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Expression of actin mRNAs in rat aortic smooth muscle cells during development, experimental intimal thickening, and
Abstract:
The expression of actin-isoform mRNAs in the smooth muscle cells (SMC) of the aortic media in rats has been studied by Northern-blot hybridization, using a general actin-cRNA probe, and two cRNA probes specific for beta- and gamma-cytoplasmic actins, during: (1) development, (2) intimal thickening after endothelial injury induced by balloon catheterization, and (3) growth in culture. In 5-day-old rats, the ratio between alpha-smooth-muscle-actin mRNA and beta- and gamma-cytoplasmic-actin mRNAs was close to 1. It increased to about 4 in 6-week-old rats. Replicating SMC from regions of intimal thickening 15 days after endothelial injury, and SMC growing in culture contained a predominance of cytoplasmic actin mRNAs. Intimal SMC 60 days after endothelial injury (at which time the endothelium had fully regenerated) demonstrated a pattern of actin mRNAs similar to that of normal media. Functional mRNA measured by translation in a reticulocyte lysate showed increases in the level of alpha-actin and decreases in beta-actin in rats from 5 days to 6 weeks of age. These results suggest that during development, under pathological conditions, and in cell culture, the expression of actin isoforms in arterial SMC depends on many factors, including the amount and translation efficiency of mRNAs, and the relative stabilities of the proteins involved.
Insights
Smooth muscle cell (SMC) actin isoform mRNA expression changes during rat development, injury, and culture. Arterial SMC actin expression is influenced by multiple factors, including mRNA levels and protein stability.
Area of Science:
- Molecular Biology
- Cell Biology
- Cardiovascular Research
Background:
- Smooth muscle cells (SMCs) express various actin isoforms.
- Actin isoform expression is dynamic and can change with cell state.
Purpose of the Study:
- To investigate actin-isoform mRNA expression in rat aortic SMCs.
- To analyze changes during development, after injury, and in cell culture.
Main Methods:
- Northern-blot hybridization with specific cRNA probes for actin isoforms.
- Analysis of mRNA expression in different physiological and experimental conditions.
- Functional mRNA assessment via reticulocyte lysate translation.
Main Results:
- Actin mRNA ratios shifted from predominantly cytoplasmic to alpha-smooth muscle actin during development.
- Injury and cell culture led to a predominance of cytoplasmic actin mRNAs.
- Actin mRNA patterns normalized in intimal SMCs after endothelial regeneration.
Conclusions:
- Arterial SMC actin isoform expression is regulated by multiple factors.
- Development, injury, and culture conditions modulate actin mRNA expression and protein translation.