Pseudomonas aeruginosa injects NDK into host cells through a type III secretion system.
Pseudomonas aeruginosa is a Gram-negative opportunistic human pathogen possessing a type III secretion system (T3SS) which injects toxic effector proteins into mammalian host cells. In previous studies, P. aeruginosa strains lacking all of the known type III effectors were shown to cause cytotoxicity upon prolonged infection time. In this study, we report the identification of a new cytotoxin, nucleoside diphosphate kinase (NDK), which is injected into eukaryotic cells in a T3SS-dependent manner. Injection of NDK is inhibited by the presence of previously known effectors of the T3SS, with an effectorless strain injecting the highest amount, suggesting active competition with the known T3SS effectors. NDK is shown to cause a cytotoxic response when expressed in eukaryotic cells, and P. aeruginosa strains harbouring NDK also show a greater toxicity than strains lacking it. Interestingly, the cytotoxic effect of intracellular NDK is independent of its kinase activity. In previous studies, NDK was shown to be secreted into culture supernatants via a type I secretion system and cause cytotoxicity in a kinase-dependent manner. Therefore, the current study highlights an alternative route of NDK secretion as well as two different cytotoxic mechanisms of NDK, depending on the extra- or intra-cellular location of the protein.
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
Dennis
D
Neeld
Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
Yongxin
Y
Jin
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
Candace
C
Bichsel
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
Jinghua
J
Jia
Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
Jianhui
J
Guo
Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
Fang
F
Bai
Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
Weihui
W
Wu
Department of Biotechnology and Bioinformatics, Korea University, Sejong, Republic of Korea.
Un-Hwan
UH
Ha
Department of Pathology, University of Florida, Gainesville, FL, USA.
Naohiro
N
Terada
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
Shouguang
S
Jin
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D058947:Bacterial Secretion Systems; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002470:Cell Survival; D005260:Female; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D009701:Nucleoside-Diphosphate Kinase / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D017384:Sequence Deletion
D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D001427:Bacterial Toxins; D011993:Recombinant Fusion Proteins; D009701:Nucleoside-Diphosphate Kinase