Loss of surface galactosyl receptor activity on isolated rat hepatocytes induced by monensin or chloroquine requires receptor internalization via a clathrin coated pit pathway
Mcabee, D.D.; Oka, J.A.; Weigel, P.H.
Biochemical and Biophysical Research Communications 161(1): 261-266
1989
ISSN/ISBN: 0006-291X PMID: 2567166 Document Number: 335118
We studied the effect of hyperosmotic inhibition of the clathrin coated pit cycle on the monensin- and chloroquine-dependent loss of surface galactosyl (Gal) receptor activity on isolated rat hepatocytes. Cells treated for 60 min without ligand at 37.degree. C with 25 .mu.M monensin or 300 .mu.M chloroquine in normal medium (osmolality .simeq. 275 mmol/kg) bound 40-60% less 125I-asialo-orosomucoid (ASOR) at 4.degree. C than untreated cells. Cells exposed to monensin or chloroquine retained progressively more surface Gal receptor activity, however, when the osmolality of the medium was increased above 400 mmol/kg (using sucrose as osmolite) 10 min prior to and during drug treatment. Cells pretreated for 10 min with hyperosmolal media (600 mmol/kg) alone internalized .ltoreq. 10% of surface-bound 125I-ASOR. Thus, the ligand-independent loss of surface Gal receptor activity on monensin- and chloroquine-treated hepatocytes requires internalization of constitutively recycling receptors via a coated pit pathway.