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A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins
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Published on: March 22, 2012

Interaction between Sam68 and Src family tyrosine kinases, Fyn and Lck, in T cell receptor signaling

N Fusaki1, A Iwamatsu, M Iwashima

  • 1Department of Microbiology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi-shi, Osaka 570, Japan.

The Journal of Biological Chemistry
|March 7, 1997
PubMed

Insights

The RNA-binding protein Sam68 (Src associated in mitosis, 68 kDa) is tyrosine-phosphorylated downstream of T cell receptor (TCR)-coupled Fyn and Lck kinases. This identifies Sam68 as a key signaling molecule in lymphocyte activation pathways.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • The Src family kinase Fyn is crucial for T cell receptor (TCR)-mediated signaling.
  • Overexpression of Fyn is observed in the human T cell leukemia virus type 1-infected T cell line, Hayai.

Purpose of the Study:

  • To identify downstream signaling molecules of Fyn in T cells.
  • To investigate the role of Sam68 in TCR signaling pathways.

Main Methods:

  • Analysis of tyrosine phosphorylation in Hayai cells.
  • Coimmunoprecipitation assays to identify interacting proteins.
  • Protein purification and microsequencing.
  • Association studies with Src family kinases.

Main Results:

  • A 68-kDa protein, identified as Sam68, was constitutively tyrosine-phosphorylated in Hayai cells.
  • Sam68 coimmunoprecipitated with multiple signaling proteins, suggesting an adapter function.
  • Sam68 associates with Fyn and Lck kinases.
  • CD3 cross-linking induced Sam68 tyrosine phosphorylation in uninfected T cells.

Conclusions:

  • Sam68 acts as a signaling molecule downstream of TCR-coupled Src family kinases (Fyn and Lck) in lymphocytes.
  • Sam68 plays a role in lymphocyte signal transduction beyond its known function in mitosis.

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