cGMP-dependent protein kinase and the regulation of vascular smooth muscle cell gene expression: Possible involvement of Elk-1 sumoylation

Chung Sik Choi, Hassan Sellak, Felricia M. Brown, Thomas M. Lincoln

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Abstract

Although the regulation of smooth muscle cell (SMC) gene expression by cGMP-dependent protein kinase (PKG) is now recognized, the mechanisms underlying these effects are not fully understood. In this study, we report that PKG-I stimulates myocardin/serum response factor (SRF)-dependent gene expression in vascular SMCs. The expression of PKG in PKG-deficient cells enhanced myocardin-induced SM22 promoter activity in a concentration-dependent fashion. However, neither SRF nor myocardin expression was affected. To investigate alternative mechanisms, we examined whether PKG affects the phosphorylation of E26-like protein-1 (Elk-1), a SRF/myocardin transcription antagonist. The activation of PKG caused an increase in a higher molecular mass form of phospho-Elk-1 that was determined to be small ubiquitin-related modifier (sumo)ylated Elk-1. PKG increased Elk-1 sumoylation twofold compared with the PKG-deficient cells, and Elk-1 sumoylation was reduced using dominant-negative sumo-conjugating enzyme, DN-Ubc9, confirming PKG-dependent sumoylation of phospho-Elk-1 in vascular SMCs. In addition, PKG stimulated Elk-1 sumoylation in COS-7 cells overexpressing Elk-1, sumo-1, and PKG-I. The increased expression of PKG in vascular SMCs inhibited Elk-1 binding to SMC-specific promoters, SM22 and smooth muscle myosin heavy chain, as measured by EMSA and chromatin immunoprecipitation assay, and PKG suppressed the Elk-1 inhibition of SM22 reporter gene expression. Taken together, these data suggest that PKG-I decreases Elk-1 activity by sumo modification of Elk-1, thereby increasing myocardin-SRF activity on SMC-specific gene expression.

Original languageEnglish (US)
Pages (from-to)H1660-H1670
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume299
Issue number5
DOIs
Publication statusPublished - Nov 1 2010

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Keywords

  • E26-like protein-1
  • Guanosine 3′,5′-cyclic monophosphate-dependent protein kinase
  • Myocardin
  • Small ubiquitin-like modifier

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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