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Redox-Sensitive Regulation of Myocardin-Related Transcription Factor (MRTF-A) Phosphorylation via Palladin in Vascular Smooth Muscle Cell Differentiation Marker Gene Expression.

Lee M, San Martín A, Valdivia A, Martin-Garrido A, Griendling KK - PLoS ONE (2016)

Bottom Line: We found that Rho kinase (ROCK)-mediated phosphorylation of MRTF-A is a key event in the regulation of SMA and CNN in VSMCs and that this phosphorylation depends upon Nox4-mediated palladin expression.Knockdown of Nox4 using siRNA decreases TGF-β -induced palladin expression and MRTF-A phosphorylation, suggesting redox-sensitive regulation of this signaling pathway.Knockdown of palladin also decreases MRTF-A phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.

ABSTRACT
Vascular smooth muscle cells (VSMCs) undergo a phenotypic switch from a differentiated to synthetic phenotype in cardiovascular diseases such as atherosclerosis and restenosis. Our previous studies indicate that transforming growth factor-β (TGF-β) helps to maintain the differentiated phenotype by regulating expression of pro-differentiation genes such as smooth muscle α-actin (SMA) and Calponin (CNN) through reactive oxygen species (ROS) derived from NADPH oxidase 4 (Nox4) in VSMCs. In this study, we investigated the relationship between Nox4 and myocardin-related transcription factor-A (MRTF-A), a transcription factor known to be important in expression of smooth muscle marker genes. Previous work has shown that MRTF-A interacts with the actin-binding protein, palladin, although how this interaction affects MRTF-A function is unclear, as is the role of phosphorylation in MRTF-A activity. We found that Rho kinase (ROCK)-mediated phosphorylation of MRTF-A is a key event in the regulation of SMA and CNN in VSMCs and that this phosphorylation depends upon Nox4-mediated palladin expression. Knockdown of Nox4 using siRNA decreases TGF-β -induced palladin expression and MRTF-A phosphorylation, suggesting redox-sensitive regulation of this signaling pathway. Knockdown of palladin also decreases MRTF-A phosphorylation. These data suggest that Nox4-dependent palladin expression and ROCK regulate phosphorylation of MRTF-A, a critical factor in the regulation of SRF responsive gene expression.

No MeSH data available.


Related in: MedlinePlus

Proposed Model of Redox-Sensitive Regulation of MRTF-A Phosphorylation via Palladin in Human VSMCs.Stimulation of Human VSMCs with TGF-β (2 ng/ml) upregulates Nox4, increasing H2O2 production. H2O2 increases expression of palladin and stimulates the activity of ROCK, which phosphorylates MRTF-A. MRTF-A binds to SRF which induces SMA and CNN expression.
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pone.0153199.g008: Proposed Model of Redox-Sensitive Regulation of MRTF-A Phosphorylation via Palladin in Human VSMCs.Stimulation of Human VSMCs with TGF-β (2 ng/ml) upregulates Nox4, increasing H2O2 production. H2O2 increases expression of palladin and stimulates the activity of ROCK, which phosphorylates MRTF-A. MRTF-A binds to SRF which induces SMA and CNN expression.

Mentions: In this study, we explored the relationship between Nox4, palladin, ROCK, MRTF-A and regulation of SMC-specific gene expression. We demonstrated that 1) TGF-β-induced phosphorylation of MRTF-A is mediated by Nox4 via ROCK and palladin; 2) TGF-β induction of palladin is redox-sensitive and requires ROS production from Nox4; and 3) knockdown of palladin, reduction in Nox4 activity or inhibition of ROCK attenuates SMA and CNN expression. Our data uncover a previously unknown mechanism for how Nox4 regulates SMA and CNN expression; that is, via regulation of palladin expression and ROCK-mediated MRTF-A phosphorylation (Fig 8).


Redox-Sensitive Regulation of Myocardin-Related Transcription Factor (MRTF-A) Phosphorylation via Palladin in Vascular Smooth Muscle Cell Differentiation Marker Gene Expression.

Lee M, San Martín A, Valdivia A, Martin-Garrido A, Griendling KK - PLoS ONE (2016)

Proposed Model of Redox-Sensitive Regulation of MRTF-A Phosphorylation via Palladin in Human VSMCs.Stimulation of Human VSMCs with TGF-β (2 ng/ml) upregulates Nox4, increasing H2O2 production. H2O2 increases expression of palladin and stimulates the activity of ROCK, which phosphorylates MRTF-A. MRTF-A binds to SRF which induces SMA and CNN expression.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835087&req=5

pone.0153199.g008: Proposed Model of Redox-Sensitive Regulation of MRTF-A Phosphorylation via Palladin in Human VSMCs.Stimulation of Human VSMCs with TGF-β (2 ng/ml) upregulates Nox4, increasing H2O2 production. H2O2 increases expression of palladin and stimulates the activity of ROCK, which phosphorylates MRTF-A. MRTF-A binds to SRF which induces SMA and CNN expression.
Mentions: In this study, we explored the relationship between Nox4, palladin, ROCK, MRTF-A and regulation of SMC-specific gene expression. We demonstrated that 1) TGF-β-induced phosphorylation of MRTF-A is mediated by Nox4 via ROCK and palladin; 2) TGF-β induction of palladin is redox-sensitive and requires ROS production from Nox4; and 3) knockdown of palladin, reduction in Nox4 activity or inhibition of ROCK attenuates SMA and CNN expression. Our data uncover a previously unknown mechanism for how Nox4 regulates SMA and CNN expression; that is, via regulation of palladin expression and ROCK-mediated MRTF-A phosphorylation (Fig 8).

Bottom Line: We found that Rho kinase (ROCK)-mediated phosphorylation of MRTF-A is a key event in the regulation of SMA and CNN in VSMCs and that this phosphorylation depends upon Nox4-mediated palladin expression.Knockdown of Nox4 using siRNA decreases TGF-β -induced palladin expression and MRTF-A phosphorylation, suggesting redox-sensitive regulation of this signaling pathway.Knockdown of palladin also decreases MRTF-A phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.

ABSTRACT
Vascular smooth muscle cells (VSMCs) undergo a phenotypic switch from a differentiated to synthetic phenotype in cardiovascular diseases such as atherosclerosis and restenosis. Our previous studies indicate that transforming growth factor-β (TGF-β) helps to maintain the differentiated phenotype by regulating expression of pro-differentiation genes such as smooth muscle α-actin (SMA) and Calponin (CNN) through reactive oxygen species (ROS) derived from NADPH oxidase 4 (Nox4) in VSMCs. In this study, we investigated the relationship between Nox4 and myocardin-related transcription factor-A (MRTF-A), a transcription factor known to be important in expression of smooth muscle marker genes. Previous work has shown that MRTF-A interacts with the actin-binding protein, palladin, although how this interaction affects MRTF-A function is unclear, as is the role of phosphorylation in MRTF-A activity. We found that Rho kinase (ROCK)-mediated phosphorylation of MRTF-A is a key event in the regulation of SMA and CNN in VSMCs and that this phosphorylation depends upon Nox4-mediated palladin expression. Knockdown of Nox4 using siRNA decreases TGF-β -induced palladin expression and MRTF-A phosphorylation, suggesting redox-sensitive regulation of this signaling pathway. Knockdown of palladin also decreases MRTF-A phosphorylation. These data suggest that Nox4-dependent palladin expression and ROCK regulate phosphorylation of MRTF-A, a critical factor in the regulation of SRF responsive gene expression.

No MeSH data available.


Related in: MedlinePlus