期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2018
卷号：115
期号：3
页码：E458-E467
DOI：10.1073/pnas.1717789115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Th17 cells are major players in multiple autoimmune diseases and are developmentally contingent on reciprocal functionality between the transcription factor Retineic acid receptor-related orphan nuclear receptor gamma (RORγt) and Forkhead box protein P3 (Foxp3). Here we deciphered a previously unappreciated role of Steroid receptor coactivator 1 (SRC1) in defining the lineage decision for the development of Th17 versus induced T-regulatory (iTreg) cells. We demonstrate that SRC1 functions as a critical coactivator for RORγt in vivo to promote the functional dominance of RORγt over Foxp3 and thus establishing an unopposed Th17 differentiation program. In the absence of SRC1, T cell polarization resulted in decreased IL-17+ and increased Foxp3+ cells during both in vitro differentiation and in vivo development of experimental autoimmune encephalomyelitis. Mechanistically, T cell receptor (TCR) signaling molecule protein kinase C theta (PKC-θ)–mediated phosphorylation of SRC1 is important for inducing enhanced RORγt–SRC1 interaction, stable DNA binding, and resultant IL-17A transcription. Furthermore, phospho-SRC1–mediated recruitment of CARM1 induced prominent asymmetric dimethylation of H3R17 while preventing repressive H3K9 trimethylation and hence further modifying the IL-17 locus for optimal transcription. Moreover, binding of phospho-SRC1 to RORγt displaced bound Foxp3, leading to prompt degradation of the dissociated Foxp3 via a ubiquitin–proteosomal pathway and hence reversing the inhibitory action of Foxp3 on RORγt activity. Thus, SRC1 acts as a crucial molecular mediator to integrate positive PKC-θ–dependent TCR signals to induce peak RORγt activity and establish phenotypic dominance of Th17 over the iTreg pathway.
