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Cytotoxic potential of ribonuclease and ribonuclease hybrid proteins.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 1991 Nov 05; Vol. 266 (31), pp. 21202-7. - Publication Year :
- 1991
-
Abstract
- Pancreatic RNase injected into Xenopus oocytes abolishes protein synthesis at concentrations comparable to the toxin ricin yet has no effect on oocyte protein synthesis when added to the extracellular medium. Therefore RNase behaves like a potent toxin when directed into a cell. To explore the cytotoxic potential of RNase toward mammalian cells, bovine pancreatic ribonuclease A was coupled via a disulfide bond to human transferrin or antibodies to the transferrin receptor. The RNase hybrid proteins were cytotoxic to K562 human erythroleukemia cells in vitro with an IC50 around 10(-7) M whereas greater than 10(-5) M native RNase was required to inhibit protein synthesis. Cytotoxicity requires both components of the conjugate since excess transferrin or ribonuclease inhibitors added to the medium protected the cells from the transferrin-RNase toxicity. Compounds that interfere with transferrin receptor cycling and compartmentalization such as ammonium chloride decreased the cytotoxicity of transferrin-RNase. After a dose-dependent lag period inactivation of protein synthesis by transferrin-RNase followed a first-order decay constant. In a clonogenic assay that measures the extent of cell death 1 x 10(-6) M transferrin-RNase killed at least 4 logs or 99.99% of the cells whereas 70 x 10(-6) M RNase was nontoxic. These results show that RNase coupled to a ligand can be cytotoxic. Human ribonucleases coupled to antibodies also may exhibit receptor-mediated toxicities providing a new approach to selective cell killing possibly with less systemic toxicity and importantly less immunogenicity than the currently employed ligand-toxin conjugates.
- Subjects :
- Ammonium Chloride pharmacology
Animals
Cell Death drug effects
Cell Line
Clone Cells
Humans
Immunotoxins toxicity
In Vitro Techniques
Microinjections
Monensin pharmacology
Oocytes
Protein Biosynthesis
Ribonucleases administration & dosage
Ribonucleases antagonists & inhibitors
Ribonucleases chemistry
Time Factors
Transferrin chemistry
Xenopus laevis
Protein Synthesis Inhibitors toxicity
Ribonucleases toxicity
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 266
- Issue :
- 31
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 1939162