Membrane IgM cross-linking is not coupled to protein kinase C translocation in WEHI-231 B lymphoma cells
- 1 July 1989
- journal article
- research article
- Published by Wiley in European Journal of Immunology
- Vol. 19 (7), 1247-1252
- https://doi.org/10.1002/eji.1830190715
Abstract
The early molecular events involved in the process of signal transduction via membrane immunoglobulins (mIg) include phosphatidyl inositol metabolism, intracellular Ca2+ mobilization, and protein kinase C (PKC) activation. Anti‐mIg antibodies exert either stimulating or inhibitory effects depending on the activation state and/or the differentiation stage of B cells. WEHI‐231 is a murine B lymphoma that becomes inactivated upon anti‐mIg treatment. This lymphoma has an immature B cell phenotype and is considered as a model for tolerance induction in B lymphocytes. In this study, we have investigated the relationship between mIg triggering, Ca2+ elevation, PKC translocation, and growth inhibition in WEHI‐231 cells. Monoclonal antibodies to μ and χ chains of the mIgM receptor promoted a rapid increase in intracytoplasmic Ca2+ and were potent inhibitors of cell growth. Ca2+ elevation and PKC translocation have been previously shown to be associated in B lymphocytes. To study the subcellular distribution of PKC in WEHI‐231 cells, we used enzymatic assays and immunodetection methods. Although phorbol 12‐myristate 13‐acetate induced a rapid and almost complete redistribution of cytosolic PKC to the membrane fraction, anti‐mIg treatment failed to modify the compartmentalization of PKC. These findings extend recent observations suggesting that B cell triggering through mIg receptors may involve additional pathways independent from PKC activation. PKC activation in normal B cells is also believed to provide a regulatory signal which limits the magnitude of the early signals produced by anti‐mIg. Such a regulatory control is unlikely in WEHI‐231 cells, due to the dissociation between Ca2+ mobilization and PKC translocation. Our findings therefore suggest that the sensitivity of immature B cells such as WEHI‐231 to the inhibitory effects of anti‐mIg antibodies may result in part from alterations of the phosphoinositide signal transduction pathway.This publication has 28 references indexed in Scilit:
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