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

PLoS One. 2016 Apr 18;11(4):e0153199. doi: 10.1371/journal.pone.0153199. eCollection 2016.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / metabolism
  • Calcium-Binding Proteins / metabolism
  • Calponins
  • Cell Differentiation / drug effects
  • Cell Differentiation / physiology*
  • Cells, Cultured
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism*
  • Gene Expression Regulation
  • Genetic Markers
  • Humans
  • Microfilament Proteins / metabolism
  • Muscle, Smooth, Vascular / cytology*
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism
  • NADPH Oxidase 4
  • NADPH Oxidases / genetics
  • NADPH Oxidases / metabolism
  • Oxidation-Reduction
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transforming Growth Factor beta / metabolism
  • Transforming Growth Factor beta / pharmacology
  • rho-Associated Kinases / metabolism

Substances

  • ACTA2 protein, human
  • Actins
  • Calcium-Binding Proteins
  • Cytoskeletal Proteins
  • Genetic Markers
  • MRTFA protein, human
  • Microfilament Proteins
  • PALLD protein, human
  • Phosphoproteins
  • Trans-Activators
  • Transforming Growth Factor beta
  • NADPH Oxidase 4
  • NADPH Oxidases
  • NOX4 protein, human
  • rho-Associated Kinases