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Updated: Jul 16, 2025

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
Published on: May 26, 2011
Lhs1 dependent ERAD is determined by transmembrane domain context.
Maria Sukhoplyasova1, Abigail M Keith1, Emma M Perrault1
1Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A.
The endoplasmic reticulum chaperone Lhs1 targets specific unglycosylated transmembrane proteins with two transmembrane domains (TMDs) for degradation. Lhs1-dependent degradation also involves the Hrd1 ubiquitin ligase, offering insights into substrate identification.
Area of Science:
- Cell Biology
- Protein Folding
- Endoplasmic Reticulum Quality Control
Background:
- Transmembrane proteins require specific folding and integration into the ER membrane.
- Folding occurs in distinct cellular compartments (ER lumen, lipid bilayer, cytosol) with unique chaperones.
- ER-associated degradation (ERAD) machinery identifies misfolded proteins.
Purpose of the Study:
- To clarify the substrate specificity of the ER lumenal chaperone Lhs1 in ERAD.
- To identify features dictating Lhs1-dependent degradation.
- To understand Lhs1's role in protein quality control.
Main Methods:
- Investigated Lhs1's role in the degradation of epithelial sodium channel (ENaC) subunits.
- Analyzed features of Lhs1-dependent ERAD substrates.
- Examined the impact of disrupting ENaC subunit assembly on degradation.
- Assessed the overlap between Lhs1 and Hrd1 ubiquitin ligase pathways.
Main Results:
- Lhs1-dependent substrates are unglycosylated and possess two transmembrane domains (TMDs).
- Orphaned or unassembled TMDs characterize Lhs1 substrates.
- Disrupting ENaC trimer assembly triggers Lhs1-dependent degradation of the entire complex.
- Lhs1 acts on a subset of ERAD substrates also requiring the Hrd1 ubiquitin ligase.
Conclusions:
- Lhs1 targets specific transmembrane proteins, characterized by unglycosylation and multiple TMDs.
- Inter-subunit interactions influence Lhs1-mediated degradation.
- Lhs1 and Hrd1 collaborate in specific ERAD pathways.
- Identified key features for Lhs1 substrate recognition, potentially applicable to mammalian homolog GRP170.
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