GEF-H1 is involved in agonist-induced human pulmonary endothelial barrier dysfunction

2006 ◽  
Vol 290 (3) ◽  
pp. L540-L548 ◽  
Author(s):  
Anna A. Birukova ◽  
Djanybek Adyshev ◽  
Boris Gorshkov ◽  
Gary M. Bokoch ◽  
Konstantin G. Birukov ◽  
...  
Keyword(s):  
Critical Role ◽  
Focal Adhesions ◽  
Stress Fiber ◽  
Small Gtpase ◽  
Fiber Formation ◽  
Cell Contact ◽  
Actin Stress Fiber ◽  
Barrier Dysfunction ◽  
Actin Remodeling ◽  
Stress Fiber Formation

Endothelial cell (EC) permeability is precisely controlled by cytoskeletal elements [actin filaments, microtubules (MT), intermediate filaments] and cell contact protein complexes (focal adhesions, adherens junctions, tight junctions). We have recently shown that the edemagenic agonist thrombin caused partial MT disassembly, which was linked to activation of small GTPase Rho, Rho-mediated actin remodeling, cell contraction, and dysfunction of lung EC barrier. GEF-H1 is an MT-associated Rho-specific guanosine nucleotide (GDP/GTP) exchange factor, which in MT-unbound state stimulates Rho activity. In this study we tested hypothesis that GEF-H1 may be a key molecule involved in Rho activation, myosin light chain phosphorylation, actin remodeling, and EC barrier dysfunction associated with partial MT disassembly. Our results show that depletion of GEF-H1 or expression of dominant negative GEF-H1 mutant significantly attenuated permeability increase, actin stress fiber formation, and increased MLC and MYPT1 phosphorylation induced by thrombin or MT-depolymerizing agent nocodazole. In contrast, expression of wild-type or activated GEF-H1 mutants dramatically enhanced thrombin and nocodazole effects on stress fiber formation and cell retraction. These results show a critical role for the GEF-H1 in the Rho activation caused by MT disassembly and suggest GEF-H1 as a key molecule involved in cross talk between MT and actin cytoskeleton in agonist-induced Rho-dependent EC barrier regulation.

Indomethacin Delays Gastric Restitution: Association with the Inhibition of Focal Adhesion Kinase and Tensin Phosphorylation and Reduced Actin Stress Fibers

2002 ◽  
Vol 227 (6) ◽  
pp. 412-424 ◽  
Author(s):  
Imre L. Szabó ◽  
Rama Pai ◽  
Michael K. Jones ◽  
George R. Ehring ◽  
Hirofumi Kawanaka ◽  
...  
Keyword(s):  
Cell Migration ◽  
Focal Adhesion ◽  
Focal Adhesions ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Actin Stress Fiber ◽  
Stress Fiber Formation ◽  
Actin Stress Fiber Formation

Repair of superficial gastric mucosal injury is accomplished by the process of restitution—migration of epithelial cells to restore continuity of the mucosal surface. Actin filaments, focal adhesions, and focal adhesion kinase (FAK) play crucial roles in cell motility essential for restitution. We studied whether epidermal growth factor (EGF) and/or indomethacin (IND) affect cell migration, actin stress fiber formation, and/or phosphorylation of FAK and tensin in wounded gastric monolayers. Human gastric epithelial monolayers (MKN 28 cells) were wounded and treated with either vehicle or 0.5 mM IND for 16 hr followed by EGF. EGF treatment significantly stimulated cell migration and actin stress fiber formation, and increased FAK localization to focal adhesions, and phosphorylation of FAK and tensin, whereas IND inhibited all these at the baseline and EGF-stimulated conditions. IND-induced inhibition of FAK phosphorylation preceded changes in actin polymerization, indicating that actin depolymerization might be the consequence of decreased FAK activity. In in vivo experiments, rats received either vehicle or IND (5 mg/kg i.g.), and 3 min later, they received water or 5% hypertonic NaCl; gastric mucosa was obtained at 1, 4, and 8 hr after injury. Four and 8 hr after hypertonic injury, FAK phosphorylation was induced in gastric mucosa compared with controls. IND pretreatment significantly delayed epithelial restitution in vivo, and reduced FAK phosphorylation and recruitment to adhesion points, as well as actin stress fiber formation in migrating surface epithelial cells. Our study indicates that FAK, tensin, and actin stress fibers are likely mediators of EGF-stimulated cell migration in wounded human gastric monolayers and potential targets for IND-induced inhibition of restitution.

scholarly journals Focal adhesion kinase signaling is decreased in polyamine-depleted IEC-6 cells

2001 ◽  
Vol 281 (2) ◽  
pp. C475-C485 ◽  
Author(s):  
Ramesh M. Ray ◽  
Mary Jane Viar ◽  
Shirley A. McCormack ◽  
Leonard R. Johnson
Keyword(s):  
Extracellular Matrix ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Focal Adhesions ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Integrin Signaling ◽  
Actin Stress Fiber ◽  
Stress Fiber Formation ◽  
And Migration

Polyamines are essential to the migration of epithelial cells in the intestinal mucosa. Cells depleted of polyamines do not attach as rapidly to the extracellular matrix and do not form the actin stress fibers essential for migration. Because both attachment and stress fiber formation depend on integrin signaling and the formation of focal adhesions, we examined these and related processes in polyamine-depleted IEC-6 cells. There was general decreased tyrosine phosphorylation of focal adhesion kinase (FAK), and, specifically, decreased phosphorylation of Tyr-925, the paxillin binding site. In control cells, FAK phosphorylation was rapid after attachment to the extracellular matrix, while attached cells depleted of polyamines had significantly delayed phosphorylation. FAK activity was also significantly inhibited in polyamine-depleted cells as was the phosphorylation of paxillin. Polyamine-depleted cells failed to spread normally after attachment, and immunocytochemistry showed little colocalization of FAK and actin compared with controls. Focal adhesion complex formation was greatly reduced in the absence of polyamines. These data suggest that defective integrin signaling may, at least in part, account for the decreased rates of attachment, actin stress fiber formation, spreading, and migration observed in polyamine-depleted cells.

scholarly journals B-RAF Regulation of Rnd3 Participates in Actin Cytoskeletal and Focal Adhesion Organization

2008 ◽  
Vol 19 (2) ◽  
pp. 498-508 ◽  
Author(s):  
R. Matthew Klein ◽  
Laurie S. Spofford ◽  
Ethan V. Abel ◽  
Arisa Ortiz ◽  
Andrew E. Aplin
Keyword(s):  
Actin Cytoskeleton ◽  
Focal Adhesion ◽  
Constitutive Expression ◽  
Focal Adhesions ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Mitogen Activated Protein Kinase ◽  
Actin Stress Fiber ◽  
Lim Kinase ◽  
Stress Fiber Formation

The actin cytoskeleton controls multiple cellular functions, including cell morphology, movement, and growth. Accumulating evidence indicates that oncogenic activation of the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 (MEK/ERK1/2) pathway is accompanied by actin cytoskeletal reorganization. However, the signaling events contributing to actin cytoskeleton remodeling mediated by aberrant ERK1/2 activation are largely unknown. Mutant B-RAF is found in a variety of cancers, including melanoma, and it enhances activation of the MEK/ERK1/2 pathway. We show that targeted knockdown of B-RAF with small interfering RNA or pharmacological inhibition of MEK increased actin stress fiber formation and stabilized focal adhesion dynamics in human melanoma cells. These effects were due to stimulation of the Rho/Rho kinase (ROCK)/LIM kinase-2 signaling pathway, cumulating in the inactivation of the actin depolymerizing/severing protein cofilin. The expression of Rnd3, a Rho antagonist, was attenuated after B-RAF knockdown or MEK inhibition, but it was enhanced in melanocytes expressing active B-RAF. Constitutive expression of Rnd3 suppressed the actin cytoskeletal and focal adhesion effects mediated by B-RAF knockdown. Depletion of Rnd3 elevated cofilin phosphorylation and stress fiber formation and reduced cell invasion. Together, our results identify Rnd3 as a regulator of cross talk between the RAF/MEK/ERK and Rho/ROCK signaling pathways, and a key contributor to oncogene-mediated reorganization of the actin cytoskeleton and focal adhesions.

scholarly journals FAK Is Required for TGFβ-induced JNK Phosphorylation in Fibroblasts: Implications for Acquisition of a Matrix-remodeling Phenotype

2007 ◽  
Vol 18 (6) ◽  
pp. 2169-2178 ◽  
Author(s):  
Shangxi Liu ◽  
Xu Shi-wen ◽  
Laura Kennedy ◽  
Daphne Pala ◽  
Yunliang Chen ◽  
...  
Keyword(s):  
Connective Tissue ◽  
Critical Role ◽  
Tissue Remodeling ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Actin Stress Fiber ◽  
Stress Fiber Formation ◽  
Matrix Contraction ◽  
Connective Tissue Remodeling ◽  
Actin Stress Fiber Formation

Transforming growth factor β (TGFβ) plays a critical role in connective tissue remodeling by fibroblasts during development, tissue repair, and fibrosis. We investigated the molecular pathways in the transmission of TGFβ signals that lead to features of connective tissue remodeling, namely formation of an α-smooth muscle actin (α-SMA) cytoskeleton, matrix contraction, and expression of profibrotic genes. TGFβ causes the activation of focal adhesion kinase (FAK), leading to JNK phosphorylation. TGFβ induces JNK-dependent actin stress fiber formation, matrix contraction, and expression of profibrotic genes in fak+/+, but not fak−/−, fibroblasts. Overexpression of MEKK1, a kinase acting upstream of JNK, rescues TGFβ responsiveness of JNK-dependent transcripts and actin stress fiber formation in FAK-deficient fibroblasts. Thus we propose a FAK-MEKK1-JNK pathway in the transmission of TGFβ signals leading to the control of α-SMA cytoskeleton reorganization, matrix contraction, and profibrotic gene expression and hence to the physiological and pathological effects of TGFβ on connective tissue remodeling by fibroblasts.

ROCK mediates thrombin's endothelial barrier dysfunction

2000 ◽  
Vol 279 (1) ◽  
pp. C195-C204 ◽  
Author(s):  
José M. Carbajal ◽  
Max L. Gratrix ◽  
Chung-Ho Yu ◽  
Richard C. Schaeffer
Keyword(s):  
Stress Fiber ◽  
Fiber Formation ◽  
Actin Stress Fiber ◽  
Endothelial Monolayer ◽  
Barrier Dysfunction ◽  
Rock Inhibitor ◽  
Independent Manner ◽  
Actin Organization ◽  
Stress Fiber Formation ◽  
Small Pore

Thrombin-induced endothelial monolayer hyperpermeability is thought to result from increased F-actin stress fiber-related contractile tension, a process regulated by the small GTP-binding protein Rho. We tested whether this process was dependent on the Rho-associated protein kinase, ROCK, using a specific ROCK inhibitor, Y-27632. The effects of Y-27632 on thrombin-induced myosin light chain phosphorylation (MLCP) and tyrosine phosphorylation of p125 focal adhesion kinase (p125FAK) and paxillin were measured by Western blotting. F-actin organization and content were analyzed by digital imaging, and endothelial monolayer permeability was measured in bovine pulmonary artery endothelial cell (EC) monolayers using a size-selective permeability assay. Y-27632 enhanced EC monolayer barrier function due to a decline in small-pore number that was associated with increased EC surface area, reduced F-actin content, and reorganization of F-actin to β-catenin-containing cell-cell adherens junctions. Although Y-27632 prevented thrombin-induced MLCP, stress fiber formation, and the increased phosphotyrosine content of paxillin and p125FAK, it attenuated but did not prevent the thrombin-induced formation of large paracellular holes. These data indicate that thrombin-induced stress fiber formation is ROCK dependent. In contrast, thrombin-induced paracellular hole formation occurs in a ROCK-independent manner, whereas thrombin-induced monolayer hyperpermeability appears to be partially ROCK dependent.

Abstract WP438: Rho Kinase-mediated Di-phosphorylation of Myosin Light Chain in the Sub-membranous Regions and Circumferential Actomyosin Contraction Mediate Thrombin-induced Barrier Disruption in Vascular Endothelial Cells

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Mayumi Hirano ◽  
Katsuya Hirano
Keyword(s):  
Endothelial Cells ◽  
Myosin Light Chain ◽  
Critical Role ◽  
Rho Kinase ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Cell Contact ◽  
Barrier Disruption ◽  
Stress Fiber Formation ◽  
Cell Cell

The disruption of blood-brain barrier plays a critical role in the pathophysiology of cerebrovascular diseases. Thrombin is one of the major factors which cause barrier disruption. The phosphorylation of myosin light chain (MLC) is a key signal of barrier disruption. MLC is thought to be di-phosphorylated sequentially at Ser19 and then Thr18, thereby inducing stress fiber formation to generate traction force to disrupt cell-cell contact. However, it is unclear how the phosphorylation at two sites contributes to barrier disruption. The present study investigated the role of mono- and di-phosphorylation of MLC (MLC-P and MLC-PP) in thrombin-induced barrier disruption. Thrombin (1 u/mL) decreased the transendothelial electrical resistance (TEER) with a peak at 3-5 min in porcine aortic endothelial cells (PAEC). A Phos-tag SDS-PAGE method was used to quantify the amount of MLC-P and MLC-PP. PAEC at confluence contained 25% MLC-P and 2% MLC-PP before stimulation. Upon thrombin stimulation, MLC-P marginally increased, while MLC-PP transiently increased to a peak of 35% at 3-5 min. MLC-P was localized mainly in the peri-nuclear region, while MLC-PP was localized mainly in the sub-membranous region of cell-cell contact. MLC-PP was also co-localized with the peripheral actin bundles. In contrast, thrombin induced stress fiber formation and localization of MLC-P and MLC-PP on the stress fibers when the cell-cell contact was loosed by removing extracellular Ca 2+ or in the cells at the growing phase with sparse cell-cell contact. Two different Rho kinase inhibitors, Y27632 and H1152, inhibited the thrombin-induced increase in MLC-PP, sub-membranous localization of MLC-PP and decrease in TEER, while having no effect on the level of MLC-P. Inhibition of myosin ATPase activity by 100 μmol/L blebbistatin inhibited the thrombin-induced decrease in TEER. The present study suggests that MLC-P and MLC-PP are independently regulated in endothelial cells, and that Rho kinase-mediated MLC-PP in the sub-membranous regions and the circumferential, but not radial, contraction plays a critical role in the thrombin-induced barrier disruption. Inhibition of MLC-PP thus provides a crucial strategy for restoring normal function of the blood-brain barrier.

scholarly journals MEKK1 Transduces Activin Signals in Keratinocytes To Induce Actin Stress Fiber Formation and Migration

2005 ◽  
Vol 25 (1) ◽  
pp. 60-65 ◽  
Author(s):  
Lin Zhang ◽  
Maoxian Deng ◽  
Ranjani Parthasarathy ◽  
Lei Wang ◽  
Maureen Mongan ◽  
...  
Keyword(s):  
Cell Migration ◽  
Epithelial Cell ◽  
Critical Role ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Actin Stress Fiber ◽  
Stress Fiber Formation ◽  
Epithelial Cell Migration ◽  
Factor C ◽  
Actin Stress Fiber Formation

ABSTRACT Activins and other members of the transforming growth factor β family play a critical role in morphological changes of the epidermis that require epithelial cell movement. We investigated the molecular pathways in the transmission of activin signals that lead to actin reorganization and epithelial cell migration. We found that activins cause the activation of RhoA but not of Rac and CDC42, leading to MEKK1-dependent phosphorylation of JNK and transcription factor c-Jun. Through a RhoA-independent mechanism, the activins also induce p38 activity in keratinocytes from wild-type but not from MEKK1-deficient mice. Although neither pathway is dependent on Smad activation, the MEKK1-mediated JNK and p38 activities are both essential for activin-stimulated and transcription-dependent keratinocyte migration. Only JNK is involved in transcription-independent actin stress fiber formation, which needs also the activity of ROCK. Because ROCK is required for JNK activation by RhoA and its overexpression leads to MEKK1 activation, we propose a RhoA-ROCK-MEKK1-JNK pathway and a MEKK1-p38 pathway as Smad-independent mechanisms in the transmission of activin signals. Together, these pathways lead to the control of actin cytoskeleton reorganization and epithelial cell migration, contributing to the physiologic and pathological effects of activins on epithelial morphogenesis.

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