Thesis
Investigating the mechanisms of membrane protein recognition during protein quality control
- Abstract:
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Misfolded proteins in the Endoplasmic Reticulum (ER) are degraded by cytosolic proteasomes via a quality control system termed ER-associated protein degradation (ERAD). ERAD consists of multiple branches operating in parallel, defined by a membrane-embedded E3 ubiquitin ligase complex with specificity towards distinct substrates. To date, mechanisms of membrane substrate recognition, as well as the role of additional factors, such as intramembrane proteases, in this process, remain elusive.
Recent genome-wide CRISPR/Cas9 genetic screen for ERAD components implicated in the clearance of a model misfolded membrane protein, CYP51A1TM, identified a novel ERAD branch comprised of the RNF185/Membralin complex. Building on these initial observations, this thesis presents a mechanistic insight into quality control factors involved in membrane protein recognition by ERAD, using a range of interdisciplinary approaches. First, I have conducted a comparative analysis of simplified model substrates, derived from twenty human ER-membrane resident cytochrome P450 enzymes and investigated features that drive substrate recognition by the E3 ubiquitin ligase complexes. In addition, I have identified an aspartyl intramembrane protease, Signal Peptide Peptidase (SPP), as a non-canonical protein quality control factor involved in recognition and clearance of the human lanosterol demethylase CYP51A1, upstream of the RNF185/MBRL complex. Finally, we have discovered a novel substrate of the RNF185/MBRL complex and characterised the key determinants of its recognition by ERAD. This thesis further advances the knowledge on remarkable specificity of distinct ERAD branches, pinpointing determinants that drive membrane substrate recognition and selection for quality control.
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Authors
Contributors
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Pathology Dunn School
- Sub department:
- Pathology Dunn School
- Oxford college:
- Lincoln College
- Role:
- Supervisor
- ORCID:
- 0000-0002-9691-5277
- Funder identifier:
- https://ror.org/0472cxd90
- Funding agency for:
- Carvalho, P
- Grant:
- ERC consolidator grant (GA 817708)
- DOI:
- Type of award:
- DPhil
- Level of award:
- Doctoral
- Awarding institution:
- University of Oxford
- Language:
-
English
- Keywords:
- Deposit date:
-
2025-07-08
Terms of use
- Copyright holder:
- Nikita Sergejevs
- Copyright date:
- 2024
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