proposed by Nobes et al. (39). We observed that Cdc42 activation led to decreased RhoA activity, stress fiber depolymerization, increased MT1-MMP cell surface localization, and greater MMP-2 activation. Concurrently, Cdc42 activation can increase Rac1 activation, which may contribute to increase endothelial sprouting.

Coordination of Cdc42 and RhoA signaling was recently demonstrated in podosome formation in primary endothelial cells (49). Cdc42 activation resulted in podosome formation, which was accompanied by localized stress fiber depolymerization and correlated with decreased RhoA activity (49). Conversely, Cdc42-dependent Rac1 activation has been reported wherein Cdc42 activates IRSp53, an intermediary protein that allows for Rac1 to bind to the WAVE-Arp 2/3 complex, and is required for Rac1-dependent lamellipodia formation (18).

Several studies indicate Cdc42-dependent activation of PI3K and AKT (10, 60), which is consistent with our observation that PI3K is required for MMP-2 activation following RhoA inhibition. When considered with the report that increased RhoA activity inhibited AKT-dependent phosphorylation of endothelial nitric oxide synthase in endothelial cells (52) and that Cdc42 activation decreases RhoA activity, we postulate that activation of Cdc42 alleviates the RhoA-induced suppression of PI3K/P-AKT signaling. The activation of these pathways then increases cell surface MT1-MMP and induces MMP-2 activation.

The mechanism by which P-AKT regulates MT1-MMP on the cell surface remains to be elucidated. Galvez et al. (14) suggested that clustering of MT1-MMP molecules is more important than internalization in regulating MT1-MMP activation of MMP-2. They proposed that MT1-MMP clustering is dependent on cortical actin polymerization, which is regulated by PI3K. Our data are consistent with this hypothesis as ROCK inhibition increased P-AKT levels at time points corresponding to increased MMP-2 activation, and inhibition of PI3K abolishes the increases in MMP-2 activation without altering the amount of MT1-MMP on the cell surface.

Our results provide evidence that VEGF induction of MMP-2 activity utilizes a combination of increased Cdc42 activity and decreased RhoA activity. The signal cascade leading to MMP-2 activation proposed here is in line with events following VEGF stimulation of endothelial cells. Cdc42 activation has been reported in response to VEGF stimulation (61) and is activated during endothelial cell haptotaxis on type I collagen (47). Interestingly, activation of Cdc42 can induce VEGF promoter activity via a c-Jun-dependent mechanism (44), and we have shown previously that c-Jun is necessary for MMP-2 mRNA expression following VEGF stimulation (24). Together, these results suggest that VEGF can induce both rapid and sustained production activation of MMP-2 through upregulation of Cdc42 activity.

In summary, inhibition of RhoA or activation of Cdc42 in microvascular endothelial cells induced a shift from stress fibers to cortical actin and increased MT1-MMP localization to the cell surface. Longer-term consequences of RhoA inhibition or Cdc42 activation included increased MMP-2 and MT1-MMP mRNA expression and greater capillary sprouting. These findings further elucidate the process of endothelial cell activation and initiation of angiogenesis.


    ACKNOWLEDGMENTS
 
Funding for this project to T. L. Haas was from the National Science and Engineering Research Council of Canada (NSERC). E. Ispanovic is the recipient of an Ontario Graduate Scholarship, and D. Serio is the recipient of an NSERC CGSM scholarship.


    FOOTNOTES
 

Address for reprint requests and other correspondence: T. L. Haas, Rm 341, Farquharson, School of Kinesiology and Health Sciences, York Univ., 4700 Keele St., Toronto, ON M3J 1P3 Canada (e-mail: thaas{at}yorku.ca)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


    REFERENCES
 TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
1. Aepfelbacher M, Essler M, Huber E, Sugai M, Weber PC. Bacterial toxins block endothelial wound repair. Evidence that Rho GTPases control cytoskeletal rearrangements in migrating endothelial cells. Arterioscler Thromb Vasc Biol 17: 1623–1629, 1997.[Abstract/Free Full Text]

2. Aimes RT, Quigley JP. Matrix metalloproteinase-2 is an interstitial collagenase. J Biol Chem 270: 5872–5876, 1995.[Abstract/Free Full Text]

3. Alahari SK. Nischarin inhibits Rac induced migration and invasion of epithelial cells by affecting signaling cascades involving PAK. Exp Cell Res 288: 415–424, 2003.[CrossRef][Web of Science][Medline]

4. Barillari G, Ensoli B. Angiogenic effects of extracellular human immunodeficiency virus type 1 Tat protein and its role in the pathogenesis of AIDS-associated Kaposi's sarcoma. Clin Microbiol Rev 15: 310–326, 2002.[Abstract/Free Full Text]

5. Barka T, Gresik ES, Henderson SC. Production of cell lines secreting TAT fusion proteins. J Histochem Cytochem 52: 469–477, 2004.[Abstract/Free Full Text]

6. Birkedal-Hansen H. Proteolytic remodeling of extracellular matrix. Curr Opin Cell Biol 7: 728–735, 1995.[CrossRef][Web of Science][Medline]

7. Birukov KG, Birukova AA, Dudek SM, Verin AD, Crow MT, Zhan X, DePaola N, Garcia JGN. Shear stress-mediated cytoskeletal remodeling and cortactin translocation in pulmonary endothelial cells. Am J Respir Cell Mol Biol 26: 453–464, 2002.[Abstract/Free Full Text]

8. Boyd PJ, Doyle J, Gee E, Pallan S, Haas TL. Mitogen-activated protein kinase signaling regulates endothelial cell assembly into networks and the expression of MT1-MMP and MMP-2. Am J Physiol Cell Physiol 288: C659–C668, 2005.[Abstract/Free Full Text]

9. Bryan BA, D'Amore PA. What tangled webs they weave: Rho-GTPase control of angiogenesis. Cell Mol Life Sci 64: 2053–2065, 2007.[CrossRef][Web of Science][Medline]

10. Clark EA, King WG, Brugge JS, Symons M, Hynes RO. Integrin-mediated signals regulated by members of the rho family of GTPases. J Cell Biol 142: 573–586, 1998.[Abstract/Free Full Text]

11. Connolly JO, Simpson N, Hewlett L, Hall A. Rac regulates endothelial morphogenesis and capillary assembly. Mol Biol Cell 13: 2474–2485, 2002.[Abstract/Free Full Text]

12. Davis GE, Bayless KJ, Mavila A. Molecular basis of endothelial cell morphogenesis in three-dimensional extracellular matrices. Anat Rec 268: 252–275, 2002.[CrossRef][Medline]

13. Fang J, Shing Y, Wiederschain D, Yan L, Butterfield C, Jackson G, Harper J, Tamvakopoulos G, Moses MA. Matrix metalloproteinase-2 is required for the switch to the angiogenic phenotype in a tumor model. Proc Natl Acad Sci USA 97: 3884–3889, 2000.[Abstract/Free Full Text]

14. Galvez BG, Genis L, Matias-Roman S, Oblander SA, Tryggvason K, Apte SS, Arroyo AG. Membrane type 1-matrix metalloproteinase is regulated by chemokines monocyte-chemoattractant protein-1/ccl2 and interleukin-8/CXCL8 in endothelial cells during angiogenesis. J Biol Chem 280: 1292–1298, 2005.[Abstract/Free Full Text]

15. Galvez BG, Genis L, Matias-Roman S, Oblander SA, Tryggvason K, Apte SS, Arroyo AG. Membrane type 1-matrix metalloproteinase is regulated by chemokines monocyte-chemoattractant protein-1/ccl2 and interleukin-8/cxcl8 in endothelial cells during angiogenesis. J Biol Chem 280: 1292–1298, 2005.[Abstract/Free Full Text]

16. Galvez BG, Matias-Roman S, Yanez-Mo M, Vicente-Manzanares M, Sanchez-Madrid F, Arroyo AG. Caveolae are a novel pathway for membrane-type 1 matrix metalloproteinase traffic in human endothelial cells. Mol Biol Cell 15: 678–687, 2004.[Abstract/Free Full Text]

17. Gottlieb TA, Ivanov IE, Adesnik M, Sabatini DD. Actin microfilaments play a critical role in endocytosis at the apical but not the basolateral surface of polarized epithelial-cells. J Cell Biol 120: 695–710, 1993.[Abstract/Free Full Text]

18. Govind S, Kozma R, Monfries C, Lim L, Ahmed S. Cdc42Hs facilitates cytoskeletal reorganization and neurite outgrowth by localizing the 58-kD insulin receptor substrate to filamentous actin. J Cell Biol 152: 579–594, 2001.[Abstract/Free Full Text]

19. Guo F, Zheng Y. Rho family GTPases cooperate with p53 deletion to promote primary mouse embryonic fibroblast cell invasion. Oncogene 23: 5577–5585, 2004.[CrossRef][Web of Science][Medline]

20. Haas TL, Davis SJ, Madri JA. Three dimensional type I collagen lattices induce coordinate expression of matrix metalloproteinases MT1-MMP and MMP-2 in microvascular endothelial cells. J Biol Chem 273: 3604–3610, 1998.[Abstract/Free Full Text]

21. Han XY, Boyd PJ, Colgan S, Madri JA, Haas TL. Transcriptional up-regulation of endothelial cell matrix metalloproteinase-2 in response to extracellular cues involves GATA-2. J Biol Chem 278: 47785–47791, 2003.[Abstract/Free Full Text]

22. Herren B, Levkau B, Raines EW, Ross R. Cleavage of beta catenin and plakoglobin and shedding of VE-cadherin during endothelial apoptosis: evidence for a role for caspases and metalloproteinases. Mol Biol Cell 9: 1589–1601, 1998.[Abstract/Free Full Text]

23. Holmbeck K, Bianco P, Caterina J, Yamada S, Kromer M, Kuznetsov SA, Mankani M, Robey PG, Poole AR, Pidoux I, Ward JM, Birkedal-Hansen H. MT1-MMP-deficient mice develop dwarfism, osteopenia, arthritis, and connective tissue disease due to inadequate collagen turnover. Cell 99: 81–92, 1999.[CrossRef][Web of Science][Medline]

24. Ispanovic E, Haas TL. JNK and PI3K differentially regulate MMP-2 and MT1-MMP mRNA and protein in response to actin cytoskeleton reorganization in endothelial cells. Am J Physiol Cell Physiol 291: C579–C588, 2006.[Abstract/Free Full Text]

25. Itoh T, Tanioka M, Yoshida H, Yoshioka T, Nishimoto H, Itohara S. Reduced angiogenesis and tumor progression in gelatinase A-deficient mice. Cancer Res 58: 1048–1051, 1998.[Abstract/Free Full Text]

26. Jiang A, Lehti K, Wang X, Weiss SJ, Keski-Oja J, Pei D. Regulation of membrane-type matrix metalloproteinase 1 activity by dynamin-mediated endocytosis. Proc Natl Acad Sci USA 98: 13693–13698, 2001.[Abstract/Free Full Text]

27. Kato T, Kure T, Chang JH, Gabison EE, Itoh T, Itohara S, Azar DT. Diminished corneal angiogenesis in gelatinase A-deficient mice. FEBS Lett 508: 187–190, 2001.[CrossRef][Web of Science][Medline]

28. Keely PJ, Westwick JK, Whitehead IP, Der CJ, Parise LV. Cdc42 and Rac1 induce integrin-mediated cell motility and invasiveness through PI(3)K. Nature 390: 632–636, 1997.[CrossRef][Web of Science][Medline]

29. Klarenbach SW, Chipiuk A, Nelson RC, Hollenberg MD, Murray AG. Differential actions of PAR2 and PAR1 in stimulating human endothelial cell exocytosis and permeability: the role of Rho-GTPases. Circ Res 92: 272–278, 2003.[Abstract/Free Full Text]

30. Kuo JC, Wang WJ, Yao CC, Wu PR, Chen RH. The tumor suppressor DAPK inhibits cell motility by blocking the integrin-mediated polarity pathway. J Cell Biol 172: 619–631, 2006.[Abstract/Free Full Text]

31. Lamalice L, Houle F, Jourdan G, Huot J. Phosphorylation of tyrosine 1214 on VEGFR2 is required for VEGF-induced activation of Cdc42 upstream of SAPK2/p38. Oncogene 23: 434–445, 2004.[CrossRef][Web of Science][Medline]

32. Le Boeuf F, Houle F, Sussman M, Huot J. Phosphorylation of focal adhesion kinase (FAK) on Ser732 is induced by rho-dependent kinase and is essential for proline-rich tyrosine kinase-2-mediated phosphorylation of FAK on Tyr407 in response to vascular endothelial growth factor. Mol Biol Cell 17: 3508–3520, 2006.[Abstract/Free Full Text]

33. Li S, Chen BPC, Azuma N, Hu YL, Wu SZ, Sumpio BE, Shyy JYJ, Chien S. Distinct roles for the small GTPases Cdc42 and Rho in endothelial responses to shear stress. J Clin Invest 103: 1141–1150, 1999.[Web of Science][Medline]

34. Malliri A, Symons M, Hennigan RF, Hurlstone AF, Lamb RF, Wheeler T, Ozanne BW. The transcription factor AP-1 is required for EGF-induced activation of rho-like GTPases, cytoskeletal rearrangements, motility, and in vitro invasion of A431 cells. J Cell Biol 143: 1087–1099, 1998.[Abstract/Free Full Text]

35. Matsumoto Y, Tanaka K, Harimaya K, Nakatani F, Matsuda S, Iwamoto Y. Small GTP-binding protein, Rho, both increased and decreased cellular motility, activation of matrix metalloproteinase 2 and invasion of human osteosarcoma cells. Jpn J Cancer Res 92: 429–438, 2001.[CrossRef][Web of Science]

36. Michiels F, Habets GG, Stam JC, van der Kammen RA, Collard JG. A role for Rac in Tiam1-induced membrane ruffling and invasion. Nature 375: 338–340, 1995.[CrossRef][Web of Science][Medline]

37. Murphy G, Nguyen Q, Cockett MI, Atkinson SJ, Allan JA, Knight CG, Willenbrock F, Docherty AJP. Assessment of the Role of the Fibronectin-Like Domain of Gelatinase-A by Analysis of A Deletion Mutant. J Biol Chem 269: 6632–6636, 1994.[Abstract/Free Full Text]

38. Nieuw Amerongen GP, Koolwijk P, Versteilen A, van Hinsbergh VW. Involvement of RhoA/Rho kinase signaling in VEGF-induced endothelial cell migration and angiogenesis in vitro. Arterioscler Thromb Vasc Biol 23: 211–217, 2003.[Abstract/Free Full Text]

39. Nobes CD, Hall A. Rho, rac, and cdc42 GTPases regulate the assembly of multimolecular focal complexes associated with actin stress fibers, lamellipodia, and filopodia. Cell 81: 53–62, 1995.[CrossRef][Web of Science][Medline]

40. Oh J, Takahashi R, Adachi E, Kondo S, Kuratomi S, Noma A, Alexander DB, Motoda H, Okada A, Seiki M, Itoh T, Itohara S, Takahashi C, Noda M. Mutations in two matrix metalloproteinase genes, MMP-2 and MT1-MMP, are synthetic lethal in mice. Oncogene 23: 5041–5048, 2004.[CrossRef][Web of Science][Medline]

41. Ohno-Matsui K, Uetama T, Yoshida T, Hayano M, Itoh T, Morita I, Mochizuki M. Reduced retinal angiogenesis in MMP-2-deficient mice. Invest Ophthalmol Vis Sci 44: 5370–5375, 2003.[Abstract/Free Full Text]

42. Puyraimond A, Fridman R, Lemesle M, Arbeille B, Menashi S. MMP-2 colocalizes with caveolae on the surface of endothelial cells. Exp Cell Res 262: 28–36, 2001.[CrossRef][Web of Science][Medline]

43. Remacle A, Murphy G, Roghi C. Membrane type I-matrix metalloproteinase (MT1-MMP) is internalised by two different pathways and is recycled to the cell surface. J Cell Sci 116: 3905–3916, 2003.[Abstract/Free Full Text]

44. Saniger ML, Oya R, Macias D, Dominguez JN, Aranega A, Luque F. c-Jun kinase mediates expression of VEGF induced at transcriptional level by Rac1 and Cdc42Hs but not by RhoA. J Cell Biochem 98: 650–660, 2006.[CrossRef][Web of Science][Medline]

45. Schnittler HJ, Schneider SW, Raifer H, Luo F, Dieterich P, Just I, Aktories K. Role of actin filaments in endothelial cell-cell adhesion and membrane stability under fluid shear stress. Pflügers Arch 442: 675–687, 2001.[CrossRef][Web of Science][Medline]

46. Shiu YT, Li S, Marganski WA, Usami S, Schwartz MA, Wang YL, Dembo M, Chien S. Rho mediates the shear-enhancement of endothelial cell migration and traction force generation. Biophys J 86: 2558–2565, 2004.[Web of Science][Medline]

47. Soga N, Namba N, McAllister S, Cornelius L, Teitelbaum SL, Dowdy SF, Kawamura J, Hruska KA. Rho family GTPases regulate VEGF-stimulated endothelial cell motility. Exp Cell Res 269: 73–87, 2001.[CrossRef][Web of Science][Medline]

48. Stam JC, Michiels F, van der Kammen RA, Moolenaar WH, Collard JG. Invasion of T-lymphoma cells: cooperation between Rho family GTPases and lysophospholipid receptor signaling. EMBO J 17: 4066–4074, 1998.[CrossRef][Web of Science][Medline]

49. Tatin F, Varon C, Genot E, Moreau V. A signalling cascade involving PKC, Src and Cdc42 regulates podosome assembly in cultured endothelial cells in response to phorbol ester. J Cell Sci 119: 769–781, 2006.[Abstract/Free Full Text]

50. Tomasek JJ, Halliday NL, Updike DL, Ahern-Moore JS, Vu TKH, Liu RW, Howard EW. Gelatinase A activation is regulated by the organization of the polymerized actin cytoskeleton. J Biol Chem 272: 7482–7487, 1997.[Abstract/Free Full Text]

51. Vischer UM, Barth H, Wollheim CB. Regulated von Willebrand factor secretion is associated with agonist-specific patterns of cytoskeletal remodeling in cultured endothelial cells. Arterioscler Thromb Vasc Biol 20: 883–891, 2000.[Abstract/Free Full Text]

52. Viswambharan H, Ming XF, Zhu S, Hubsch A, Lerch P, Vergeres G, Rusconi S, Yang Z. Reconstituted high-density lipoprotein inhibits thrombin-induced endothelial tissue factor expression through inhibition of RhoA and stimulation of phosphatidylinositol 3-kinase but not Akt/endothelial nitric oxide synthase. Circ Res 94: 918–925, 2004.[Abstract/Free Full Text]

53. Wang Z, Oh E, Thurmond DC. Glucose-stimulated Cdc42 signaling is essential for the second phase of insulin secretion. J Biol Chem 282: 9536–9546, 2007.[Abstract/Free Full Text]

54. Westermarck J, Kahari VM. Regulation of matrix metalloproteinase expression in tumor invasion. FASEB J 13: 781–792, 1999.[Abstract/Free Full Text]

55. Wilkinson S, Paterson HF, Marshall CJ. Cdc42-MRCK and Rho-ROCK signalling cooperate in myosin phosphorylation and cell invasion. Nat Cell Biol 7: 255–261, 2005.[CrossRef][Web of Science][Medline]

56. Woessner JF Jr. The family of matrix metalloproteinases. Ann NY Acad Sci 732: 11–21, 1994.[Web of Science][Medline]

57. Wojciak-Stothard B, Ridley AJ. Shear stress-induced endothelial cell polarization is mediated by Rho and Rac but not Cdc42 or PI 3-kinases. J Cell Biol 161: 429–439, 2003.[Abstract/Free Full Text]

58. Wu RF, Gu Y, Xu YC, Mitola S, Bussolino F, Terada LS. Human immunodeficiency virus type 1 Tat regulates endothelial cell actin cytoskeletal dynamics through PAK1 activation and oxidant production. J Virol 78: 779–789, 2004.[Abstract/Free Full Text]

59. Yan L, Moses MA, Huang S, Ingber DE. Adhesion-dependent control of matrix metalloproteinase-2 activation in human capillary endothelial cells. J Cell Sci 113: 3979–3987, 2000.[Abstract]

60. Yang W, Lin Q, Guan JL, Cerione RA. Activation of the Cdc42-associated tyrosine kinase-2 (ACK-2) by cell adhesion via integrin beta1. J Biol Chem 274: 8524–8530, 1999.[Abstract/Free Full Text]

61. Zeng H, Zhao D, Mukhopadhyay D. Flt-1-mediated down-regulation of endothelial cell proliferation through pertussis toxin-sensitive G proteins, beta gamma subunits, small GTPase CDC42, and partly by Rac-1. J Biol Chem 277: 4003–4009, 2002.[Abstract/Free Full Text]

62. Zhou Z, Apte SS, Soininen R, Cao R, Baaklini GY, Rauser RW, Wang J, Cao Y, Tryggvason K. Impaired endochondral ossification and angiogenesis in mice deficient in membrane-type matrix metalloproteinase I. Proc Natl Acad Sci USA 97: 4052–4057, 2000.[Abstract/Free Full Text]

63. Zhuge Y, Xu J. Rac1 mediates type I collagen-dependent MMP-2 activation. Role in cell invasion across collagen barrier. J Biol Chem 276: 16248–16256, 2001.[Abstract/Free Full Text]

64. Zucker S, Hymowitz M, Conner CE, DiYanni EA, Cao J. Rapid trafficking of membrane type 1-matrix metalloproteinase to the cell surface regulates progelatinase a activation. Lab Invest 82: 1673–1684, 2002.[Web of Science][Medline]




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