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Syk is involved in NLRP3 inflammasome-mediated caspase-1 activation through adaptor ASC phosphorylation and enhanced

Ying-Cing Lin1, Duen-Yi Huang1, Jang-Shiun Wang1

  • 1*Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Medical Sciences and Institute for Cancer Biology and Drug Discovery, Taipei Medical University, Taipei, Taiwan; Institute of Biomedical Sciences and Genomics Research Center, Academia Sinica, Taipei, Taiwan; and Department of Family Medicine, National Taiwan University Hospital, Taipei, Taiwan.

Journal of Leukocyte Biology
|January 22, 2015
PubMed

Insights

Spleen tyrosine kinase (Syk) directly phosphorylates the ASC adaptor protein, enhancing NLRP3 inflammasome assembly and caspase-1 activation. This discovery reveals a new Syk-dependent pathway for controlling immune responses and treating related diseases.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cellular Signaling

Background:

  • NLRP3 inflammasome activation is critical for detecting danger signals and initiating immune responses.
  • Dysregulated NLRP3 inflammasome activity contributes to various inflammatory diseases.
  • The precise mechanism by which Spleen tyrosine kinase (Syk) influences NLRP3 inflammasome activation remains incompletely understood.

Purpose of the Study:

  • To elucidate the molecular mechanism linking Syk to NLRP3 inflammasome activation.
  • To investigate Syk's role in procaspase-1 processing and caspase-1 activation.
  • To identify specific interactions and modifications mediated by Syk within the inflammasome complex.

Main Methods:

  • Utilized a reconstituted NLRP3 inflammasome system in HEK293T cells.
  • Investigated Syk's kinase activity requirement for caspase-1 activation.
  • Performed co-immunoprecipitation assays to assess protein-protein interactions.
  • Identified and validated phosphorylation sites on the ASC adaptor protein using mutagenesis and phospho-specific antibodies.

Main Results:

  • Syk kinase activity is essential for potentiating NLRP3-induced caspase-1 activation.
  • Syk directly binds to both NLRP3 and the ASC adaptor protein via its kinase domain.
  • Syk phosphorylates ASC at tyrosine residues Y146 and Y187.
  • Phosphorylation of ASC by Syk is critical for enhanced ASC oligomerization and procaspase-1 recruitment.

Conclusions:

  • Syk acts as a key signaling molecule that promotes NLRP3 inflammasome formation through ASC phosphorylation.
  • This newly identified Syk-dependent pathway offers a potential therapeutic target for modulating NLRP3 inflammasome activation.
  • Targeting Syk activity may provide a strategy for treating NLRP3-associated inflammatory and immune diseases.
Keywords:
ATPIL-1βNLRtyrosine kinase

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