Conjugation of blocked ricin to an anti-CD19 monoclonal antibody increases antibody-induced cell calcium mobilization and CD19 internalization
| Autor: | A C, Goulet, V S, Goldmacher, J M, Lambert, C, Baron, D C, Roy, E, Kouassi |
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| Rok vydání: | 1997 |
| Předmět: |
Protein Synthesis Inhibitors
Membrane Glycoproteins Immunotoxins Antigens CD19 Antibodies Monoclonal Lactose Ricin Protein-Tyrosine Kinases Antigens CD20 ADP-ribosyl Cyclase 1 Antigens Differentiation Structure-Activity Relationship NAD+ Nucleosidase Antigens CD Tumor Cells Cultured Humans Calcium Enzyme Inhibitors ADP-ribosyl Cyclase Dimerization Signal Transduction |
| Zdroj: | Blood. 90(6) |
| ISSN: | 0006-4971 |
| Popis: | CD19 (B4) is a signal transduction molecule restricted to the B-cell lineage and the target of the immunotoxin anti-B4-blocked ricin (anti-B4-bR), which is composed of the monoclonal antibody (MoAb) anti-B4 and the modified plant toxin blocked ricin. To explore the influence of conjugation of blocked ricin to anti-B4 on functional activation of CD19, we investigated the effects of anti-B4-bR, and that of unconjugated anti-B4, on intracellular calcium mobilization and ligand/receptor internalization. The data showed that anti-B4-bR was more potent than anti-B4 in triggering cell calcium mobilization. Two other immunotoxins that bind to the B-cell surface, anti-CD20-bR and anti-CD38-bR, were devoid of the calcium increasing effect of anti-B4-bR. Furthermore, anti-B4 conjugated to ricin A-chain was also without effect in Namalwa cells, indicating that the ricin B-chain component was required for anti-B4-bR effect. Anti-B4-bR-induced calcium mobilization was inhibited in the presence of lactose, yet the calcium response induced by cross-linking anti-B4-bR with a second step antibody was not affected. The extent of CD19 modulation induced by anti-B4-bR was higher than that induced by anti-B4, and lactose dampened the effect of the immunotoxin down to that of the MoAb. Moreover, the number of internalized immunotoxin molecules was higher than that of unconjugated MoAb. Although a mechanism involving dimerization of the immunotoxin cannot be excluded, our findings suggest that the residual binding activity of the blocked ricin B-chain to cell surface molecules plays an important role in the greater calcium fluxes and greater internalization rate of anti-B4-bR, and is of functional significance in the mechanism of intoxication of cells by the immunotoxin. |
| Databáze: | OpenAIRE |
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