The proteasome cap RPT5/Rpt5p subunit prevents aggregation of unfolded ricin A chain
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Standard
The proteasome cap RPT5/Rpt5p subunit prevents aggregation of unfolded ricin A chain. / Pietroni, Paola; Vasisht, Nishi; Cook, Jonathan P; Roberts, David M; Lord, J Michael; Hartmann-Petersen, Rasmus; Roberts, Lynne M; Spooner, Robert A.
I: Biochemical Journal, Bind 453, Nr. 3, 2013, s. 435-445.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - The proteasome cap RPT5/Rpt5p subunit prevents aggregation of unfolded ricin A chain
AU - Pietroni, Paola
AU - Vasisht, Nishi
AU - Cook, Jonathan P
AU - Roberts, David M
AU - Lord, J Michael
AU - Hartmann-Petersen, Rasmus
AU - Roberts, Lynne M
AU - Spooner, Robert A
PY - 2013
Y1 - 2013
N2 - The plant cytotoxin ricin enters mammalian cells by receptor-mediated endocytosis, undergoing retrograde transport to the endoplasmic reticulum (ER) where its catalytic A chain (RTA) is reductively separated from the holotoxin to enter the cytosol and inactivate ribosomes. The currently accepted model is that the bulk of ER-dislocated RTA is degraded by proteasomes. We show here that the proteasome has a more complex role in ricin intoxication than previously recognised, that the previously reported increase in sensitivity of mammalian cells to ricin in the presence of proteasome inhibitors simply reflects toxicity of the inhibitors themselves, and that RTA is a very poor substrate for proteasomal degradation. Denatured RTA and casein compete for a binding site on the regulatory particle of the 26S proteasome, but their fates differ. Casein is degraded, but the mammalian 26S proteasome AAA-ATPase subunit RPT5 acts as a chaperone that prevents aggregation of denatured RTA and stimulates recovery of catalytic RTA activity in vitro. Furthermore, in vivo, the ATPase activity of Rpt5p is required for maximal toxicity of RTA dislocated from the Saccharomyces cerevisiae ER. Our results implicate RPT5/Rpt5p in the triage of substrates in which either activation (folding) or inactivation (degradation) pathways may be initiated.
AB - The plant cytotoxin ricin enters mammalian cells by receptor-mediated endocytosis, undergoing retrograde transport to the endoplasmic reticulum (ER) where its catalytic A chain (RTA) is reductively separated from the holotoxin to enter the cytosol and inactivate ribosomes. The currently accepted model is that the bulk of ER-dislocated RTA is degraded by proteasomes. We show here that the proteasome has a more complex role in ricin intoxication than previously recognised, that the previously reported increase in sensitivity of mammalian cells to ricin in the presence of proteasome inhibitors simply reflects toxicity of the inhibitors themselves, and that RTA is a very poor substrate for proteasomal degradation. Denatured RTA and casein compete for a binding site on the regulatory particle of the 26S proteasome, but their fates differ. Casein is degraded, but the mammalian 26S proteasome AAA-ATPase subunit RPT5 acts as a chaperone that prevents aggregation of denatured RTA and stimulates recovery of catalytic RTA activity in vitro. Furthermore, in vivo, the ATPase activity of Rpt5p is required for maximal toxicity of RTA dislocated from the Saccharomyces cerevisiae ER. Our results implicate RPT5/Rpt5p in the triage of substrates in which either activation (folding) or inactivation (degradation) pathways may be initiated.
U2 - 10.1042/BJ20130133
DO - 10.1042/BJ20130133
M3 - Journal article
C2 - 23617410
VL - 453
SP - 435
EP - 445
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
IS - 3
ER -
ID: 47229600