The palmitoylation switch in activated T cells.
In this proposal we investigate the palmitoylation switch in T cells after stimulation. So far, proteins with in- creased palmitoylation upon cellular activation were identified by a systematic screen. On the one hand, we focused on the molecular characterization of certain DHHC enzymes (DHHC18 and DHHC20) that are found inducibly autopalmitoylated and thus are likely to be responsible for increased target palmitoylation. On the other hand, we investigated the role of palmitoylation for the SNARE protein VAMP7, which is a known player in cytokine secretion of T cells. Development of an On-plate-palmitoylation assay (OPPA) allowed us to demonstrate that DHHC18 effectively palmitoylates VAMP7 at cysteine 183 and that the short but not the long isoform of DHHC18 requires autopalmitoylation at a membrane proximal cysteine (Cys-138) to exert its activity. Functional investigations on the role of VAMP7’s palmitoylated cysteine are ongoing and are supported by lipidomics and proteomics studies investigating the microenvironment of these proteins in dependence of pal- mitoylation. We will build on these findings and further delineate both the mechanistic underpinnings and func- tional roles of the palmitoylation switch for DHHC18 and VAMP7 in the coming funding period. We will extend this analysis to question the role of DHHC3 and of palmitoylated target proteins such as the Gα subunits of trimeric G proteins for T cell stimulation-dependent processes. The overarching goal is to relate the composi- tional and conformational changes of selected proteins with the palmitoylation-induced alterations in cellular function following a TCR stimulatory event.