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At least 919 records · Page 51Linked to original sources
PubMed1998

CD44 isoform-cytoskeleton interaction in oncogenic signaling and tumor progression.

CD44, a major hyaluronan receptor, exists as several isoforms and is widely distributed in different cells and tissues. The isoforms of CD44, such as CD44s (the standard form), CD44E (the epithelial form) and CD44v (variant isoforms) (arise from differential splicing of one to ten (or eleven) variable exons that encode portions of the membrane proximal extracellular domain. The molecular diversity of CD44 isoforms is further compounded by differential biosynthetic processes and post-translational modifications [e.g. N-/O-glycosylation or glycosaminoglycan (GAG) addition]. This structural arrangement, which occurs within either the invariant region or the extracellular domain of the variant region, is important for CD44-mediated communication between extracellular matrix materials [ECM-hyaluronic acid (HA), collagen and fibronectin] and intracellular protein components (e.g cytoskeletal proteins and various regulatory enzymes). The 15 amino acid sequence [e.g. NSGNGAVEDRKPSGL (in human) or NGGNGTVEDRKPSEL (in mouse)] residing in the cytoplasmic domain of CD44 isoforms is the ankyrin-binding domain of this family of transmembrane glycoproteins. Biochemical analyses plus in vitro mutagenesis indicate that the ankyrin-binding domain is required for CD44-mediated "outside-in" and "inside-out" cell activation events. Furthermore, CD44s-cytoskeleton interaction is tightly coupled with signal transducing molecules (e.g. p185HER2 or Src kinases) during oncogenic signaling. Moreover, the transmembrane linkage between CD44v isoforms (CD44v10 and CD44v3) and the cytoskeleton up-regulates invasive and metastatic-specific tumor phenotypes [e.g. matrix degradation (MMPs) activities, tumor cell invasion and migration]. These findings strongly suggest that the interaction between CD44 isoforms and the cytoskeleton plays a pivotal role in the onset of oncogenesis and tumor progression.

Animals↗
PubMed1991

Sulfhydryl reagents alter epidermal growth factor receptor affinity and association with the cytoskeleton.

Sulfhydryl (SH) reagents are known to influence the characteristics of many ligand-receptor systems. The SH reagent N-ethylmaleimide has been demonstrated to interact with EGF receptors, and to inhibit EGF receptor kinase activity. The data presented in this paper concern the effect of SH reagents on two intriguing features of the EGF receptor system, namely the presence of low and high affinity EGF binding sites, and the interaction of EGF receptors with the cytoskeleton. SH reagents were observed to induce a disappearance of high, but not low, affinity EGF receptors from the cell surface, and an increase in receptor-cytoskeleton interaction. Comparison of the effects of membrane-permeant and membrane-impermeant SH reagents on wild type and structurally modified EGF receptors suggested that sulfhydryl groups on the cytoplasmic, rather than the extracellular, receptor domain are involved. This indicates that the cytoplasmic domain of the EGF receptor plays a role in the high affinity binding of EGF, and in the interaction of EGF receptors with the cytoskeleton. Experiments with an anti-EGF receptor antibody that specifically blocks the binding of EGF to low affinity receptors indicated that EGF induces a shift in the EGF receptor from low to high affinity. SH reagents probably affect EGF binding by inhibiting this EGF-induced receptor conversion.

3T3 Cells↗
PubMed2001

The dendritic cell cytoskeleton is critical for the formation of the immunological synapse.

The binding of a T cell to an APC results in T cell actin cytoskeletal rearrangement leading to the formation of an immunological synapse. The APC cytoskeleton has been thought to play a passive role in this process. In this study, we demonstrate that dendritic cells (DC), unlike other APC, actively polarize their actin cytoskeleton during interaction with T cells. DC cytoskeletal rearrangement was critical for both the clustering and the activation of resting T cells. This study provides compelling evidence that the APC cytoskeleton plays an active role in the immunological synapse and may explain the unique ability of DC to activate resting T cells.

Actins↗
PubMed2006

Role of Fyn in the rearrangement of tubulin cytoskeleton induced through TCR.

The translocation of the microtubule-organizing center (MTOC), its associated signaling complex, and the secretory apparatus is the most characteristic early event that involves the tubulin cytoskeleton of T or NK cells after their interaction with APC or target cells. Our results show that Fyn kinase activity is essential for MTOC reorientation in an Ag-dependent system. Moreover, T cells from Fyn-deficient mice are unable to rearrange their tubulin cytoskeleton in response to anti-CD3-coated beads. Analysis of conjugates of T cells from transgenic OT-I mice with dendritic cells revealed that an antagonist peptide induces translocation of the MTOC, and that this process is impaired in T cells from Fyn(-/-) OT-I mice. In addition, Fyn deficiency significantly affects the MTOC relocation mediated by agonist peptide stimulation. These results reveal Fyn to be a key regulator of tubulin cytoskeleton reorganization in T cells.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Src-dependence and pertussis-toxin sensitivity of urokinase receptor-dependent chemotaxis and cytoskeleton reorganization in rat smooth muscle cells.

The catalytically inactive precursor of urokinase-type plasminogen activator (pro-u-PA) induced a chemotactic response in rat smooth muscle cells (RSMC) through binding to the membrane receptor of urokinase (u-PA receptor [u-PAR]). A soluble form of u-PAR activated by chymotrypsin cleavage as well as a peptide located between domain 1 and 2 of u-PAR reproduced the effect of pro-u-PA on cell migration. The chemotactic pro-u-PA effect correlates with a dramatic reorganization of actin cytoskeleton, of adhesion plaques, and with major cell shape changes in RSMC. Pro-u-PA induced a decrease in stress fiber content, membrane ruffling, actin ring formation, and disruption leading to the characteristic elongated cell shape of motile cells with an actin semi-ring located close to the leading edge of cells. u-PAR effects on both chemotaxis and cytoskeleton were sensitive to pertussis toxin and, hence, possibly require G proteins. u-PAR effects are accompanied by a relocation of u-PAR, vitronectin receptor (VNR) alphavbeta3, beta1 integrin subunit, and Src tyrosine kinase to the leading membrane of migrating cells. In conclusion, our data show that pro-u-PA, via binding to u-PAR, controls a signaling pathway, regulated by tyrosine kinases and possibly G proteins, leading to cell cytoskeleton reorganization and cell migration.

Actins↗
PubMed2000

Actin cytoskeleton and exocytosis in rat melanotrophs.

We monitored secretory activity of single rat melanotrophs by the patch-clamp membrane capacitance measurements (Cm). Secretory activity was stimulated by cytosol dialysis with a patch-pipette solution containing 1 microM [Ca2+]i. Actin cytoskeleton was disaggregated by pretreating cells with Clostridium spiroforme toxin, which specifically ADP-ribosylates cellular actin. The extent of cytoskeleton disaggregation was monitored by phalloidin immunostaining. The maximal rate of secretion increases two folds in toxin-treated cells in comparison to controls, whereas the extent of calcium-induced secretory response was similar to that obtained in the non-treated cells. The results show that the subcortical actin network attenuates the rate of secretory activity, which we interpret to reflect a barrier function of cytoskeleton for exocytosis.

Actins↗
PubMed1999

Tyrosine phosphorylation of focal adhesion kinase and paxillin regulates the signaling mechanism of the rapid nongenomic action of dexamethasone on actin cytoskeleton.

We have previously shown that dexamethasone (DEX) stimulates rapid polymerization of actin and stabilization of microfilaments in human endometrial adenocarcinoma cells. As the content of total cellular actin and the concentration of the actin transcript did not change, we concluded that polymerization of actin by glucocorticoids involves nongenomic mechanisms. However, the signaling events by which the latter is achieved remain unknown. In the present study we evaluated whether tyrosine phosphorylation is required for the rapid, nongenomic DEX effect on actin assembly. In cells preincubated with the tyrosine kinase inhibitors, genistein or erbstatin analogue (EA), before adding DEX the G-/total actin ratio remained unchanged, whereas DEX in the absence of both inhibitors reduced the ratio by 25%. In addition, when cells were preincubated with the protein tyrosine phosphatase inhibitor pervanadate and subsequently incubated with DEX, the G-/total actin ratio was dramatically reduced by 65%. Furthermore, DEX increased transiently the levels of tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin within 2 to 15 min, without a change in their expression levels. Pervanadate mimicked this effect of DEX and enhanced tyrosine phosphorylation of both proteins. In addition, when cells were exposed to the anticytoskeletal agent cytochalasin B, the basal levels of tyrosine phosphorylation of both proteins were reduced. This effect was reversed by DEX, indicating that actin cytoskeleton integrity is required for the effect of DEX on tyrosine phosphorylation of FAK and paxillin. Finally, we documented enhanced expression of the Ras-related GTP-binding protein Rho-B after long-term (12- and 24-hr) treatment with DEX, whereas Rho-B levels remained unchanged after short-term (3- and 6-hr) treatment. Our observations demonstrate a novel mechanism through which the rapid nongenomic effect of DEX on actin assembly requires tyrosine phosphorylation of the cytoskeleton-associated proteins FAK and paxillin. We also propose that the DEX-induced actin polymerization may constitute a mechanism for transduction of signals resulting in tyrosine phosphorylation of FAK and paxillin. Moreover, the enhanced Rho-B levels observed after long-term treatment with DEX imply a mechanism for the well-described, long-term effects of glucocorticoids on actin cytoskeleton.

Actins↗
PubMed1999

Dual effect of pseudorabies virus growth factor (PRGF) displayed on actin cytoskeleton.

Pseudorabies virus growth factor (PRGF) was shown to possess transforming activity as well as transformation repressing activity in in vitro systems. In order to better understand these phenomena we studied actin cytoskeleton and its alterations induced by PRGF using normal human fibroblasts VH-10 and transformed cell line HeLa. For specific detection of filamentous actin cells were stained with phalloidin conjugated with fluorescein isothiocyanate (FITC)-phalloidin. PRGF was applied to VH-10 cells for various length of time from 10 min up to 48 h. The effect was very fast and changes in actin filament composition could be detected already after 10 min. In comparison to untreated cells the staining of treated cells was more diffuse and a number of actin microfilaments in individual stress fibers became reduced. After 30 min thick short actin bundles appeared in the perinuclear region. A 24-h exposure resulted in a large reduction of actin bundles. After additional 24 h a partial restoration of actin cytoskeleton in cells was observed. In transformed HeLa cells PRGF induced opposite process than in normal cells: the number of filamentous actin structures increased. We hypothesise that PRGF may act as a transcription-like factor and may initiate changes in gene expression which consequently result in actin cytoskeleton alterations.

Actins↗
PubMed2000

Farnesylcysteine analogues inhibit store-regulated Ca2+ entry in human platelets: evidence for involvement of small GTP-binding proteins and actin cytoskeleton.

We have investigated the mechanism of Ca(2+) entry into fura-2-loaded human platelets by preventing the prenylation of proteins such as small GTP-binding proteins. The farnesylcysteine analogues farnesylthioacetic acid (FTA) and N-acetyl-S-geranylgeranyl-L-cysteine (AGGC), which are inhibitors of the methylation of prenylated and geranylgeranylated proteins respectively, significantly decreased thrombin-evoked increases in intracellular free Ca(2+) concentration ([Ca(2+)](i)) in the presence, but not in the absence, of external Ca(2+), suggesting a relatively selective inhibition of Ca(2+) entry over internal release. Both these compounds and N-acetyl-S-farnesyl-L-cysteine, which had similar effects to those of FTA, also decreased Ca(2+) entry evoked by the depletion of intracellular Ca(2+) stores with thapsigargin. The inactive control N-acetyl-S-geranyl-L-cysteine was without effect. Patulin, an inhibitor of prenylation that is inert with respect to methyltransferases, also decreased store-regulated Ca(2+) entry. Cytochalasin D, an inhibitor of actin polymerization, significantly decreased store-regulated Ca(2+) entry in a time-dependent manner. Both cytochalasin D and the farnesylcysteine analogues FTA and AGGC inhibited actin polymerization; however, when evoking the same extent of decrease in actin filament formation, FTA and AGGC showed greater inhibitory effects on Ca(2+) entry, indicating a cytoskeleton-independent component in the regulation of Ca(2+) entry by small GTP-binding-protein. These findings suggest that prenylated proteins such as small GTP-binding proteins are involved in store-regulated Ca(2+) entry through actin cytoskeleton-dependent and cytoskeleton-independent mechanisms in human platelets.

Actins↗
PubMed1999

Vinflunine, a new vinca alkaloid: cytotoxicity, cellular accumulation and action on the interphasic and mitotic microtubule cytoskeleton of PtK2 cells.

Vinflunine, a newly synthesized derivative, possesses marked in vivo antitumor properties and, like other alkaloids, inhibits in vitro tubulin assembly at microM concentrations. However, in contrast to other vinca alkaloids, vinflunine exhibits relatively low in vitro cytotoxic potency. The aim of this report was to investigate whether the action(s) of vinflunine on the microtubule cytoskeleton could account for its cytotoxicity or if its cellular action requires another molecular target. Four vinca alkaloids used in cancer therapy and vinflunine were studied using PtK2 cells. Their activities on the most dynamic microtubules were investigated in mitosis and in interphase by evaluating the disturbance of the metaphase plate and the splitting of the diplosome, respectively. No correlation was observed between the cellular accumulation of these compounds and either their cytotoxicity or their action(s) on the microtubule cytoskeleton. In contrast, cytotoxicity, mitotic disturbance and diplosome splitting were observed in the nM range for vinblastine, vincristine, vindesine and vinorelbine, although these events occurred at 10 times higher concentrations in the case of vinflunine. Hence, dynamic modifications of both the mitotic and interphasic microtubule cytoskeleton are compatible with in vitro cytotoxicity of vinflunine, raising questions about the conventional biochemical screening of these vinca alkaloids.

Animals↗
PubMed1999

Bacterial toxins modifying the actin cytoskeleton.

Numerous bacterial toxins recognize the actin cytoskeleton as a target. The clostridial binary toxins (Iota and C2 families) ADP-ribosylate the actin monomers causing the dissociation of the actin filaments. The large clostridial toxins from Clostridium difficile, Clostridium sordellii and Clostridium novyi inactivate, by glucosylation, proteins from the Rho family that regulate actin polymerization. In contrast, the cytotoxic necrotic factor from Escherichia coli activates Rho by deamidation and increases the formation of actin filaments. The enterotoxin of Bacteroides fragilis is a protease specific for E-cadherin and it promotes the reorganization of the actin cytoskeleton. The bacterial toxins that modify the actin cytoskeleton induce various cell disfunctions including changes in cell barrier permeability and disruption of intercellular junctions.

ADP Ribose Transferases↗
PubMed1998

[Expression of CD44V6 and its effects on cytoskeleton in human colorectal carcinoma cell lines].

OBJECTIVE: To observe the expression of CD44V6 and its effects on cytoskeleton in human colorectal carcinoma(HCC) HT29 and LoVo cell lines. METHODS: Expression of CD44V6 variant in HCC HT29 and LoVo cell lines was investigated by in situ hybridization, immunohistochemistry and quantitative immunofluorescence technique. The effects of CD44V6 variants on cytoskeleton was studied by immunofluorescence and confocal 3 dimension reconstruction technique. RESULTS: CD44V6 was expressed at the mRNA and protein levels in both HT29 and LoVo cell lines, but the expression was higher in LoVo cells than in HT29 cells. When the HT29 cells and LoVo cells were blocked by monoclonal antibodies, it was found that changes developed in the cytoskeleton of these cells. CONCLUSIONS: The expression of CD44V6 is related to the metastatic potentiality of human colorectal carcinoma cells. CD44V6 may affect the distribution, polymerization and depolymerization of actin of HCC cells and promote HCC cell metastasis.

Actins↗
PubMed2001

[Change in fibroblast polarization during change in contractility of the actin cytoskeleton].

The aim of this work was to study role of the contractility in the process of fibroblast spreading. We investigated the morphology and cytoskeleton of cells seeded in the medium containing 2,3 butanedione monoxime (BDM), an inhibitor of myosin II and myosin-ATPase. Time-lapse video observation and immunofluorescence microscopy were used. BDM caused delay in spreading and blocked cell polarization, that led eventually to the conservation of disk-like cell morphology. The actin-myosin cytoskeleton was also BDM-changed. The number and thickness of stress-fibers decreased. Myosin II orientation was dramatically disturbed to obtain a difuse pattern in the cytoplasm. Paxillin-containing focal adhesions decreased in length and their distribution was changed. The movement of concanavalin A receptors and concanavalin A-coated beads on the lamellar cell surface was also BDM inhibited. It indicates an obvious depression of the lamellar cytoplasm activity and points to the damage of the actin-myosin cytoskeleton. Thus, the change in contractility of the latter alters significantly the morphogenesis of fibroblast spreading.

Actins↗
PubMed2001

[Pathogenicity of bacteria and the actin cytoskeleton].

Actin system of eukaryotic cells creates the driving force for alteration of the phagocytic cytoplasmatic membrane shape, which is needed for cell movement in the space and for microorganism capturing. Manipulation by actin cytoskeleton mediated through specialized bacterial products can promote proliferation of bacteria in the host. Published reports indicate that bacterial regulation of the actin system activity can be carried out by two modes: 1) by bacterial interactions with surface receptors regulating the cytoskeleton status and 2) by introduction of bacterial products targeted to the cytoskeleton components into the cells. Intracellular pathogens (Legionella) possess ligands which interact with eukaryotic receptors and type IV secretion system fit for translocation of heretofore unknown effector molecules into the cytoplasm. This can result in stimulation of actin polymerization activity and accelerated phagocytosis of the bacteria with rapid multiplication in tissues. By contrast, representatives of extracellular pathogens (Clostridium) produce substances penetrating inside the eukaryotic cells and destroying the actin network, thus making capturing and intracellular digestion of these microorganisms impossible.

Actins↗
PubMed2002

[The effects of the mechanical stress on the cytoskeleton filament F-actin of osteoblast-like cells in vitro].

OBJECTIVE: Mechanical stimulation alters cell's metabolism, but little is known about the effects of mechanical strain on the cytoskeleton of osteoblasts. This study was to investigate the changes of F-actin, a cytoskeleton protein of rat-derived osteoblast-like cell line UMR-106, and to provide theoretical basis for further investigation of mechanism of bone-remodeling. METHODS: Centrifugation was used to inflict UMR-106 the top-bottom axial stress (225 x g) expected and, confocal laser scanning microscope (LSCM) was used to examine the morphological changes 15, 30 min, and 1, 4, 6, 12, and 24 hr after undergoing physical strain. Unstrained cells were used as the controls respectively. The distribution of F-actin was observed after immunofluorescent staining and electronic photo was scanned for further analysis of osteoblasts' average fluorescence by spectrofluorimetric quantification. RESULTS: Except the 24 hr group, the actin filaments of the strained osteoblasts were much shorter, more flimsy and tenuous than that of untreated osteoblasts and unlike the normal distribution of bundles or membrane-like of the control group, and they were arranged without direction. Its quantified fluorescence was significantly less than that of the controls. But the 24 hr group showed a normal distribution and a stronger fluorescence. CONCLUSION: It is concluded that the cytoskeleton of the strained osteoblasts has a reduced number of F-actin fibers and a unique abnormal morphology and could recover in 24 hr.

Actins↗
PubMed2003

Ezrin, actin and cytoskeleton in apoptosis of esophageal epithelial cells induced by arsenic trioxide.

Ezrin is a key protein in membrane-cytoskeleton interaction. Expression of ezrin in actin-rich cell surfaces may play a role in the modulation of cell shape and adhesion. The aim of this study was to detect ezrin, actin and cytoskeleton and to explore their relationship in the apoptosis of esophageal epithelial cells (SHEE) induced by arsenic trioxide (As2O3). The SHEE is an immortalized human fetal esophageal epithelial cell line, and the cells were treated by administering 5, 10 and 20 micromol of As2O3. the proliferation and apoptosis of SHEE cells were examined by flow cytometry with propidium iodide staining. Ezrin expression was detected by immunocytochemistry and Western blotting. Actin filament was stained by FITC-labeled phalloidin and detected quantitatively by fluorescent microscopy. Cell morphology and microfilaments were examined by electron microscopy. The results revealed that As2O3 induced an inhibition of proliferation and the promotion of apoptosis in SHEE cells. The ezrin, actin and cytoskeleton were decreased after As2O3 treatment and the cellular morphology of apoptosis developed. Our results suggested that the morphological changes of arsenic-induced apoptosis of human esophageal epithelial cells were initiated by ezrin and actin-cytoskeletal aberrance.

Actins↗
PubMedDate not supplied

Volume-dependent regulation of ion carriers in human and rat erythrocytes: role of cytoskeleton and protein phosphorylation.

This study examines the effect of heat-induced cytoskeleton transitions and phosphoprotein phosphatase inhibitors on the activity of shrinkage-induced Na+, K+, 2Cl- cotransport and Na+/H+ exchange in rat erythrocytes and swelling-induced K+, Cl- cotransport in human and rat blood cells. Preincubation of human and rat erythrocytes at 49 degrees C drastically activated K+, Cl- cotransport and completely (rat) or partly (human) abolished its volume-dependent regulation. The same procedure did not affect basal activity of Na+, K+, 2Cl- cotransport but completely abolished its activation by shrinkage thus suggesting the involvement of a thermosensitive element of cytoskeleton network in the volume-dependent regulation of cotransporters. Both the shrinkage- and electrochemical proton gradient-induced Na+/H+ exchange was inhibited by the heat treatment to the same extent (50-70%), thus indicating the different signaling pathways involved in the activation of Na+, K+, 2Cl- cotransport and Na+/H+ exchange by cell shrinkage. This suggestion is in accordance with data on the different kinetics of volume-dependent activation and inactivation of these carriers as well as on their sensitivity to medium osmolality. Both swelling- and heat-induced increments of K+, Cl- cotransport activity were diminished by inhibitors of phosphoprotein phosphatases (okadaic acid and calyculin). In rat erythrocytes these compounds potentiate shrinkage-induced Na+/H+ exchange. On the contrary, neither basal nor shrinkage-induced Na+, K+, 2Cl- cotransport was affected by these compounds. Our results indicate a key role of cytoskeleton network in volume-dependent activation of K+, Cl- and Na+, K+, 2Cl- cotransport and the involvement of protein phosphorylation-dephosphorylation cycle in regulation of the activity of K+, Cl- cotransport and Na+/H+ exchange.

Animals↗
PubMed2003

FGF-2 induced reorganization and disruption of actin cytoskeleton through PI 3-kinase, Rho, and Cdc42 in corneal endothelial cells.

PURPOSE: Corneal endothelial cells (CECs) undergo endothelial to mesenchymal transformation (EMT) in response to FGF-2 stimulation. One phenotypic change that occurs during EMT is a change in cell shape from polygonal to elongated fibroblast-like cells. We investigated whether FGF-2 plays a role in this morphogenetic pathway by reorganizing actin cytoskeleton through the actions of phosphatidylinositol (PI) 3-kinase and the Ras related Rho family of small guanosine triphosphatases (GTPases). METHODS: Cell morphology was analyzed using phase contrast microscopy, and the organization of actin cytoskeleton and focal adhesions were analyzed by immunofluorescent staining. Expression of vinculin and beta-actin was determined by immunoblot analysis. Pharmacologic inhibitors (LY294002, C3 exoenzyme, Y27632, or PD98059) or neutralizing antibody to FGF-2, respectively, were used to block PI 3-kinase, Rho, Rho associated kinase, extracellular signal regulated kinase, or FGF-2 pathways. RESULTS: CECs treated with FGF-2 became smaller and lost their characteristic polygonal cell morphology. Such cell shape change was completely blocked by treatment with LY294002. CECs in culture have abundant stress fibers that are oriented radially across the cell. However, FGF-2 caused a loss of these stress fibers and focal adhesions. The modulated cells contained a cortical actin ring while LY294002 completely abolished this action of FGF-2 on actin cytoskeleton. Treatment of cells with C3 exoenzyme or Y27632 in the presence of FGF-2 induced spindle shaped cells with prominent pseudopodia which were rapidly formed upon exposure to the inhibitor. The expression level of vinculin was found to be similar in all experimental conditions but vinculin was mostly translocated to the cytoplasm in response to FGF-2 stimulation. CECs plated on Matrigel matrix demonstrated findings similar to those from cells plated on the conventional culture dishes, except that Matrigel facilitated the formation of pseudopodia. We further investigated in vivo actin organization using organ cultures of corneal endothelium (CE) on Descemet's membrane. The contact inhibited endothelial monolayer demonstrated a circumferential actin ring, and no stress fibers were observed. When CE was treated with FGF-2, a half population of CE lost its characteristic contact inhibited cobblestone morphology. Actin cortex was greatly disrupted in these modulated cells. Both neutralizing antibody to FGF-2 and LY294002 completely impeded the modulating activity of FGF-2 on the endothelial monolayer. When CE was simultaneously treated with FGF-2 and Y27632, the circumferential actin cortex was greatly disrupted and the endothelial monolayer was transformed into multi-layers of fibroblastic cells containing pseudopodia. Both LY294002 and neutralizing antibody to FGF-2 antagonized the actions of FGF-2 and Y27632. CONCLUSIONS: These data indicate that CECs in culture have constitutively active Rho activity as evidenced by stress fiber formation and that PI 3-kinase negatively regulates the formation of stress fibers and focal adhesions, perhaps antagonizing the Rho pathways. Formation of pseudopodia in response to FGF-2 and Y27632 may suggest that the Rho/ROCK pathway negatively regulates Cdc42.

Actins↗