Hypusinated EIF5A as a feasible drug target for Advanced Medicinal Therapies in the treatment of pathogenic parasites and therapy-resistant tumors

Insights into eukaryotic translation initiation factor 5A: Its role and mechanisms in protein synthesis

The protein synthesis within eukaryotic cells is a complex process involving various translation factors. Among these factors, eukaryotic translation initiation factor 5 A (eIF5A) emerges as a crucial translation factor with high evolutionary conservation. eIF5A is unique as it is the only protein in eukaryotic cells containing the hypusine modification. Initially presumed to be a translation initiation factor, eIF5A was subsequently discovered to act mainly during the translation elongation phase. Notably, eIF5A facilitates the translation of peptide sequences containing polyproline stretches and exerts a universal regulatory effect on the elongation and termination phases of protein synthesis. Additionally, eIF5A indirectly affects various physiological processes within the cell by modulating the translation of specific proteins. This review provides a comprehensive overview of the structure, physiological functions, various post-translational modifications of eIF5A, and its association with various human diseases. The comparison between eIF5A and its bacterial homolog, EF-P, extends the discussion to the evolutionary conservation of eIF5A. This highlights its significance across different domains of life.

The first evidence of biological activity for free Hypusine, an enigmatic amino acid discovered in the '70s

Hypusine amino acid [N^ε-(4-amino-2-hydroxybutyl)-lysine] was first isolated in 1971 from bovine brain extracts. Hypusine originates from a post-translational modification at the eukaryotic translation initiation factor 5A (eIF5A), a protein produced by archaebacteria and eukaryotes. The eIF5A protein is the only one described containing the hypusine residue, which is essential for its activity. Hypusine as a free amino acid is a consequence of proteolytic degradation of eIF5A. Herein, we showed, for the first time, evidence of biological activity for the free hypusine. C6 rat glioma cells were treated with hypusine, and different cellular parameters were evaluated. Hypusine treatment significantly reduced C6 cell proliferation and potently suppressed their clonogenic capacity without leading to apoptosis. Hypusine also decreased the Eif5A transcript content and the global protein synthesis profile that may occur due to negative feedback in response to high hypusine concentration, controlling the content of newly synthesized eIF5A, which can affect the translation process. Besides, hypusine treatment also altered cellular metabolism by changing the pathways for energy production, reducing cellular respiration coupled with oxidative phosphorylation, and increasing the anaerobic metabolism. These observed results and the relationship between eIF5A and tumor processes led us to test the combination of hypusine with the chemotherapeutic drug temozolomide. Combining temozolomide with hypusine reduced the MTT conversion to the same levels as those observed using double temozolomide dosage alone, demonstrating a synergetic action between the compounds. Thus, since 1971, this is the first study showing evidence of biological activity for hypusine not associated with being an essential component of the eiF5A protein. Finding out the molecular targets of hypusine are the following efforts to completely characterize its biological activity.

Translation Factor Accelerating Peptide Bond Formation on the Ribosome: EF-P and eIF5A as Entropic Catalysts and a Potential Drug Targets

Elongation factor P (EF-P) and its eukaryotic homolog eIF5A are auxiliary translation factors that facilitate peptide bond formation when several sequential proline (Pro) residues are incorporated into the nascent chain. EF-P and eIF5A bind to the exit (E) site of the ribosome and contribute to favorable entropy of the reaction by stabilizing tRNA binding in the peptidyl transferase center of the ribosome. In most organisms, EF-P and eIF5A carry a posttranslational modification that is crucial for catalysis. The chemical nature of the modification varies between different groups of bacteria and between pro- and eukaryotes, making the EF-P-modification enzymes promising targets for antibiotic development. In this review, we summarize our knowledge of the structure and function of EF-P and eIF5A, describe their modification enzymes, and present an approach for potential drug screening aimed at EarP, an enzyme that is essential for EF-P modification in several pathogenic bacteria.