Location of Repository

Folding-competent and folding-defective forms of Ricin A chain have different fates following retrotranslocation from the endoplasmic reticulum

By Shuyu Li, Robert A. Spooner, Stuart C. H. Allen, Christopher P. Guise, Graham Ladds, Tina Schnöder, Manfred J. Schmitt, Mike Lord and L. M. (Lynne M.) Roberts


We report that a toxic polypeptide retaining the potential to refold upon dislocation from the endoplasmic reticulum (ER)\ud to the cytosol (ricin A chain; RTA) and a misfolded version that cannot (termed RTAΔ), follow ER-associated degradation\ud (ERAD) pathways in Saccharomyces cerevisiae that substantially diverge in the cytosol. Both polypeptides are dislocated\ud in a step mediated by the transmembrane Hrd1p ubiquitin ligase complex and subsequently degraded. Canonical\ud polyubiquitylation is not a prerequisite for this interaction because a catalytically inactive Hrd1p E3 ubiquitin ligase\ud retains the ability to retrotranslocate RTA, and variants lacking one or both endogenous lysyl residues also require the\ud Hrd1p complex. In the case of native RTA, we established that dislocation also depends on other components of the\ud classical ERAD-L pathway as well as an ongoing ER–Golgi transport. However, the dislocation pathways deviate\ud strikingly upon entry into the cytosol. Here, the CDC48 complex is required only for RTAΔ, although the involvement of\ud individual ATPases (Rpt proteins) in the 19S regulatory particle (RP) of the proteasome, and the 20S catalytic chamber\ud itself, is very different for the two RTA variants. We conclude that cytosolic ERAD components, particularly the\ud proteasome RP, can discriminate between structural features of the same substrate

Topics: QP
Publisher: American Society for Cell Biology
Year: 2010
OAI identifier: oai:wrap.warwick.ac.uk:4230

Suggested articles



  1. (2006). A luminal surveillance complex that selects misfolded glycoproteins for ER-associated degradation. doi
  2. (1999). A RING-H2 finger motif is essential for the function of Der3/Hrd1 in endoplasmic reticulum associated protein degradation in the yeast Saccharomyces cerevisiae. doi
  3. (2008). Cue1p is an activator of Ubc7p E2 activity in vitro and in vivo. doi
  4. (2001). Degradation of endoplasmic reticulum (ER) quality control substrates requires transport between the ER and Golgi. doi
  5. (2004). Distinct steps in dislocation of luminal endoplasmic reticulum-associated degradation substrates: roles of endoplasmic reticulum-bound p97/Cdc48p and proteasome. doi
  6. (2006). Distinct ubiquitin-ligase complexes define convergent pathways for the degradation of ER proteins. doi
  7. (2005). Endoplasmic reticulum-associated degradation of ricin A chain has unique and plant-specific features. doi
  8. (2003). ER-to-Golgi transport: doi
  9. (2001). HRD4/NPL4 is required for the proteasomal processing of ubiquitinated ER proteins. doi
  10. (1995). Intracellular folding of tissue-type plasminogen activator. Effects of disulfide bond formation on N-linked glycosylation and secretion. doi
  11. (2009). Mammalian OS-9 is upregulated in response to endoplasmic reticulum stress and facilitates ubiquitination of misfolded glycoproteins. doi
  12. (1993). Mutagenesis and kinetic analysis of the active site doi
  13. (2004). Reductive activation of ricin and ricin A-chain immunotoxins by protein disulfide isomerase and thioredoxin reductase. doi
  14. (2000). Ribosome-mediated folding of partially unfolded ricin A-chain. doi
  15. (1997). Role of Cue1p in ubiquitination and degradation at the ER surface. doi
  16. (1993). SEC12 encodes a guanine-nucleotideexchange factor essential for transport vesicle budding from the ER. doi
  17. (2007). The isolation and characterization of temperature-dependent ricin A chain molecules in Saccharomyces cerevisiae. doi
  18. (2002). The low lysine content of ricin A chain reduces the risk of proteolytic degradation after translocation from the endoplasmic reticulum to the cytosol. doi
  19. (2005). The role of p97/Cdc48p in endoplasmic reticulum-associated degradation: from the immune system to yeast. doi
  20. (2007). To be, or not to be—molecular chaperones in protein degradation. Cell Mol. Life Sci. doi
  21. (2010). Usa1p is required for optimal function and regulation of the Hrd1p ER-associated degradation (ERAD) ubiquitin ligase. doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.