Tyrosine Phosphorylation of Phospholipase C Induced by Membrane Immunoglobulin in B Lymphocytes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 7; pp. 2745 - 2749
• Main Authors: Carter, Robert H., Park, Do Joon, Rhee, Sue Goo, Fearon, Douglas T.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.04.1991; National Acad Sciences
• Subjects: Aluminum - pharmacology; Aluminum Compounds; Animals; Antibodies; B lymphocytes; B-Lymphocytes - enzymology; B-Lymphocytes - immunology; Benzoquinones; Biological and medical sciences; Cell Line; Cell lines; Cell Membrane - immunology; Cell physiology; Enzyme Activation; Fluorides - pharmacology; Fundamental and applied biological sciences. Psychology; Immunoglobulin M - physiology; Immunoglobulins; Inositol phosphates; Inositol Phosphates - metabolism; Kinetics; Lactams, Macrocyclic; Ligation; Molecular and cellular biology; Phosphorylation; Protein-Tyrosine Kinases - antagonists & inhibitors; Quinones - pharmacology; Receptors; Receptors, Antigen, B-Cell - physiology; Rifabutin - analogs & derivatives; Signal transduction; T lymphocytes; Type C Phospholipases - metabolism; Tyrosine; Tyrphostins; Human; Tyrosine; Phosphorylation; Membrane protein; Enzyme inhibitor; Crosslinking; B-Lymphocyte; IgM; Phospholipase C; Signal transduction; Immunoprecipitation reaction; Kinase; Immunoblotting assay; Mechanism of action
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.7.2745

Ligation of membrane IgM on B lymphocytes causes activation of a protein-tyrosine kinase(s) (PTK) and of phospholipase C (PLC). To determine whether these are elements of a common signal-transduction pathway, the effect of three PTK inhibitors on the rise in intracellular free Ca2+concentration ([Ca2+]i) in human B-lymphoblastoid cell lines was assessed. Tyrphostin completely suppressed the increase in [Ca2+]iand the generation of inositol phosphates induced by ligation of membrane immunoglobulin (mIg) M. Herbimycin and genistein reduced by 30% and 50%, respectively, the rise in [Ca2+]icaused by optimal ligation of mIgM, and they abolished it in cells activated by suboptimal ligation of mIgM. Tyrphostin had no effect on the capacity of aluminum fluoride to increase [Ca2+]i. To determine whether a function of PTK is the phosphorylation of PLC, immunoprecipitates obtained with anti-phosphotyrosine from detergent lysates of B-lymphoblastoid cells were assayed for PLC activity. Ligation of mIgM increased immunoprecipitable PLC activity 2-fold by 90 sec and 4-fold by 30 min. Specific immunoprecipitation and Western blot analysis identified tyrosine phosphorylation of the γ1 isoform of PLC after 60 sec of stimulation. Activation of PLC in B cells by mIgM requires PTK function and is associated with tyrosine phosphorylation of PLC-γ1, suggesting a mechanism of PLC activation similar to that described for certain receptor PTKs.