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Regulation of expression of transforming growth factor-beta 2 by transforming growth factor-beta isoforms is
M A O'Reilly1, D Danielpour, A B Roberts
1Laboratory of Chemoprevention, National Cancer Institute, National Institutes of Health, Bethesda, MD 20814.
Abstract:
The effect of three different isoforms of transforming growth factor-beta (TGF-beta) on the expression of TGF-beta 2 mRNA was studied in several continuous tumor cell lines. As previously reported for the mouse fibroblast cell line AKR-2B, the expression of TGF-beta 2 mRNA transcripts of 5.4, 4.7, 3.7 and 3.0 kb was decreased after a 24 hr treatment with 5 ng/ml of TGF-beta 1, TGF-beta 2 or TGF-beta 3. In A549, HBL-100 and BSC-1 epithelial cell lines, five distinct TGF-beta 2 mRNA transcripts of 5.8, 5.1, 4.0, 3.8 and 2.8 kb were detected by Northern blot analysis. Treatment of these cells with TGF-beta 1, TGF-beta 2 or TGF-beta 3 for 24 hr resulted in a 2-3 fold increase in the 5.8, 4.0 and 3.8 kb transcripts, with little detectable change in abundance of the 5.1 and 2.8 kb transcripts. The effect of the TGF-beta proteins was dose (5 ng/ml) and time (3-6 hr) dependent. A similar 2-3 fold increase in the level of secreted TGF-beta 2 was observed following treatment of A549 cells with TGF-beta 1. Basal level and induced expression of TGF-beta 2 mRNA in response to TGF-beta isoforms was decreased in the presence of actinomycin D. In all cell lines studied, the expression of the 2.5 kb TGF-beta 1 mRNA was relatively unchanged or markedly increased in response to treatment with TGF-beta.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Transforming growth factor-beta (TGF-beta) isoforms differentially regulate TGF-beta 2 mRNA expression. While TGF-beta isoforms decrease TGF-beta 2 mRNA in fibroblasts, they increase specific transcripts in epithelial cells.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Transforming growth factor-beta (TGF-beta) is a key regulator of cellular processes.
- Differential expression of TGF-beta isoforms plays a role in various biological functions.
- Understanding TGF-beta's impact on its own gene expression is crucial.
Purpose of the Study:
- To investigate the effect of different TGF-beta isoforms on TGF-beta 2 mRNA expression.
- To compare the regulatory effects across different cell types (fibroblast vs. epithelial).
Main Methods:
- Northern blot analysis to detect TGF-beta 2 mRNA transcripts.
- Treatment of continuous tumor cell lines with TGF-beta 1, TGF-beta 2, and TGF-beta 3.
- Dose and time-dependency studies, including actinomycin D treatment.
Main Results:
- TGF-beta isoforms decreased TGF-beta 2 mRNA in mouse fibroblasts (AKR-2B).
- In epithelial cell lines (A549, HBL-100, BSC-1), TGF-beta isoforms increased specific TGF-beta 2 mRNA transcripts (5.8, 4.0, 3.8 kb).
- TGF-beta 1 treatment also increased secreted TGF-beta 2 levels in A549 cells.
Conclusions:
- TGF-beta isoforms exhibit cell-type-specific regulation of TGF-beta 2 mRNA expression.
- Epithelial cells show an induction of specific TGF-beta 2 mRNA transcripts by TGF-beta isoforms.
- These findings highlight the complex feedback mechanisms within the TGF-beta signaling pathway.