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 3

PAD2-mediated citrullination reciprocally regulates the activity of GATA3 and RORγt.

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PAD2-mediated citrullination reciprocally regulates the activity of GATA...
(A and B) Differentiated WT DBA/1J (W) and PAD2-KO (K) Th cells were restimulated with anti-CD3 (A and B) or left unstimulated (B) for 24 hours. The transcript levels of GATA3 and RORγt from 3 independent experiments are shown in A (2-tailed Student’s t test). The levels of GATA3 and RORγt proteins were analyzed with Western blotting. Representative Western blots from 5 independent experiments are shown in B. The normalized density of GATA3 and RORγt proteins is shown in the bar graphs of B (2-tailed Student’s t test). The averaged levels in WT cells without restimulation were arbitrarily set as 1. (C and D) HEK-293 cells were transfected with indicated luciferase reporters and expression vectors. Luciferase activity obtained from cells without exogenous PAD2, GATA3, and RORγt was arbitrarily set as 1 (2-tailed paired Student’s t test). Data points from the same experiments are connected with lines. Fractions of the cell extract from 2 experiments was subjected to Western blotting using indicated antibodies to demonstrate the expression of exogenous proteins and endogenous Lamin B. Representative Western blots are shown.