title: Possible involvement of Helios in controlling the immature B cell functions via transcriptional regulation of protein kinase Cs.
abstract: The transcription factor Ikaros family consists of five zinc-finger proteins: Ikaros, Aiolos, Helios, Eos and Pegasus; these proteins except Pegasus are essential for development and differentiation of lymphocytes. However, in B lymphocytes, the physiological role of Helios remains to be elucidated yet, because its expression level is very low. Here, we generated the Helios-deficient DT40 cells, Helios (-/-), and showed that the Helios-deficiency caused significant increases in transcriptions of four protein kinase Cs (PKCs); PKC-δ, PKC-ε, PKC-η and PKC-ζ, whereas their expressions were drastically down-regulated in the Aiolos-deficient DT40 cells, Aiolos (-/-). In addition, Helios (-/-) was remarkably resistant against phorbol 12-myristate 13-acetate (PMA)/ionomycin treatment, which mimics the B cell receptor (BCR)-mediated stimulation. In the presence of PMA/ionomycin, their viability was remarkably higher than that of DT40, and their DNA fragmentation was less severe than that of DT40 in the opposite manner for the Aiolos-deficiency. The resistance against the PMA/ionomycin-induced apoptosis of Helios (-/-) was sensitive to Rottlerin but not to Go6976. In addition, the Helios-deficiency caused remarkable up-regulation of the Rottlerin-sensitive superoxide (O2 (-))-generating activity. These data suggest that Helios may contribute to the regulation of the BCR-mediated apoptosis and O2 (-)-generating activity, via transcriptional regulation of these four PKCs (especially PKC-δ) in immature B lymphocytes. Together with previous data, our findings may significantly help in the understanding of the B lymphocyte-specific expressions of PKC genes and molecular mechanisms of both the BCR-mediated apoptosis involved in negative selection and the O2 (-)-generating system in immature B lymphocytes.
authors.affiliation: Section of Biochemistry and Molecular Biology, Department of Medical Sciences, Miyazaki Medical College, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Kikuchi
authors.affiliation: Section of Biochemistry and Molecular Biology, Department of Medical Sciences, Miyazaki Medical College, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Nakayama
authors.affiliation: Section of Biochemistry and Molecular Biology, Department of Medical Sciences, Miyazaki Medical College, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Takami
authors.affiliation: Department of Biochemistry, Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan.
authors.forename: Futoshi
authors.initials: F
authors.lastname: Kuribayashi
authors.affiliation: Section of Biochemistry and Molecular Biology, Department of Medical Sciences, Miyazaki Medical College, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Nakayama
keywords: Apoptosis; BCR, B cell receptor; DT40; Gene targeting; Helios; O2−, superoxide; PKC, protein kinase C; PMA, phorbol 12-myristate 13-acetate; Protein kinase C; Superoxide