Uptake and intracellular fate of gelonin, a ribosome-inactivating protein, in rat liver.
Gelonin, a type 1 ribosome-inactivating protein, has been used as toxin conjugate for several therapeutic purposes. We have investigated the endocytosis of gelonin by rat liver in vivo. Subcellular distribution of [125I]gelonin was established after differential and isopycnic centrifugation. Fractions were analyzed for acid-soluble and acid-precipitable radioactivity. Results show that gelonin is rapidly cleared from the blood and within 15min reaches a peak (25% of total injected) in the liver. With time, radioactivity associated with the liver markedly decreases. Two important observations are made: (a) Radioactivity associated with all fractions, at any time point, is greater than 80% acid precipitable. (b) Even at 5min, a significant amount of intact gelonin is present in the cytosolic fraction. Our work suggests that, though gelonin is rapidly cleared from the blood, there are still intact molecules that have entered the cytosol where they could exert their toxic effect.
Biochemistry Department, The Institute of Science, 15 Madam Cama Road, 400 032, Mumbai, India. colacos@vsnl.com
Melwin
M
Colaço
M M
MM
Bapat
Sandra
S
Misquith
Michel
M
Jadot
Simone
S
Wattiaux-De Coninck
Robert
R
Wattiaux
D000818:Animals; D002457:Cell Extracts / Q000737:chemistry; D002500:Centrifugation, Isopycnic; D004151:Dipeptides / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006026:Glycoside Hydrolases / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects; D008297:Male; D008862:Microsomes, Liver / Q000737:chemistry; D008930:Mitochondria, Liver / Q000737:chemistry / Q000187:drug effects; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000032:analysis / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017208:Rats, Wistar; D054789:Ribosome Inactivating Proteins, Type 1; D012270:Ribosomes / Q000187:drug effects; D043324:beta-Fructofuranosidase
D002457:Cell Extracts; D004151:Dipeptides; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D054789:Ribosome Inactivating Proteins, Type 1; C041865:glycylphenylalanine 2-naphthylamide; C025674:GEL protein, Gelonium multiflorum; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase