Identification of Inhibitors for eIF5A2-Dependent Translation Elongation by Monitoring the Translational Efficiency of Polyproline Motif in Mitochondrial Fission Regulator 1

We previously reported that eukaryotic translation initiation factor 5A2 (eIF5A2), rather than eIF5A1, is important for the proliferation of HeLa S3 and MDA-MB-231 cells, despite the 84% amino acid sequence identity between eIF5A1 and eIF5A2. In addition, individual upregulated genes, including mitochondrial fission regulator 1 (MTFR1), which has a proline-rich motif, by eIF5A2 were different from those in eIF5A1. Thus, eIF5A2-dependent translational elongation is a promising target for cancer treatment with minimal side effects. In this study, we constructed a high-throughput screening system to identify eIF5A2-dependent translation elongation inhibitors by monitoring the translation efficiency of the MTFR1-luciferase fusion protein in HeLa S3 cells. Orlistat and andrographolide (AGP) were suggested as inhibitors of eIF5A2-dependent translation elongation among 1744 compounds from libraries. In addition to the findings related to AGP, the present study revealed that orlistat and the silencing of eIF5A2 suppressed the invasive activity of MDA-MB-231 cells. Downregulation of heparanase 1 expression, but not of matrix metalloproteinase-2 (MMP2) and MMP9, by eIF5A2 silencing was similar to that by treatment with orlistat and AGP, suggesting that orlistat and AGP were, at least in part, capable of attenuating eIF5A2-dependent translation elongation through the repression of eIF5A2 expression. Based on these observations, monitoring the translational efficiency of MTFR1 synthesis may be useful for identifying new eIF5A2 inhibitors.