Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:2.7.11.12 (
PKG
)
2,515
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
We have previously reported that in ovine fetal pulmonary venous smooth muscle cells (FPVSMC), decreased expression of
cGMP-dependent protein kinase
(
PKG
) by hypoxia could explain hypoxia-induced SMC phenotype modulation. In this study, we investigated the role of
myocardin
, a possible downstream effector of
PKG
, in SMC phenotype modulation induced by 1 and 24 h of hypoxia. Hypoxia for 1 h induced the phosphorylation of E-26-like protein 1 (Elk-1), indicating a quick activation of Elk-1 after hypoxia. Either hypoxia (1 h) or treatment with DT-3, a
PKG
inhibitor, increased associations of Elk-1 with myosin heavy chain (MHC) gene and serum response factor (SRF), which was paralleled by a decrease in association of
myocardin
with MHC gene and SRF. Exposure to hypoxia of FPVSMC for 24 h significantly decreased the promoter activity of multiple SMC marker genes, downregulated protein and mRNA expression of
myocardin
, and upregulated mRNA expression of Elk-1, but had no significant effects on the phosphorylation of Elk-1. Inhibition of
myocardin
by siRNA transfection downregulated the expression of SMC marker proteins, while overexpression of
myocardin
prevented the hypoxia-induced decrease in expression of SMC marker proteins. Inhibition of
PKG
by siRNA transfection downregulated the expression of
myocardin
, but upregulated that of Elk-1. Overexpression of
PKG
prevented hypoxia-induced effects on protein expression of
myocardin
and Elk-1. These data suggest that
PKG
induces displacement of
myocardin
from SRF and upregulates
myocardin
expression, thus activating the SMC genes transcription. The inhibitory effects of hypoxia on
PKG
may explain hypoxia-induced SMC phenotype modulation by decreasing the effects of
PKG
on
myocardin
.
...
PMID:Modulation of pulmonary vascular smooth muscle cell phenotype in hypoxia: role of cGMP-dependent protein kinase and myocardin. 1925 41
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.
...
PMID:cGMP-dependent protein kinase and the regulation of vascular smooth muscle cell gene expression: possible involvement of Elk-1 sumoylation. 2080 37
