BopC is a novel type III effector secreted by Bordetella bronchiseptica and has a critical role in type III-dependent necrotic cell death.
In Bordetella bronchiseptica, the functional type III secretion system (TTSS) is required for the induction of necrotic cell death in infected mammalian cells. To identify the factor(s) involved in necrotic cell death, type III-secreted proteins from B. bronchiseptica were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and electrospray ionization tandem mass spectrometry. We identified a 69-kDa secreted protein designated BopC. The gene encoding BopC is located outside of the TTSS locus and is also highly conserved in both Bordetella parapertussis and Bordetella pertussis. The results of a lactate dehydrogenase release assay and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assay demonstrated that BopC is required for necrotic cell death. It has been reported that tyrosine-phosphorylated proteins (PY) of host cells are dephosphorylated during B. bronchiseptica infection in a TTSS-dependent manner. We found that BopC is also involved in PY dephosphorylation in infected host cells. It appears that the necrotic cell death triggered by BopC occurs prior to the PY reduction in host cells, because Bordetella-induced cell death was not affected even in the presence of a dephosphorylation inhibitor. Furthermore, a translocation assay showed that the signal sequence for both secretion into culture supernatant and translocation into the host cell is located in 48 amino acid residues of the BopC N terminus. This report reveals for the first time that a novel type III effector, BopC, is required for the induction of necrotic cell death during Bordetella infection.
Kuwae
Asaomi
A
Laboratory of Bacterial Infection, Kitasato Institute for Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, USA.
Matsuzawa
Takeshi
T
Ishikawa
Naoto
N
Abe
Hiroyuki
H
Nonaka
Takashi
T
Fukuda
Hiroyuki
H
Imajoh-Ohmi
Shinobu
S
Abe
Akio
A
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001885:Bordetella Infections / Q000378:metabolism* / Q000473:pathology; D016950:Bordetella bronchiseptica / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006801:Humans; D009336:Necrosis; D010766:Phosphorylation; D014443:Tyrosine / Q000378:metabolism
D001426:Bacterial Proteins; D014443:Tyrosine