title: Redox-Sensitive Regulation of Myocardin-Related Transcription Factor (MRTF-A) Phosphorylation via Palladin in Vascular Smooth Muscle Cell Differentiation Marker Gene Expression.
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.
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.
authors.forename: Minyoung
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.
authors.forename: Alejandra
authors.initials: A
authors.lastname: San Martín
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Valdivia
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.
authors.forename: Abel
authors.initials: A
authors.lastname: Martin-Garrido
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, United Sates of America.
authors.forename: Kathy K
authors.initials: KK
authors.lastname: Griendling
mesh_terms: D000199:Actins / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D005819:Genetic Markers; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000378:metabolism; D000096985:Calponins
chemical_list: D000199:Actins; D002135:Calcium-Binding Proteins; D003598:Cytoskeletal Proteins; D005819:Genetic Markers; D008840:Microfilament Proteins; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; D010750:Phosphoproteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D054460:rho-Associated Kinases; D000096985:Calponins; C541116:ACTA2 protein, human; C431575:MRTFA protein, human; C412722:PALLD protein, human; C498910:NOX4 protein, human