Controlled Access. Restriction lift date: 2034-12-31
Differential regulation of the phosphorylated and dephosphorylated forms of the ubiquitin-conjugating enzyme Ubc6e
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Date
2024
Authors
Burns, Stephanie
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
The ubiquitin proteasome system (UPS) is a key stress response employed by cells to remove damaged and misfolded proteins that accumulate in the endoplasmic reticulum (ER) during energy deprivation, hypoxia, or viral infection. Ubc6e is an ER-localised ubiquitin-conjugating enzyme that plays an important role in the proteasomal degradation of misfolded proteins and can be phosphorylated at serine residue 184. Recent studies have demonstrated that Ubc6e is co-localised with p62/sequestrosome, which is a cargo receptor that delivers ubiquitinated cargo to autophagosomes for degradation.
To further investigate the possible role that Ubc6e may play in autophagy, we aimed to investigate any protein-protein interactions between p62 and Ubc6e and we also aimed to investigate the effect of autophagic-related proteins, p62 and ULK1 on Ubc6e. From our research, we saw that Ubc6e levels are reduced when co-expressed with proteins that promote autophagy. Specifically for the autophagy inducer ULK1, we saw differential regulation between the phosphorylated and dephosphorylated forms of Ubc6e, suggesting that the S184 phosphorylation may protect the protein from autophagic degradation.
Degradation of the dephosphorylated form, on the other hand, did not depend on S184 phosphorylation, or the catalytic activity of Ubc6e. Neither was it dependent absolutely on ER localisation. Finally, although ULK1 co-expression did not appear to specifically alter the ER/ perinuclear localisation of Ubc6e, it was noted that amino-terminal tagging with GFP led to a ULK1-related localisation of Ubc6e to intracellular vesicles. Together our results suggest that Ubc6e does play a role in autophagy however it is not mediated by the direct interaction with p62.
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Controlled Access
Keywords
Ubiquitin-conjugating enzyme , Ubc6e , Autophagy , p62 , ULK1 , The unfolded protein response , Endoplasmic reticulum-associated degradation
Citation
Burns, S. 2024. Differential regulation of the phosphorylated and dephosphorylated forms of the ubiquitin-conjugating enzyme Ubc6e. MRes Thesis, University College Cork.