Ricin-resistant cells

A ricin-resistant mouse lymphoma cell line has been isolated which was shown to possess a normal number of ricin-binding sites [63-66]. These cells internalized reduced amounts of ferritin-ricin complexes at low toxin concentrations compared with the parent cells. Resistance in this cell line is therefore due to a defect in transferring ricin from the cell surface to the cytoplasm, since... 

A two-dimensional mapping procedure, involving isoelectric focusing and sodium dodecylsulphate electrophoresis, has been used in a comparative study of the surface anatomy of baby hamster kidney cells and three clones resistant to ricin. Abnormal patterns were observed in all three mutant clones indicating different mechanisms of ricin resistance glycoproteins, which may be involved in cellular reactions, were identified. 

Abrin- and ricin-resistant variants of established HeLa cell lines have been characterized. The reduced number of binding sites on two of the cell variants is due to an increased level of neuraminic acid on oligosaccharide chains terminated at the non-reducing end by D-galactose. However, these over-sialylated variants are not cross-resistant to another plant toxin, modeccin,... 

C. Campbell, P. Stanley, A dominant mutation to ricin resistance in Chinese hamster ovary cells induces UDP-GlcNAc glycopeplidc p-4-N-acetylglucosaminyltransferase III activity, J Biol Chem, 1984, 259, 13370-13378. 

The importance of carbohydrate binding for ricin toxicity is supported by the observation that cell lines lacking galactosyl transferase are resistant to ricin (Foddy and Hughes, 1986). The potency of ricin or related toxins does not correlate directly, however, with the number of receptors present... 

Olsnes, S. and Refsnes, K. (1978) On the mechanism of toxin resistance in cell variants resistant to abrin and ricin. Eur J Biochem, 88, 7-15. 

Olsnes, S., Sandvig, K., Eiklid, K. and Pihl, A. (1978b) Properties and action mechanism of the toxic lectin modeccin interaction with cell fines resistant to modeccin, abrin, and ricin. J Supramol Struct, 9, 15-25. 

Tamura, T., Oda, T. and Muramatsu, T. (2002a) Resistance against ricin-induced apoptosis in a brefeldin A-resistant mutant cell line (BER-40) of Veto cells. J Biochem (Tokyo), 132, 441-449. 

Teter, K. and Holmes, R.K. (2002) Inhibition of endoplasmic reticulum-associated degradation in CHO cells resistant to cholera toxin. Pseudomonas aeruginosa exotoxin A, and ricin. Infect Immun, 70, 6172-6179. 

The binding, entry, and action of ricin, abrin, and modeccin on eukaryotic cellular systems have been reviewed.Modeccin binds to surface receptors containing terminal D-galactosyl residues, and like abrin and ricin it inhibits protein synthesis by inactivating the 60 S ribosomal sub-units. Competition experiments with various glycoproteins have indicated that the modeccin receptors are different from abrin receptors. Mutant cell lines resistant to abrin and ricin were not resistant to modeccin and vice-versa. 

Golgi network membrane into the cytosol, can refold into a protease-resistant, enzymatically active structure (Lord et al., 2003). Just a single ricin molecule entering the cytosol of a living cell with a K at of 1,500/min can inactivate enough ribosomes to ultimately result in cell death (Endo et al., 1987). 

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