Tyrosine phosphorylation of phospholipase C induced by membrane immunoglobulin in B lymphocytes.
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+]i and 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+]i caused 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 gamma 1 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-gamma 1, suggesting a mechanism of PLC activation similar to that described for certain receptor PTKs.
Carter
R H
RH
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Park
D J
DJ
Rhee
S G
SG
Fearon
D T
DT
D000535:Aluminum / Q000494:pharmacology; D017607:Aluminum Compounds; D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D016227:Benzoquinones; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology; D007075:Immunoglobulin M / Q000502:physiology*; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D047029:Lactams, Macrocyclic; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011809:Quinones / Q000494:pharmacology*; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D017828:Rifabutin / Q000031:analogs & derivatives; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine
D017607:Aluminum Compounds; D016227:Benzoquinones; D007075:Immunoglobulin M; D007295:Inositol Phosphates; D047029:Lactams, Macrocyclic; D011809:Quinones; D011947:Receptors, Antigen, B-Cell; D017828:Rifabutin; D014443:Tyrosine; C020754:herbimycin; D000535:Aluminum; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; D005459:Fluorides; C032311:aluminum fluoride