Tyrosine phosphorylation of phospholipase C induced by membrane immunoglobulin in B lymphocytes

Proc Natl Acad Sci U S A. 1991 Apr 1;88(7):2745-9. 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+]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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aluminum / pharmacology
  • Aluminum Compounds*
  • Animals
  • B-Lymphocytes / enzymology*
  • B-Lymphocytes / immunology
  • Benzoquinones
  • Cell Line
  • Cell Membrane / immunology
  • Enzyme Activation
  • Fluorides / pharmacology
  • Immunoglobulin M / physiology*
  • Inositol Phosphates / metabolism
  • Kinetics
  • Lactams, Macrocyclic
  • Phosphorylation
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Quinones / pharmacology*
  • Receptors, Antigen, B-Cell / physiology*
  • Rifabutin / analogs & derivatives
  • Type C Phospholipases / metabolism*
  • Tyrosine*


  • Aluminum Compounds
  • Benzoquinones
  • Immunoglobulin M
  • Inositol Phosphates
  • Lactams, Macrocyclic
  • Quinones
  • Receptors, Antigen, B-Cell
  • Rifabutin
  • Tyrosine
  • herbimycin
  • Aluminum
  • Protein-Tyrosine Kinases
  • Type C Phospholipases
  • Fluorides
  • aluminum fluoride