Lamina-associated polypeptide 2α is required for intranuclear MRTF-A activity

Myocardin-related transcription factor A (MRTF-A), a coactivator of serum response factor (SRF), regulates the expression of many cytoskeletal genes in response to cytoplasmic and nuclear actin dynamics. Here we describe a novel mechanism to regulate MRTF-A activity within the nucleus by showing that lamina-associated polypeptide 2α (Lap2α), the nucleoplasmic isoform of Lap2, is a direct binding partner of MRTF-A, and required for the efficient expression of MRTF-A/SRF target genes. Mechanistically, Lap2α is not required for MRTF-A nuclear localization, unlike most other MRTF-A regulators, but is required for binding of MRTF-A to its target genes. This regulatory step takes place prior to MRTF-A chromatin binding, because Lap2α neither interacts with, nor specifically influences active histone marks on MRTF-A/SRF target genes. Phenotypically, Lap2α is required for serum-induced cell migration, and deregulated MRTF-A activity may also contribute to muscle and proliferation phenotypes associated with loss of Lap2α. Our studies therefore add another regulatory layer to the control of MRTF-A-SRF-mediated gene expression, and broaden the role of Lap2α in transcriptional regulation.

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The Cytoskeleton-associated PDZ-LIM Protein, ALP, Acts on Serum Response Factor Activity to Regulate Muscle Differentiation

Molecular Biology of the Cell ◽

10.1091/mbc.e06-09-0815 ◽

2007 ◽

Vol 18 (5) ◽

pp. 1723-1733 ◽

Cited By ~ 19

Author(s):

Pascal Pomiès ◽

Mohammad Pashmforoush ◽

Cristina Vegezzi ◽

Kenneth R. Chien ◽

Charles Auffray ◽

...

Keyword(s):

Serum Response Factor ◽

Critical Role ◽

Muscle Differentiation ◽

Actin Dynamics ◽

Response Factor ◽

Cytoskeletal Regulation ◽

Expression Construct ◽

Filament Bundles ◽

Serum Response

In this report, an antisense RNA strategy has allowed us to show that disruption of ALP expression affects the expression of the muscle transcription factors myogenin and MyoD, resulting in the inhibition of muscle differentiation. Introduction of a MyoD expression construct into ALP-antisense cells is sufficient to restore the capacity of the cells to differentiate, illustrating that ALP function occurs upstream of MyoD. It is known that MyoD is under the control of serum response factor (SRF), a transcriptional regulator whose activity is modulated by actin dynamics. A dramatic reduction of actin filament bundles is observed in ALP-antisense cells and treatment of these cells with the actin-stabilizing drug jasplakinolide stimulates SRF activity and restores the capacity of the cells to differentiate. Furthermore, we show that modulation of ALP expression influences SRF activity, the level of its coactivator, MAL, and muscle differentiation. Collectively, these results suggest a critical role of ALP on muscle differentiation, likely via cytoskeletal regulation of SRF.

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Myocardin-Related Transcription Factor A Activation by Competition with WH2 Domain Proteins for Actin Binding

Molecular and Cellular Biology ◽

10.1128/mcb.01097-15 ◽

2016 ◽

Vol 36 (10) ◽

pp. 1526-1539 ◽

Cited By ~ 9

Author(s):

Julia Weissbach ◽

Franziska Schikora ◽

Anja Weber ◽

Michael Kessels ◽

Guido Posern

Keyword(s):

Serum Response Factor ◽

De Novo ◽

Actin Dynamics ◽

Actin Binding ◽

Serum Stimulation ◽

Competitive Mechanism ◽

Related Transcription Factor ◽

Simultaneous Inhibition ◽

Serum Response

The myocardin-related transcription factors (MRTFs) are coactivators of serum response factor (SRF)-mediated gene expression. Activation of MRTF-A occurs in response to alterations in actin dynamics and critically requires the dissociation of repressive G-actin–MRTF-A complexes. However, the mechanism leading to the release of MRTF-A remains unclear. Here we show that WH2 domains compete directly with MRTF-A for actin binding. Actin nucleation-promoting factors, such as N-WASP and WAVE2, as well as isolated WH2 domains, including those of Spire2 and Cobl, activate MRTF-A independently of changes in actin dynamics. Simultaneous inhibition of Arp2-Arp3 or mutation of the CA region only partially reduces MRTF-A activation by N-WASP and WAVE2. Recombinant WH2 domains and the RPEL domain of MRTF-A bind mutually exclusively to cellular and purified G-actinin vitro. The competition by different WH2 domains correlates with MRTF-SRF activation. Following serum stimulation, nonpolymerizable actin dissociates from MRTF-A, andde novoformation of the G-actin–RPEL complex is impaired by a transferable factor. Our work demonstrates that WH2 domains activate MRTF-A and contribute to target gene regulation by a competitive mechanism, independently of their role in actin filament formation.

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Nuclear-capture of endosomes depletes nuclear G-actin to promote SRF/MRTF activation and cancer cell invasion

Nature Communications ◽

10.1038/s41467-021-26839-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Sergi Marco ◽

Matthew Neilson ◽

Madeleine Moore ◽

Arantxa Perez-Garcia ◽

Holly Hall ◽

...

Keyword(s):

Nuclear Import ◽

Tyrosine Kinases ◽

Target Genes ◽

Serum Response Factor ◽

Actin Binding ◽

Cell Scattering ◽

Nuclear Localisation Sequence ◽

Related Transcription Factor ◽

Endosomal System ◽

Serum Response

AbstractSignals are relayed from receptor tyrosine kinases (RTKs) at the cell surface to effector systems in the cytoplasm and nucleus, and coordination of this process is important for the execution of migratory phenotypes, such as cell scattering and invasion. The endosomal system influences how RTK signalling is coded, but the ways in which it transmits these signals to the nucleus to influence gene expression are not yet clear. Here we show that hepatocyte growth factor, an activator of MET (an RTK), promotes Rab17- and clathrin-dependent endocytosis of EphA2, another RTK, followed by centripetal transport of EphA2-positive endosomes. EphA2 then mediates physical capture of endosomes on the outer surface of the nucleus; a process involving interaction between the nuclear import machinery and a nuclear localisation sequence in EphA2’s cytodomain. Nuclear capture of EphA2 promotes RhoG-dependent phosphorylation of the actin-binding protein, cofilin to oppose nuclear import of G-actin. The resulting depletion of nuclear G-actin drives transcription of Myocardin-related transcription factor (MRTF)/serum-response factor (SRF)-target genes to implement cell scattering and the invasive behaviour of cancer cells.

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Soluble Epoxide Hydrolase Inhibitors Regulate Ischemic Arrhythmia by Targeting MicroRNA-1

Frontiers in Physiology ◽

10.3389/fphys.2021.717119 ◽

2021 ◽

Vol 12 ◽

Author(s):

Yanying Chen ◽

Qiong Liu ◽

Tian Yang ◽

Li Shen ◽

Danyan Xu

Keyword(s):

Epoxide Hydrolase ◽

Target Genes ◽

Serum Response Factor ◽

Soluble Epoxide Hydrolase ◽

Soluble Epoxide Hydrolase Inhibitors ◽

Interfering Rna ◽

Serum Response ◽

Ischemic Arrhythmia ◽

Antiarrhythmic Effects

Background: Soluble epoxide hydrolase inhibitors (sEHis) inhibit the degradation of epoxyeicosatrienoic acids (EETs) in cells, and EETs have antiarrhythmic effects. Our previous experiments confirmed that t-AUCB, a preparation of sEHis, inhibited ischemic arrhythmia by negatively regulating microRNA-1 (miR-1), but its specific mechanism remained unclear.Aim: This study aimed to examine the role of serum response factor (SRF) and the PI3K/Akt/GSK3β pathway in t-AUCB-mediated regulation of miR-1 and the interaction between them.Methods/Results: We used SRF small interfering RNA (siSRF), SRF small hairpin (shSRF) RNA sequence adenovirus, PI3K/Akt/GSK3β pathway inhibitors, t-AUCB, and 14,15-EEZE (a preparation of EETs antagonists) to treat mouse cardiomyocytes overexpressing miR-1 and mice with myocardial infarction (MI). We found that silencing SRF attenuated the effects on miR-1 and its target genes KCNJ2 and GJA1 in the presence of t-AUCB, and inhibition of the PI3K/Akt/GSK3β pathway antagonized the effects of t-AUCB on miR-1, KCNJ2, and GJA1, which were associated with PI3Kα, Akt, and Gsk3β but not PI3Kβ or PI3Kγ. Moreover, the PI3K/Akt/GSK3β pathway was involved in the regulation of SRF by t-AUCB, and silencing SRF inhibited the t-AUCB-induced increases in Akt and Gsk3β phosphorylation.Conclusions: Both the SRF and the PI3K/Akt/GSK3β pathway are involved in the t-AUCB-mediated regulation of miR-1, and these factors interact with each other.

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Actin-mediated gene expression in neurons: the MRTF-SRF connection

Biological Chemistry ◽

10.1515/bc.2010.061 ◽

2010 ◽

Vol 391 (6) ◽

Cited By ~ 17

Author(s):

Bernd Knöll

Keyword(s):

Gene Expression ◽

Nervous System ◽

Serum Response Factor ◽

Actin Dynamics ◽

Response Factor ◽

Related Transcription Factor ◽

Gene Regulatory ◽

Regulatory Loop ◽

Serum Response ◽

Prime Target

Abstract The traditional view of cellular actin is a rather autarkic cytoskeletal framework function confined to the cytoplasm. However, there is now evidence that alterations in actin dynamics are sensed by the nucleus and subsequently modulate gene expression. In communicating with the nucleus, cytoplasmic, and most likely also nucleus-resident actin, provides a further (gene) regulatory loop to cell motility. A transcription module composed of MRTF (myocardin-related transcription factor) and SRF (serum response factor) emerges as prime target of such actin signaling. Here, I focus on the nervous system, where the actin-MRTF-SRF entity governs multiple aspects of neuronal motility.

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Interaction of Serum Response Factor (SRF) with the Elk-1 B Box Inhibits RhoA-Actin Signaling to SRF and Potentiates Transcriptional Activation by Elk-1

Molecular and Cellular Biology ◽

10.1128/mcb.22.20.7083-7092.2002 ◽

2002 ◽

Vol 22 (20) ◽

pp. 7083-7092 ◽

Cited By ~ 40

Author(s):

Kasumi Murai ◽

Richard Treisman

Keyword(s):

Binding Site ◽

Transcriptional Activation ◽

Rho Gtpases ◽

Target Genes ◽

Serum Response Factor ◽

Relative Sensitivity ◽

Actin Dynamics ◽

Physical Interaction ◽

Response Factor ◽

Serum Response

ABSTRACT Serum response factor (SRF) is a transcription factor which regulates many immediate-early genes. Rho GTPases regulate SRF activity through changes in actin dynamics, but some SRF target genes, such as c-fos, are insensitive to this pathway. At the c-fos promoter, SRF recruits members of the ternary complex factor (TCF) family of Ets domain proteins through interactions with the TCF B-box region. Analysis of c-fos promoter mutations demonstrates that the TCF and ATF/AP1 sites adjoining the SRF binding site inhibit activation of the promoter by RhoA-actin signaling. The presence of the TCF binding site is sufficient for inhibition, and experiments with an altered-specificity Elk-1 derivative demonstrate that inhibition can be mediated by the Elk-1 TCF. Using Elk-1 fusion proteins that can bind DNA autonomously, we show that inhibition of RhoA-actin signaling requires physical interaction between the Elk-1 B box and SRF. These results account for the insensitivity of c-fos to RhoA-actin signaling. Interaction of the B box with SRF also potentiates transcriptional activation by the Elk-1 C-terminal activation domain. Combinatorial interactions between SRF and TCF proteins are thus likely to play an important role in determining the relative sensitivity of SRF target genes to Ras- and Rho-controlled signal transduction pathways.

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Serum response factor: master regulator of the actin cytoskeleton and contractile apparatus

AJP Cell Physiology ◽

10.1152/ajpcell.00386.2006 ◽

2007 ◽

Vol 292 (1) ◽

pp. C70-C81 ◽

Cited By ~ 298

Author(s):

Joseph M. Miano ◽

Xiaochun Long ◽

Keigi Fujiwara

Keyword(s):

Transcription Factor ◽

Actin Cytoskeleton ◽

Target Genes ◽

Serum Response Factor ◽

Cellular Growth ◽

Cellular Migration ◽

Actin Dynamics ◽

Response Factor ◽

Master Regulator ◽

Serum Response

Serum response factor (SRF) is a highly conserved and widely expressed, single copy transcription factor that theoretically binds up to 1,216 permutations of a 10-base pair cis element known as the CArG box. SRF-binding sites were defined initially in growth-related genes. Gene inactivation or knockdown studies in species ranging from unicellular eukaryotes to mice have consistently shown loss of SRF to be incompatible with life. However, rather than being critical for proliferation and growth, these genetic studies point to a crucial role for SRF in cellular migration and normal actin cytoskeleton and contractile biology. In fact, recent genomic studies reveal nearly half of the >200 SRF target genes encoding proteins with functions related to actin dynamics, lamellipodial/filopodial formation, integrin-cytoskeletal coupling, myofibrillogenesis, and muscle contraction. SRF has therefore emerged as a dispensable transcription factor for cellular growth but an absolutely essential orchestrator of actin cytoskeleton and contractile homeostasis. This review summarizes the recent genomic and genetic analyses of CArG-SRF that support its role as an ancient, master regulator of the actin cytoskeleton and contractile machinery.

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The nature and intensity of mechanical stimulation drive different dynamics of MRTF-A nuclear redistribution after actin remodeling in myoblasts

10.1101/395962 ◽

2018 ◽

Author(s):

Lorraine Montel ◽

Athanassia Sotiropoulos ◽

Sylvie Hénon

Keyword(s):

Mechanical Stimulation ◽

Actin Polymerization ◽

Target Genes ◽

Serum Response Factor ◽

Magnetic Tweezers ◽

Point Of View ◽

Nuclear Accumulation ◽

Related Transcription Factor ◽

Global Increase ◽

Serum Response

AbstractSerum response factor and its cofactor myocardin-related transcription factor (MRTF) are key elements of muscle-mass adaptation to workload. The transcription of target genes is activated when MRTF is present in the nucleus. The localization of MRTF is controlled by its binding to G-actin. Thus, the pathway can be mechanically activated through the mechanosensitivity of the actin cytoskeleton. The pathway has been widely investigated from a biochemical point of view, but its mechanical activation and the timescales involved are poorly understood. Here, we applied local and global mechanical cues to myoblasts through two custom-built set-ups, magnetic tweezers and stretchable substrates. Both induced nuclear accumulation of MRTF-A. However, the dynamics of the response varied with the nature and level of mechanical stimulation and correlated with the polymerization of different actin sub-structures. Local repeated force induced local actin polymerization and nuclear accumulation of MRTF-A by 30 minutes, whereas a global static strain induced both rapid (minutes) transient nuclear accumulation, associated with the polymerization of an actin cap above the nucleus, and long-term (hours) accumulation, with a global increase in polymerized actin. Conversely, high strain induced actin depolymerization at intermediate times, associated with cytoplasmic MRTF accumulation.

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The Aging Vasculature: Glucose Tolerance, Hypoglycemia and the Role of the Serum Response Factor

Journal of Cardiovascular Development and Disease ◽

10.3390/jcdd8050058 ◽

2021 ◽

Vol 8 (5) ◽

pp. 58

Author(s):

Hazel Aberdeen ◽

Kaela Battles ◽

Ariana Taylor ◽

Jeranae Garner-Donald ◽

Ana Davis-Wilson ◽

...

Keyword(s):

Glucose Tolerance ◽

Molecular Mechanisms ◽

Serum Response Factor ◽

Response Factor ◽

Homeostatic Control ◽

Older Americans ◽

The Subject ◽

Serum Response

The fastest growing demographic in the U.S. at the present time is those aged 65 years and older. Accompanying advancing age are a myriad of physiological changes in which reserve capacity is diminished and homeostatic control attenuates. One facet of homeostatic control lost with advancing age is glucose tolerance. Nowhere is this more accentuated than in the high proportion of older Americans who are diabetic. Coupled with advancing age, diabetes predisposes affected subjects to the onset and progression of cardiovascular disease (CVD). In the treatment of type 2 diabetes, hypoglycemic episodes are a frequent clinical manifestation, which often result in more severe pathological outcomes compared to those observed in cases of insulin resistance, including premature appearance of biomarkers of senescence. Unfortunately, molecular mechanisms of hypoglycemia remain unclear and the subject of much debate. In this review, the molecular basis of the aging vasculature (endothelium) and how glycemic flux drives the appearance of cardiovascular lesions and injury are discussed. Further, we review the potential role of the serum response factor (SRF) in driving glycemic flux-related cellular signaling through its association with various proteins.

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