Cirtical role for Salmonella effector SopB in regulating inflammasome activation

Mol Immunol. 2017 Oct:90:280-286. doi: 10.1016/j.molimm.2017.07.011. Epub 2017 Aug 30.


Objective: Salmonella is known to evolve many mechanisms to avoid or delay inflammasome activation which remain largely unknown. In this study, we investigated whether the SopB protein critical to bacteria virulence capacity was an effector that involved in the regulation of inflammasome activation.

Methods: BMDMs from NLRC4-, NLRP3-, caspase-1/-11-, IFI16- and AIM2-deficient mice were pretreated with LPS, and subsequently stimulated with a series of SopB-related strains of Salmonella, inflammasome induced cell death, IL-1β secretion, cleaved caspase-1 production and ASC speckle formation were detected.

Results: We found that SopB could inhibit host IL-1β secretion, caspase-1 activation and inflammasome induced cell death using a series of SopB-related strains of Salmonella; however the reduction of IL-1β secretion was not dependent on sensor that contain PYD domain, such as NLRP3, AIM2 or IFI16, but dependent on NLRC4. Notably, SopB specifically prevented ASC oligomerization and the enzymatic activity of SopB was responsible for the inflammasome inhibition. Furthermore, inhibition of Akt signaling induced enhanced inflammasome activation.

Conclusions: These results revealed a novel role in inhibition of NLRC4 inflammasome for Salmonella effector SopB.

Keywords: Inflammasome activation; NLRC4; Phosphatase activity; Salmonella; SopB.

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / genetics*
  • Apoptosis Regulatory Proteins / metabolism
  • Bacterial Proteins / genetics*
  • CARD Signaling Adaptor Proteins
  • Calcium-Binding Proteins / genetics*
  • Caspase 1 / genetics
  • Caspase 1 / metabolism*
  • Caspases / genetics
  • Caspases, Initiator
  • DNA-Binding Proteins / genetics
  • Enzyme Activation / immunology
  • Immune Evasion*
  • Inflammasomes / immunology*
  • Interleukin-1beta / metabolism
  • Lipopolysaccharides / pharmacology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • NLR Family, Pyrin Domain-Containing 3 Protein / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Salmonella / genetics
  • Salmonella / immunology*


  • Aim2 protein, mouse
  • Apoptosis Regulatory Proteins
  • Bacterial Proteins
  • CARD Signaling Adaptor Proteins
  • Calcium-Binding Proteins
  • DNA-Binding Proteins
  • IL1B protein, mouse
  • Inflammasomes
  • Interleukin-1beta
  • Ipaf protein, mouse
  • Lipopolysaccharides
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Nlrp3 protein, mouse
  • Pycard protein, mouse
  • Proto-Oncogene Proteins c-akt
  • SopB protein, Salmonella
  • Casp4 protein, mouse
  • Caspases
  • Caspases, Initiator
  • Caspase 1