TY - JOUR
T1 - The mTOR-Bach2 cascade controls cell cycle and class switch recombination during B cell differentiation
AU - Tamahara, Toru
AU - Ochiai, Kyoko
AU - Muto, Akihiko
AU - Kato, Yukinari
AU - Sax, Nicolas
AU - Matsumoto, Mitsuyo
AU - Koseki, Takeyoshi
AU - Igarashi, Kazuhiko
N1 - Funding Information:
This study was supported by grants-in-aid from the Ministry of Education, Science, Sport, and Culture of Japan (KAKENHI 16K15227, 15H02506, 24390066, 16K19026, 16H01295) and AMED-CREST. This project was supported by Astellas Foundation for Research on Metabolic Disorders (K.O.). This work was supported in part by Platform Project for Supporting Drug Discovery and Life Science Research (Basis for Supporting Innovative Drug Discovery and Life Science Research [BINDS]) from AMED from Japan Agency for Medical Research and development, AMED (Y.K.).
Funding Information:
We thank the members of the Igarashi laboratory for helpful discussions and T. Kurosaki (Osaka University) and M. Nussenzweig (Rockfeller University) for providing BCR transgenic B1-8hi mice. This study was supported by grants-in-aid from the Ministry of Education, Science, Sport, and Culture of Japan (KAKENHI 16K15227, 15H02506, 24390066, 16K19026, 16H01295) and AMED-CREST. This project was supported by Astellas Foundation for Research on Metabolic Disorders (K.O.). This work was supported in part by Platform Project for Supporting Drug Discovery and Life Science Research (Basis for Supporting Innovative Drug Discovery and Life Science Research [BINDS]) from AMED from Japan Agency for Medical Research and development, AMED (Y.K.). K.O. and K.I. designed and T.T. performed the majority of the experiments with assistance from K.O. K.O. performed the ChIP assay, the analysis of Bach2-RFP mice by using flow cytometry, the microarray of the comparison between wild-type versus Bach2-deficient splenic B cells, the immunoblot analysis of retrovirus transduction using B1-8hi splenic B cells, and the experiments using Bach2-deficient splenic B cells with B1-8hi background. A.M. supported the screening of Bach2 binding sites in Ccnd3 and Ccne locus. Y.K. assisted A.M. in designing and generating the specific antibodies against Bach2 S535 phosphorylation. N.S. assisted A.M. in experiments. M.M. supported with data analysis the microarray that K.O. performed. T.K. contributed to analysis and evaluation of data. T.T., K.O., and K.I. wrote the manuscript.
Publisher Copyright:
© 2017 American Society for Microbiology.
PY - 2017/12/1
Y1 - 2017/12/1
N2 - The transcription factor Bach2 regulates both acquired and innate immunity at multiple steps, including antibody class switching and regulatory T cell development in activated B and T cells, respectively. However, little is known about the molecular mechanisms of Bach2 regulation in response to signaling of cytokines and antigen. We show here that mammalian target of rapamycin (mTOR) controls Bach2 along B cell differentiation with two distinct mechanisms in pre-B cells. First, mTOR complex 1 (mTORC1) inhibited accumulation of Bach2 protein in nuclei and reduced its stability. Second, mTOR complex 2 (mTORC2) inhibited FoxO1 to reduce Bach2 mRNA expression. Using expression profiling and chromatin immunoprecipitation assay, the Ccnd3 gene, encoding cyclin D3, was identified as a new direct target of Bach2. A proper cell cycle was lost at pre-B and mature B cell stages in Bach2-deficient mice. Furthermore, AZD8055, an mTOR inhibitor, increased class switch recombination in wild-type mature B cells but not in Bach2-deficient cells. These results suggest that the mTOR-Bach2 cascade regulates proper cell cycle arrest in B cells as well as immunoglobulin gene rearrangement.
AB - The transcription factor Bach2 regulates both acquired and innate immunity at multiple steps, including antibody class switching and regulatory T cell development in activated B and T cells, respectively. However, little is known about the molecular mechanisms of Bach2 regulation in response to signaling of cytokines and antigen. We show here that mammalian target of rapamycin (mTOR) controls Bach2 along B cell differentiation with two distinct mechanisms in pre-B cells. First, mTOR complex 1 (mTORC1) inhibited accumulation of Bach2 protein in nuclei and reduced its stability. Second, mTOR complex 2 (mTORC2) inhibited FoxO1 to reduce Bach2 mRNA expression. Using expression profiling and chromatin immunoprecipitation assay, the Ccnd3 gene, encoding cyclin D3, was identified as a new direct target of Bach2. A proper cell cycle was lost at pre-B and mature B cell stages in Bach2-deficient mice. Furthermore, AZD8055, an mTOR inhibitor, increased class switch recombination in wild-type mature B cells but not in Bach2-deficient cells. These results suggest that the mTOR-Bach2 cascade regulates proper cell cycle arrest in B cells as well as immunoglobulin gene rearrangement.
KW - B cells
KW - Cell cycle
KW - Immunoglobulin gene rearrangement
KW - MTOR
KW - Transcription factor
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U2 - 10.1128/MCB.00418-17
DO - 10.1128/MCB.00418-17
M3 - Article
C2 - 28993481
AN - SCOPUS:85035817043
VL - 37
JO - Molecular and Cellular Biology
JF - Molecular and Cellular Biology
SN - 0270-7306
IS - 24
M1 - e00418-17
ER -