The effect of vanadate on receptor-mediated endocytosis of asialoorosomucoid in rat liver parenchymal cells
- Univ. of Oslo (Norway)
Vanadate is a phosphate analogue that inhibits enzymes involved in phosphate release and transfer reactions. 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; 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.
- OSTI ID:
- 6693243
- Journal Information:
- Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 265:16; ISSN JBCHA; ISSN 0021-9258
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINES
ANIMAL CELLS
ANIMALS
AROMATICS
ATP
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BODY
CARBOHYDRATES
CELL CONSTITUENTS
CELLOBIOSE
CENTRIFUGATION
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DISACCHARIDES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
FRACTIONATION
GLANDS
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIVER
LYSOSOMES
MAMMALS
MEMBRANE PROTEINS
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
OXYGEN COMPOUNDS
PHAGOCYTOSIS
PHENOLS
PROTEINS
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SACCHARIDES
SEPARATION PROCESSES
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRANSITION ELEMENT COMPOUNDS
TYRAMINE
ULTRACENTRIFUGATION
VANADATES
VANADIUM COMPOUNDS
VERTEBRATES