title: ATP-dependent inactivation and reactivation of constitutively recycling galactosyl receptors in isolated rat hepatocytes.
abstract: Isolated rat hepatocytes depleted of ATP with NaN3 without ligand lose galactosyl (Gal) receptors from the cell surface and accumulate inactive receptors within the cell [McAbee, D. D., & Weigel, P. H. (1987) J. Biol. Chem. 262, 1942-1945]. Here, we describe the kinetics of receptor redistribution and inactivation after ATP depletion with NaN3 and of receptor redistribution and reactivation after ATP recovery. Only intact cells (greater than 98% viable) isolated from Percoll gradients were assayed. Gal receptor activity and protein were measured by the binding of 125I-asialoorosomucoid (125I-ASOR) and 125I-anti-Gal receptor IgG (125I-IgGR), respectively, at 4 degrees C. Surface and total (surface and intracellular) cellular Gal receptors were measured in the absence or presence, respectively, of digitonin. Following ATP depletion, 60-70% of Gal receptor activity and protein were lost from cell surfaces with first-order kinetics (t1/2 = 6.5 min, k = 0.107 min-1) at an initial rate of 11,000 125I-ASOR binding sites cell-1 min-1. Lost cell-surface Gal receptors were transiently recovered still active inside the cell. After a short lag, total cellular receptor inactivation then proceeded with first-order kinetics (t1/2 = 13 min, k = 0.053 min-1) at an initial rate of 14,000 125I-ASOR binding sites cell-1 min-1. Up to half of all cellular Gal receptors were inactivated by 40 min. 125I-IgGR binding to NaN3-treated, permeable cells, however, was virtually constant. The distribution of total cellular receptors changed from 35% on the cell surface initially to 10% after 40 min of ATP depletion.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77550.
authors.forename: D D
authors.initials: DD
authors.lastname: McAbee
authors.forename: P H
authors.initials: PH
authors.lastname: Weigel
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D005690:Galactose / Q000378:metabolism*; D007118:Immunoassay; D007074:Immunoglobulin G; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G; D011956:Receptors, Cell Surface; C039707:galactose receptor; D000255:Adenosine Triphosphate; D005690:Galactose