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Cytochalasin releases mRNA from the cytoskeletal framework and inhibits protein synthesis
Abstract:
Cytochalasin D was shown to be a reversible inhibitor of protein synthesis in HeLa cells. The inhibition was detectable at drug levels typically used to perturb cell structure and increased in a dose-dependent manner. The drug also released mRNA from the cytoskeletal framework in direct proportion to the inhibition of protein synthesis. The released mRNA was unaltered in its translatability as measured in vitro but was no longer translated in the cytochalasin-treated HeLa cells. The residual protein synthesis occurred on polyribosomes that were reduced in amount but displayed a normal sedimentation distribution. The results support the hypothesis that mRNA binding to the cytoskeletal framework is necessary although not sufficient for translation. Analysis of the cytoskeletal framework, which binds the polyribosomes, revealed no alterations in composition or amount of protein as a result of treatment with cytochalasin D. Electron microscopy with embedment-free sections shows the framework in great detail. The micrographs revealed the profound reorganization effected by the drug but did not indicate substantial disaggregation of the cytoskeletal elements.
Insights
Cytochalasin D reversibly inhibits protein synthesis in HeLa cells by releasing mRNA from the cytoskeleton. This released mRNA remains translatable but is no longer utilized for protein production in treated cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Protein synthesis is crucial for cellular function.
- The cytoskeleton plays a role in cellular processes.
- Cytochalasin D is known to affect cell structure.
Purpose of the Study:
- To investigate the effect of Cytochalasin D on protein synthesis in HeLa cells.
- To determine the mechanism by which Cytochalasin D inhibits protein synthesis.
- To examine the relationship between mRNA, the cytoskeleton, and protein translation.
Main Methods:
- HeLa cells were treated with varying concentrations of Cytochalasin D.
- Protein synthesis inhibition was measured.
- mRNA release from the cytoskeletal framework was assessed.
- In vitro translation assays were performed.
- Polyribosome analysis was conducted.
- Cytoskeletal framework composition was analyzed.
- Electron microscopy was used to visualize the cytoskeleton.
Main Results:
- Cytochalasin D caused a dose-dependent, reversible inhibition of protein synthesis.
- mRNA was released from the cytoskeleton proportionally to the inhibition of protein synthesis.
- Released mRNA retained its translatability in vitro but was not translated in treated cells.
- Residual protein synthesis occurred on fewer, but normally sedimenting, polyribosomes.
- The cytoskeletal framework composition and amount remained unchanged.
- Electron microscopy showed cytoskeletal reorganization but not significant disaggregation.
Conclusions:
- mRNA binding to the cytoskeleton is necessary, but not sufficient, for translation.
- Cytochalasin D disrupts the translation process by interfering with mRNA-cytoskeleton interactions.
- The drug reorganizes the cytoskeleton without causing substantial disaggregation.