The membrane IgM-associated proteins MB-1 and Ig-beta are sufficient to promote surface expression of a partially functional B-cell antigen receptor in a nonlymphoid cell line

Proc Natl Acad Sci U S A. 1992 Apr 15;89(8):3404-8. doi: 10.1073/pnas.89.8.3404.


The B-cell antigen receptors consist of membrane immunoglobulins (mIgs) noncovalently associated with two accessory proteins, MB-1 and Ig-beta. We used transfection into a nonlymphoid cell line to test whether MB-1 and Ig-beta were sufficient to promote cell surface expression of mIgM capable of signal transduction. Expression of MB-1 and Ig-beta, but not MB-1 alone, allowed high-level surface expression of mIgM in the AtT20 endocrine cell line, which presumably lacks other B-cell-specific components. The reconstituted antigen receptor was capable of mediating some of the signaling reactions characteristic of mIgM in B lymphocytes. Crosslinking mIgM on transfected AtT20 cells stimulated tyrosine phosphorylation of MB-1 and Ig-beta and also increased the amount of phosphatidylinositol 3-kinase activity that could be precipitated with anti-phosphotyrosine antibodies. When total cell lysates were analyzed by anti-phosphotyrosine immunoblotting, however, no induced phosphorylation of more abundant proteins was detected. Moreover, crosslinking of the receptor in AtT20 cells did not stimulate inositol phospholipid breakdown. Thus, the transfected B-cell antigen receptor could initiate some signal transduction events but AtT20 cells may lack components required for other signaling events associated with mIgM.

Publication types

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

MeSH terms

  • Animals
  • Antigens, CD*
  • CD79 Antigens
  • Cell Line
  • Cell Membrane / immunology
  • Immunoglobulin mu-Chains / genetics
  • Immunoglobulin mu-Chains / immunology
  • Inositol Phosphates / metabolism
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / immunology*
  • Molecular Weight
  • Phosphatidylinositol 3-Kinases
  • Phosphoproteins / genetics
  • Phosphoproteins / immunology*
  • Phosphorylation
  • Phosphotransferases / metabolism
  • Phosphotyrosine
  • Protein-Tyrosine Kinases / metabolism
  • Receptors, Antigen, B-Cell / genetics*
  • Receptors, Antigen, B-Cell / metabolism
  • Restriction Mapping
  • Signal Transduction
  • Transfection
  • Tyrosine / analogs & derivatives
  • Tyrosine / analysis


  • Antigens, CD
  • CD79 Antigens
  • Immunoglobulin mu-Chains
  • Inositol Phosphates
  • Membrane Glycoproteins
  • Phosphoproteins
  • Receptors, Antigen, B-Cell
  • Phosphotyrosine
  • Tyrosine
  • Phosphotransferases
  • Phosphatidylinositol 3-Kinases
  • Protein-Tyrosine Kinases