The RNA-binding protein IMP2 drives a stromal-Th17 cell circuit in autoimmune neuroinflammation
Rami Bechara, Nilesh Amatya, Saikat Majumder, Chunsheng Zhou, Yang Li, Qixing Liu, Mandy J. McGeachy, Sarah L. Gaffen
Rami Bechara, Nilesh Amatya, Saikat Majumder, Chunsheng Zhou, Yang Li, Qixing Liu, Mandy J. McGeachy, Sarah L. Gaffen
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Research Article Immunology

The RNA-binding protein IMP2 drives a stromal-Th17 cell circuit in autoimmune neuroinflammation

Abstract

Stromal cells are emerging as key drivers of autoimmunity, partially because they produce inflammatory chemokines that orchestrate inflammation. Chemokine expression is regulated transcriptionally but also through posttranscriptional mechanisms, the specific drivers of which are still incompletely defined. CCL2 (MCP1) is a multifunctional chemokine that drives myeloid cell recruitment. During experimental autoimmune encephalomyelitis (EAE), an IL-17–driven model of multiple sclerosis, CCL2 produced by lymph node (LN) stromal cells was essential for immunopathology. Here, we showed that Ccl2 mRNA upregulation in human stromal fibroblasts in response to IL-17 required the RNA-binding protein IGF-2 mRNA-binding protein 2 (IGF2BP2, IMP2), which is expressed almost exclusively in nonhematopoietic cells. IMP2 binds directly to CCL2 mRNA, markedly extending its transcript half-life, and is thus required for efficient CCL2 secretion. Consistent with this, Imp2−/− mice showed reduced CCL2 production in LNs during EAE, causing impairments in monocyte recruitment and Th17 cell polarization. Imp2–/– mice were fully protected from CNS inflammation. Moreover, deletion of IMP2 after EAE onset was sufficient to mitigate disease severity. These data showed that posttranscriptional control of Ccl2 in stromal cells by IMP2 was required to permit IL-17–driven progression of EAE pathogenesis.

Authors

Rami Bechara, Nilesh Amatya, Saikat Majumder, Chunsheng Zhou, Yang Li, Qixing Liu, Mandy J. McGeachy, Sarah L. Gaffen

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Figure 4

Th1- and Th17-extrinsic activities of IMP2.

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Th1- and Th17-extrinsic activities of IMP2. (A) IMP2 expression by Weste...
(A) IMP2 expression by Western blot on whole cell lysates from CD4+ T cells cultured in Th0 conditions (lanes 1, 3, 5, 7) and Th17 conditions (IL-6, IL-23, TGF-β, and IL-1β) (lanes 2, 4, 6, 8). Control lysates from Imp2+/+ and Imp2–/– MEFs (lanes 9 and 10). (B) Diagram of in vitro CD4+ T cell polarization conditions. (C–E) CD4+ T cells were isolated from spleen and stimulated for 3 days with plate-bound anti-CD3 and anti-CD28 under Th0 or optimal Th17 conditions (IL-6, IL-23, TGF-β, and IL-1β) for 3 days. (C) Cells were stimulated with PMA/ionomycin for 4 hours, stained for CD4 and IL-17, and quantified by flow cytometry. Right: representative FACS plots from 3 independent experiments. (D) ELISA was performed on supernatants collected after 3 days of treatment with anti-CD3 and anti-CD28. Data were pooled from 2 independent experiments. (E) qPCR of the indicated mRNAs in T cells after 3 days of anti-CD3 and anti-CD28. Data show fold change mean ± SEM from 2 independent experiments. (F) CD4+ T cells were isolated from spleen and stimulated for 3 days with plate-bound anti-CD3 and anti-CD28 under Th0 or Th1 conditions (IL-12). ELISA was performed on supernatants collected after 3 days of anti-CD3 plus anti-CD28. (G and H) CD4+ T cells were isolated from spleen and stimulated for 3 days with plate-bound anti-CD3 and anti-CD28 under Th0 or optimal Th17 conditions (G) (IL-6, IL-23, TGF-β, and IL-1β) or suboptimal Th17 conditions (H) (IL-6 and TGF-β) ± CCL2 for 3 days. ELISA was performed on supernatants collected after 3 days of anti-CD3 plus anti-CD28. Each symbol represents 1 mouse. *P < 0.05, **P < 0.01, ****P < 0.0001 by ANOVA with post hoc Tukey’s test.