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.