TATSUMA BAN, Assistant Professor , Department of Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Dr. Ban received his Ph.D. in 2012 from the University of Tokyo, Japan under the mentorship of Prof. Tadatsugu Taniguchi. During his Ph.D. course, he studied the innate immune sensing mechanisms of nucleic acids derived from viruses or other pathogens, and contributed to publishing two Nature papers and three Proc Natl Acad Sci USA papers. After receiving his Ph.D., Dr. Ban joined the laboratory of Prof. Tomohiko Tamura at the Department of Immunology, Yokohama City University Graduate School of Medicine, and has been studying the activation mechanism of the IRF transcription factor family, and developing novel therapeutics for autoimmune diseases. He showed in a mouse model of systemic lupus erythematosus (SLE) that hyperactivation of IRF5 causes the development of an SLE-like disease, and that the selective suppression of IRF5 is key to the new therapeutics for SLE. His work was published in Immunity in 2016. He recently works on a project for the development of the IRF5 inhibitor as an innovative drug for SLE.
Abstract for Young Investigator Awards Session at Cytokines 2017 in Kanazawa, Japan:
The transcription factor interferon regulatory factor-5 (IRF5) plays an important role in Toll-like receptor (TLR)-mediated innate immune responses, whereas it contributes to the pathogenesis of systemic lupus erythematosus (SLE). However, little is known about the mechanism regulating the extent of IRF5 activation, especially the negative regulatory mechanism. Lyn, a Src family kinase, is also implicated in human SLE, and Lyn–/– mice develop an SLE-like disease. Here we show that Lyn selectively inhibits the activity of IRF5 in the TLR-MyD88 pathway, thereby restraining the development of autoimmunity. Interestingly, Lyn inhibited IRF5 in a kinase activity-independent manner; it bound to IRF5 and inhibited ubiquitination and phosphorylation of IRF5. Consistently, these post-translational modifications of IRF5 were significantly enhanced in TLR7/9-stimulated Lyn–/– bone marrow-derived dendritic cells (BMDCs), resulting in the boost of IRF5-dependent type-I IFN induction. Moreover, DCs freshly isolated from Lyn–/– mice exhibited phosphorylation and enhanced nuclear translocation of IRF5. These results suggest that IRF5 is constitutively activated in vivo in DCs, if Lyn is lost. Importantly, even monoallelic ablation of the Irf5 gene was sufficient to alleviate the hyper-production of type-I IFNs in TLR7/9-stimulated Lyn–/– BMDCs, and to ameliorate the development of SLE-like symptoms in Lyn–/– mice. Taken together, our results identify Lyn as a critical suppressor of IRF5 in the TLR-MyD88 pathway, and implicate that the selective control of IRF5 activity may contribute to better therapeutics for SLE. We will also show our recent results of high-throughput-screening of small molecular compounds that inhibit IRF5 transcriptional activity.