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Phosphotyrosine-dependent association between CD22 and protein tyrosine phosphatase 1C

M A Campbell1, N R Klinman

  • 1Department of Immunology, Scripps Research Institute, La Jolla, CA 92037, USA.

European Journal of Immunology
|June 1, 1995
PubMed

Insights

Protein tyrosine phosphatase 1C (PTP1C) associates with CD22, a B cell surface protein, upon B cell activation. This interaction is crucial for signaling pathways linking membrane immunoglobulin to downstream cellular events.

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • CD22 is a B lymphocyte-specific glycoprotein involved in B cell activation.
  • Tyrosine phosphorylation of CD22 occurs upon B cell activation, suggesting a role in signaling.

Purpose of the Study:

  • To investigate if tyrosine phosphorylated CD22 links membrane immunoglobulin (mIg) signaling to downstream effectors.
  • To identify molecules that associate with CD22 after B cell activation.

Main Methods:

  • B cells were stimulated with anti-immunoglobulin (anti-Ig).
  • Coprecipitation assays were used to identify molecules associated with CD22.
  • Western blotting was employed to confirm protein identity and phosphorylation status.

Main Results:

  • A 60-kDa molecule was found to stably associate with CD22 after mIg cross-linking.
  • This 60-kDa molecule was identified as protein tyrosine phosphatase 1C (PTP1C).
  • The association between PTP1C and CD22 requires CD22 tyrosine phosphorylation but not PTP1C tyrosine phosphorylation.

Conclusions:

  • Tyrosine phosphorylated CD22 couples to PTP1C, a key signaling molecule in B lymphocytes.
  • This interaction suggests a novel signaling pathway mediated by CD22 in B cell activation.
  • PTP1C may play a regulatory role in CD22-mediated signaling downstream of mIg.

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