scholarly journals Loss of γ-cytoplasmic actin triggers myofibroblast transition of human epithelial cells

2014 ◽  
Vol 25 (20) ◽  
pp. 3133-3146 ◽  
Author(s):  
Susana Lechuga ◽  
Somesh Baranwal ◽  
Chao Li ◽  
Nayden G. Naydenov ◽  
John F. Kuemmerle ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Actin Polymerization ◽  
Serum Response Factor ◽  
Rho Gtpase ◽  
Smooth Muscle Actin ◽  
Tissue Fibrosis ◽  
Cytoplasmic Actin ◽  
Epithelial Plasticity ◽  
Epithelial Phenotype ◽  
Serum Response

Transdifferentiation of epithelial cells into mesenchymal cells and myofibroblasts plays an important role in tumor progression and tissue fibrosis. Such epithelial plasticity is accompanied by dramatic reorganizations of the actin cytoskeleton, although mechanisms underlying cytoskeletal effects on epithelial transdifferentiation remain poorly understood. In the present study, we observed that selective siRNA-mediated knockdown of γ-cytoplasmic actin (γ-CYA), but not β-cytoplasmic actin, induced epithelial-to-myofibroblast transition (EMyT) of different epithelial cells. The EMyT manifested by increased expression of α-smooth muscle actin and other contractile proteins, along with inhibition of genes responsible for cell proliferation. Induction of EMyT in γ-CYA–depleted cells depended on activation of serum response factor and its cofactors, myocardial-related transcriptional factors A and B. Loss of γ-CYA stimulated formin-mediated actin polymerization and activation of Rho GTPase, which appear to be essential for EMyT induction. Our findings demonstrate a previously unanticipated, unique role of γ-CYA in regulating epithelial phenotype and suppression of EMyT that may be essential for cell differentiation and tissue fibrosis.

scholarly journals Enhancement of mDia2 activity by Rho-kinase-dependent phosphorylation of the diaphanous autoregulatory domain

2011 ◽  
Vol 439 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Dean P. Staus ◽  
Joan M. Taylor ◽  
Christopher P. Mack
Keyword(s):  
Smooth Muscle ◽  
Actin Polymerization ◽  
Serum Response Factor ◽  
Rho Kinase ◽  
Specific Gene ◽  
Related Transcription Factor ◽  
Inhibitory Domain ◽  
Serum Response ◽  
Acidic Region ◽  
Basic Region

It is clear that RhoA activates the DRF (diaphanous-related formin) mDia2 by disrupting the molecular interaction between the DAD (diaphanous autoregulatory domain) and the DID (diaphanous inhibitory domain). Previous studies indicate that a basic motif within the DAD contributes to mDia2 auto-inhibition, and results shown in the present study suggest these residues bind a conserved acidic region within the DID. Furthermore, we demonstrate that mDia2 is phosphorylated by ROCK (Rho-kinase) at two conserved residues (Thr1061 and Ser1070) just C-terminal to the DAD basic region. Phosphomimetic mutations to these residues in the context of the full-length molecule enhanced mDia2 activity as measured by increased actin polymerization, SRF (serum response factor)-dependent smooth muscle-specific gene transcription, and nuclear localization of myocardin-related transcription factor B. Biochemical and functional data indicate that the T1061E/S1070E mutation significantly inhibited the ability of DAD to interact with DID and enhanced mDia2 activation by RhoA. Taken together, the results of the present study indicate that ROCK-dependent phosphorylation of the mDia2 DAD is an important determinant of mDia2 activity and that this signalling mechanism affects actin polymerization and smooth muscle cell-specific gene expression.

scholarly journals Cellular Mechanisms of Tissue Fibrosis. 8. Current and future drug targets in fibrosis: focus on Rho GTPase-regulated gene transcription

2014 ◽  
Vol 307 (1) ◽  
pp. C2-C13 ◽  
Author(s):  
Pei-Suen Tsou ◽  
Andrew J. Haak ◽  
Dinesh Khanna ◽  
Richard R. Neubig
Keyword(s):  
Growth Factor ◽  
Gene Transcription ◽  
Drug Targets ◽  
Transforming Growth Factor ◽  
Serum Response Factor ◽  
Rho Gtpase ◽  
Tissue Growth ◽  
Cellular Mechanisms ◽  
Tissue Fibrosis ◽  
Matrix Deposition

Tissue fibrosis occurs with excessive extracellular matrix deposition from myofibroblasts, resulting in tissue scarring and inflammation. It is driven by multiple mediators, such as the G protein-coupled receptor ligands lysophosphatidic acid and endothelin, as well as signaling by transforming growth factor-β, connective tissue growth factor, and integrins. Fibrosis contributes to 45% of deaths in the developed world. As current therapeutic options for tissue fibrosis are limited and organ transplantation is the only effective treatment for end-stage disease, there is an imminent need for efficacious antifibrotic therapies. This review discusses the various molecular pathways involved in fibrosis. It highlights the Rho GTPase signaling pathway and its downstream gene transcription output through myocardin-related transcription factor and serum response factor as a convergence point for targeting this complex set of diseases.

scholarly journals Rho family GTPases control entry of Shigella flexneri into epithelial cells but not intracellular motility

1999 ◽  
Vol 112 (13) ◽  
pp. 2069-2080 ◽  
Author(s):  
J. Mounier ◽  
V. Laurent ◽  
A. Hall ◽  
P. Fort ◽  
M.F. Carlier ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Rho Gtpases ◽  
Actin Polymerization ◽  
Rho Gtpase ◽  
Shigella Flexneri ◽  
Intercellular Junctions ◽  
Small Gtpases ◽  
Comet Tail ◽  
Rho Family ◽  
Intracellular Motility

Shigella flexneri, an invasive bacterial pathogen, promotes formation of two cytoskeletal structures: the entry focus that mediates bacterial uptake into epithelial cells and the actin-comet tail that enables the bacteria to spread intracellularly. During the entry step, secretion of bacterial invasins causes a massive burst of subcortical actin polymerization leading the formation of localised membrane projections. Fusion of these membrane ruffles leads to bacterial internalization. Inside the cytoplasm, polar expression of the IcsA protein on the bacterial surface allows polymerization of actin filaments and their organization into an actin-comet tail leading to bacterial spread. The Rho family of small GTPases plays an essential role in the organization and regulation of cellular cytoskeletal structures (i.e. filopodia, lamellipodia, adherence plaques and intercellular junctions). We show here that induction of Shigella entry foci is controlled by the Cdc42, Rac and Rho GTPases, but not by RhoG. In contrast, actin-driven intracellular motility of Shigella does not require Rho GTPases. Therefore, Shigella appears to manipulate the epithelial cell cytoskeleton both by Rho GTPase-dependent and -independent processes.

scholarly journals The Diaphanous-related Formin mDia1 Controls Serum Response Factor Activity through its Effects on Actin Polymerization

2002 ◽  
Vol 13 (11) ◽  
pp. 4088-4099 ◽  
Author(s):  
John W. Copeland ◽  
Richard Treisman
Keyword(s):  
Actin Polymerization ◽  
Serum Response Factor ◽  
Signal Pathway ◽  
Small Gtpase ◽  
Actin Dynamics ◽  
Actin Assembly ◽  
Extracellular Signals ◽  
Activation Assay ◽  
The Relationship ◽  
Serum Response

SRF-dependent transcription is regulated by the small GTPase RhoA via its effects on actin dynamics. The diaphanous-related formin (DRF) proteins have been identified as candidate RhoA effectors mediating signaling to SRF. Here we investigate the relationship between SRF activation and actin polymerization by the DRF mDia1. We show that the ability of mDia1 to potentiate SRF activity is strictly correlated with its ability to promote F-actin assembly. Both processes can occur independently of the mDia1 FH1 domain but require sequences in an extended C-terminal region encompassing the conserved FH2 domain. mDia-mediated SRF activation, but not F-actin assembly, can be blocked by a nonpolymerizable actin mutant, placing actin downstream of mDia in the signal pathway. The SRF activation assay was used to identify inactive mDia1 derivatives that inhibit serum- and LPA-induced signaling to SRF. We show that these interfering mutants also block F-actin assembly, whether induced by mDia proteins or extracellular signals. These results identify novel functional elements of mDia1 and show that it regulates SRF activity by inducing depletion of the cellular pool of G-actin.

scholarly journals MRTF: Basic Biology and Role in Kidney Disease

2021 ◽  
Vol 22 (11) ◽  
pp. 6040
Author(s):  
Maria Zena Miranda ◽  
Zsuzsanna Lichner ◽  
Katalin Szászi ◽  
András Kapus
Keyword(s):  
Kidney Disease ◽  
Actin Polymerization ◽  
Serum Response Factor ◽  
Inflammatory Responses ◽  
Regulation Of Gene Expression ◽  
Rho Family Gtpases ◽  
Epithelial Phenotype ◽  
Related Transcription Factor ◽  
Cytoskeleton Remodeling ◽  
Basic Biology

A lesser known but crucially important downstream effect of Rho family GTPases is the regulation of gene expression. This major role is mediated via the cytoskeleton, the organization of which dictates the nucleocytoplasmic shuttling of a set of transcription factors. Central among these is myocardin-related transcription factor (MRTF), which upon actin polymerization translocates to the nucleus and binds to its cognate partner, serum response factor (SRF). The MRTF/SRF complex then drives a large cohort of genes involved in cytoskeleton remodeling, contractility, extracellular matrix organization and many other processes. Accordingly, MRTF, activated by a variety of mechanical and chemical stimuli, affects a plethora of functions with physiological and pathological relevance. These include cell motility, development, metabolism and thus metastasis formation, inflammatory responses and—predominantly-organ fibrosis. The aim of this review is twofold: to provide an up-to-date summary about the basic biology and regulation of this versatile transcriptional coactivator; and to highlight its principal involvement in the pathobiology of kidney disease. Acting through both direct transcriptional and epigenetic mechanisms, MRTF plays a key (yet not fully appreciated) role in the induction of a profibrotic epithelial phenotype (PEP) as well as in fibroblast-myofibroblast transition, prime pathomechanisms in chronic kidney disease and renal fibrosis.

scholarly journals The actin-MRTF-SRF transcriptional circuit controls tubulin acetylation via α-TAT1 gene expression

2018 ◽  
Vol 217 (3) ◽  
pp. 929-944 ◽  
Author(s):  
Jaime Fernández-Barrera ◽  
Miguel Bernabé-Rubio ◽  
Javier Casares-Arias ◽  
Laura Rangel ◽  
Laura Fernández-Martín ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Actin Polymerization ◽  
Serum Response Factor ◽  
Cell Types ◽  
Mrna Levels ◽  
Tubulin Acetylation ◽  
Hereditary Disorders ◽  
Related Transcription Factor ◽  
Transcriptional Complex ◽  
Serum Response

The role of formins in microtubules is not well understood. In this study, we have investigated the mechanism by which INF2, a formin mutated in degenerative renal and neurological hereditary disorders, controls microtubule acetylation. We found that silencing of INF2 in epithelial RPE-1 cells produced a dramatic drop in tubulin acetylation, increased the G-actin/F-actin ratio, and impaired myocardin-related transcription factor (MRTF)/serum response factor (SRF)–dependent transcription, which is known to be repressed by increased levels of G-actin. The effect on tubulin acetylation was caused by the almost complete absence of α-tubulin acetyltransferase 1 (α-TAT1) messenger RNA (mRNA). Activation of the MRTF-SRF transcriptional complex restored α-TAT1 mRNA levels and tubulin acetylation. Several functional MRTF-SRF–responsive elements were consistently identified in the α-TAT1 gene. The effect of INF2 silencing on microtubule acetylation was also observed in epithelial ECV304 cells, but not in Jurkat T cells. Therefore, the actin-MRTF-SRF circuit controls α-TAT1 transcription. INF2 regulates the circuit, and hence microtubule acetylation, in cell types where it has a prominent role in actin polymerization.

SO013CRUCIAL ROLE OF SERUM RESPONSE FACTOR IN EPITHELIAL-MESENCHYMAL TRANSITION OF RENAL TUBULAR EPITHELIAL CELLS IN HYPERUREICEMIC NEPHROPATHY

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Long Zhao ◽  
Yan Xu
Keyword(s):  
Epithelial Cells ◽  
Serum Response Factor ◽  
Epithelial Mesenchymal Transition ◽  
Tubular Epithelial Cells ◽  
Renal Tubular Epithelial Cells ◽  
Mesenchymal Transition ◽  
Molecule Inhibitor ◽  
Renal Tubular ◽  
Serum Response

Abstract Background and Aims To investigate the role of serum response factor (SRF) in epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells (TECs) in hyperuricemic nephropathy (HN). Method The expression of SRF, epithelial markers (E-cadherin and ZO-1) and mesenchymal markers (fibronectin, α-SMA, FSP-1) was examined in rat renal tubular epithelial cells (NRK-52E cells) or renal medulla tissues following uric acid (UA). SRF was upregulated by SRF plasmids and downregulated by CCG-1423(a small molecule inhibitor of SRF) to investigate how SRF influenced EMT in TECs of HN. Oxonic acid (OA) was used to generate HN in rats. Results Conclusion Together, increased SRF activity promotes EMT and dysfunction of TECs in HN. Targeting SRF by small molecule inhibitor may be an attractive therapeutic strategy for HN.

scholarly journals LIM kinase and Diaphanous cooperate to regulate serum response factor and actin dynamics

2002 ◽  
Vol 157 (5) ◽  
pp. 831-838 ◽  
Author(s):  
Olivier Geneste ◽  
John W. Copeland ◽  
Richard Treisman
Keyword(s):  
Actin Polymerization ◽  
Serum Response Factor ◽  
Rho Kinase ◽  
Small Gtpase ◽  
Actin Dynamics ◽  
Response Factor ◽  
Lim Kinase ◽  
Serum Stimulation ◽  
Effector Pathways ◽  
Serum Response

The small GTPase RhoA controls activity of serum response factor (SRF) by inducing changes in actin dynamics. We show that in PC12 cells, activation of SRF after serum stimulation is RhoA dependent, requiring both actin polymerization and the Rho kinase (ROCK)–LIM kinase (LIMK)–cofilin signaling pathway, previously shown to control F-actin turnover. Activation of SRF by overexpression of wild-type LIMK or ROCK-insensitive LIMK mutants also requires functional RhoA, indicating that a second RhoA-dependent signal is involved. This is provided by the RhoA effector mDia: dominant interfering mDia1 derivatives inhibit both serum- and LIMK-induced SRF activation and reduce the ability of LIMK to induce F-actin accumulation. These results demonstrate a role for LIMK in SRF activation, and functional cooperation between RhoA-controlled LIMK and mDia effector pathways.

MAL/SRF complex is involved in platelet formation and megakaryocyte migration by regulating MYL9 (MLC2) and MMP9

Blood ◽  
2009 ◽  
Vol 114 (19) ◽  
pp. 4221-4232 ◽  
Author(s):  
Laure Gilles ◽  
Dominique Bluteau ◽  
Siham Boukour ◽  
Yunhua Chang ◽  
Yanyan Zhang ◽  
...  
Keyword(s):  
Serum Response Factor ◽  
Rho Gtpase ◽  
Gene Encoding ◽  
Megakaryoblastic Leukemia ◽  
Proplatelet Formation ◽  
Stromal Cell Derived Factor ◽  
Gtpase Activation ◽  
Serum Response ◽  
Platelet Formation

Abstract Megakaryoblastic leukemia 1 (MAL) is a transcriptional coactivator of serum response factor (SRF). In acute megakaryoblastic leukemia, the MAL gene is translocated and fused with the gene encoding one twenty-two (OTT). Herein, we show that MAL expression increases during the late differentiation steps of neonate and adult human megakaryopoiesis and localized into the nucleus after Rho GTPase activation by adhesion on collagen I or convulxin. MAL knockdown in megakaryocyte progenitors reduced the percentage of cells forming filopodia, lamellipodia, and stress fibers after adhesion on the same substrates, and reduced proplatelet formation. MAL repression led to dysmorphic megakaryocytes with disorganized demarcation membranes and α granules heterogeneously scattered in the cytoplasm. Gene expression profiling revealed a marked decrease in metalloproteinase 9 (MMP-9) and MYL9 expression after MAL inhibition. Luciferase assays in HEK293T cells and chromatin immunoprecipitation in primary megakaryocytes showed that the MAL/SRF complex directly regulates MYL9 and MMP9 in vitro. Megakaryocyte migration in response to stromal cell–derived factor 1, through Matrigel was considerably decreased after MAL knockdown, implicating MMP9 in migration. Finally, the use of a shRNA to decrease MYL9 expression showed that MYL9 was involved in proplatelet formation. MAL/SRF complex is thus involved in platelet formation and megakaryocyte migration by regulating MYL9 and MMP9.

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