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Biomedical subjects

Rikiro Fukunaga

Publications and source records attributed to Rikiro Fukunaga.

6 recordsLinked to original sources
PubMed2005

Identification of CCR2, flotillin, and gp49B genes as new G-CSF targets during neutrophilic differentiation.

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that stimulates myeloid progenitor cells to proliferate and differentiate into neutrophilic granulocytes. To identify genes induced by G-CSF during neutrophil differentiation, interleukin-3-dependent murine myeloid precursor FDC-P1 cells expressing the G-CSF receptor were stimulated with G-CSF, and the gene expression profile was characterized by DNA microarray analysis. In addition to known signal transducer and activator of transcription-3 target genes, such as suppressor of cytokine signaling-3 (SOCS3), JunB, and p19(INK4D), we newly identified several G-CSF targets, including genes for the CC chemokine receptor-2 (CCR2), raft proteins flotillin-1 and flotillin-2, and immunoglobulin-like receptor gp49B. Real-time, quantitative polymerase chain reaction analyses revealed that the expression of these genes was induced in various myeloid cell lines by G-CSF. Furthermore, when HoxA9-immortalized bone marrow progenitors were induced by G-CSF to differentiate into mature neutrophils, all of these genes were strongly activated. These genes could be categorized into three groups based on their time-course of expression: immediate-early (approximately 20 min, SOCS3), mid-early (2-4 h, flotillin-1/2 and gp49B), and late (>12 h, CCR2). This suggests that different transcriptional mechanisms are involved in the regulation of these genes. We show that bone marrow neutrophils express functional CCR2, which suggest that CC chemokines may play previously unknown roles in neutrophil activation and chemotaxis.

Animals↗
PubMed2005

SEI family of nuclear factors regulates p53-dependent transcriptional activation.

SEI family proteins, p34SEI-1 and SEI-2(TRIP-Br2), are nuclear factors that are implicated in cell cycle regulation through interaction with CDK4/CyclinD and E2F-1/DP-1 complexes. Here we report that the SEI family proteins regulate transcriptional activity of p53 tumor suppressor protein. Expression of SEI-1, SEI-2 or SEI-3 strongly stimulates p53-dependent gene activation in HeLa and U2OS cells but not in p53-deficient Saos2 or p53-knockdown HeLa cells. SEI proteins possess an intrinsic transactivation activity, interact with the coactivator CREB-binding protein, and cooperate synergistically with the ING family of chromatin-associated proteins to stimulate the transactivation function of p53. Doxycycline-induced expression of SEI proteins results in activation of the p21 gene and inhibition of cell growth, but the growth arrest was not suppressed by the siRNA-mediated knockdown of the endogenous p53 protein. These results indicate that the SEI family of nuclear proteins regulates p53 transcriptional activity and a p53-independent signaling pathway leading to growth inhibition.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Mnk2 and Mnk1 are essential for constitutive and inducible phosphorylation of eukaryotic initiation factor 4E but not for cell growth or development.

Mnk1 and Mnk2 are protein kinases that are directly phosphorylated and activated by extracellular signal-regulated kinase (ERK) or p38 mitogen-activated protein (MAP) kinases and implicated in the regulation of protein synthesis through their phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) at Ser209. To investigate their physiological functions, we generated mice lacking the Mnk1 or Mnk2 gene or both; the resulting KO mice were viable, fertile, and developed normally. In embryonic fibroblasts prepared from Mnk1-Mnk2 DKO mice, eIF4E was not detectably phosphorylated at Ser209, even when the ERK and/or p38 MAP kinases were activated. Analysis of embryonic fibroblasts from single KO mice revealed that Mnk1 is responsible for the inducible phosphorylation of eIF4E in response to MAP kinase activation, whereas Mnk2 mainly contributes to eIF4E's basal, constitutive phosphorylation. Lipopolysaccharide (LPS)- or insulin-induced upregulation of eIF4E phosphorylation in the spleen, liver, or skeletal muscle was abolished in Mnk1(-/-) mice, whereas the basal eIF4E phosphorylation levels were decreased in Mnk2(-/-) mice. In Mnk1-Mnk2 DKO mice, no phosphorylated eIF4E was detected in any tissue studied, even after LPS or insulin injection. However, neither general protein synthesis nor cap-dependent translation, as assayed by a bicistronic reporter assay system, was affected in Mnk-deficient embryonic fibroblasts, despite the absence of phosphorylated eIF4E. Thus, Mnk1 and Mnk2 are exclusive eIF4E kinases both in cultured fibroblasts and adult tissues, and they regulate inducible and constitutive eIF4E phosphorylation, respectively. These results strongly suggest that eIF4E phosphorylation at Ser209 is not essential for cell growth during development.

Animals↗
PubMed2003

A SWI2/SNF2-type ATPase/helicase protein, mDomino, interacts with myeloid zinc finger protein 2A (MZF-2A) to regulate its transcriptional activity.

BACKGROUND: The myeloid zinc finger protein 2A (MZF-2A) is a Krüppel-type C2H2 zinc finger transcription factor expressed in myeloid cells and involved in the growth, differentiation and tumorigenesis of myeloid progenitors. Previously we identified a 180 amino acid domain in MZF-2A which is responsible for the transcriptional activation of MZF-2A. To understand the mechanism of the MZF-2A-dependent transcriptional activation, we screened for molecules that interact with the transactivation domain (TAD) of MZF-2A. RESULTS: By using the yeast Ras recruitment two-hybrid screening, we identified a novel SWI2/SNF2-related protein, termed mammalian Domino (mDomino), as an MZF-2A-binding partner. The mDomino protein, which shows a marked similarity to the Drosophila Domino protein, contains a SWI2/SNF2-type ATPase/helicase domain, a SANT domain, and a glutamine-rich (Q-rich) domain. The C-terminal Q-rich domain of mDomino physically associates with the TAD of MZF-2A in mammalian cells as well as in yeast. Expression of the mDomino Q-rich domain, together with MZF-2A in myeloid LGM-1 cells, enhanced the MZF-2A-mediated activation of a reporter gene. CONCLUSIONS: These results strongly suggest that an ATP-dependent chromatin-remodelling complex containing mDomino interacts with MZF-2A to regulate gene expression in myeloid cells.

Adenosine Triphosphatases↗
PubMed2002

Regulation of myeloid zinc finger protein 2A transactivation activity through phosphorylation by mitogen-activated protein kinases.

The myeloid zinc finger protein (MZF)-2 is a C(2)H(2) zinc finger transcription factor that is expressed in myeloid cells and involved in the growth, differentiation, and tumorigenesis of myeloid progenitors. Here we describe a novel isoform of MZF-2, designated MZF-2A, and show that it is phosphorylated by the mitogen-activated protein (MAP) kinases. An in vitro phosphorylation experiment revealed that the transactivation domain (TAD) of MZF-2A was phosphorylated strongly by extracellular signal-regulated kinase (ERK) and phosphorylated weakly by p38 MAP kinase but not by Jun N-terminal kinase. Experiments using "add-back" mutants showed that three serine residues (Ser(257), Ser(275), and Ser(295)) in the TAD were phosphorylated in vitro by ERK. In myeloid LGM-1 cells, various extracellular stimuli induced the phosphorylation of these serine residues, which was differentially inhibited by the protein kinase inhibitors U0126 and SB203580. Substitution of these phosphorylation sites with alanines resulted in a strong enhancement of the ability of MZF-2A to activate transcription in a luciferase reporter assay. Taken together, these results indicate that MZF-2A is a novel target for the ERK and p38 MAP kinase signaling pathways, and its transactivation activity is negatively regulated by MAP kinase-mediated phosphorylation of the TAD.

Alternative Splicing↗