Membrane-organizing protein moesin controls Treg differentiation and antitumor immunity via TGF-β signaling
Ephraim A. Ansa-Addo, Yongliang Zhang, Yi Yang, George S. Hussey, Breege V. Howley, Mohammad Salem, Brian Riesenberg, Shaoli Sun, Don C. Rockey, Serhan Karvar, Philip H. Howe, Bei Liu, Zihai Li
Ephraim A. Ansa-Addo, Yongliang Zhang, Yi Yang, George S. Hussey, Breege V. Howley, Mohammad Salem, Brian Riesenberg, Shaoli Sun, Don C. Rockey, Serhan Karvar, Philip H. Howe, Bei Liu, Zihai Li
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Research Article Immunology

Membrane-organizing protein moesin controls Treg differentiation and antitumor immunity via TGF-β signaling

Abstract

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that are important for organizing membrane domains and receptor signaling and regulating the migration of effector T cells. Whether moesin plays any role during the generation of TGF-β–induced Tregs (iTregs) is unknown. Here, we have discovered that moesin is translationally regulated by TGF-β and is also required for optimal TGF-β signaling that promotes efficient development of iTregs. Loss of moesin impaired the development and function of both peripherally derived iTregs and in vitro–induced Tregs. Mechanistically, we identified an interaction between moesin and TGF-β receptor II (TβRII) that allows moesin to control the surface abundance and stability of TβRI and TβRII. We also found that moesin is required for iTreg conversion in the tumor microenvironment, and the deletion of moesin from recipient mice supported the rapid expansion of adoptively transferred CD8+ T cells against melanoma. Our study establishes moesin as an important regulator of the surface abundance and stability of TβRII and identifies moesin’s role in facilitating the efficient generation of iTregs. It also provides an advancement to our understanding about the role of the ERM proteins in regulating signal transduction pathways and suggests that modulation of moesin is a potential therapeutic target for Treg-related immune disorders.

Authors

Ephraim A. Ansa-Addo, Yongliang Zhang, Yi Yang, George S. Hussey, Breege V. Howley, Mohammad Salem, Brian Riesenberg, Shaoli Sun, Don C. Rockey, Serhan Karvar, Philip H. Howe, Bei Liu, Zihai Li

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Figure 6

Cell-intrinsic moesin controls efficient surface abundance of TβRII.

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Cell-intrinsic moesin controls efficient surface abundance of TβRII. (A ...
(A and B) Flow cytometry analysis of surface TβRII on CD4+, CD8+, and B220+ cells from the spleen (A) and mesenteric lymph node (MLN) (B) of 6- to 8-week-old straight-WT and Msn KO littermate mice. (C) Reconstituted 1:1 mix of WT (CD45.1, black) and Msn KO (CD45.2, red) bone marrow chimeric mice were euthanized after 10 weeks, and surface TβRII expression on CD4+, CD8+ T cells in the spleen was analyzed. Spleen: WT n = 7, Msn KO n = 8; MLN: WT n = 8, Msn KO n = 10; mBMCs: n = 5. (D) Flow cytometry analysis of surface TβRII expression on differentiated iTregs from WT and Msn KO mice. ΔMFI represents differences between WT and Msn KO cells. (E) Flow cytometry of intracellular moesin and surface TβRII levels on scrambled or Msn KD EL4 cells without TGF-β stimulation. (F) Immunoblot of TβRII, pSMAD3, total SMAD3, phospho-Akt2 (pAkt2), and total Akt2 in EL4 cells untreated (UT) or stimulated for 30 minutes with TGF-β (5 ng/ml). Data are representative of several independent experiments (E and F). (G and H) Confocal microscopy images of unstimulated EL4 thymoma cells fixed/permeabilized and stained intracellularly with anti-TβRII antibodies. Data represent at least 3 experiments. Blue dashed lines (right panel) indicate magnified region of interest; red arrowheads indicate surface TβRII. Relative fluorescence intensity was calculated using ImageJ software (NIH). Scale bar: 3 μm. (I) Immunoblot following Endo H and PNGase F treatment of whole cell lysate of CD4+ T cells from WT and Msn KO mice. Data represent the mean ± SEM (A–C) or mean ± SD (H). **P < 0.01, ***P < 0.001 by Student’s t test.