Differential signaling through the Ig-alpha and Ig-beta components of the B cell antigen receptor

Eur J Immunol. 1993 Apr;23(4):911-6. doi: 10.1002/eji.1830230422.

Abstract

The B cell antigen receptor is a complex containing the antigen-binding immunoglobulin molecules and the Ig-alpha/Ig-beta heterodimer which presumably connects the B cell antigen receptor to intracellular signaling components. To analyze the functional properties of the cytoplasmic parts of the B cell antigen receptor, we used the K46 B lymphoma line (IgG2a, kappa) to express chimeric molecules composed of the extracellular and transmembrane part of the CD8 alpha molecule and the cytoplasmic sequence of either the Ig-alpha (CD8 alpha/Ig-alpha), the Ig-beta (CD8 alpha/Ig-beta) protein or the membrane-bound gamma 2a heavy chain (CD8 alpha/gamma 2a). From these three types of chimeric molecules only (CD8 alpha/Ig-alpha and CD8 alpha/Ig-beta, but not CD8 alpha/gamma 2a, could transduce signals, thus providing the first evidence that the cytoplasmic tail of Ig-alpha and Ig-beta have a signaling capacity. After cross-linking with anti-CD8 alpha antibodies, both molecules induced a similar increase in intracellular free calcium ion and in MAP kinase phosphorylation. Protein tyrosine kinases, however, were strongly activated via the CD8 alpha/Ig-alpha and only marginally via the CD8 alpha/Ig-beta molecule. This suggests that the Ig-alpha and Ig-beta proteins have distinct roles during signal transduction through the B cell antigen receptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigens, CD*
  • Base Sequence
  • CD79 Antigens
  • CD8 Antigens / physiology
  • Calcium / physiology
  • Cytoplasm / physiology
  • Membrane Glycoproteins / physiology*
  • Mice
  • Molecular Sequence Data
  • Phosphoproteins / metabolism
  • Phosphoproteins / physiology*
  • Phosphorylation
  • Phosphotyrosine
  • Receptors, Antigen, B-Cell / physiology*
  • Recombinant Fusion Proteins
  • Signal Transduction
  • Transfection
  • Tyrosine / analogs & derivatives
  • Tyrosine / metabolism

Substances

  • Antigens, CD
  • CD79 Antigens
  • CD8 Antigens
  • Cd79a protein, mouse
  • Cd79b protein, mouse
  • Membrane Glycoproteins
  • Phosphoproteins
  • Receptors, Antigen, B-Cell
  • Recombinant Fusion Proteins
  • Phosphotyrosine
  • Tyrosine
  • Calcium