T cell receptor (TCR) stimulation activates the small GTPase Rap1A, which is reported to antagonize Ras signaling and induces T cell anergy. To address its role in vivo, we generated transgenic mice that constitutively expressed active Rap1A within the T cell lineage. We found that active Rap1A did not interfere with the Ras signaling pathway or antagonize T cell activation. Instead of anergy, the T lymphocytes that constitutively expressed active Rap1A showed enhanced TCR-mediated responses, both in thymocytes and mature T cells. In addition, Rap1A activation was sufficient to induce strong activation of the 1 and 2 integrins via an avidity-modulation mechanism. This shows that, far from playing an inhibitory role during T cell activation, Rap1A positively influences T cells by augmenting lymphocyte responses and directing integrin activation.
- T lymphocytes
Sebzda, E., Bracke, M., Tugal, T., Hogg, N., & Cantrell, D. A. (2002). Rap1A positively regulates T cells via integrin activation rather than inhibiting lymphocyte signaling. Nature Immunology, 3(3), 251-258. https://doi.org/10.1038/ni765