When starved of nutrients, Dictyostelium amoebae stop dividing and aggregate into multicellular entities. Multicellular development is followed by the cellular differentiation of unique cell types. The PI of this award will address the fundamental question of how environmental signals (amino acid deprivation in particular) trigger the amoeba to aggregate. The PI previously found that the protein GCN2 is a sensor of amino acid deprivation in Dictyostelium. Dictyostelium actually has three GCN2 proteins, termed Ifks (initiation factor kinases) that are important in the synthesis of proteins. GCN2 has two distinct domains: a protein kinase domain that phosphorylates the alpha subunit of eIF2, and a histidyl-tRNA synthetase (HisRS) domain that binds uncharged tRNAs that accumulate during amino acid starvation. The PI has proposed a model suggesting that GCN2 binds to uncharged tRNA, which elicits a conformation change in GCN2. This change facilitates phosphorylation of the eIF2 domain and, thus, regulates translation of other proteins. With this award, the PI will test this model by 1) extending their genetic analyses of GCN2 proteins to IfkC, 2) creating mutant forms of eIF-2alpha, and 3) searching for new substrates of the Ifks using a proteomics approach. In addition to discovering how GCN2 proteins function in regulating Dictyostelium development, the findings from this study may reveal the functions of GCN2 proteins and other eIF2 kinases in the development of other organisms, including humans. Much of the past work in the PIs laboratory was accomplished by undergraduates performing independent and honors research. This will continue for the proposed experiments, along with appropriate and extensive mentoring activities to assist in training the next generation of scientists.
