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Stabilization of elastin mRNA by TGF-beta: initial characterization of signaling pathway
U Kucich1, J C Rosenbloom, W R Abrams
1Department of Anatomy and Histology, University of Pennsylvania School of Dental Medicine, Philadelphia 19104, USA.
Abstract:
The cytokine transforming growth factor-beta (TGF-beta) has multiple effects on a wide variety of cell types. These effects include modulation of growth and regulation of gene transcription. In a few instances, TGF-beta has also been shown to regulate gene expression posttranscriptionally by altering message stability, but the pathway by which this activity is executed remains largely unknown. In the present work, we demonstrate that TGF-beta 1 has no effect on transcription of the elastin gene in cultured human fetal lung fibroblasts, but does stabilize elastin messenger RNA (mRNA), leading to a dramatic increase in the steady-state level of elastin mRNA. A corresponding increase in production of tropoelastin accompanies the increase in elastin mRNA. Through the use of specific inhibitors, we demonstrate that phosphatidylcholine (PC)-specific phospholipase C (PLC) and protein kinase C (PKC) are involved in mediating the elastin message stabilization. In contrast, G proteins and extracellularly regulated kinases do not appear to be involved. These results suggest that although the TGF-beta signaling pathway leading to message stabilization shares components with that modulating transcription, the message-stabilization pathway also contains diverse other elements.
Insights
Transforming growth factor-beta (TGF-beta) stabilizes elastin messenger RNA (mRNA) in human lung fibroblasts. This posttranscriptional regulation increases tropoelastin production via phosphatidylcholine-specific phospholipase C and protein kinase C signaling.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Transforming growth factor-beta (TGF-beta) is a pleiotropic cytokine regulating cell growth and gene transcription.
- TGF-beta can also regulate gene expression posttranscriptionally by affecting mRNA stability, but the underlying mechanisms are poorly understood.
Purpose of the Study:
- To investigate the mechanism by which TGF-beta regulates elastin gene expression at the posttranscriptional level.
- To identify the specific signaling molecules involved in TGF-beta-mediated elastin mRNA stabilization.
Main Methods:
- Cultured human fetal lung fibroblasts were treated with TGF-beta 1.
- Elastin gene transcription and mRNA levels were quantified.
- Messenger RNA (mRNA) stability was assessed.
- Specific inhibitors were used to probe signaling pathways, including phosphatidylcholine (PC)-specific phospholipase C (PLC) and protein kinase C (PKC).
Main Results:
- TGF-beta 1 did not affect elastin gene transcription but significantly stabilized elastin mRNA.
- Stabilized elastin mRNA led to a marked increase in steady-state elastin mRNA levels and subsequent tropoelastin production.
- Involvement of PC-specific phospholipase C (PLC) and protein kinase C (PKC) in mediating elastin mRNA stabilization was demonstrated.
- G proteins and extracellularly regulated kinases were found not to be involved in this pathway.
Conclusions:
- TGF-beta 1 enhances tropoelastin production by stabilizing elastin mRNA in human fetal lung fibroblasts.
- The TGF-beta signaling pathway for elastin mRNA stabilization involves PC-specific phospholipase C and protein kinase C.
- This pathway diverges from the transcriptional regulation pathway, incorporating distinct signaling components.