Related Experiment Videos
Dominant-negative caveolin inhibits H-Ras function by disrupting cholesterol-rich plasma membrane domains
S Roy1, R Luetterforst, A Harding
1Queensland Cancer Fund Laboratory of Experimental Oncology, Department of Pathology, University of Queensland Medical School, Brisbane, Australia.
Abstract:
The plasma membrane pits known as caveolae have been implicated both in cholesterol homeostasis and in signal transduction. CavDGV and CavKSY, two dominant-negative amino-terminal truncation mutants of caveolin, the major structural protein of caveolae, significantly inhibited caveola-mediated SV40 infection, and were assayed for effects on Ras function. We find that CavDGV completely blocked Raf activation mediated by H-Ras, but not that mediated by K-Ras. Strikingly, the inhibitory effect of CavDGV on H-Ras signalling was completely reversed by replenishing cell membranes with cholesterol and was mimicked by cyclodextrin treatment, which depletes membrane cholesterol. These results provide a crucial link between the cholesterol-trafficking role of caveolin and its postulated role in signal transduction through cholesterol-rich surface domains. They also provide direct evidence that H-Ras and K-Ras, which are targeted to the plasma membrane by different carboxy-terminal anchors, operate in functionally distinct microdomains of the plasma membrane.
Insights
Caveolin mutants disrupt H-Ras signaling, highlighting cholesterol
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Caveolae, plasma membrane invaginations, are involved in cholesterol homeostasis and signal transduction.
- Caveolin is the primary structural protein of caveolae.
Purpose of the Study:
- To investigate the role of caveolin mutants in Ras signaling.
- To explore the link between caveolin's cholesterol-trafficking function and its role in signal transduction.
Main Methods:
- Utilized dominant-negative caveolin mutants (CavDGV, CavKSY).
- Assayed effects on Ras signaling pathways, specifically Raf activation.
- Manipulated membrane cholesterol levels using replenishment and cyclodextrin treatment.
Main Results:
- CavDGV inhibited H-Ras-mediated Raf activation but not K-Ras-mediated activation.
- Cholesterol depletion mimicked the inhibitory effect of CavDGV.
- Restoring membrane cholesterol reversed the inhibitory effect of CavDGV on H-Ras signaling.
Conclusions:
- Establishes a link between caveolin's cholesterol transport and its role in signal transduction via cholesterol-rich domains.
- Provides evidence for distinct functional microdomains of the plasma membrane for H-Ras and K-Ras.
- Suggests cholesterol's critical role in regulating H-Ras signaling within specific membrane domains.