Date of Award
2025
Document Type
Thesis (Ph.D.)
Department or Program
Biochemistry and Cell Biology
First Advisor
Charles Barlowe
Abstract
The Endoplasmic Reticulum (ER), the site of secretory protein biosynthesis
provides a favorable environment to promote polypeptide folding, protein
oligomerization and export. Although the ER contains many chaperones and other
factors that assist in protein folding, this process is error prone. Eukaryotes have
evolved protein quality control checkpoints to maintain homeostasis in the secretory
pathway, however these processes are imperfect and may result in proteotoxicity
when toxic levels or aggregates of proteins arise. Mutations in proteins involved in
trafficking in the early secretory pathway are closely associated with disease states.
Therefore, it is of great interest to further understand how misfolded proteins and the
potentially toxic effects of such proteins are mitigated in the early secretory pathway.
The Erv41-Erv46 complex is a retrograde cargo receptor that has been
shown to retrieve ER resident proteins from the Golgi back to the ER. Intriguingly,
other studies have shown that deletion of the Erv41 subunit which destabilizes the
complex results in increased turnover of a model misfolded substrate, CPY* and
unfolded protein response (UPR) down-regulation. With this knowledge, we propose
that Erv41-Erv46, in addition to retrieval of ER resident cargo, also functions in
retrograde trafficking of misfolded proteins. Through this body of work, we support a
model in which Erv41-Erv46 preferentially retrieves misfolded proteins with luminal
lesions from the Golgi to the ER. Cycloheximide chase and immunoprecipitation (IP)
experiments show that Erv41-Erv46 deficient cells fail to retrieve CPY*, resulting in
its vacuolar degradation or secretion. Additionally, Erv41-Erv46 directly and
preferentially binds this misfolded protein over its native, folded counterpart, CPY in
IP and in vitro reconstitution assays. These data and findings from this study
support a model in which Erv41-Erv46 directly binds misfolded proteins at the Golgi
for return to the ER.
Recommended Citation
Fuesler, John Andrew, "Characterization of the Erv41-Erv46 complex as a retrograde receptor for misfolded secretory proteins" (2025). Dartmouth College Ph.D Dissertations. 405.
https://digitalcommons.dartmouth.edu/dissertations/405
