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

• Type of Material: Article
• Authors: Minyoung Lee, Emory University; M San Martin, Emory University; Alejandra Valdivia, Emory University; Abel Martin-Garrido, Emory University; Kathy Griendling, Emory University
• Language: English
• Date: 2016-04-18
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2016 Lee et al.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pone.0153199
• Title of Journal or Parent Work: PLoS ONE
• ISSN: 1932-6203
• Volume: 11
• Issue: 4
• Start Page: e0153199
• End Page: e0153199
• Grant/Funding Information: This work was supported by NIH grants P01HL095070 (KKG and ASM), R01HL38206 (KKG), and R01HL113167 (ASM).
• Keywords: NOX4; Small interfering RNAs; Science & Technology; Marker genes; SERUM RESPONSE FACTOR; Cardiology; ACTIN; Gene expression; Phosphorylation; Protein extraction; Multidisciplinary Sciences; Immunoprecipitation; Muscle differentiation; PROTEIN PALLADIN; NUCLEAR-LOCALIZATION; Gene regulation; POLDIP2
• Research Categories: Health Sciences, General; Biology, Genetics; Health Sciences, Pathology

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 á-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.