Reciprocal regulation of Th2 and Th17 cells by PAD2-mediated citrullination
Bo Sun, Hui-Hsin Chang, Ari Salinger, Beverly Tomita, Mandar Bawadekar, Caitlyn L. Holmes, Miriam A. Shelef, Eranthie Weerapana, Paul R. Thompson, I-Cheng Ho
Bo Sun, Hui-Hsin Chang, Ari Salinger, Beverly Tomita, Mandar Bawadekar, Caitlyn L. Holmes, Miriam A. Shelef, Eranthie Weerapana, Paul R. Thompson, I-Cheng Ho
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Research Article Immunology

Reciprocal regulation of Th2 and Th17 cells by PAD2-mediated citrullination

Abstract

Dysregulated citrullination, a unique form of posttranslational modification catalyzed by the peptidylarginine deiminases (PADs), has been observed in several human diseases, including rheumatoid arthritis. However, the physiological roles of PADs in the immune system are still poorly understood. Here, we report that global inhibition of citrullination enhances the differentiation of type 2 helper T (Th2) cells but attenuates the differentiation of Th17 cells, thereby increasing the susceptibility to allergic airway inflammation. This effect on Th cells is due to inhibition of PAD2 but not PAD4. Mechanistically, PAD2 directly citrullinates GATA3 and RORγt, 2 key transcription factors determining the fate of differentiating Th cells. Citrullination of R330 of GATA3 weakens its DNA binding ability, whereas citrullination of 4 arginine residues of RORγt strengthens its DNA binding. Finally, PAD2-deficient mice also display altered Th2/Th17 immune response and heightened sensitivity to allergic airway inflammation. Thus, our data highlight the potential and caveat of PAD2 as a therapeutic target of Th cell–mediated diseases.

Authors

Bo Sun, Hui-Hsin Chang, Ari Salinger, Beverly Tomita, Mandar Bawadekar, Caitlyn L. Holmes, Miriam A. Shelef, Eranthie Weerapana, Paul R. Thompson, I-Cheng Ho

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Figure 1

Modulation of in vivo and in vitro differentiation of Th cells by global inhibition of citrullination.

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Modulation of in vivo and in vitro differentiation of Th cells by global...
(A) Indicated C57BL/6 Th cells were left unstimulated (–) or restimulated with anti-CD3 (+) overnight. The level of cit-H3 was examined with Western blotting using anti–cit-H3. The normalized density of cit-H3 is shown in the bar graph (n = 3, 1-way ANOVA). (B and C) C57BL/6 effector Th cells were generated in the presence of Cl-am at indicated concentrations for 5 days. Whole Th2 extract was examined with Western blotting using indicated antibodies. Representative blots and normalized density of cit-H3 from 2 experiments are shown in B. The expression of indicated cytokines by the Th cells after restimulation with anti-CD3 is shown in C (n = 4, 1-way ANOVA). (D) Primary human Th cells from 5 healthy donors were differentiated in vitro into Th2 or Th17 cells in the presence or absence of Cl-am (100 μM). The production of IL-4 and IL-17A after restimulation with anti-CD3 was quantified with ELISA. Data points from the same donors are connected with lines (1-tailed paired Student’s t test). (E–I) Allergic airway inflammation was induced in C57BL/6 mice (n = 6 per group) in the absence or presence of Cl-am. Splenocytes were restimulated with ovalbumin for 72 hours. The levels of IL-4 and IL-17A in supernatant are shown in E. Imm, immunized; cha, challeneged. The levels of ovalbumin-specific (ova-specific) IgE and IgG1 in serum are shown in F. Representative H&E staining of the lung tissue is shown in G. Scale bars: 100 μm. The total number of cells (H) and the percentage of eosinophils (I) in bronchial lavage are also shown. Statistical analysis for E, F, H, and I was performed with 2-tailed Student’s t test.