SseL, a Salmonella deubiquitinase required for macrophage killing and virulence.
Expression of the Salmonella enterica serovar Typhimurium pathogenicity island 2 (SPI-2) type III secretion system is controlled by the two-component regulatory system SsrA-SsrB. We used a transcriptomic approach to help define the SsrA-SsrB regulon. We identified a gene encoding an uncharacterized effector (SseL) whose translocation into host cells depends on the SPI-2 secretion system. SseL has similarities to cysteine proteases with deubiquitinating activity. A GST-SseL fusion protein specifically hydrolyzed mono- and polyubiquitin substrates in vitro with a preference for K63-linked ubiquitin chains. Ubiquitin-modified proteins accumulated in macrophages infected with Salmonella sseL mutant strains but to a lesser extent when infected with bacteria expressing active protein, demonstrating that SseL functions as a deubiquitinase in vivo. Salmonella sseL mutant strains did not show a replication defect or induce altered levels of cytokine production upon infection of macrophages but were defective for a delayed cytotoxic effect and were attenuated for virulence in mice.
Rytkönen
Anne
A
Department of Infectious Diseases, Centre for Molecular Microbiology and Infection and Division of Molecular Biosciences, Imperial College London, Flowers Building, Armstrong Road, London SW7 2AZ, United Kingdom.
Poh
John
J
Garmendia
Junkal
J
Boyle
Cliona
C
Thompson
Arthur
A
Liu
Mei
M
Freemont
Paul
P
Hinton
Jay C D
JC
Holden
David W
DW
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics* / Q000378:metabolism; D007118:Immunoassay; D047468:Immunoprecipitation; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020411:Oligonucleotide Array Sequence Analysis; D018085:Regulon / Q000235:genetics*; D012475:Salmonella / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism
D001426:Bacterial Proteins; D008565:Membrane Proteins; C440638:SPI-2 protein, Salmonella; C119761:SsrB protein, Salmonella typhimurium; D014157:Transcription Factors; D025801:Ubiquitin; D010450:Endopeptidases