Elucidating the role of eIF5A and the polyamine pathway during cellular senescence

• Applicant: Fabricio Loayza-Puch, Ph.D.
• Subject Area: Cell Biology ; General Genetics and Functional Genome Biology ; Biochemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545215964

Senescence is a cellular stress program that impedes the replication of aging and damaged cells. Senescent cells release various cytokines collectively known as the senescence-associated secretory phenotype (SASP), impacting surrounding tissue and immune response. In early tumorigenesis stages, the SASP primarily plays a protective role by stimulating the immune system to clear pre-malignant cells. Prolonged exposure to the SASP, however, is linked to chronic inflammation and the malignant conversion of neighboring cells. Thus, selectively eliminating senescent cells (senolytics) or modulating specific SASP components (senostatics) is a promising strategy for cancer treatment. Although many transcriptional regulators of the SASP have been extensively characterized, little is known about translational control during cellular senescence. Our team discovered that senescent cells exhibit higher rates of protein synthesis compared to proliferating cells. Using a novel CRISPR-Cas9 screen, we found that senescent cells are highly dependent on the activity of eIF5A to sustain high rates of protein synthesis. Additionally, we uncovered key components of polyamine metabolism as direct targets of p53, suggesting that p53 may contribute to sustaining the activity of eIF5A during cellular senescence. Proteomics experiments revealed that upon eIF5A inactivation, mitochondrial ribosomal proteins are selectively down-regulated in senescent cells, indicating that eIF5A is required to sustain mitochondrial translation and function. Building on these findings, we propose to elucidate the role of eIF5A in cellular senescence and uncover the polyamine pathway's role in this process, with three independent and complementary aims. Aim 1: Determine whether mitochondrial translation and function are regulated by eIF5A. For this purpose, we propose to combine functional assays and ribosome profiling to study the effect of eIF5A on mitochondrial activity and the generation of the mitochondrial translation machinery in different senescence contexts. Aim 2: Elucidate the role of the polyamine pathway in regulating the activity of eIF5A during cellular senescence. Using metabolite tracing and biochemical approaches, we will determine how the polyamine pathway is rewired during cellular senescence and how it affects eIF5A activity. Aim 3: Elucidate the role of eIF5A in senescence in vivo. Here, we will employ well-established mouse models of oncogene-induced senescence in vivo to define the role of eIF5A during senescence surveillance and to study the effect of eIF5A on the tumor-promoting functions of the SASP. The results of this proposal will elucidate how eIF5A and the polyamine pathway regulate mitochondrial translation and function and how they affect immune surveillance and the growth of fully established tumors. These findings will have important implications for the development of novel senostatic therapeutic strategies.

• DFG Programme: Research Grants