Differential effects of leupeptin, monensin and colchicine on ligand degradation mediated by the two asialoglycoprotein receptor pathways in isolated rat hepatocytes

B. L. Clarke, P. H. Weigel

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

We have shown that degradation of asialo-orosomucoid (ASOR) in isolated rat hepatocytes occurs by two different intracellular pathways [Clarke, Oka and Weigel (1987) J. Biol. Chem. 262, 17384-17392] mediated by two subpopulations of cell surface galactosyl (Gal) receptors, designated State 1 or State 2 receptors. In the present study, several inhibitors were tested for their effects on ligand degradation by the State 1 or State 2 pathway. Leupeptin, monensin and chloroquine completely inhibited degradation of 125I-labelled ASOR in both pathways. Dose-response studies showed, however, that the State 2 pathway was more sensitive to leupeptin or monensin than the State 1 pathway. No differences were observed with chloroquine. For example, the onset of the inhibition in the State 2 and State 1 pathways occurred at about 0.05 and 0.3 μM-leupeptin respectively, a 6-fold difference. At 3.5 μM-monensin, 125I-ASOR degradation in the State 2 pathway was completely blocked, whereas degradation in the State 1 pathway was essentially unaffected. Colchicine was observed to give the largest differential sensitivity between the two pathways. The State 2 degradation pathway was about 30-fold more sensitive to colchicine than the State 1 pathway. Lumicolchicine had no affect. The onset of inhibition of the rate of 125I-ASOR degradation in the State 2 and State 1 pathways occurred at ~ 0.1 and 3.0 μM-colchicine respectively. At very high concentrations (> 0.1 mM), the State 1 pathway could be completely inhibited. We conclude that intracellular 125I-ASOR processing or delivery to degradative compartments in both the State 1 and State 2 Gal receptor pathways requires low pH. Ligand delivery to the degradative compartment does not require microtubules in the State 1 pathway, consistent with the very rapid onset of degradation in this pathway. The State 2 degradation pathway does require microtubules.

Original languageEnglish (US)
Pages (from-to)277-284
Number of pages8
JournalBiochemical Journal
Volume262
Issue number1
DOIs
StatePublished - 1989

Fingerprint Dive into the research topics of 'Differential effects of leupeptin, monensin and colchicine on ligand degradation mediated by the two asialoglycoprotein receptor pathways in isolated rat hepatocytes'. Together they form a unique fingerprint.

Cite this