title: The Transcription Factor Bach2 Is Phosphorylated at Multiple Sites in Murine B Cells but a Single Site Prevents Its Nuclear Localization.
abstract: The transcription factor Bach2 regulates the immune system at multiple points, including class switch recombination (CSR) in activated B cells and the function of T cells in part by restricting their terminal differentiation. However, the regulation of Bach2 expression and its activity in the immune cells are still unclear. Here, we demonstrated that Bach2 mRNA expression decreased in Pten-deficient primary B cells. Bach2 was phosphorylated in primary B cells, which was increased upon the activation of the B cell receptor by an anti-immunoglobulin M (IgM) antibody or CD40 ligand. Using specific inhibitors of kinases, the phosphorylation of Bach2 in activated B cells was shown to depend on the phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway. The complex of mTOR and Raptor phosphorylated Bach2 in vitro. We identified multiple new phosphorylation sites of Bach2 by mass spectrometry analysis of epitope-tagged Bach2 expressed in the mature B cell line BAL17. Among the sites identified, serine 535 (Ser-535) was critical for the regulation of Bach2 because a single mutation of Ser-535 abolished cytoplasmic accumulation of Bach2, promoting its nuclear accumulation in pre-B cells, whereas Ser-509 played an auxiliary role. Bach2 repressor activity was enhanced by the Ser-535 mutation in B cells. These results suggest that the PI3K-Akt-mTOR pathway inhibits Bach2 by both repressing its expression and inducing its phosphorylation in B cells.
authors.affiliation: From the Departments of Biochemistry,; Pediatric Surgery, and.
authors.forename: Ryo
authors.initials: R
authors.lastname: Ando
authors.affiliation: From the Departments of Biochemistry,; CREST, Japan Science and Technology Agency, Seiryo-machi 2-1, Sendai 980-8575, and.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shima
authors.affiliation: From the Departments of Biochemistry,; CREST, Japan Science and Technology Agency, Seiryo-machi 2-1, Sendai 980-8575, and; the Department of Preventive Dentistry, Tohoku University Graduate School of Dentistry, Seiryo-machi 4-1, Sendai 980-8575.
authors.forename: Toru
authors.initials: T
authors.lastname: Tamahara
authors.affiliation: From the Departments of Biochemistry.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sato
authors.affiliation: From the Departments of Biochemistry.
authors.forename: Miki
authors.initials: M
authors.lastname: Watanabe-Matsui
authors.affiliation: From the Departments of Biochemistry.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kato
authors.affiliation: From the Departments of Biochemistry,; CREST, Japan Science and Technology Agency, Seiryo-machi 2-1, Sendai 980-8575, and.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sax
authors.affiliation: Department of Gene Expression Regulation, Institute of Development, Aging, and Cancer, Tohoku University, Seiryo-machi 4-1, Sendai 980-8575.
authors.forename: Hozumi
authors.initials: H
authors.lastname: Motohashi
authors.affiliation: Medical Biochemistry, Tohoku University Graduate School of Medicine, Seiryo-machi 2-1, Sendai 980-8575.
authors.forename: Keiko
authors.initials: K
authors.lastname: Taguchi
authors.affiliation: Medical Biochemistry, Tohoku University Graduate School of Medicine, Seiryo-machi 2-1, Sendai 980-8575.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Pediatric Surgery, and.
authors.forename: Masaki
authors.initials: M
authors.lastname: Nio
authors.affiliation: the Laboratory of Membrane Proteins, Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Tokyo 113-0032, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Maeda
authors.affiliation: From the Departments of Biochemistry,; CREST, Japan Science and Technology Agency, Seiryo-machi 2-1, Sendai 980-8575, and; Center for Regulatory Epigenome and Diseases, Tohoku University Graduate School of Medicine, Seiryo-machi 2-1, Sendai 980-8575.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Ochiai
authors.affiliation: From the Departments of Biochemistry,; CREST, Japan Science and Technology Agency, Seiryo-machi 2-1, Sendai 980-8575, and.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Muto
authors.affiliation: From the Departments of Biochemistry,; CREST, Japan Science and Technology Agency, Seiryo-machi 2-1, Sendai 980-8575, and; Center for Regulatory Epigenome and Diseases, Tohoku University Graduate School of Medicine, Seiryo-machi 2-1, Sendai 980-8575,. Electronic address: igarashi@med.tohoku.ac.jp.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Igarashi
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D054448:Precursor Cells, B-Lymphoid / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C102109:Bach2 protein, mouse; C546843:mTOR protein, mouse
keywords: cell signaling; gene regulation; immunology; lymphocyte; mammalian target of rapamycin (mTOR); phosphatidylinositide 3-kinase (PI 3-kinase); protein phosphorylation; transcription factor