PP2A enables IL-2 signaling by preserving IL-2Rβ chain expression during Treg development
Amir Sharabi, … , Vaishali R. Moulton, George C. Tsokos
Amir Sharabi, … , Vaishali R. Moulton, George C. Tsokos
Published March 26, 2019
Citation Information: JCI Insight. 2019;4(9):e126294. https://doi.org/10.1172/jci.insight.126294.
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Research Article Cell biology

PP2A enables IL-2 signaling by preserving IL-2Rβ chain expression during Treg development

Abstract

Tregs require IL-2 signaling for signal transducer and activator of transcription 5–mediated (STAT5-mediated) induction of Foxp3. Although phosphatase 2A (PP2A) is a negative regulator of IL-2 production in effector T cells and Tregs do not produce IL-2, it is not known whether PP2A controls IL-2 signaling in Tregs. To explore the role of PP2A in IL-2 signaling in Tregs, we studied mice engineered to lack PP2A in all Foxp3-expressing cells. We report that PP2A is required to enable Foxp3 expression and to maintain sufficient numbers of Tregs in the thymus. We show for the first time to our knowledge that PP2A prevents the selective loss of surface IL-2Rβ and preserves IL-2R signaling potency in Tregs. The loss of IL-2Rβ in thymus- and spleen-derived Tregs that lack PP2A is because of increased sheddase activity. Pan-sheddase or selective ADAM10 (a disintegrin and metalloproteinase 10) inhibition, like forced expression of IL-2Rβ in PP2A-deficient Tregs, restored IL-2Rβ expression and signaling. Thus, PP2A restrains the sheddase activity of ADAM10 in Tregs to prevent the cleavage of IL-2Rβ from the cell surface to enable competent IL-2R signaling, which is essential for Tregs’ development and homeostasis.

Authors

Amir Sharabi, Hao Li, Isaac R. Kasper, Wenliang Pan, Esra Meidan, Maria G. Tsokos, Vaishali R. Moulton, George C. Tsokos

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Figure 2

PP2A controls IL-2Rβ expression and IL-2 signaling in thymic CD4+ Tregs.

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PP2A controls IL-2Rβ expression and IL-2 signaling in thymic CD4+ Tregs....
(A) Phosphorylated STAT5 (p-STAT5) following stimulation with IL-2 (20 mM, 20 minutes) in PP2A-sufficient (WT) and PP2A-deficient (KO) thymic CD4+ Tregs from individual mice (n = 4–5/group). Representative histograms and cumulative data (mean ± SEM) from a representative of 3 experiments are shown. (B) Nonlinear regression analysis of dose-response curves (top) reflecting the MFI levels of p-STAT5 in WT and KO thymic CD4+ Tregs following stimulation with a dose range of IL-2 and a table for p-STAT5 EC50 values as calculated from these curves (bottom) from a representative of 3 biological replicates. (C) Expression of the IL-2Rβ chain (CD122) and IL-2Rγ chain (CD132) in thymic CD4+ Tregs from WT and KO mice (n = 5/group). Representative histograms and cumulative data (mean ± SEM) from a representative of 3 experiments are shown. Dashed-line histograms represent negative control. (D) IL-2Rβ expression in thymic CD4+ Tregs from WT mice (n = 3) following incubation with the PP2A inhibitor okadaic acid. Representative histograms and cumulative data (mean ± SEM) from a representative of 3 experiments are shown. (E) Tyrosine phosphorylation (p-Y364) of CD122 and total levels of CD122 and β-actin in thymic CD4+ Tregs as detected by Western blot analysis of lysates that were pooled from WT and KO mice (n = 3–4/group). Representative blots and cumulative data (mean ± SEM) from 2 independent experiments are shown. *P < 0.05; ***P < 0.001.