Biological Novelty through Adaptive Protein Synthesis in the Octopus - Abstract Biological Novelty through Adaptive Protein Synthesis in the Octopus Dysregulation of proteostasis coincides with the accumulation and aggregation of misfolded proteins, leading to neurodegeneration and pathogenesis of diseases such as Alzheimer’s, Parkinson’s, and Spinocerebellar ataxia. As the machinery responsible for synthesis of correctly decoded, functional proteins, ribosomes play a major role in determining proteostasis. Biochemical or genetic disruptions to ribosome accuracy are known to disrupt cellular proteostasis, causing neuronal death and severe cognitive or aging related defects. However, there has been minimal exploration of how to increase translation accuracy, and how this impacts proteostasis. Octopus bimaculoides presents an ideal model to study adaptation of the ribosome to improve proteostasis in a multicellular organism. Octopuses rely heavily on proteostasis, as they develop rapidly and possess extremely complex nervous systems consisting of approximately 500 million neurons, the most of any invertebrate animal. I recently made the serendipitous discovery that the large 28S rRNA of the octopus contains a unique rRNA break in the highly conserved catalytic center of the ribosome. This rRNA break is conserved among octopuses but not other cephalopods or mollusks. Importantly, my preliminary findings reveal that the octopus rRNA break increases accuracy of protein synthesis. By obtaining a cryo-EM structure of the O. bimaculoides ribosome, I find the octopus-specific break is found in the E-site near the site of deacylated tRNA binding. I propose to determine how this modification affects the ribosome and manifests in larger phenotypes through a combination of biochemical, structural, and cellular approaches. I will compare the direct functional consequences of this modification to the ribosomal active site by utilizing ribosome-dependent in vitro reconstitution assays. This will be complemented by performing cryo-EM on the octopus ribosome in different states of protein synthesis to determine how these functional changes manifest on a molecular level on the ribosome. Lastly, I will investigate differences in protein aggregation and resistance to neurotoxicity mediated by this novel ribosomal modification. This will be investigated in vitro using my reconstitution system, and in vivo through a comparative biology approach with animal neuron primary culture. I will also utilize a yeast genetics model to demonstrate targeting of the ribosomal RNA to mimic the break with the goal of improving translation accuracy and proteostasis. The proposed experiments will elucidate a novel mechanism underlying the ribosome regulation of protein synthesis which can lead to greater cellular functions and resistances.
