Poster abstracts
Poster number 74 submitted by Daniel Judge
Studying the Mechanism for Ribosome-Inactivating Protein-Induced Apoptosis
Daniel M. Judge (West Virginia University), Jennifer E.G. Gallagher (West Virginia University)
Abstract:
Apoptosis, a conserved process of programmed cell death, can be activated through diverse cellular mechanisms, many of which remain poorly understood. This study focuses on a specific mechanism triggered by ribosome-inactivating proteins (RIP), a category of potent toxins such as ricin and sarcin. Ricin halts translation by irreversibly damaging large ribosomal subunit rRNA through an adenine N-glycosidic cleavage referred to as depurination. While the role of the catalytic subunit of ricin, known as ricin toxin A chain (RTA), is well-established, the precise process that initiates apoptosis in RTA-compromised cells remains unclear. Importantly, while ricin induces apoptosis, translation inhibitors employing mechanisms other than depurination, such as the peptidyl transferase inhibitor anisomycin, often only induce cell cycle arrest. Ribosome depurination may be a critical step in initiating apoptosis. We hypothesize that ribosomes translating on the same mRNA would collide with the stalled depurinated ribosome resulting in improper recycling when translation terminates. The resulting physical damage to ribosomes would activate ribosome quality control mechanisms, ultimately leading to apoptosis. In this study, we will utilize an in vivo ricin reporter plasmid to modulate RTA gene expression and examine the apoptotic response in Saccharomyces cerevisiae. We will closely monitor ribosomal biogenesis, localization, and degradation before and during apoptosis and compare the effects of wildtype RTA to catalytically dead mutants such as E177K, S215F, and P95L, which do not induce apoptosis. Genetic screens will be conducted to identify the essential elements required for ricin-induced apoptosis, and in-lab evolution experiments will be carried out to identify mutations that confer resistance to ricin-induced apoptosis. Long-term, this research aims to provide a comprehensive understanding of the cellular pathways affected after exposure to RTA and establish a controlled method for reliably inducing apoptosis in specific target cells. The insights gained from this study are likely to have broader implications in the fields of cancer biology, embryology, and immunology, offering new avenues for exploring cellular homeostasis and understanding how cells respond to stress.
Keywords: Stress, Ribosomes, Apoptosis