Research objectives and content
The small GTP binding protein Ras plays an important role on T cell receptor-induced regulation of transcriptional activation (NFAT activation) in T cells, acting through multiple effector pathways. One of these pathways is dependent on the GTPase Rac-1 that links Ras to transcription factors phosphorylation and AP-1 activation. The aim of the present project is to characterize the Rac-dependent Ras effector pathways that regulate AP-1/NFAT transcriptional activation in T cells. The objectives will be the analysis of the upstream pathways involved in the regulation of Rac by Ras, and the study of the proximal Rac effector pathways leading to transcriptional regulation. By the use of mutants of Ras that selectively activate different effector pathways of Ras combined with inhibitory mutants of Rac the pathways involved on Rac-dependent responses leading to transcriptional activation will be studied. The role of PI 3-kinase on Rac activation will be analyzed studying the ability of constitutively active forms of the enzyme to induce Rac-dependent responses in T cells. Mutated forms of Rac that selectively interact with specific Rac target molecules will be generated and used to establish the Rac effector pathways responsible for transcriptional activation. Constitutively active and inhibitory mutants of the Ser/Thr kinase PAK will be also generated and used to establish the role of this Rac target in T cell responses. By screening T cell cDNA libraries looking for proteins that contain the established Rac binding motif (CRIB motif) novel putative T cell Rac effectors will be identified.
Training content (objective, benefit and expected impact)
With the completion of this research project we expect to characterize Rac signalling pathways involved in the regulation of T lymphocyte activation. These results would contribute to improve our understanding of how Ras controlls this process, and add novel insights into the mechanisms of regulation by Ras of other lymphocyte functions relevant for immune responses.