scholarly journals The small GTPase Rif is an alternative trigger for the formation of actin stress fibers in epithelial cells

2010 ◽  
Vol 123 (8) ◽  
pp. 1247-1252 ◽  
Author(s):  
L. Fan ◽  
S. Pellegrin ◽  
A. Scott ◽  
H. Mellor
Keyword(s):  
Epithelial Cells ◽  
Small Gtpase ◽  
Stress Fibers ◽  
Actin Stress Fibers

Rho-kinase regulates myosin II activation in MDCK cells during recovery after ATP depletion

2001 ◽  
Vol 281 (5) ◽  
pp. F810-F818 ◽  
Author(s):  
Timothy A. Sutton ◽  
Henry E. Mang ◽  
Simon J. Atkinson
Keyword(s):  
Epithelial Cells ◽  
Actin Cytoskeleton ◽  
Mdck Cells ◽  
Myosin Ii ◽  
Atp Depletion ◽  
Stress Fibers ◽  
Tubular Epithelial Cells ◽  
Renal Tubular Epithelial Cells ◽  
Renal Tubular ◽  
Actin Stress Fibers

Alterations in the actin cytoskeleton of renal tubular epithelial cells during periods of ischemic injury and recovery have important consequences for normal cell and kidney function. Myosin II has been demonstrated to be an important effector in organizing basal actin structures in some cell types. ATP depletion in vitro has been demonstrated to recapitulate alterations of the actin cytoskeleton in renal tubular epithelial cells observed during renal ischemia in vivo. We utilized this reversible cell culture model of ischemia to examine the correlation of the activation state and cellular distribution of myosin II with disruption of actin stress fibers in Madin-Darby canine kidney (MDCK) cells during ATP depletion and recovery from ATP depletion. We found that myosin II inactivation occurs rapidly and precedes dissociation of myosin II from actin stress fibers during ATP depletion. Myosin II activation temporally correlates with colocalization of myosin II to reorganizing stress fibers during recovery from ATP depletion. Furthermore, myosin activation and actin stress fiber formation were found to be Rho-associated Ser/Thr protein kinase dependent during recovery from ATP depletion.

scholarly journals Induced Expression of Rnd3 Is Associated with Transformation of Polarized Epithelial Cells by the Raf–MEK–Extracellular Signal-Regulated Kinase Pathway

2000 ◽  
Vol 20 (24) ◽  
pp. 9364-9375 ◽  
Author(s):  
Steen H. Hansen ◽  
Mirjam M. P. Zegers ◽  
Melissa Woodrow ◽  
Pablo Rodriguez-Viciana ◽  
Pierre Chardin ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Actin Cytoskeleton ◽  
Active Form ◽  
Stress Fibers ◽  
Cortical Actin ◽  
Induced Expression ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Kinase Pathway ◽  
Actin Stress Fibers

ABSTRACT Madin-Darby canine kidney (MDCK) epithelial cells transformed by oncogenic Ras and Raf exhibit cell multilayering and alterations in the actin cytoskeleton. The changes in the actin cytoskeleton comprise a loss of actin stress fibers and enhanced cortical actin. Using MDCK cells expressing a conditionally active form of Raf, we have explored the molecular mechanisms that underlie these observations. Raf activation elicited a robust increase in Rac1 activity consistent with the observed increase in cortical actin. Loss of actin stress fibers is indicative of attenuated Rho function, but no change in Rho-GTP levels was detected following Raf activation. However, the loss of actin stress fibers in Raf-transformed cells was preceded by the induced expression of Rnd3, an endogenous inhibitor of Rho protein function. Expression of Rnd3 alone at levels equivalent to those observed following Raf transformation led to a substantial loss of actin stress fibers. Moreover, cells expressing activated RhoA failed to multilayer in response to Raf. Pharmacological inhibition of MEK activation prevented all of the biological and biochemical changes described above. Consequently, the data are consistent with a role for induced Rnd3 expression downstream of the Raf–MEK–extracellular signal-regulated kinase pathway in epithelial oncogenesis.

scholarly journals TPM3.1 association with actin stress fibers is required for lens epithelial to mesenchymal transition

2019 ◽  
Author(s):  
Justin Parreno ◽  
Michael B. Amadeo ◽  
Elizabeth H. Kwon ◽  
Velia M. Fowler
Keyword(s):  
Epithelial Cells ◽  
Epithelial To Mesenchymal Transition ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Lens Epithelial Cells ◽  
Mesenchymal Transition ◽  
Stress Fiber Formation ◽  
Actin Stress Fibers

AbstractPurposeEpithelial to mesenchymal transition (EMT) is a cause of anterior and posterior subcapsular cataracts. Central to EMT is the formation of actin stress fibers. Targeting specific, stress fiber associated tropomyosin in epithelial cells may be a means to prevent stress fiber formation and repress lens EMT.MethodsWe identified Tpm isoforms in mouse immortalized lens epithelial cells and isolated whole lenses by semi-quantitative PCR followed Sanger sequencing. We focused on the role of one particular tropomyosin isoform, Tpm3.1, in EMT. To stimulate EMT, we cultured cells or native lenses in TGFβ2. To test the function of Tpm3.1, we exposed cells or whole lenses to a Tpm3.1-specific chemical inhibitor, TR100, as well as investigated lenses from Tpm3.1 knockout mice. We examined stress fiber formation by confocal microscopy and assessed EMT progression by αsma mRNA (qPCR) and protein (WES immunoassay) analysis.ResultsLens epithelial cells express eight tropomyosin isoforms. Cell culture studies showed that TGFβ2 treatment results in an upregulation of Tpm3.1, which associates with actin in stress fibers. TR100 prevents stress fiber formation and reduces αsma in TGFβ2 treated cells. We confirmed the role of Tpm3.1 in lens epithelial cells in the native lens ex vivo. Culture of whole lenses in the presence of TGFβ2 results in stress fiber formation at the basal regions of epithelial cells. Knockout of Tpm3.1 or treatment of lenses with TR100 prevents basal stress fiber formation and reduces epithelial αsma levels.ConclusionTargeting specific stress fiber associated tropomyosin isoform, Tpm3.1, is a means to represses lens EMT.

scholarly journals Yersinia enterocolitica Adhesin A Induces Production of Interleukin-8 in Epithelial Cells

2004 ◽  
Vol 72 (12) ◽  
pp. 6780-6789 ◽  
Author(s):  
Yvonne Schmid ◽  
Guntram A. Grassl ◽  
Oliver T. Bühler ◽  
Mikael Skurnik ◽  
Ingo B. Autenrieth ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Yersinia Enterocolitica ◽  
Hela Cells ◽  
Map Kinases ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Interleukin 8 ◽  
Β1 Integrin ◽  
Β1 Integrins ◽  
Tissue Reactions

ABSTRACT The major invasive factor of Yersinia enterocolitica, the invasin (Inv) protein, induces proinflammatory host cell responses, including interleukin-8 (IL-8) secretion from human epithelial cells, by engagement of β1 integrins. The Inv-triggered β1 integrin signaling involves the small GTPase Rac; the activation of MAP kinases, such as p38, MEK1, and JNK; and the activation of the transcription factor NF-κB. In the present study, we demonstrate that Y. enterocolitica YadA, which is a major adhesin of Y. enterocolitica with pleiotropic virulence effects, induces IL-8 secretion in epithelial cells. The abilites of YadA and Inv to promote adhesion to and invasion of HeLa cells and to induce IL-8 production by the cells were investigated by expression of YadA and Inv in Escherichia coli. While YadA mediates efficacious adhesion to HeLa cells, it mediates marginal invasion compared with Inv. Both YadA and Inv trigger comparable levels of IL-8 production. Conformational changes of the YadA head domain by mutation of NSVAIG-S motifs, which abolish collagen binding, also abolish adhesion of Yersinia to HeLa cells and YadA-mediated IL-8 secretion. Furthermore, experiments in which blocking antibodies against β1 integrins were used demonstrate that β1 integrins are crucial for YadA-mediated IL-8 secretion. Inhibitor studies demonstrate the involvement of small GTPases and MAP kinases, such as p38, MEK1, and JNK, indicating that β1 integrin-dependent signaling mediated by Inv or YadA involves similar signaling pathways. These data present YadA, in addition to Inv, YopB, and Yersinia lipopolysaccharide, as a further inducer of proinflammatory molecules by which Y. enterocolitica might promote inflammatory tissue reactions.

scholarly journals ROCK and mDia1 antagonize in Rho-dependent Rac activation in Swiss 3T3 fibroblasts

2002 ◽  
Vol 157 (5) ◽  
pp. 819-830 ◽  
Author(s):  
Takahiro Tsuji ◽  
Toshimasa Ishizaki ◽  
Muneo Okamoto ◽  
Chiharu Higashida ◽  
Kazuhiro Kimura ◽  
...  
Keyword(s):  
Focal Adhesions ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Stress Fibers ◽  
Induced Membrane ◽  
3T3 Fibroblasts ◽  
C3 Exoenzyme ◽  
Swiss 3T3 ◽  
Swiss 3T3 Fibroblasts ◽  
Membrane Ruffle

The small GTPase Rho acts on two effectors, ROCK and mDia1, and induces stress fibers and focal adhesions. However, how ROCK and mDia1 individually regulate signals and dynamics of these structures remains unknown. We stimulated serum-starved Swiss 3T3 fibroblasts with LPA and compared the effects of C3 exoenzyme, a Rho inhibitor, with those of Y-27632, a ROCK inhibitor. Y-27632 treatment suppressed LPA-induced formation of stress fibers and focal adhesions as did C3 exoenzyme but induced membrane ruffles and focal complexes, which were absent in the C3 exoenzyme-treated cells. This phenotype was suppressed by expression of N17Rac. Consistently, the amount of GTP-Rac increased significantly by Y-27632 in LPA-stimulated cells. Biochemically, Y-27632 suppressed tyrosine phosphorylation of paxillin and focal adhesion kinase and not that of Cas. Inhibition of Cas phosphorylation with PP1 or expression of a dominant negative Cas mutant inhibited Y-27632–induced membrane ruffle formation. Moreover, Crk-II mutants lacking in binding to either phosphorylated Cas or DOCK180 suppressed the Y-27632–induced membrane ruffle formation. Finally, expression of a dominant negative mDia1 mutant also inhibited the membrane ruffle formation by Y-27632. Thus, these results have revealed the Rho-dependent Rac activation signaling that is mediated by mDia1 through Cas phosphorylation and antagonized by the action of ROCK.

scholarly journals Mechanically induced deformation and strain dynamics in actin stress fibers

2012 ◽  
Vol 5 (6) ◽  
pp. 627-630 ◽  
Author(s):  
Sebastian Hadjiantoniou ◽  
Louise Guolla ◽  
Andrew E. Pelling
Keyword(s):  
Stress Fibers ◽  
Actin Stress Fibers

scholarly journals Delayed stress fiber formation mediates pulmonary myofibroblast differentiation in response to TGF-β

2011 ◽  
Vol 301 (5) ◽  
pp. L656-L666 ◽  
Author(s):  
Nathan Sandbo ◽  
Andrew Lau ◽  
Jacob Kach ◽  
Caitlyn Ngam ◽  
Douglas Yau ◽  
...  
Keyword(s):  
Rho Kinase ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Nuclear Accumulation ◽  
Myofibroblast Differentiation ◽  
Latrunculin B ◽  
Stress Fiber Formation ◽  
Actin Expression ◽  
Actin Stress Fibers

Myofibroblast differentiation induced by transforming growth factor-β (TGF-β) and characterized by de novo expression of smooth muscle (SM)-specific proteins is a key process in wound healing and in the pathogenesis of fibrosis. We have previously shown that TGF-β-induced expression and activation of serum response factor (SRF) is required for this process. In this study, we examined the signaling mechanism for SRF activation by TGF-β as it relates to pulmonary myofibroblast differentiation. TGF-β stimulated a profound, but delayed (18–24 h), activation of Rho kinase and formation of actin stress fibers, which paralleled SM α-actin expression. The translational inhibitor cycloheximide blocked these processes without affecting Smad-dependent gene transcription. Inhibition of Rho kinase by Y-27632 or depolymerization of actin by latrunculin B resulted in inhibition TGF-β-induced SRF activation and SM α-actin expression, having no effect on Smad signaling. Conversely, stabilization of actin stress fibers by jasplakinolide was sufficient to drive these processes in the absence of TGF-β. TGF-β promoted a delayed nuclear accumulation of the SRF coactivator megakaryoblastic leukemia-1 (MKL1)/myocardin-related transcription factor-A, which was inhibited by latrunculin B. Furthermore, TGF-β also induced MKL1 expression, which was inhibited by latrunculin B, by SRF inhibitor CCG-1423, or by SRF knockdown. Together, these data suggest a triphasic model for myofibroblast differentiation in response to TGF-β that involves 1) initial Smad-dependent expression of intermediate signaling molecules driving Rho activation and stress fiber formation, 2) nuclear accumulation of MKL1 and activation of SRF as a result of actin polymerization, and 3) SRF-dependent expression of MKL1, driving further myofibroblast differentiation.

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