The effect of vanadate on receptor-mediated endocytosis of asialoorosomucoid in rat liver parenchymal cells

• Published in: The Journal of biological chemistry Vol. 265; no. 16; pp. 8999 - 9005
• Main Authors: KINDBERG, G. M, GUDMUNDSEN, O, BERG, T
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05-06-1990
• Subjects: 550501 > Metabolism > Tracer Techniques; Adenosine Triphosphate - metabolism; AMINES; ANIMAL CELLS; ANIMALS; AROMATICS; Asialoglycoprotein Receptor; Asialoglycoproteins; asialoorosomucoid; ATP; AUTONOMIC NERVOUS SYSTEM AGENTS; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; BIOCHEMICAL REACTION KINETICS; Biological and medical sciences; BIOLOGICAL EFFECTS; BODY; CARBOHYDRATES; CELL CONSTITUENTS; Cell Fractionation; Cell physiology; CELLOBIOSE; CENTRIFUGATION; Centrifugation, Density Gradient; DAYS LIVING RADIOISOTOPES; DIGESTIVE SYSTEM; DISACCHARIDES; DRUGS; ELECTRON CAPTURE RADIOISOTOPES; Endocytosis; Endocytosis - drug effects; FRACTIONATION; Fundamental and applied biological sciences. Psychology; GLANDS; HYDROXY COMPOUNDS; INTERMEDIATE MASS NUCLEI; IODINE 125; IODINE ISOTOPES; Iodine Radioisotopes; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; LIVER; Liver - metabolism; Liver - ultrastructure; LYSOSOMES; Lysosomes - metabolism; MAMMALS; MEMBRANE PROTEINS; Molecular and cellular biology; NUCLEI; NUCLEOTIDES; ODD-EVEN NUCLEI; OLIGOSACCHARIDES; ORGANIC COMPOUNDS; ORGANOIDS; ORGANS; Orosomucoid - analogs & derivatives; Orosomucoid - metabolism; OXYGEN COMPOUNDS; PHAGOCYTOSIS; PHENOLS; PROTEINS; RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT; RADIOISOTOPES; RATS; REACTION KINETICS; RECEPTORS; Receptors, Immunologic - physiology; RODENTS; SACCHARIDES; SEPARATION PROCESSES; SYMPATHOMIMETICS; TRACER TECHNIQUES; TRANSITION ELEMENT COMPOUNDS; TYRAMINE; ULTRACENTRIFUGATION; Vacuoles - drug effects; Vacuoles - metabolism; vanadate; VANADATES; Vanadates - pharmacology; VANADIUM COMPOUNDS; VERTEBRATES 560300 > Chemicals Metabolism & Toxicology; Radiolabelling; Rat; Liver; Rodentia; Vanadates Ions; Parenchyma; Glycoproteins; Vertebrata; Endocytosis; Membrane receptor; Regulation(control); Mammalia; Binding capacity; Kinetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(19)38802-7

Vanadate is a phosphate analogue that inhibits enzymes involved in phosphate release and transfer reactions (Simons, T. J.
B. (1979) Nature 281, 337-338). Since such reactions may play important roles in endocytosis, we studied the effects of vanadate
on various steps in receptor-mediated endocytosis of asialoorosomucoid labeled with 125I-tyramine-cellobiose (125I-TC-AOM).
The labeled degradation products formed from 125I-TC-AOM are trapped in the lysosomes and may therefore serve as lysosomal
markers in subcellular fractionation studies. Vanadate reduced the amount of active surface asialoglycoprotein receptors approximately
70%, but had no effect on the rate of internalization and retroendocytosis of ligand. The amount of surface asialoglycoprotein
receptors can be reduced by lowering the incubation temperature gradually from 37 to 15 degrees C (Weigel, P. H., and Oka,
J. A. (1983) J. Biol. Chem. 258, 5089-5094); vanadate affected only the temperature--sensitive receptors. Vanadate inhibited
degradation of 125I-TC-AOM 70-80%. Degradation was much more sensitive to vanadate than binding; half-maximal effects were
seen at approximately 1 mM vanadate for binding and approximately 0.1 mM vanadate for degradation. By subcellular fractionation
in sucrose and Nycodenz gradients, it was shown that vanadate completely prevented the transfer of 125I-TC-AOM from endosomes
to lysosomes. Therefore, the inhibition of degradation by vanadate was indirect; in the presence of vanadate, ligand did not
gain access to the lysosomes. The limited degradation in the presence of vanadate took place in a prelysosomal compartment.
Vanadate did not affect cell viability and ATP content.