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. 1974 Nov 1;63(2):430–440. doi: 10.1083/jcb.63.2.430

PROTEIN DEGRADATION IN CULTURED CELLS

II. The Uptake of Chloroquine by Rat Fibroblasts and the Inhibition of Cellular Protein Degradation and Cathepsin B1

Maurice Wibo 1, Brian Poole 1
PMCID: PMC2110942  PMID: 4607946

Abstract

The degradation of cellular proteins in fibroblasts, both those of rapid and those of slow turnover rates, was inhibited by low concentrations of chloroquine or neutral red in the medium. Cells inhibited by chloroquine can be inhibited further by fluoride. Chloroquine was taken up by the fibroblasts and the concentration in the cells reached several hundred times that in the medium. Isopycnic fractionation studies showed that within the cells the chloroquine was concentrated in the lysosomes, and that these chloroquine-containing lysosomes had a lower equilibrium density than the lysosomes of untreated cells. Chloroquine, at concentrations attained inside the lysosomes, inhibited cathepsin B1 but not cathepsin D. It is concluded that chloroquine impairs the breakdown of cellular proteins after these have entered the lysosome system, probably through inhibition of cathepsin B1.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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