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Recognition of a single transmembrane degron by sequential quality control checkpoints
Laurence Fayadat1, Ron R Kopito
1Department of Biological Sciences, Stanford University, California 94305-5020, USA.
Molecular Biology of the Cell
|March 13, 2003
Summary
This study reveals two quality control checkpoints in the secretory pathway that degrade misfolded influenza hemagglutinin (HA) proteins, ensuring proper protein folding and cell surface display.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Folding
Background:
- The secretory pathway employs quality control mechanisms to ensure proper protein folding and trafficking.
- Proteolysis is a key process in protein degradation and quality control.
Purpose of the Study:
- To investigate the interplay between protein conformational maturation and quality control-mediated proteolysis.
- To determine if the secretory pathway has multiple checkpoints for protein quality control.
Main Methods:
- Engineered a known degron into the transmembrane domain of influenza hemagglutinin (HA).
- Assessed protein secondary structure, membrane integration, and N-linked glycosylation.
- Utilized site-specific cleavage and conformation-specific antibodies.
- Investigated degradation pathways using proteasome inhibitors and lysosomotropic amines.
Main Results:
- Mutant HA (HA++) with a membrane degron integrated into the membrane approximately 50% of the time.
- Non-integrated HA++ chains were degraded via the proteasome.
- Integrated HA++ molecules matured to the plasma membrane with native conformation.
- These native HA++ molecules were rapidly degraded via a lysosome-dependent pathway.
Conclusions:
- The secretory pathway possesses at least two sequential quality control checkpoints.
- These checkpoints recognize the same transmembrane degron.
- This system ensures the fidelity of protein deployment to the plasma membrane.