Independent Roles of Hypusinated and Unhypusinated eIF5A in Pancreas Growth and Development

The growth of the pancreas, including that of insulin-producing β cells, is dependent on the regulation of protein translation. The eukaryotic translation elongation factor eIF5A, when hypusinated by dexoyhypusine synthase (DHPS), is important for normal protein translation. Inhibition of DHPS impairs translation, growth, and proliferation of pancreatic cells; however, it is unknown if these consequences are due to loss of hypusinated eIF5A (eIF5A^Hyp) or to the accumulation of unhypusinated eIF5A (eIF5A^Lys). This dissertation interrogates this question through two main aims. First, DHPS or eIF5A expression is impaired in zebrafish embryos and in the β cells of HFD-fed mice. By comparing the phenotypes of these animals, it is possible to discern whether eIF5A^Lys has an active role in the inhibited pancreas tissue growth caused by DHPS loss. Second, pathways of eIF5A^Lys action are investigated by RNA-sequencing, and cell culture is used to detect interactions between eIF5A^Lys and proteins highlighted by RNA-sequencing. Overall, the data presented support the conclusion that eIF5A^Lys actively impairs pancreas cell growth by suppressing translation initiation through the integrated stress response kinase GCN2. This is a completely novel finding, as no independent function of eIF5A^Lys has been documented to date