Phorbol esters and dioctanoylglycerol block anti-IgM-stimulated phosphoinositide hydrolysis in the murine B cell lymphoma WEHI-231

• Published in: The Journal of immunology (1950) Vol. 138; no. 3; pp. 868 - 876
• Main Authors: Gold, MR, DeFranco, AL
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Assoc Immnol 01.02.1987; American Association of Immunologists
• Subjects: B-Lymphocytes - metabolism; Biological and medical sciences; Calcium - analysis; Cells, Cultured; Diglycerides - pharmacology; Enzyme Activation; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Glycerides - pharmacology; Hydrolysis; Immunobiology; Immunoglobulin M - analysis; Immunoglobulin M - immunology; Immunological reactions in vitro; Lymphoblastic transformation (stimulation by antigen, mitogen, mixed lymphocyte reactions); Lymphoma - metabolism; Phorbol Esters - pharmacology; Phosphatidic Acids - metabolism; Phosphatidylinositols - metabolism; Protein Kinase C - analysis; Receptors, Antigen, B-Cell - analysis; Cell proliferation; Protein kinase C; Rodentia; Activation; B-Lymphocyte; Metabolism; Lymphoma; IgM; Signal transduction; Vertebrata; Regulation(control); Mammalia; Mouse; Animal; Inositophospholipide; Plasma membrane
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.138.3.868

Cross-linking of membrane IgM (mIgM) on both normal resting B cells and on the murine B cell lymphoma WEHI-231 activates the phosphoinositide signal transduction pathway. The initial event in this pathway is the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdInsP2), which results in the generation of two second-messengers: inositol trisphosphate (InsP3), which can cause the release of Ca2+ from intracellular stores, and diacylglycerol (DG), which activates protein kinase C. In examining the effects of exogenous activation of protein kinase C on WEHI-231 cells, we found that phorbol esters blocked some of the biologic effects of anti-IgM on WEHI-231 cells. The mechanism of this effect was investigated. Phorbol ester treatment of WEHI-231 cells blocked the ability of anti-IgM to stimulate production of inositol phosphates and accumulation of phosphatidic acid, the phosphorylated product of DG. Phorbol esters also blocked the ability of anti-IgM to cause an increase in intracellular Ca2+. Thus, it is clear that phorbol esters block anti-IgM-stimulated PtdInsP2 hydrolysis in WEHI-231 cells. In addition, a synthetic DG, dioctanoylglycerol (diC8), also blocked anti-IgM-stimulated inositol phosphate production and the anti-IgM-stimulated rise in cytoplasmic Ca2+. The ability of phorbol esters and diC8 to block mIgM-mediated signaling may reflect a feedback inhibition mechanism by which activated protein kinase C limits the magnitude and duration of receptor signaling.