RasGRP1 Transduces Low-Grade TCR Signals which Are Critical for T Cell Development, Homeostasis, and Differentiation

• Published in: Immunity (Cambridge, Mass.) Mass.), 2002-11, Vol.17 (5), p.617-627
• Main Authors: Priatel, John J, Teh, Soo-Jeet, Dower, Nancy A, Stone, James C, Teh, Hung-Sia
• Format: Article
• Language: English
• Subjects: Animals; Cell Differentiation - immunology; DNA-Binding Proteins - immunology; Flow cytometry; Gene expression; Guanine Nucleotide Exchange Factors; Homeostasis - immunology; Hypotheses; Kinases; Labeling; Ligands; Lymphocyte Activation - immunology; Lymphocytes; MAP Kinase Signaling System - immunology; Medical research; Mice; Receptors, Antigen, T-Cell - immunology; Rodents; Signal Transduction - immunology; T-Lymphocyte Subsets - immunology
• ISSN: 1074-7613; 1097-4180
• DOI: 10.1016/S1074-7613(02)00451-X

Two important Ras-guanyl nucleotide exchange factors, Sos and RasGRP1, control Ras activation in thymocytes. However, the relative contribution of these two exchange factors to Ras/ERK activation and their resulting impact on positive and negative selection is unclear. We have produced two lines of RasGRP1 −/− TCR transgenic mice to determine the effect of RasGRP1 in T cell development under conditions of defined TCR signaling. Our results demonstrate that RasGRP1 is crucial for thymocytes expressing weakly selecting TCRs whereas those that express stronger selecting TCRs are more effective at utilizing RasGRP1-independent mechanisms for ERK activation and positive selection. Analysis of RasGRP1 −/− peripheral T cells also revealed hitherto unidentified functions of RasGRP1 in regulating T cell homeostasis and sustaining antigen-induced developmental programming.