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Pax-5 is a key regulator of the B cell-restricted expression of the CD23a isoform

Ioana Visan1, Martin Goller, Ingolf Berberich

  • 1Medizinische Poliklinik, University of Würzburg, Würzburg, Germany.

European Journal of Immunology
|May 6, 2003
PubMed

Insights

Pax-5, a B-cell transcription factor, drives B-cell-specific CD23a isoform expression. This finding reveals Pax-5 as a key regulator for CD23a, impacting inflammatory responses.

Area of Science:

  • Immunology
  • Molecular Biology

Background:

  • Human CD23, the low-affinity IgE receptor, is a B cell marker implicated in inflammation.
  • Two isoforms, CD23a and CD23b, exist, differing in cytoplasmic domains and expression patterns.
  • CD23b is induced by IL-4 in B and myeloid cells, while CD23a is B-cell restricted.

Purpose of the Study:

  • To investigate the role of Pax-5 transcription factor in regulating the B-cell-specific CD23a isoform expression.
  • To elucidate the molecular mechanisms underlying CD23a promoter activation by Pax-5.

Main Methods:

  • Analysis of the CD23a promoter for Pax-5 binding sites using electrophoretic mobility shift assays.
  • Site-directed mutagenesis to assess the functional importance of the identified Pax-5 binding site.
  • Reporter gene assays in 293 cells to measure promoter activity upon Pax-5 expression.
  • Ectopic expression of Pax-5 in U-937 monocytic cells to evaluate CD23a induction.

Main Results:

  • A functional Pax-5 binding site was identified in the CD23a promoter.
  • Pax-5 binding to this site was confirmed via electrophoretic mobility shift assays and abrogated by mutation.
  • Pax-5 significantly activated the CD23a core promoter in 293 cells.
  • Ectopic Pax-5 expression in U-937 cells induced CD23a expression under specific stimulation conditions.

Conclusions:

  • Pax-5 is a critical regulator of B-cell-specific CD23a isoform expression.
  • The findings highlight Pax-5's role in controlling CD23a transcription, potentially influencing B cell differentiation and inflammatory processes.

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