Chiharu Itagaki
University of Tokyo
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Featured researches published by Chiharu Itagaki.
Molecular & Cellular Proteomics | 2005
Kazuto Nunomura; Kohji Nagano; Chiharu Itagaki; Masato Taoka; Nobuko Okamura; Yoshio Yamauchi; Sumio Sugano; Nobuhiro Takahashi; Tomonori Izumi; Toshiaki Isobe
Although interactions between cell surface proteins and extracellular ligands are key to initiating embryonic stem cell differentiation to specific cell lineages, the plasma membrane protein components of these cells are largely unknown. We describe here a group of proteins expressed on the surface of the undifferentiated mouse embryonic stem cell line D3. These proteins were identified using a combination of cell surface labeling with biotin, subcellular fractionation of plasma membranes, and mass spectrometry-based protein identification technology. From 965 unique peptides carrying biotin labels, we assigned 324 proteins including 235 proteins that have putative signal sequences and/or transmembrane segments. Receptors, transporters, and cell adhesion molecules were the major classes of proteins identified. Besides known cell surface markers of embryonic stem cells, such as alkaline phosphatase, the analysis identified 59 clusters of differentiation-related molecules and more than 80 components of multiple cell signaling pathways that are characteristic of a number of different cell lineages. We identified receptors for leukemia-inhibitory factor, interleukin 6, and bone morphogenetic protein, which play critical roles in the maintenance of undifferentiated mouse embryonic stem cells. We also identified receptors for growth factors/cytokines, such as fibroblast growth factor, platelet-derived growth factor, ephrin, Hedgehog, and Wnt, which transduce signals for cell differentiation and embryonic development. Finally we identified a variety of integrins, cell adhesion molecules, and matrix metalloproteases. These results suggest that D3 cells express diverse cell surface proteins that function to maintain pluripotency, enabling cells to respond to various external signals that initiate differentiation into a variety of cell types.
Oncogene | 2006
Kohji Nagano; Chiharu Itagaki; Tomonori Izumi; Kazuto Nunomura; Yasushi Soda; Kenzaburo Tani; Nobuhiro Takahashi; T Takenawa; Toshiaki Isobe
The retinoblastoma (Rb) gene product is a tumor suppressor that is mutated or inactivated in many types of human cancers. Although Rb is known to be an upstream negative regulator of Abl protein tyrosine kinase, we propose here that Rb also functions as a downstream effector of Abl that plays a positive role in survival of Abl-dependent human tumor cells, including Bcr/Abl-positive chronic myelogenous leukemia (CML). We show that Rb is constitutively phosphorylated at tyrosine in Abl-dependent tumor cells, and that Abl phosphorylates Rb specifically at Y805 within the C-terminal domain of the molecule. We also show that ectopic expression of Rb induces apoptosis in Abl-dependent tumor cells by inhibiting the Abl tyrosine kinase activity, and that Rb-induced apoptosis is compromised by Abl-catalysed phosphorylation of Rb at Y805. Furthermore, the silencing of endogenous Rb by RNA interference induced apoptosis in Abl-dependent tumor cells. Thus, our findings suggest that Abl-catalysed tyrosine phosphorylation of Rb is necessary for survival of Abl-dependent human tumor cells, and raises the possibility that this phosphorylated Rb can be a molecular target for cancer therapy aimed at inducing apoptosis of Abl-dependent tumor cells, such as Bcr/Abl-positive CML.
Archive | 2002
Tohru Ichimura; Chiharu Itagaki; Akiko Wakamiya; Toshiaki Isobe
The 14–3–3 protein is a family of acidic, dimeric proteins distributed widely among eukaryotic cells. This protein family binds to a variety of proteins in a phosphorylation-dependent manner and participates in the regulation of cell proliferation, differentiation and function. To date, more than 70 proteins, localized in the cell membrane to nuclei, are reported to bind with the 14–3–3 family. These proteins include at least 19 membrane components (receptors, ion channels and effectors), 22 signal transduction kinases and phosphatases, 5 cytoskelton proteins, 18 nuclear proteins including transcription factors, 10 metabolic enzymes, and others. We previously showed, using PC12nnr5 cells transfected with myc-tagged 14–3–3β and η) isoforms, that 14–3–3s form a complex with tyrosine hydroxylase (TH) particularly when the hydroxylase is phosphorylated at Ser-19 by endogeneous Ca2+, calmodulin-dependent protein kinase II1. In this study we have employed proteomic techniques for systematic characterization of PC12 proteins and identified the TH protein as a major constituent of the proteins that are co-immunoprecipitated with 14–3–3. We have also shown that the TH protein is predominantly associated with 14–3-3e and η isoforms, but not with ζ and θ isoforms. These results indicate that the activity of TH is regulated through phosphorylation-dependent interaction with limited members of the 14–3–3 family.
Developmental Biology | 2004
Satoko Fujimoto; Naoko Yoshida; Tomoyuki Fukui; Manami Amanai; Toshiaki Isobe; Chiharu Itagaki; Tomonori Izumi; Anthony C.F. Perry
Proteomics | 2005
Kohji Nagano; Masato Taoka; Yoshio Yamauchi; Chiharu Itagaki; Takashi Shinkawa; Kazuto Nunomura; Nobuko Okamura; Nobuhiro Takahashi; Tomonori Izumi; Toshiaki Isobe
Genome Research | 2004
Masaaki Oyama; Chiharu Itagaki; Hiroko Hata; Yutaka Suzuki; Tomonori Izumi; Tohru Natsume; Toshiaki Isobe; Sumio Sugano
Biochemistry | 1999
Chiharu Itagaki; Toshiaki Isobe; Masato Taoka; Tohru Natsume; Noriko Nomura; Tsuneyoshi Horigome; Saburo Omata; Hiroshi Ichinose; Toshiharu Nagatsu; Lloyd A. Greene; Tohru Ichimura
Biochemistry | 2002
Tohru Ichimura; Akiko Wakamiya-Tsuruta; Chiharu Itagaki; Masato Taoka; Toshiya Hayano; Tohru Natsume; Toshiaki Isobe
FEBS Letters | 1997
Tohru Ichimura; Mitsuki Ito; Chiharu Itagaki; Masuhiro Takahashi; Tsuneyosi Horigome; Saburo Omata; Shigeo Ohno; Toshiaki Isobe
Archive | 2005
Kazuto Nunomura; Kohji Nagano; Chiharu Itagaki; Masato Taoka; Nobuko Okamura; Sumio Sugano; Nobuhiro Takahashi; Tomonori Izumi; Toshiaki Isobe; Nihon Millipore