EDEM is involved in retrotranslocation of ricin from the endoplasmic reticulum to the cytosol

The plant toxin ricin is transported retrogradely from the cell surface to the endoplasmic reticulum (ER) from where the enzymatically active part is retrotranslocated to the cytosol, presumably by the same mechanism as used by misfolded proteins. The ER degradation enhancing alpha-mannosidase I-lik...

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Bibliographic Details
Published in:Molecular biology of the cell 2006-04, Vol.17 (4), p.1664-1675
Main Authors: Slominska-Wojewodzka, Monika, Gregers, Tone F, Wälchli, Sébastien, Sandvig, Kirsten
Format: Article
Language:English
Subjects:
Alkaloids - pharmacology
Animals
Cells, Cultured
Cytosol - metabolism
Endoplasmic Reticulum - metabolism
Enzyme Inhibitors - pharmacology
Humans
Immunoprecipitation
Membrane Proteins - antagonists & inhibitors
Membrane Proteins - genetics
Membrane Proteins - metabolism
Mice
Neoplasm Proteins - genetics
Neoplasm Proteins - metabolism
Protein Folding
Protein Transport - genetics
Puromycin - pharmacology
Ricin - metabolism
RNA Interference
SEC Translocation Channels
Transcriptional Activation
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Summary:The plant toxin ricin is transported retrogradely from the cell surface to the endoplasmic reticulum (ER) from where the enzymatically active part is retrotranslocated to the cytosol, presumably by the same mechanism as used by misfolded proteins. The ER degradation enhancing alpha-mannosidase I-like protein, EDEM, is responsible for directing aberrant proteins for ER-associated protein degradation. In this study, we have investigated whether EDEM is involved in ricin retrotranslocation. Overexpression of EDEM strongly protects against ricin. However, when the interaction between EDEM and misfolded proteins is inhibited by kifunensin, EDEM promotes retrotranslocation of ricin from the ER to the cytosol. Furthermore, puromycin, which inhibits synthesis and thereby transport of proteins into the ER, counteracted the protection seen in EDEM-transfected cells. Coimmunoprecipitation studies revealed that ricin can interact with EDEM and with Sec61alpha, and both kifunensin and puromycin increase these interactions. Importantly, vector-based RNA interference against EDEM, which leads to reduction of the cellular level of EDEM, decreased retrotranslocation of ricin A-chain to the cytosol. In conclusion, our results indicate that EDEM is involved in retrotranslocation of ricin from the ER to the cytosol.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.e05-10-0961