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SLAP, a dimeric adapter protein, plays a functional role in T cell receptor signaling
J Tang1, S Sawasdikosol, J H Chang
1Department of Pediatric Oncology, Dana-Farber Cancer Institute and Department of Pediatrics, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA.
Abstract:
Engagement of the T cell antigen receptor (TCR) leads to rapid activation of protein tyrosine kinases, which in turn phosphorylate downstream enzymes and adapter proteins. Some adapter proteins, such as SLP-76, Vav, and LAT, positively regulate TCR-mediated signal transduction, whereas others, such as Cbl, play an inhibitory role. SLAP (Src-like adapter protein), an adapter protein containing a Src homology 3 and a Src homology 2 domain, was isolated from a yeast interacting screen by using N-terminal Cbl as bait. N-terminal Cbl interacts with SLAP in vivo and in vitro in a tyrosine phosphorylation-independent manner. We observed that SLAP is expressed in T cells, and upon TCR activation, SLAP interacts with ZAP-70, Syk, LAT, and TCRzeta chain in Jurkat T cells. In transiently transfected COS-7 cells, SLAP forms separate complexes with ZAP-70, Syk, and LAT through its Src homology 2 domain. Overexpression of a C-terminal-truncated SLAP mutant down-regulates nuclear factor of activated T cells-AP1 activity. We have evidence that SLAP forms homodimers through its C-terminal region. Serial truncations and mutations in the C terminus of SLAP demonstrate that there is a correlation between the loss of dimerization and the inhibition of nuclear factor of activated T cells-AP1 activity. The in vivo association of SLAP with key signaling molecules and its inhibition of T cell activation suggests that SLAP plays an important role in TCR-mediated signal transduction.
Insights
Src-like adapter protein (SLAP) inhibits T cell activation by interacting with key signaling molecules after T cell receptor engagement. This interaction is crucial for regulating T cell signaling pathways.
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- T cell receptor (TCR) engagement activates protein tyrosine kinases, initiating signal transduction pathways.
- Adapter proteins play critical roles in modulating TCR signaling, with some acting as positive regulators (e.g., SLP-76, Vav, LAT) and others as inhibitors (e.g., Cbl).
Purpose of the Study:
- To investigate the role of Src-like adapter protein (SLAP) in T cell receptor-mediated signal transduction.
- To elucidate the molecular mechanisms by which SLAP influences T cell activation.
Main Methods:
- Yeast interacting screen using N-terminal Cbl as bait to identify SLAP.
- In vivo and in vitro interaction studies.
- Analysis of SLAP interactions with signaling molecules (ZAP-70, Syk, LAT, TCRzeta) in Jurkat T cells upon TCR activation.
- Transient transfection of COS-7 cells to study SLAP complex formation.
- Overexpression of SLAP mutants to assess effects on nuclear factor of activated T cells-AP1 activity.
- Analysis of SLAP homodimerization through its C-terminal region.
Main Results:
- SLAP interacts with Cbl in a tyrosine phosphorylation-independent manner.
- SLAP is expressed in T cells and forms complexes with ZAP-70, Syk, LAT, and TCRzeta upon TCR activation.
- SLAP's Src homology 2 domain mediates interactions with ZAP-70, Syk, and LAT.
- Overexpression of a C-terminal-truncated SLAP mutant inhibits nuclear factor of activated T cells-AP1 activity.
- SLAP forms homodimers via its C-terminal region, and loss of dimerization correlates with inhibition of NFAT-AP1 activity.
Conclusions:
- SLAP associates with key signaling molecules in T cells following TCR engagement.
- SLAP functions as an inhibitor of T cell activation, likely through its ability to dimerize and modulate signaling pathways.
- SLAP plays a significant role in the regulation of TCR-mediated signal transduction.