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Poly(ADP‐ribosyl)ation of Signal Transducer And Activator of Transcription (STAT)6 by Poly(ADP‐ribose) Polymerase (PARP)‐1 Is Critical for Its Integrity And Subsequent Regulation of Th2 Cytokines during Asthma
Author(s) -
Wang Jeffrey,
Ghonim Mohamed,
Ibba Salome Valentina,
Pyakurel Kusma,
Lammi Matthew,
Boulares Hamid
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.820.7
Subject(s) - poly adp ribose polymerase , stat protein , stat6 , transcription factor , biology , signal transduction , dna damage , microbiology and biotechnology , stat , stat3 , cytokine , cancer research , immunology , chemistry , interleukin 4 , enzyme , polymerase , dna , biochemistry , gene
Background Although asthma is often controlled by corticosteroids and β2‐adrenergic agonists, many individuals cannot control the disease with these therapies. Identifying the key molecular mechanisms the disease is key to establishing strategies to improve the quality of life of asthmatics. Our laboratory performed a series of pioneering studies revealing the critical role of PARP‐1, classically regarded as a DNA repair enzyme, in asthma pathogenesis by controlling NF‐kB nuclear retention and STAT6 integrity. PARP‐1 inhibition destabilizes STAT6, a transcription factor central to Th2 cytokine signaling, upon IL‐4 or allergen exposure, potentially through a calpain‐dependent mechanism. Hypothesis PARP‐1 interacts with IL‐4‐activated STAT6 and modifies it for maintaining STAT6 integrity leading, ultimately, to expression of Th2 cytokines. Methods A cell‐free recombinant protein‐based enzymatic reactions, in vitro stimulation of primary splenocytes with IL‐4, histidine‐tag pulldown, and co‐immunoprecipitation with subsequent immunoblot were utilized to conduct the studies. Results PARP‐1 was activated in lungs and PBMCs of human asthmatics. STAT6 interacted with and was poly(ADP‐ribosyl)ated (PARylated) by PARP‐1 in both the cell‐free system and in IL‐4‐treated mouse splenocytes. PARylation of STAT6 was enhanced by JAK kinase‐3. Phosphorylation rendered STAT6 more susceptible to degradation by mu‐calpain but PARylation protected it from such degradation. Intriguingly, these events occurred in the complete absence of damaged DNA. Consistent with these results, IL‐4 stimulation‐induced PARylation of STAT6 by PARP‐1 was not accompanied with a DNA damage response as assessed by p53 phosphorylation. Conclusion Modification of STAT6 by PARP‐1 through a DNA damage‐independent mechanism is critical in Th2 responses and overall asthma pathogenesis. Based on the prediction that the IL4/STAT6 pathway is upregulated in asthma, concomitant with elevated phosphorylation of STAT6, activated STAT6 in cells of patients with the disease should be highly susceptible to degradation upon PARP inhibition, leading to an extensive reduction in the expression of Th2 genes. Support or Funding Information Louisiana Cancer Research Center Cancer Center