The effects of basic substances and acidic ionophores on the digestion of exogenous and endogenous proteins in mouse peritoneal macrophages.
Open Access
- 1 March 1986
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 102 (3) , 959-966
- https://doi.org/10.1083/jcb.102.3.959
Abstract
Basic substances and acidic inophores that increase the lysosomal pH in cultured macrophages (Ohkuma, S., and B. Poole, 1978, Proc. Natl. Acad. Sci. USA., 75:3327-3331; Poole, B., and S. Ohkuma, 1981, J. Cell Biol., 90:665-669) inhibited the digestion of heat-denatured acetylated bovine serum albumin (BSA) taken up by the cells. For several substances, the shift in pH sufficed to explain the inhibition of proteolysis. Additional effects, presumably on enzyme activities, have to be postulated for tributylamine, amantadine, and chloroquine. Sodium fluoride (10 mM) had no significant effect on the breakdown of BSA by macrophages. The breakdown of endogenous macrophage proteins, whether short lived or long lived, was inhibited .apprx. 40% by 10 mM NaF and 30%, or sometimes less in the case of long-lived proteins, by 100 .mu.M chloroquine. When the cells were supplied with BSA, a mixture of cell proteins, or even inert endocytosible materials the breakdown of endogenous long-lived proteins and the inhibitory effect of chloroquine on this process were selectively reduced. Inhibition of endocytosis by cytochalasins B or D did not affect the chloroquine-sensitive breakdown of endogenous proteins, indicating that the proteins degraded by this process were truly endogenous and not taken in from the outside by cellular cannibalism. On the other hand, when macrophage proteins were supplied extracellularly, their breakdown occurred at the same rate for short-lived and long-lived proteins, and it was strongly inhibited by chloroquine and not by NaF. It is concluded from these results that the breakdown of endogenous proteins, both short-lived and long-lived, probably takes place partly (.apprx. 30%) in lysosomes and partly through one or more nonlysosomal mechanism(s) unaffected by chloroquine and presumably susceptible to inhibition by fluoride. A difference must exist between short-lived and long-lived proteins in the manner in which they reach lysosomes or are handled by these organelles; this difference would account for the selective effect of the supply of endocytosible materials on the lysosomal processing of long-lived proteins.This publication has 17 references indexed in Scilit:
- Fluorescence probe measurement of the intralysosomal pH in living cells and the perturbation of pH by various agents.Proceedings of the National Academy of Sciences, 1978
- The accumulation of weakly basic substances in lysosomes and the inhibition of intracellular protein degradationPublished by Walter de Gruyter GmbH ,1977
- Effect of microtubular or translational inhibitors on general cell protein degradation. Evidence for a dual catabolic pathwayBiochemical Journal, 1977
- Lysosomal Enzymes as Agents of Turnover of Soluble Cytoplasmic ProteinsEuropean Journal of Biochemistry, 1975
- PROTEIN DEGRADATION IN CULTURED CELLSThe Journal of cell biology, 1974
- Relationship between digradation rates of proteins in vivo and their susceptibility to lysosomal proteases.1974
- Lysosomotropic agentsBiochemical Pharmacology, 1974
- Protein degradation in cultured cells. The effect of fresh medium, fluoride, and iodoacetate on the digestion of cellular protein of rat fibroblasts.1973
- DIGESTIVE ACITIVITY OF LYSOSOMES .I. DIGESTION OF PROTEINS BY EXTRACTS OF RAT LIVER LYSOSOMES1968
- THE DIFFERENTIATION OF MONONUCLEAR PHAGOCYTESThe Journal of Experimental Medicine, 1965