The human asialoglycoprotein receptor is palmitoylated and fatty deacylation causes inactivation of state 2 receptors.
We report here for the first time that ASGP-Rs expressed in the human hepatoma cell lines HuH-7 and HepG2 are fatty acylated. Cells were metabolically labeled with [3H]palmitate and active ASGP-Rs, which contain two subunits (HHL1 and HHL2), were purified by affinity chromatography and subjected to nonreducing SDS-PAGE and fluorography. [3H]Palmitate was covalently incorporated into both HHL1 and HHL2. When gel slices containing HHL1/HHL2 were treated at neutral pH with 1 M hydroxylamine, but not 1 M Tris, > 95% of the radioactivity was removed, indicating that the attachment of palmitate to ASGP-Rs is to cysteines. Furthermore, the same mild hydroxylamine treatment caused partial ASGP-R inactivation; 50-70% of receptors corresponding to the previously characterized State 2 ASGP-Rs were inactivated. We conclude that both HHL1 and HHL2 are covalently modified by fatty acylation, which may regulate the ligand-binding activity of human State 2 ASGP-Rs. We propose that fatty acylation/deacylation of cytoplasmic domains is a general mechanism by which extracellular ligand-binding activity of oligomeric transmembrane receptors can be regulated.
Zeng
F Y
FY
Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
Oka
J A
JA
Weigel
P H
PH
D037263:Asialoglycoprotein Receptor; D001212:Asialoglycoproteins / Q000378:metabolism; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D006706:Homeostasis; D006801:Humans; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D015151:Immunoblotting; D007700:Kinetics; D008113:Liver Neoplasms; D046911:Macromolecular Substances; D008961:Models, Structural; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D037263:Asialoglycoprotein Receptor; D001212:Asialoglycoproteins; D006898:Hydroxylamines; D046911:Macromolecular Substances; D010169:Palmitic Acids; D011956:Receptors, Cell Surface; D019811:Hydroxylamine; D019308:Palmitic Acid