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LAB: a new membrane-associated adaptor molecule in B cell activation

Erin Janssen1, Minghua Zhu, Weijia Zhang

  • 1Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA.

Nature Immunology
|January 7, 2003
PubMed

Insights

Researchers identified a new protein, linker for activation of B cells (LAB), crucial for B cell receptor signaling. LAB connects B cell activation to downstream pathways, impacting calcium flux and Erk activation.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • The adaptor protein Linker for Activation of T cells (LAT) is critical for T cell activation and development.
  • A similar adaptor molecule in B cells has not been identified, leaving a gap in understanding B cell receptor (BCR) signaling.

Purpose of the Study:

  • To identify and characterize a novel adaptor protein involved in B cell activation.
  • To elucidate the role of this new protein in BCR-mediated downstream signaling pathways.

Main Methods:

  • Identification and characterization of the novel adaptor protein, termed Linker for Activation of B cells (LAB).
  • Localization studies of LAB within lipid rafts.
  • Analysis of LAB phosphorylation and interaction with Grb2 upon BCR activation.
  • Assessment of BCR-mediated calcium flux and Erk activation in cells with altered LAB expression.
  • Evaluation of LAB's function in T cell-deficient (LAT(-/-)) mice models.

Main Results:

  • A new adaptor protein, LAB, was identified in B cells.
  • LAB was found to localize to lipid rafts, similar to LAT.
  • Upon BCR engagement, LAB undergoes phosphorylation and interacts with Grb2.
  • Reduced LAB expression diminished BCR-induced calcium flux and Erk activation.
  • LAB expression could rescue thymocyte development but not T cell activation in LAT(-/-) mice.

Conclusions:

  • LAB is a key adaptor protein that links BCR engagement to critical downstream signaling cascades.
  • LAB plays a significant role in B cell activation, calcium flux, and Erk pathway activation.
  • LAB's function appears specific to B cell signaling, as it did not restore normal T cell activation in LAT-deficient mice.

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