Subtilase cytotoxin, produced by Shiga-toxigenic Escherichia coli, transiently inhibits protein synthesis of Vero cells via degradation of BiP and induces cell cycle arrest at G1 by downregulation of cyclin D1.
Subtilase cytotoxin (SubAB) is a AB(5) type toxin produced by Shiga-toxigenic Escherichia coli, which exhibits cytotoxicity to Vero cells. SubAB B subunit binds to toxin receptors on the cell surface, whereas the A subunit is a subtilase-like serine protease that specifically cleaves chaperone BiP/Grp78. As noted previously, SubAB caused inhibition of protein synthesis. We now show that the inhibition of protein synthesis was transient and occurred as a result of ER stress induced by cleavage of BiP; it was closely associated with phosphorylation of double-stranded RNA-activated protein kinase-like ER kinase (PERK) and eukaryotic initiation factor-2alpha (eIF2alpha). The phosphorylation of PERK and eIF2alpha was maximal at 30-60 min and then returned to the control level. Protein synthesis after treatment of cells with SubAB was suppressed for 2 h and recovered, followed by induction of stress-inducible C/EBP-homologous protein (CHOP). BiP degradation continued, however, even after protein synthesis recovered. SubAB-treated cells showed cell cycle arrest in G1 phase, which may result from cyclin D1 downregulation caused by both SubAB-induced translational inhibition and continuous prolonged proteasomal degradation.
Morinaga
Naoko
N
Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8- Inohana,Chiba 260-8670, Japan. nmorinaga@faculty.chiba-u.jp
Yahiro
Kinnosuke
K
Matsuura
Gen
G
Moss
Joel
J
Noda
Masatoshi
M
D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects*; D002522:Chlorocebus aethiops; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D029968:Escherichia coli Proteins / Q000494:pharmacology*; D005434:Flow Cytometry; D016193:G1 Phase / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054323:Shiga-Toxigenic Escherichia coli / Q000201:enzymology*; D013381:Subtilisins / Q000494:pharmacology*; D014709:Vero Cells
D000091342:Endoplasmic Reticulum Chaperone BiP; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D019938:Cyclin D1; D013381:Subtilisins; C527234:subtilase cytotoxin, E coli