Cellular effects of eIF5A and of the hypusination inhibitor GC7 in autophagy using Saccharomyces cerevisiae as a model

Abstract

The eukaryotic translation factor 5A (eIF5A) is a highly conserved eukaryotic and archaea protein, essential for cell viability, and is involved in the control of cell proliferation, and in neoplastic and inflammatory processes. eIF5A has a unique amino acid, called hypusine, formed by a post-translational modification. The hypusine biosynthesis is dependent on the polyamine spermidine and involves two steps, catalyzed, respectively, by the enzymes deoxyhypusine synthase (DHS) and deoxyhypusinehydroxylase (DOHH). eIF5A is required for translation elongation of sequences of three or more amino acid residues that can cause ribosomal stalling, probably for assisting in the correct positioning of the peptidyl-tRNA for more efficient peptide-binding activity of the ribosome. The activity of eIF5A is inhibited by the N1-Guanyl-1,7-diaminoheptane (GC7) molecule, a structural analog of spermidine that competes for binding to DHS. However, GC7 has cellular effects independent of inhibition of hypusination, suggesting that this compound has other cellular targets. In addition, eIF5A and GC7 were related to autophagy, a catabolic lysosomal / vacuolar degradation process essential for the recycling of damaged or unnecessary cytoplasmic components and organelles. In the literature, there is controversy regarding the effect of eIF5A and GC7 on the regulation of autophagy. In addition, recent results from our laboratory suggest an effect of GC7 on a specific type of autophagy, ribophagy. Therefore, in this study, the relationship of eIF5A and GC7 in nonselective and selective autophagy using Saccharomyces cerevisiae yeast as a model will be investigated. We propose to analyze the cellular effects of eIF5A mutants and GC7 in relation to nonselective autophagy and ribophagy, as well as the lifespan phenotypes correlated with autophagy. (AU)