Open AccessRelationship between Membrane Permeability and the Translation Capacity of Human HeLa Cells Studied by Means of the Ionophore Nigericin
Author(s) -
ALONSO Miguel A.,
CARRASCO Luis
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb06399.x
Subject(s) - nigericin , ionophore , hela , protein biosynthesis , chemistry , membrane , biochemistry , biophysics , cytoplasm , membrane permeability , mechanism of action , translation (biology) , cell , biology , messenger rna , in vitro , gene
Treatment of HeLa cells with the ionophore nigericin causes a drastic inhibition of protein synthesis which is dependent on the concentration of monovalent ions present in the medium. 0.7 μM nigericin inhibits protein synthesis by almost 100% in a culture medium containing 5 mM KCl and 40 mM NaCl while no inhibition is observed with similar concentrations of nigericin in a medium containing 50 mM KCl and 25 mM NaCl. Moreover, once the inhibition of protein synthesis by the action of the ionophore has occurred in the former medium, it can be readily reversed to control levels by placing the cells in a medium with the appropriate concentration of monovalent ions, even though nigencin is still present. These results do not support the idea that the inhibition of translation by nigericin in intact cells involves the stable modification of the protein‐synthesizing machinery, nor even that translation inhibitors are generated by the action of nigericin on the cell membrane. The hypothesis that the blockade of translation by nigericin is produced by the modification of the monovalent ion concentration in the cell cytoplasm is reinforced in this work by several lines of evidence. Firstly, a striking parallelism between the inhibition of protein synthesis and the modification of the 86 Rb + content of HeLa cells was detected. Secondly, no variation in the cellular ATP content was observed at concentrations of nigericin that drastically blocked protein synthesis, and thirdly, no inhibition of the uptake of the radioactive amino acid precursor took place. Several ionophores, mainly A 23187, monensin, gramicidin D and valinomycin, all reduced both the translation capacity and the levels of 86 Rb + ions in cultured HeLa cells. These results reinforce the idea that macromolecular synthesis in mammalian cells might be regulated by membrane‐mediated events that in turn influence the concentration of monovalent ions in the cell.