Platelet-derived growth factor-BB and Ets-1 transcription factor negatively regulate transcription of multiple smooth muscle cell differentiation marker genes

2004 ◽  
Vol 286 (6) ◽  
pp. H2042-H2051 ◽  
Author(s):  
Frédéric Dandré ◽  
Gary K. Owens
Keyword(s):  
Transcription Factor ◽  
Smooth Muscle ◽  
Growth Factor ◽  
Tyrosine Phosphatase ◽  
Marker Gene ◽  
Platelet Derived Growth Factor ◽  
Phenotypic Switching ◽  
Marker Genes ◽  
Gene Promoters ◽  
Marker Expression

Platelet-derived growth factor (PDGF)-BB, a potent mitogen for mesenchymal cells, also downregulates expression of multiple smooth muscle (SM) cell (SMC)-specific markers. However, there is conflicting evidence whether PDGF-BB represses SMC marker expression at a transcriptional or posttranscriptional level, and little is known regarding the mechanisms responsible for these effects. Results of the present studies provide clear evidence that PDGF-BB treatment strongly repressed SM α-actin, SM myosin heavy chain (MHC), and SM22α promoters in SMCs. Of major significance for resolving previous controversies in the field, we found PDGF-BB-induced repression of SMC marker gene promoters in subconfluent, but not postconfluent, cultures. Treatment of postconfluent SMCs with a tyrosine phosphatase inhibitor restored PDGF-BB-induced repression, whereas treatment of subconfluent SMCs with a tyrosine kinase blocker abolished PDGF-BB-induced repression, suggesting that a tyrosine phosphorylation event mediates cell density-dependent effects. On the basis of previous observations that Ets-1 transcription factor is upregulated within phenotypically modulated neointimal SMCs, we tested whether Ets-1 would repress SMC marker expression. Consistent with this hypothesis, results of cotransfection experiments indicated that Ets-1 overexpression reduced transcriptional activity of SMC marker promoter constructs in SMCs, whereas it increased activity of SM α-actin promoter in endothelial cells. PDGF-BB treatment increased expression of Ets-1 in cultured SMCs, and SM α-actin mRNA expression was reduced in multiple independent clones of SMCs stably transfected with an Ets-1-overexpressing construct. Taken together, results of these experiments provide novel insights regarding possible mechanisms whereby PDGF-BB and Ets-1 may contribute to SMC phenotypic switching associated with vascular injury.

scholarly journals Platelet-derived growth factor-BB represses smooth muscle cell marker genes via changes in binding of MKL factors and histone deacetylases to their promoters

2007 ◽  
Vol 292 (2) ◽  
pp. C886-C895 ◽  
Author(s):  
Tadashi Yoshida ◽  
Qiong Gan ◽  
Yueting Shang ◽  
Gary K. Owens
Keyword(s):  
Smooth Muscle ◽  
Growth Factor ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Histone Deacetylases ◽  
Marker Gene ◽  
Platelet Derived Growth Factor ◽  
Phenotypic Switching ◽  
Marker Genes ◽  
Gene Promoters

A hallmark of smooth muscle cell (SMC) phenotypic switching is suppression of SMC marker gene expression. Although myocardin has been shown to be a key regulator of this process, the role of its related factors, MKL1 and MKL2, in SMC phenotypic switching remains unknown. The present studies were aimed at determining if: 1) MKL factors contribute to the expression of SMC marker genes in cultured SMCs; and 2) platelet-derived growth factor-BB (PDGF-BB)-induced repression of SMC marker genes is mediated by suppression of MKL factors. Results of gain- and loss-of-function experiments showed that MKL factors regulated the expression of single and multiple CArG [CC(AT-rich)6GG]-containing SMC marker genes, such as smooth muscle (SM) α-actin and telokin, but not CArG-independent SMC marker genes such as smoothelin-B. Treatment with PDGF-BB reduced the expression of CArG-containing SMC marker genes, as well as myocardin expression in cultured SMCs, while it had no effect on expression of MKL1 and MKL2. However, of interest, PDGF-BB induced the dissociation of MKL factors from the CArG-containing region of SMC marker genes, as determined by chromatin immunoprecipitation assays. This dissociation was caused by the competition between MKL factors and phosphorylated Elk-1 at early time points, but subsequently by the reduction in acetylated histone H4 levels at these promoter regions mediated by histone deacetylases, HDAC2, HDAC4, and HDAC5. Results provide novel evidence that PDGF-BB-induced repression of SMC marker genes is mediated through combinatorial mechanisms, including downregulation of myocardin expression and inhibition of the association of myocardin/MKL factors with CArG-containing SMC marker gene promoters.

scholarly journals Multiple repressor pathways contribute to phenotypic switching of vascular smooth muscle cells

2007 ◽  
Vol 292 (1) ◽  
pp. C59-C69 ◽  
Author(s):  
Keiko Kawai-Kowase ◽  
Gary K. Owens
Keyword(s):  
Smooth Muscle ◽  
Molecular Mechanisms ◽  
Platelet Derived Growth Factor ◽  
Phenotypic Switching ◽  
Marker Genes ◽  
Environmental Cues ◽  
Selective Marker ◽  
Current State ◽  
Active Repressor

Smooth muscle cell (SMC) differentiation is an essential component of vascular development and these cells perform biosynthetic, proliferative, and contractile roles in the vessel wall. SMCs are not terminally differentiated and possess the ability to modulate their phenotype in response to changing local environmental cues. The focus of this review is to provide an overview of the current state of knowledge of molecular mechanisms involved in controlling phenotypic switching of SMC with particular focus on examination of processes that contribute to the repression of SMC marker genes. We discuss the environmental cues which actively regulate SMC phenotypic switching, such as platelet-derived growth factor-BB, as well as several important regulatory mechanisms required for suppressing expression of SMC-specific/selective marker genes in vivo, including those dependent on conserved G/C-repressive elements, and/or highly conserved degenerate CArG elements found in the promoters of many of these marker genes. Finally, we present evidence indicating that SMC phenotypic switching involves multiple active repressor pathways, including Krüppel-like zinc finger type 4, HERP, and ERK-dependent phosphorylation of Elk-1 that act in a complementary fashion.

Transcription factor CHF1/Hey2 regulates the global transcriptional response to platelet-derived growth factor in vascular smooth muscle cells

2007 ◽  
Vol 30 (1) ◽  
pp. 61-68 ◽  
Author(s):  
Shervin M. Shirvani ◽  
Linette Mookanamparambil ◽  
Marco F. Ramoni ◽  
Michael T. Chin
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Smooth Muscle ◽  
Growth Factors ◽  
Growth Factor ◽  
Smooth Muscle Cells ◽  
Platelet Derived Growth Factor ◽  
Expression Data ◽  
Wild Type ◽  
Muscle Response

The cardiovascular restricted transcription factor CHF1/Hey2 has been previously shown to regulate the smooth muscle response to growth factors. To determine how CHF1/Hey2 affects the smooth muscle response to growth factors, we performed a genomic screen for transcripts that are differentially expressed in wild-type and knockout smooth muscle cells after stimulation with platelet-derived growth factor. We screened 45,101 probes representing >39,000 transcripts derived from at least 34,000 genes, at eight different time points. We analyzed the expression data utilizing an algorithm based on Bayesian statistics to derive the best polynomial clustering model to fit the expression data. We found that in a total of 9,827 transcripts the normalized ratio of knockout to wild-type expression diverged more than threefold from baseline in at least one time point, and these transcripts separated into 17 distinct clusters. Further analysis of each cluster revealed distinct alterations in gene expression patterns for immediate early genes, transcription factors, matrix metalloproteinases, signaling molecules, and other molecules important in vascular biology. Our findings demonstrate that CHF1/Hey2 profoundly affects vascular smooth muscle phenotype by altering both the absolute expression level of a variety of genes and the kinetics of growth factor-induced gene expression.

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