Folding-competent and folding-defective forms of ricin A chain have different fates after retrotranslocation from the endoplasmic reticulum
| Autor: | Lynne M. Roberts, Shuyu Li, Graham Ladds, Stuart C H Allen, Tina Schnöder, Robert A. Spooner, Manfred J. Schmitt, Christopher P. Guise, J. Michael Lord |
|---|---|
| Rok vydání: | 2010 |
| Předmět: |
Proteasome Endopeptidase Complex
Protein Folding Saccharomyces cerevisiae Proteins Biosynthesis and Biodegradation Golgi Apparatus Ricin Saccharomyces cerevisiae Endoplasmic-reticulum-associated protein degradation Endoplasmic Reticulum Models Biological 03 medical and health sciences chemistry.chemical_compound symbols.namesake Cytosol Ubiquitin Molecular Biology 030304 developmental biology Gene Library 0303 health sciences biology Endoplasmic reticulum Hrd1p ubiquitin ligase complex Lysine 030302 biochemistry & molecular biology Ubiquitination Cell Biology Articles Golgi apparatus QP Ubiquitin ligase Cell biology Protein Transport chemistry Proteasome Biochemistry biology.protein symbols Mutant Proteins Protein Processing Post-Translational Gene Deletion Molecular Chaperones |
| Zdroj: | Molecular Biology of the Cell |
| ISSN: | 1939-4586 |
| Popis: | This study reveals that components of the yeast ERAD-L pathway can discriminate between two subtly different forms of the same toxin substrate. Although precytosolic requirements are similar for both toxin structures, there is a divergence in fate on the cytosolic face of the ER membrane. We report that a toxic polypeptide retaining the potential to refold upon dislocation from the endoplasmic reticulum (ER) to the cytosol (ricin A chain; RTA) and a misfolded version that cannot (termed RTAΔ), follow ER-associated degradation (ERAD) pathways in Saccharomyces cerevisiae that substantially diverge in the cytosol. Both polypeptides are dislocated in a step mediated by the transmembrane Hrd1p ubiquitin ligase complex and subsequently degraded. Canonical polyubiquitylation is not a prerequisite for this interaction because a catalytically inactive Hrd1p E3 ubiquitin ligase retains the ability to retrotranslocate RTA, and variants lacking one or both endogenous lysyl residues also require the Hrd1p complex. In the case of native RTA, we established that dislocation also depends on other components of the classical ERAD-L pathway as well as an ongoing ER–Golgi transport. However, the dislocation pathways deviate strikingly upon entry into the cytosol. Here, the CDC48 complex is required only for RTAΔ, although the involvement of individual ATPases (Rpt proteins) in the 19S regulatory particle (RP) of the proteasome, and the 20S catalytic chamber itself, is very different for the two RTA variants. We conclude that cytosolic ERAD components, particularly the proteasome RP, can discriminate between structural features of the same substrate. |
| Databáze: | OpenAIRE |
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