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The nonimmunoglobulin portion of lambda5 mediates cell-autonomous pre-B cell receptor signaling

Kazuo Ohnishi1, Fritz Melchers

  • 1National Institute of Infectious Diseases, Department of Immunology, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan. ohnishik@nih.go.jp

Nature Immunology
|August 5, 2003
PubMed

Insights

The pre-B cell receptor (preBCR) signals immune cells to proliferate without external triggers. Specific arginine residues in its lambda5 component are crucial for this self-activating signaling pathway.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • The pre-B cell receptor (preBCR) is essential for B cell development.
  • preBCR signaling drives B cell proliferation, even without apparent ligand binding.

Purpose of the Study:

  • To investigate the role of the non-immunoglobulin (nonlg) portion of lambda5 in preBCR signaling.
  • To identify specific residues within lambda5 critical for preBCR-mediated signal transduction.

Main Methods:

  • Genetic manipulation of the lambda5 protein, including deletion and site-directed mutagenesis of arginine residues.
  • Analysis of preBCR expression, aggregation, internalization, and tyrosine phosphorylation in mutant cells.

Main Results:

  • Mutations in the nonlg portion of lambda5, specifically seven arginine residues, impaired preBCR signaling.
  • Mutant preBCRs exhibited increased cell surface presence, reduced aggregation, and diminished internalization.
  • Tyrosine phosphorylation of preBCR complexes with mutant lambda5 was abolished.

Conclusions:

  • The nonlg portion of lambda5, particularly seven arginine residues, is vital for preBCR signal transduction.
  • preBCR signaling appears to be ligand-independent and potentially cell-autonomous.
  • These findings provide insights into the constitutive signaling capacity of the preBCR.

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