Kenji Moriyama
University of Tokyo
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Featured researches published by Kenji Moriyama.
Genes to Cells | 1996
Kenji Moriyama; Kazuko Iida; Ichiro Yahara
Background: Cofilin is a low‐molecular weight actin‐modulating protein, and is structurally and functionally conserved in eucaryotes from yeast to mammals. The functions of cofilin appear to be regulated by phosphorylation and dephosphorylation.
Nature Neuroscience | 2001
Hiroyuki Aizawa; Shuji Wakatsuki; Ai Ishii; Kenji Moriyama; Yukio Sasaki; Kazumasa Ohashi; Yoko Sekine-Aizawa; Atsuko Sehara-Fujisawa; Kensaku Mizuno; Yoshio Goshima; Ichiro Yahara
Semaphorin 3A is a chemorepulsive axonal guidance molecule that depolymerizes the actin cytoskeleton and collapses growth cones of dorsal root ganglia neurons. Here we investigate the role of LIM-kinase 1, which phosphorylates an actin-depolymerizing protein, cofilin, in semaphorin 3A-induced growth cone collapse. Semaphorin 3A induced phosphorylation and dephosphorylation of cofilin at growth cones sequentially. A synthetic cell-permeable peptide containing a cofilin phosphorylation site inhibited LIM-kinase in vitro and in vivo, and essentially suppressed semaphorin 3A-induced growth cone collapse. A dominant-negative LIM kinase, which could not be activated by PAK or ROCK, suppressed the collapsing activity of semaphorin 3A. Phosphorylation of cofilin by LIM-kinase may be a critical signaling event in growth cone collapse by semaphorin 3A.
The EMBO Journal | 1991
Yukiko Gotoh; Kenji Moriyama; Satoshi Matsuda; Eiichi Okumura; Takeo Kishimoto; Hiroshi Kawasaki; K Suzuki; Ichiro Yahara; Hiroshi Sakai; Eisuke Nishida
MAP kinase is activated and phosphorylated during M phase of the Xenopus oocyte cell cycle, and induces the interphase‐M phase transition of microtubule dynamics in vitro. We have carried out molecular cloning of Xenopus M phase MAP kinase and report its entire amino acid sequence. There is no marked change in the MAP kinase mRNA level during the cell cycle. Moreover, studies with an anti‐MAP kinase antiserum indicate that MAP kinase activity may be regulated posttranslationally, most likely by phosphorylation. We show that MAP kinase can be activated by microinjection of MPF into immature oocytes or by adding MPF to cell‐free extracts of interphase eggs. These results suggest that MAP kinase functions as an intermediate between MPF and the interphase‐M phase transition of microtubule organization.
The EMBO Journal | 1992
Satoshi Matsuda; Hidetaka Kosako; Katsuya Takenaka; Kenji Moriyama; Hiroshi Sakai; Tetsu Akiyama; Yukiko Gotoh; Eisuke Nishida
MAP kinase is thought to play a pivotal role not only in the growth factor‐stimulated signalling pathway but also in the M phase phosphorylation cascade downstream of MPF. MAP kinase is fully active only when both tyrosine and threonine/serine residues are phosphorylated. We have now identified and purified a Xenopus MAP kinase activator from mature oocytes that is able to induce activation and phosphorylation on tyrosine and threonine/serine residues of an inactive form of Xenopus MAP kinase. The Xenopus MAP kinase activator itself is a 45 kDa phosphoprotein and is inactivated by protein phosphatase 2A treatment in vitro. Microinjection of the purified activator into immature oocytes results in immediate activation of MAP kinase. Further experiments using microinjection as well as cell free extracts have shown that Xenopus MAP kinase activator is an intermediate between MPF and MAP kinase. Thus, MAP kinase activator plays a key role in the phosphorylation cascade.
Gene | 1993
Kazuko Iida; Kenji Moriyama; Seiji Matsumoto; Hiroshi Kawasaki; Eisuke Nishida; Ichiro Yahara
We have cloned a Saccharomyces cerevisiae gene (COF1) encoding a low-M(r) actin-binding protein of 143 amino acid (aa) residues (yeast cofilin; Cof); its aa sequence is 35% identical to porcine Cof. The yeast recombinant Cof produced in Escherichia coli exhibited in vitro activities on actin filaments similar to those of mammalian and avian Cof. Gene disruption and tetrad analysis showed that gene COF1 is essential for yeast cell growth. Expression of the cDNA of porcine Cof or destrin (Des), the latter a Cof-related protein, complemented the cof1 null allele in yeast cells.
The EMBO Journal | 1999
Kenji Moriyama; Ichiro Yahara
The biochemical activities of cofilin are controversial. We demonstrated that porcine cofilin severs actin filaments and accelerates monomer release at the pointed ends. At pH 7.1, 0.8 μM cofilin cut filaments (2.2 μM actin) about every 290 subunits and increased the depolymerization rate 6.4‐fold. A kink in the major α‐helix of cofilin is thought to constitute a contact site for actin. Side chain hydroxyl groups of Ser119, Ser120 and Tyr82 in cofilin form hydrogen bonds with main chain carbonyl moieties from the helix, causing the kink. We eliminated side chain hydroxyls by Ser→Ala and/or Tyr→Phe mutagenesis. Severing and depolymerization‐enhancing activities were reduced dramatically in an Ala120 mutant, whereas the latter was decreased in a Phe82 mutant with a relatively small effect on severing, suggesting different structural bases for the two activities of cofilin. The Ala120‐equivalent mutation in yeast cofilin affected cell growth, whereas that of the Phe82‐equivalent had no effect in yeast. These results indicate the physiological significance of the severing activity of cofilin that is brought about by the kink in the helix.
Journal of Cell Science | 2002
Kenji Moriyama; Ichiro Yahara
Journal of Biological Chemistry | 1990
Kenji Moriyama; Eisuke Nishida; Naoto Yonezawa; Hiroshi Sakai; Seiji Matsumoto; Kazuko Iida; Ichiro Yahara
Journal of Biological Chemistry | 1992
Kenji Moriyama; Naoto Yonezawa; Hiroshi Sakai; Ichiro Yahara; Eisuke Nishida
Cell Structure and Function | 1996
Ichiro Yahara; Hiroyuki Aizawa; Kenji Moriyama; Kazuko Iida; Naoto Yonezawa; Eisuke Nishida; Hideki Hatanaka; Fuyuhiko Inagaki