Phosphorylation status determines the opposing functions of Smad2/Smad3 as STAT3 cofactors in TH17 differentiation.

Jeong-Hwan Yoon,Dae-Kee Kim,Takeshi Imamura,Susumu Nakae,Katsuko Sudo,Takayuki Sumida,Masahiko Kuroda,Ji Hyeon Ju,Isao Matsumoto,Mitsuyasu Kato,Koichi Matsuzaki,Juryun Kim,Jin Soo Han,In-Kyu Lee,Mizuko Mamura,Michael Weinstein

doi:10.1038/ncomms8600

Abstract

Transforming growth factor-β (TGF-β) and interleukin-6 (IL-6) are the pivotal cytokines to induce IL-17-producing CD4+ T helper cells (TH17); yet their signalling network remains largely unknown. Here we show that the highly homologous TGF-β receptor-regulated Smads (R-Smads): Smad2 and Smad3 oppositely modify STAT3-induced transcription of IL-17A and retinoic acid receptor-related orphan nuclear receptor, RORγt encoded by Rorc, by acting as a co-activator and co-repressor of STAT3, respectively. Smad2 linker phosphorylated by extracellular signal-regulated kinase (ERK) at the serine 255 residue interacts with STAT3 and p300 to transactivate, whereas carboxy-terminal unphosphorylated Smad3 interacts with STAT3 and protein inhibitor of activated STAT3 (PIAS3) to repress the Rorc and Il17a genes. Our work uncovers carboxy-terminal phosphorylation-independent noncanonical R-Smad–STAT3 signalling network in TH17 differentiation.

Highlights

Transforming growth factor-b (TGF-b) and interleukin-6 (IL-6) are the pivotal cytokines to induce IL-17-producing CD4 þ T helper cells (TH17); yet their signalling network remains largely unknown
Because IL-6 or TGF-b alone has little effect on TH17 differentiation[3] and STAT3mediated IL-6 signalling is crucial for TH17 differentiation[16], we examined whether regulated Smads (R-Smads) regulate STAT3-induced transcription of RORgt and IL-17A in CD4 þ T cells cultured under TH17-polarizing condition by promoter assays with the luciferase reporters spanning 2 kb upstream of the first exons of the Rorc and Il17a genes (Fig. 2c)
We examined the effects of intensities and inhibitions of TGF-b/IL-6/T-cell receptor (TCR) signals on the interactions of STAT3 with pSmad2L or unphosphorylated Smad3C in TH17 cells

Summary

Introduction

Transforming growth factor-b (TGF-b) and interleukin-6 (IL-6) are the pivotal cytokines to induce IL-17-producing CD4 þ T helper cells (TH17); yet their signalling network remains largely unknown. We show that the highly homologous TGF-b receptor-regulated Smads (R-Smads): Smad[2] and Smad[3] oppositely modify STAT3-induced transcription of IL-17A and retinoic acid receptor-related orphan nuclear receptor, RORgt encoded by Rorc, by acting as a co-activator and co-repressor of STAT3, respectively. CD4 þ T helper cell (TH17) through inducing a master transcription factor, retinoic acid-related orphan receptor-gt (RORgt) and IL-17 (refs 3,4), context-dependent multidirectional roles of TGF-b have been highlighted in immune regulation, to its roles in carcinogenesis and cancer progression[5]. Intracellular signal transduction of TGF-b superfamily cytokines is initiated by two types of serine/threonine kinase transmembrane receptors[9,10]. TGF-b ligands bind to TGF-b type II receptor (TbRII), which transphosphorylates and activates

Methods

Results

Conclusion