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Ras proteins regulate multiple mitogenic pathways in A10 vascular smooth muscle cells
K Irani1, S Herzlinger, T Finkel
1Cardiology Branch, NHLBI, NIH, Bethesda, MD.
Abstract:
We examined the role of ras proteins in mitogenesis and proliferation of A10 smooth muscle cells. An assay was developed in which a dominant negative ras gene could be transiently expressed in vascular smooth muscle cells. As opposed to cells transfected with a control plasmid, those transfected with a dominant negative ras expression plasmid exhibited a decrease in thymidine uptake in response to serum, platelet-derived growth factor, epidermal growth factor, fibroblast growth factor and thrombin stimulation. In addition, expression of dominant negative ras blocked smooth muscle cell proliferation as assessed by the number of surviving colonies after transfection and neomycin selection. Our data is the first to show that ras is essential for smooth muscle cell proliferation and is a mediator in multiple smooth muscle cell mitogenic signalling pathways.
Insights
Ras proteins are essential for vascular smooth muscle cell proliferation and mitogenesis. Inhibiting ras function significantly decreases cell proliferation and thymidine uptake, confirming its role in multiple signaling pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Vascular Biology
Background:
- Ras proteins are key regulators of cell signaling.
- Understanding their role in vascular smooth muscle cell (VSMC) proliferation is crucial for cardiovascular health.
Purpose of the Study:
- To investigate the role of ras proteins in the mitogenesis and proliferation of A10 smooth muscle cells.
- To determine if ras mediates signaling pathways triggered by common mitogens.
Main Methods:
- Development of an assay for transient expression of a dominant-negative ras gene in VSMCs.
- Assessment of thymidine uptake in response to various growth factors and mitogens.
- Evaluation of smooth muscle cell proliferation via colony formation assays.
Main Results:
- Dominant-negative ras expression significantly reduced thymidine uptake stimulated by serum, PDGF, EGF, FGF, and thrombin.
- Inhibition of ras blocked smooth muscle cell proliferation, as evidenced by reduced colony formation.
- Ras is demonstrated to be essential for VSMC proliferation.
Conclusions:
- Ras proteins are indispensable for smooth muscle cell proliferation.
- Ras acts as a central mediator in multiple mitogenic signaling pathways regulating VSMC growth.
- Targeting ras may offer therapeutic strategies for vascular diseases involving VSMC hyperplasia.