Recycling of the asialoglycoprotein receptor and the effect of lysosomotropic amines in hepatoma cells

A. L. Schwartz, A. Bolognesi, S. E. Fridovich

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134 Scopus citations

Abstract

Receptor-mediated uptake and degradation of 125I-asialoorosomucoid (ASOR) in human hepatoma HepG2 cells is inhibited by the lysosomotropic amines chloroquine and primaquine. In the absence of added ligand at 37°C, these amines induce a rapid (t(1/2) 5.5-6 min) and reversible loss of cell surface 125I-ASOR binding sites as well as a rapid decrease in 125I-ASOR uptake and degradation. There is no effect of these amines on the binding of 125I-ASOR to the cell surface at 4°C or on the rate of internalization of prebound 125I-ASOR. The loss of 125 I-ASOR surface binding at 37°C is not attributable to altered affinity of ligand-receptor binding. In the presence of added ligand at 37°C, there is a more rapid (t(1/2) 2.5-3 min) loss of hepatoma cell surface receptors. In addition, the amines inhibit the rapid return of the internalized receptor to the cell surface. We examined the nature of this loss of 125I-ASOR surface binding sites by following the fate of receptor molecules after biosynthetic labeling and after cell surface iodination. At 37°C, chloroquine and primaquine induce a loss of asialoglycoprotein receptor molecules from the hepatoma cell surface to an internal pool.

Original languageEnglish
Pages (from-to)732-738
Number of pages7
JournalJournal of Cell Biology
Volume98
Issue number2
DOIs
StatePublished - 1984

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