Figure 2. Rho-GTPases regulate signaling pathways induced after TCR engagement. Schematic view of the signaling events induced in mature T cells after the recognition of an antigen presenting cell (APC) expressing peptide-MHC complexes. Binding of the T-cell receptor (TCR) to its ligand leads to a complex cascade of biochemical events that initiate distinct signaling pathways including (1) the Mitogen Activated Protein Kinase (MAPK) pathway including extracellular signal–regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK) and p38, (2) the Ca/calcineurin/NFAT pathway, and (3) the NF-κB pathway. Eventually, these signaling pathways result in the activation of transcription factors like AP-1, NFAT, and NF-κB, which control the gene expression program characteristic of activated T cells. Rho-GTPases regulate positively (blue arrows) or negatively (red lines) these TCR signaling pathways. For more details, see text.