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Published on: February 26, 2011
Effect of ionophores and metabolic inhibitors on protein synthesis in rabbit reticulocytes
Abstract:
The effect of some ionophores and metabolic inhibitors on reticulocytes protein synthesis was examined. At microM concentrations, valinomycin, nigericin and CCCP rapidly inhibit protein synthesis, while with antimycin-A or DCCD the inhibition is rather slow. The onset of the arrest of protein synthesis coincides with a 20--30% drop in the intracellular ATP content. No inhibition in protein synthesis or drop in ATP was found after 1 h incubation without glucose or in the presence of 2-deoxyglucose. It is shown that the inhibition by valinomycin, nigericin or CCCP is not due to their effect on K+ and/or H+ fluxes through the plasma membrane. Reticulocytes incubated at pH 8.2 show much lower inhibition of protein synthesis by nigericin, CCCP, DCCD or antimycin-A. On the other hand, at this alkaline pH, starvation to glucose causes high inhibition of protein synthesis. It is concluded that the ionophores inhibit protein synthesis due to their uncoupling effect on mitochondrial ATP synthesis. At high pH, the glycolytic activity is relatively high, and the ATP generated by the glycolysis can compensate to some degree for the ATP loss in the oxidative phosphorylation.
Insights
Ionophores like valinomycin rapidly inhibit reticulocyte protein synthesis by disrupting ATP production. This effect is linked to mitochondrial ATP synthesis uncoupling, not ion fluxes.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Reticulocytes are crucial for studying protein synthesis.
- Ionophores and metabolic inhibitors can disrupt cellular processes.
Purpose of the Study:
- To investigate the impact of ionophores and metabolic inhibitors on reticulocyte protein synthesis.
- To elucidate the mechanisms underlying the observed inhibition.
Main Methods:
- Incubation of reticulocytes with various ionophores (valinomycin, nigericin, CCCP) and metabolic inhibitors (antimycin-A, DCCD).
- Measurement of protein synthesis rates and intracellular ATP content.
- Assessment of ion fluxes (K+, H+) and cellular response at different pH levels and glucose availability.
Main Results:
- Valinomycin, nigericin, and CCCP rapidly inhibited protein synthesis, coinciding with a 20-30% drop in intracellular ATP.
- Antimycin-A and DCCD showed slower inhibition kinetics.
- Inhibition was not attributed to K+ or H+ fluxes.
- Alkaline pH (8.2) reduced inhibition by ionophores but increased inhibition by glucose starvation.
- Glycolysis compensated for ATP loss at high pH.
Conclusions:
- Ionophores inhibit reticulocyte protein synthesis primarily by uncoupling mitochondrial ATP synthesis.
- Cellular ATP levels and protein synthesis are sensitive to metabolic conditions and pH.
- Glycolytic ATP production plays a significant role in maintaining protein synthesis, especially under conditions of impaired oxidative phosphorylation.
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