Functional characterization of the hypusine amino acid

Author(s)

Leticia Tamborlin

• Document type: Doctoral Thesis
• Press: Rio Claro. 2023-03-29.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
• Defense date: 2023-02-24
• Advisor: Augusto Ducati Luchessi

Abstract

Hypusine amino acid [Nε-(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 the cells to apoptosis. The treatment also decreased the content of the eIF5A-encoding transcript and the global protein synthesis profile, which may occur due to negative feedback in response to high hypusine concentration. Hypusine could have affected the protein content and/or the hypusination of newly synthesized eIF5A and led to stagnation in 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 results, and the relationship between eIF5A and tumoral development, 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 as a free amino acid and not as an essential component of the eiF5A protein. (AU)

• FAPESP's process: 17/21914-1 - Functional characterization of the amino acid hypusine
• Grantee: Leticia Tamborlin
• Support Opportunities: Scholarships in Brazil - Doctorate