研究者詳細 - 河野　洋治

論文 - 河野　洋治

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Stem Cell Factors BAM1 and WOX1 Suppressing Longitudinal Cell Division of Margin Cells Evoked by Low-Concentration Auxin in Young Cotyledon of Arabidopsis

Yuli Jiang, Jian Liang, Chunyan Wang, Li Tan, Yoji Kawano, Shingo Nagawa

International Journal of Molecular Sciences 26 ( 10 ) 4724 - 4724 2025年5月

掲載種別：研究論文（学術雑誌）出版者・発行元：MDPI AG

Highly differentiated tissues and organs play essential biological functions in multicellular organisms. Coordination of organ developmental process with tissue differentiation is necessary to achieve proper development of mature organs, but mechanisms for such coordination are not well understood. We used cotyledon margin cells from Arabidopsis plant as a new model system to investigate cell elongation and cell division during organ growth and found that margin cells endured a developmental phase transition from the “elongation” phase to the “elongation and division” phase at the early stage in germinating seedlings. We also discovered that the stem cell factors BARELY ANY MERISTEM 1 (BAM1) and WUSCHEL-related homeobox1 (WOX1) are involved in the regulation of margin cell developmental phase transition. Furthermore, exogenous auxin treatment (1 nanomolar,nM) promotes cell division, especially longitudinal cell division. This promotion of cell division did not occur in bam1 and wox1 mutants. Based on these findings, we hypothesized a new “moderate auxin concentration” model which emphasizes that a moderate auxin concentration is the key to triggering the developmental transition of meristematic cells.

DOI： 10.3390/ijms26104724

A PRA-Rab trafficking machinery modulates NLR immune receptor plasma membrane microdomain anchoring and blast resistance in rice 査読

Di Liang, Dongyong Yang, Tai Li, Zhe Zhu, Bingxiao Yan, Yang He, Xiaoyuan Li, Keran Zhai, Jiyun Liu, Yoji Kawano, Yiwen Deng, Xu Na Wu, Junzhong Liu, Zuhua He

Science Bulletin 2024年12月

The mutual regulation between the pattern recognition receptor OsCERK1 and the E3 ubiquitin ligase OsCIE1 controls induction and homeostasis of immunity 査読

Qiong Wang, Yoji Kawano

Science Bulletin 2024年7月

An NLR paralog Pit2 generated from tandem duplication of Pit1 fine-tunes Pit1 localization and function. 査読国際誌

Yuying Li, Qiong Wang, Huimin Jia, Kazuya Ishikawa, Ken-Ichi Kosami, Takahiro Ueba, Atsumi Tsujimoto, Miki Yamanaka, Yasuyuki Yabumoto, Daisuke Miki, Eriko Sasaki, Yoichiro Fukao, Masayuki Fujiwara, Takako Kaneko-Kawano, Li Tan, Chojiro Kojima, Rod A Wing, Alfino Sebastian, Hideki Nishimura, Fumi Fukada, Qingfeng Niu, Motoki Shimizu, Kentaro Yoshida, Ryohei Terauchi, Ko Shimamoto, Yoji Kawano

Nature Communications 15 ( 1 ) 4610 - 4610 2024年5月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

NLR family proteins act as intracellular receptors. Gene duplication amplifies the number of NLR genes, and subsequent mutations occasionally provide modifications to the second gene that benefits immunity. However, evolutionary processes after gene duplication and functional relationships between duplicated NLRs remain largely unclear. Here, we report that the rice NLR protein Pit1 is associated with its paralogue Pit2. The two are required for the resistance to rice blast fungus but have different functions: Pit1 induces cell death, while Pit2 competitively suppresses Pit1-mediated cell death. During evolution, the suppression of Pit1 by Pit2 was probably generated through positive selection on two fate-determining residues in the NB-ARC domain of Pit2, which account for functional differences between Pit1 and Pit2. Consequently, Pit2 lost its plasma membrane localization but acquired a new function to interfere with Pit1 in the cytosol. These findings illuminate the evolutionary trajectory of tandemly duplicated NLR genes after gene duplication.

DOI： 10.1038/s41467-024-48943-5

The secreted immune response peptide 1 functions as a phytocytokine in rice immunity 査読

Pingyu Wang, Huimin Jia, Ting Guo, Yuanyuan Zhang, Wanqing Wang, Hideki Nishimura, Zhengguo Li, Yoji Kawano

Journal of Experimental Botany 74 ( 3 ) 1059 - 1073 2023年2月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：Oxford University Press (OUP)

Abstract

Small signalling peptides play important roles in various plant processes, but information regarding their involvement in plant immunity is limited. We previously identified a novel small secreted protein in rice, called immune response peptide 1 (IRP1). Here, we studied the function of IRP1 in rice immunity. Rice plants overexpressing IRP1 enhanced resistance to the virulent rice blast fungus. Application of synthetic IRP1 to rice suspension cells triggered the expression of IRP1 itself and the defence gene phenylalanine ammonia-lyase 1 (PAL1). RNA-seq results revealed that 84% of genes up-regulated by IRP1, including 13 OsWRKY transcription factors, were also induced by a microbe-associated molecular pattern (MAMP), chitin, indicating that IRP1 and chitin share a similar signalling pathway. Co-treatment with chitin and IRP1 elevated the expression level of PAL1 and OsWRKYs in an additive manner. The increased chitin concentration arrested the induction of IRP1 and PAL1 expression by IRP1, but did not affect IRP1-triggered mitogen-activated protein kinases (MAPKs) activation. Collectively, our findings indicate that IRP1 functions as a phytocytokine in rice immunity regulating MAPKs and OsWRKYs that can amplify chitin and other signalling pathways, and provide new insights into how MAMPs and phytocytokines cooperatively regulate rice immunity.

DOI： 10.1093/jxb/erac455

その他リンク： https://academic.oup.com/jxb/article-pdf/74/3/1059/49092088/erac455.pdf

Improving disease resistance to rice false smut without yield penalty by manipulating the expression of effector target 査読

Qiong Wang, Yoji Kawano

Molecular Plant 15 ( 12 ) 1834 - 1837 2022年12月

Three highly conserved hydrophobic residues in the predicted α2‐helix of rice NLR protein Pit contribute to its localization and immune induction 査読国際誌

Qiong Wang, Yuying Li, Ken‐ichi Kosami, Chaochao Liu, Jing Li, Dan Zhang, Daisuke Miki, Yoji Kawano

Plant, Cell & Environment 45 ( 6 ) 1876 - 1890 2022年6月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

Nucleotide-binding leucine-rich repeat (NLR) proteins work as crucial intracellular immune receptors. N-terminal domains of NLRs fall into two groups, coiled-coil (CC) and Toll-interleukin 1 receptor domains, which play critical roles in signal transduction and disease resistance. However, the activation mechanisms of NLRs, and how their N-termini function in immune induction, remain largely unknown. Here, we revealed that the CC domain of a rice NLR Pit contributes to self-association. The Pit CC domain possesses three conserved hydrophobic residues that are known to be involved in oligomer formation in two NLRs, barley MLA10 and Arabidopsis RPM1. Interestingly, the function of these residues in Pit differs from that in MLA10 and RPM1. Although three hydrophobic residues are important for Pit-induced disease resistance against rice blast fungus, they do not participate in self-association or binding to downstream signalling molecules. By homology modelling of Pit using the Arabidopsis ZAR1 structure, we tried to clarify the role of three conserved hydrophobic residues and found that they are located in the predicted α2-helix of the Pit CC domain and involved in the plasma membrane localization. Our findings provide novel insights for understanding the mechanisms of NLR activation as well as the relationship between subcellular localization and immune induction.

DOI： 10.1111/pce.14315

その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/pce.14315

Fine-tuning ROS homeostasis by ROD1 is a battleground between rice and Magnaporthe oryzae 査読

Yoji Kawano

Molecular Plant 14 ( 12 ) 1979 - 1981 2021年12月

NB-LRR-encoding genes conferring susceptibility to organophosphate pesticides in sorghumNB-LRR-encoding genes conferring susceptibility to organophosphate pesticides in sorghum 査読

Zihuan Jing, Fiona Wacera W., Tsuneaki Takami, Hideki Takanashi, Fumi Fukada, Yoji Kawano, Hiromi Kajiya-Kanegae, Hiroyoshi Iwata, Nobuhiro Tsutsumi, Wataru Sakamoto

Scientific Reports 11 ( 1 ) 2021年12月

The Small GTPase OsRac1 Forms Two Distinct Immune Receptor Complexes Containing the PRR OsCERK1 and the NLR Pit 査読

Akira Akamatsu, Masayuki Fujiwara, Satoshi Hamada, Megumi Wakabayashi, A i Yao, Qiong Wang, Ken-ichi Kosami, Thu Thi Dang, Takako Kaneko-Kawano, Fumi Fukada, K o Shimamoto, Yoji Kawano

Plant and Cell Physiology 62 ( 11 ) 1662 - 1675 2021年8月

Identification of endogenous small peptides involved in rice immunity through transcriptomics‐ and proteomics‐based screening 査読

Pingyu Wang, Shaolun Yao, Ken‐ichi Kosami, Ting Guo, Jing Li, Yuanyuan Zhang, Yoichiro Fukao, Takako Kaneko‐Kawano, Heng Zhang, Yi‐Min She, Pengcheng Wang, Weiman Xing, Kousuke Hanada, Renyi Liu, Yoji Kawano

Plant Biotechnology Journal 18 ( 2 ) 415 - 428 2020年2月

In vivo monitoring of plant small GTPase activation using a Förster resonance energy transfer biosensor 査読国際誌

Hann Ling Wong, Akira Akamatsu, Qiong Wang, Masayuki Higuchi, Tomonori Matsuda, Jun Okuda, Ken-ichi Kosami, Noriko Inada, Tsutomu Kawasaki, Takako Kaneko-Kawano, Shingo Nagawa, Li Tan, Yoji Kawano, Ko Shimamoto

Plant Methods 14 ( 1 ) 56 - 56 2018年12月

Resistance protein Pit interacts with the GEF OsSPK1 to activate OsRac1 and trigger rice immunity 査読

Qiong Wang, Yuying Li, Kazuya Ishikawa, Ken-ichi Kosami, Kazumi Uno, Shingo Nagawa, Li Tan, Jiamu Du, Ko Shimamoto, Yoji Kawano

Proceedings of the National Academy of Sciences 201813058 2018年11月

The Intronic cis Element SE1 Recruits trans-Acting Repressor Complexes to Repress the Expression of ELONGATED UPPERMOST INTERNODE1 in Rice 査読

Yongyao Xie, Yaling Zhang, Jingluan Han, Jikai Luo, Gousi Li, Jianle Huang, Haibin Wu, Qingwei Tian, Qinlong Zhu, Yuanling Chen, Yoji Kawano, Yao-Guang Liu, Letian Chen

Molecular Plant 11 ( 5 ) 720 - 735 2018年5月

Plasma Membrane Microdomains Are Essential for Rac1-RbohB/H-Mediated Immunity in Rice 査読国際誌

Minoru Nagano, Toshiki Ishikawa, Masayuki Fujiwara, Yoichiro Fukao, Yoji Kawano, Maki Kawai-Yamada, Ko Shimamoto

The Plant Cell 28 ( 8 ) 1966 - 1983 2016年8月

Crosstalk of Signaling Mechanisms Involved in Host Defense and Symbiosis Against Microorganisms in Rice 査読

Akira Akamatsu, Ko Shimamoto, Yoji Kawano

CURRENT GENOMICS 17 ( 4 ) 297 - 307 2016年

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：BENTHAM SCIENCE PUBL LTD

Rice is one of the most important food crops, feeding about half population in the world. Rice pathogens cause enormous damage to rice production worldwide. In plant immunity research, considerable progress has recently been made in our understanding of the molecular mechanisms underlying microbe-associated molecular pattern (MAMP)-triggered immunity. Using genome sequencing and molecular techniques, a number of new MAMPs and their receptors have been identified in the past two decades. Notably, the mechanisms for chitin perception via the lysine motif (LysM) domain-containing receptor OsCERK1, as well as the mechanisms for bacterial MAMP (e.g. flg22, elf18) perception via the leucine-rich repeat (LRR) domain-containing receptors FLS2 and EFR, have been clarified in rice and Arabidopsis, respectively. In chitin signaling in rice, two direct substrates of OsCERK1, Rac/ROP GTPase guanine nucleotide exchange factor OsRacGEF1 and receptor-like cytoplasmic kinase OsRLCK185, have been identified as components of the OsCERK1 complex and are rapidly phosphorylated by OsCERK1 in response to chitin. Interestingly, OsCERK1 also participates in symbiosis with arbuscular mycorrhizal fungi (AMF) in rice and plays a role in the recognition of short-chitin molecules (CO4/5), which are symbiotic signatures included in AMF germinated spore exudates and induced by synthetic strigolactone. Thus, OsCERK1 contributes to both immunity and symbiotic responses. In this review, we describe recent studies on pathways involved in rice immunity and symbiotic signaling triggered by interactions with microorganisms. In addition, we describe recent advances in genetic engineering by using plant immune receptors and symbiotic microorganisms to enhance disease resistance of rice.

DOI： 10.2174/1389202917666160331201602

The RhoGAP SPIN6 Associates with SPL11 and OsRac1 and Negatively Regulates Programmed Cell Death and Innate Immunity in Rice 査読

Jinling Liu, Chan Ho Park, Feng He, Minoru Nagano, Mo Wang, Maria Bellizzi, Kai Zhang, Xiaoshan Zeng, Wende Liu, Yuese Ning, Yoji Kawano, Guo-Liang Wang

PLOS PATHOGENS 11 ( 2 ) 2015年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PUBLIC LIBRARY SCIENCE

The ubiquitin proteasome system in plants plays important roles in plant-microbe interactions and in immune responses to pathogens. We previously demonstrated that the rice U-box E3 ligase SPL11 and its Arabidopsis ortholog PUB13 negatively regulate programmed cell death (PCD) and defense response. However, the components involved in the SPL11/PUB13-mediated PCD and immune signaling pathway remain unknown. In this study, we report that SPL11-interacting Protein 6 (SPIN6) is a Rho GTPase-activating protein (RhoGAP) that interacts with SPL11 in vitro and in vivo. SPL11 ubiquitinates SPIN6 in vitro and degrades SPIN6 in vivo via the 26S proteasome-dependent pathway. Both RNAi silencing in transgenic rice and knockout of Spin6 in a T-DNA insertion mutant lead to PCD and increased resistance to the rice blast pathogen Magnaporthe oryzae and the bacterial blight pathogen Xanthomonas oryzae pv. oryzae. The levels of reactive oxygen species and defense-related gene expression are significantly elevated in both the Spin6 RNAi and mutant plants. Strikingly, SPIN6 interacts with the small GTPase OsRac1, catalyze the GTP-bound OsRac1 into the GDP-bound state in vitro and has GAP activity towards OsRac1 in rice cells. Together, our results demonstrate that the RhoGAP SPIN6 acts as a linkage between a U-box E3 ligase-mediated ubiquitination pathway and a small GTPase-associated defensome system for plant immunity.

DOI： 10.1371/journal.ppat.1004629

New insights into the dimerization of small GTPase Rac/ROP guanine nucleotide exchange factors in rice. 査読国際誌

Akamatsu Akira, Uno Kazumi, Kato Midori, Wong Hann Ling, Shimamoto Ko, Kawano Yoji

Plant signaling & behavior 10 ( 7 ) e1044702 2015年

The Crystal Structure of the Plant Small GTPase OsRac1 Reveals Its Mode of Binding to NADPH Oxidase 査読

Ken-ichi Kosami, Izuru Ohki, Minoru Nagano, Kyoko Furuita, Toshihiko Sugiki, Yoji Kawano, Tsutomu Kawasaki, Toshimichi Fujiwara, Atsushi Nakagawa, Ko Shimamoto, Chojiro Kojima

JOURNAL OF BIOLOGICAL CHEMISTRY 289 ( 41 ) 28569 - 28578 2014年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Rac/Rop proteins are Rho-type small GTPases that act as molecular switches in plants. Recent studies have identified these proteins as key components in many major plant signaling pathways, such as innate immunity, pollen tube growth, and root hair formation. In rice, the Rac/Rop protein OsRac1 plays an important role in regulating the production of reactive oxygen species (ROS) by the NADPH oxidase OsRbohB during innate immunity. However, the molecular mechanism by which OsRac1 regulates OsRbohB remains unknown. Here, we report the crystal structure of OsRac1 complexed with the non-hydrolyzable GTP analog guanosine 5'-(beta,gamma-imido) triphosphate at 1.9 angstrom resolution; this represents the first active-form structure of a plant small GTPase. To elucidate the ROS production in rice cells, structural information was used to design OsRac1 mutants that displayed reduced binding to OsRbohB. Only mutations in the OsRac1 Switch I region showed attenuated interactions with OsRbohB in vitro. In particular, Tyr(39) and Asp(45) substitutions suppressed ROS production in rice cells, indicating that these residues are critical for interaction with and activation of OsRbohB. Structural comparison of active-form OsRac1 with AtRop9 in its GDP-bound inactive form showed a large conformational difference in the vicinity of these residues. Our results provide new insights into the molecular mechanism of the immune response through OsRac1 and the various cellular responses associated with plant Rac/Rop proteins.

DOI： 10.1074/jbc.M114.603282

Rho family GTPase-dependent immunity in plants and animals 査読

Yoji Kawano, Takako Kaneko-Kawano, Ko Shimamoto

FRONTIERS IN PLANT SCIENCE 5 2014年10月

担当区分：筆頭著者,　責任著者記述言語：英語出版者・発行元：FRONTIERS RESEARCH FOUNDATION

In plants, sophisticated forms of immune systems have developed to cope with a variety of pathogens. Accumulating evidence indicates that Rac (also known as Rop), a member of the Rho family of small GTPases, is a key regulator of immunity in plants and animals. Like other small GTPases, Rac/Rop GTPases function as a molecular switch downstream of immune receptors by cycling between GDP-bound inactive and GTP-bound active forms in cells. Rac/Rop GTPases trigger various immune responses, thereby resulting in enhanced disease resistance to pathogens. In this review, we highlight recent studies that have contributed to our current understanding of the Rac/Rop family GTPases and the upstream and downstream proteins involved in plant immunity. We also compare the features of effector-triggered immunity between plants and animals, and discuss the in vivo monitoring of Rac/Rop activation.

DOI： 10.3389/fpls.2014.00522

The NB-LRR proteins RGA4 and RGA5 interact functionally and physically to confer disease resistance 査読

Stella Cesari, Hiroyuki Kanzaki, Tadashi Fujiwara, Maud Bernoux, Veronique Chalvon, Yoji Kawano, Ko Shimamoto, Peter Dodds, Ryohei Terauchi, Thomas Kroj

EMBO JOURNAL 33 ( 17 ) 1941 - 1959 2014年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

Plant resistance proteins of the class of nucleotide-binding and leucine-rich repeat domain proteins (NB-LRRs) are immune sensors which recognize pathogen-derived molecules termed avirulence (AVR) proteins. We show that RGA4 and RGA5, two NB-LRRs from rice, interact functionally and physically to mediate resistance to the fungal pathogen Magnaporthe oryzae and accomplish different functions in AVR recognition. RGA4 triggers an AVR-independent cell death that is repressed in the presence of RGA5 in both rice protoplasts and Nicotiana benthamiana. Upon recognition of the pathogen effector AVR-Pia by direct binding to RGA5, repression is relieved and cell death occurs. RGA4 and RGA5 form homo-and hetero-complexes and interact through their coiled-coil domains. Localization studies in rice protoplast suggest that RGA4 and RGA5 localize to the cytosol. Upon recognition of AVR-Pia, neither RGA4 nor RGA5 is re-localized to the nucleus. These results establish a model for the interaction of hetero-pairs of NB-LRRs in plants: RGA4 mediates cell death activation, while RGA5 acts as a repressor of RGA4 and as an AVR receptor.

DOI： 10.15252/embj.201487923

Palmitoylation-dependent Membrane Localization of the Rice Resistance Protein Pit Is Critical for the Activation of the Small GTPase OsRac1 査読

Yoji Kawano, Tadashi Fujiwara, Ai Yao, Yusuke Housen, Keiko Hayashi, Ko Shimamoto

JOURNAL OF BIOLOGICAL CHEMISTRY 289 ( 27 ) 19079 - 19088 2014年7月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Nucleotide binding domain and leucine-rich repeat (NLR)-containing family proteins function as intracellular immune sensors in both plants and animals. In plants, the downstream components activated by NLR family proteins and the immune response mechanisms induced by these downstream molecules are largely unknown. We have previously found that the small GTPase OsRac1, which acts as a molecular switch in rice immunity, is activated by Pit, an NLR-type resistance (R) protein to rice blast fungus, and this activation plays critical roles in Pit-mediated immunity. However, the sites and mechanisms of activation of Pit in vivo remain unknown. To clarify the mechanisms involved in the localization of Pit, we searched for consensus sequences in Pit that specify membrane localization and found a pair of potential palmitoylation sites in the N-terminal coiled-coil region. Although wild-type Pit was localized mainly to the plasma membrane, this membrane localization was compromised in a palmitoylation-deficient mutant of Pit. The palmitoylation- deficient Pit displayed significantly lower affinity for OsRac1 on the plasma membrane, thereby resulting in failures of the Pit-mediated cell death, the production of reactive oxygen species, and disease resistance to rice blast fungus. These results indicate that palmitoylation-dependent membrane localization of Pit is required for the interaction with and the activation of OsRac1 and that OsRac1 activation by Pit is vital for Pit-mediated disease resistance to rice blast fungus.

DOI： 10.1074/jbc.M114.569756

alpha-Taxilin Interacts with Sorting Nexin 4 and Participates in the Recycling Pathway of Transferrin Receptor 査読

Hiroshi Sakane, Yukimi Horii, Satoru Nogami, Yoji Kawano, Takako Kaneko-Kawano, Hiromichi Shirataki

PLOS ONE 9 ( 4 ) e93509 2014年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PUBLIC LIBRARY SCIENCE

Membrane traffic plays a crucial role in delivering proteins and lipids to their intracellular destinations. We previously identified alpha-taxilin as a binding partner of the syntaxin family, which is involved in intracellular vesicle traffic. alpha-Taxilin is overexpressed in tumor tissues and interacts with polymerized tubulin, but the precise function of alpha-taxilin remains unclear. Receptor proteins on the plasma membrane are internalized, delivered to early endosomes and then either sorted to the lysosome for degradation or recycled back to the plasma membrane. In this study, we found that knockdown of alpha-taxilin induced the lysosomal degradation of transferrin receptor (TfnR), a well-known receptor which is generally recycled back to the plasma membrane after internalization, and impeded the recycling of transferrin. alpha-Taxilin was immunoprecipitated with sorting nexin 4 (SNX4), which is involved in the recycling of TfnR. Furthermore, knockdown of alpha-taxilin decreased the number and length of SNX4-positive tubular structures. We report for the first time that alpha-taxilin interacts with SNX4 and plays a role in the recycling pathway of TfnR.

DOI： 10.1371/journal.pone.0093509

その他リンク： http://orcid.org/0000-0003-0687-2777

Gene Editing a Constitutively Active OsRac1 by Homologous Recombination-Based Gene Targeting Induces Immune Responses in Rice 査読

Thu Thi Dang, Zenpei Shimatani, Yoji Kawano, Rie Terada, Ko Shimamoto

PLANT AND CELL PHYSIOLOGY 54 ( 12 ) 2058 - 2070 2013年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OXFORD UNIV PRESS

OsRac1 is a member of the plant small GTPase Rac/Rop family and plays a key role in rice immunity. The constitutively active (CA) G19V mutation of OsRac1 was previously shown to induce reactive oxygen species production, phytoalexin synthesis and defense gene activation, leading to resistance to rice blast infection. To study further the effect of the G19V mutation in disease resistance, we introduced a single base substitution by gene targeting and removed the selectable marker using Cre-loxP site-specific recombination. The CA-OsRac1 gene generated by gene targeting was termed CA-gOsRac1. The G19V mutation was transferred from a targeting vector to the OsRac1 locus and stably transmitted to the next generation. In the leaf blade of homozygous CA-gOsRac1 plants, mutant transcript levels were much lower than in those of wild-type plants. In contrast, mutant transcripts in roots, leaf sheaths and panicles were more abundant than those in leaf blades. However, upon chitin treatment, the expression of defense-related genes PAL1 and PBZ1 in the cell culture was greater in the mutants compared with wild-type plants. Furthermore, induction of hypersensitive response (HR)-like cell death was observed in the leaf sheaths of mutant plants infected with a compatible race of rice blast fungus. In the CA-gOsRac1 plants, a number of genes previously shown to be induced by Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae (Xoo) infection were induced in the leaf sheath without pathogen infection. These results suggest that gene targeting will provide mutations useful for gene function studies and crop improvement.

DOI： 10.1093/pcp/pct147

Early signaling network in rice PRR-mediated and R-mediated immunity 査読

Yoji Kawano, Ko Shimamoto

CURRENT OPINION IN PLANT BIOLOGY 16 ( 4 ) 496 - 504 2013年8月

担当区分：筆頭著者記述言語：英語出版者・発行元：CURRENT BIOLOGY LTD

Recent studies on plant immunity and pathogen infection have revealed sophisticated forms of plant-pathogen interaction. Considerable progress has been made recently in our understanding of the molecular mechanism underlying chitin signaling in rice. The identification and characterization of two direct substrates, OsRacGEF1 and OsRLCK185, as components in the chitin receptor complex of OsCERK1 have revealed how pattern recognition receptors transduce pathogen signals to downstream molecules in rice. In this review, we highlight these and other recent studies that have contributed to our current understanding of the signaling network in rice immunity, especially with regard to pattern recognition receptors, disease resistance (R) proteins, and their downstream targets.

DOI： 10.1016/j.pbi.2013.07.004

An OsCEBiP/OsCERK1-OsRacGEF1-OsRac1 Module Is an Essential Early Component of Chitin-Induced Rice Immunity 査読

Akira Akamatsu, Hann Lin Wong, Masayuki Fujiwara, Jun Okuda, Keita Nishide, Kazumi Uno, Keiko Imai, Kenji Umemura, Tsutomu Kawasaki, Yoji Kawano, Ko Shimamoto

CELL HOST & MICROBE 13 ( 4 ) 465 - 476 2013年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CELL PRESS

OsCEBiP, a chitin-binding protein, and OsCERK1, a receptor-like kinase, are plasma membrane (PM) proteins that form a receptor complex essential for fungal chitin-driven immune responses in rice. The signaling events immediately following chitin perception are unclear. Investigating the spatiotemporal regulation of the rice small GTPase OsRac1, we find that chitin induces rapid activation of OsRac1 at the PM. Searching for OsRac1 interactors, we identified OsRacGEF1 as a guanine nucleotide exchange factor for OsRac1. OsRacGEF1 interacts with OsCERK1 and is activated when its C-terminal S549 is phosphorylated by the cytoplasmic domain of OsCERK1 in response to chitin. Activated OsRacGEF1 is required for chitin-driven immune responses and resistance to rice blast fungus infection. Further, a protein complex including OsCERK1 and OsRacGEF1 is transported from the endoplasmic reticulum to the PM. Collectively, our results suggest that OsCEBiP, OsCERK1, OsRacGEF1, and OsRac1 function as key components of a "defensome" critically engaged early during chitin-induced immunity.

DOI： 10.1016/j.chom.2013.03.007

OsRap2.6 transcription factor contributes to rice innate immunity through its interaction with Receptor for Activated Kinase-C 1 (RACK1) 査読

Mwathi Jane Wamaitha, Risa Yamamoto, Hann Ling Wong, Tsutomu Kawasaki, Yoji Kawano, Ko Shimamoto

RICE 5 ( 1 ) 35 2012年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Background: The rice small GTPase OsRac1 is a molecular switch in rice innate immunity. The Receptor for Activated Kinase C-1 (RACK1) interacts with OsRac1 to suppress the growth of the rice blast fungus, Magnaporthe oryzae. RACK1 has two homologs in rice, RACK1A and RACK1B. Overexpressing RACK1A enhances resistance to the rice blast fungus. However, RACK1A downstream signals are largely unknown.
Results: Here, we report the identification of OsRap2.6, a transcription factor that interacts with RACK1A. We found a 94% similarity between the OsRap2.6 AP2 domain and Arabidopsis Rap2.6 (AtRap2.6). Bimolecular fluorescence complementation (BiFC) assays in rice protoplasts using tagged OsRap2.6 and RACK1A with the C-terminal and N-terminal fragments of Venus (Vc/Vn) indicated that OsRap2.6 and RACK1A interacted and localized in the nucleus and the cytoplasm. Moreover, OsRap2.6 and OsMAPK3/6 interacted in the nucleus and the cytoplasm. Expression of defense genes PAL1 and PBZ1 as well as OsRap2.6 was induced after chitin treatment. Disease resistance analysis using OsRap2.6 RNAi and overexpressing (Ox) plants infected with the rice blast fungus indicated that OsRap2.6 RNAi plants were highly susceptible, whereas OsRap2.6 Ox plants had an increased resistance to the compatible blast fungus.
Conclusions: OsRap2.6 contributes to rice innate immunity through its interaction with RACK1A in compatible interactions.

DOI： 10.1186/1939-8433-5-35

その他リンク： http://orcid.org/0000-0003-0687-2777

Dynamic Regulation of Myosin Light Chain Phosphorylation by Rho-kinase 査読

Takako Kaneko-Kawano, Fugo Takasu, Honda Naoki, Yuichi Sakumura, Shin Ishii, Takahiro Ueba, Akinori Eiyama, Aiko Okada, Yoji Kawano, Kenji Suzuki

PLOS ONE 7 ( 6 ) 2012年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PUBLIC LIBRARY SCIENCE

Myosin light chain (MLC) phosphorylation plays important roles in various cellular functions such as cellular morphogenesis, motility, and smooth muscle contraction. MLC phosphorylation is determined by the balance between activities of Rho-associated kinase (Rho-kinase) and myosin phosphatase. An impaired balance between Rho-kinase and myosin phosphatase activities induces the abnormal sustained phosphorylation of MLC, which contributes to the pathogenesis of certain vascular diseases, such as vasospasm and hypertension. However, the dynamic principle of the system underlying the regulation of MLC phosphorylation remains to be clarified. Here, to elucidate this dynamic principle whereby Rho-kinase regulates MLC phosphorylation, we developed a mathematical model based on the behavior of thrombin-dependent MLC phosphorylation, which is regulated by the Rho-kinase signaling network. Through analyzing our mathematical model, we predict that MLC phosphorylation and myosin phosphatase activity exhibit bistability, and that a novel signaling pathway leading to the auto-activation of myosin phosphatase is required for the regulatory system of MLC phosphorylation. In addition, on the basis of experimental data, we propose that the auto-activation pathway of myosin phosphatase occurs in vivo. These results indicate that bistability of myosin phosphatase activity is responsible for the bistability of MLC phosphorylation, and the sustained phosphorylation of MLC is attributed to this feature of bistability.

DOI： 10.1371/journal.pone.0039269

The bHLH Rac Immunity1 (RAI1) Is Activated by OsRac1 via OsMAPK3 and OsMAPK6 in Rice Immunity 査読

Sung-Hyun Kim, Tetsuo Oikawa, Junko Kyozuka, Hann Ling Wong, Kenji Umemura, Mitsuko Kishi-Kaboshi, Akira Takahashi, Yoji Kawano, Tsutomu Kawasaki, Ko Shimamoto

PLANT AND CELL PHYSIOLOGY 53 ( 4 ) 740 - 754 2012年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OXFORD UNIV PRESS

The Rac/Rop GTPase OsRac1 plays an essential role in rice immunity. However, the regulatory genes acting downstream of OsRac1 are largely unknown. We focused on the RAI1 gene, which is up-regulated in suspension cells expressing a constitutively active form of OsRac1. RAI1 encodes a putative basic helix-loop-helix transcription factor. A microarray analysis of cells transformed with an inducible RAI1 construct showed increased expression of PAL1 and OsWRKY19 genes after induction, suggesting that these genes are regulated by RAI1. This was confirmed using RAI1 T-DNA activation-tagged and RNA interference lines. The PAL1 and OsWRKY19 genes were also up-regulated by sphingolipid and chitin elicitors, and the RAI1 activation-tagged plants had increased resistance to a rice blast fungus. These results indicated that RAI1 is involved in defense responses in rice. RAI1 interacted with OsMAPK3 and OsMAPK6 proteins in vivo and in vitro. Also, RAI1 was phosphorylated by OsMAPK3/6 and OsMKK4-dd in vitro. Overexpression of OsMAPK6 and/or OsMAPK3 together with OsMKK4-dd increased PAL1 and OsWRKY19 expression in rice protoplasts. Therefore, the regulation of PAL1 and OsWRKY19 expression by RAI1 could be controlled via an OsMKK4-OsMAPK3/6 cascade. Co-immunoprecipitation assays indicated that OsMAPK3 and OsRac1 occur in the same complex as OsMAPK6. Taken together, our results indicate that RAI1 could be regulated by OsRac1 through an OsMAPK3/6 cascade. In this study, we have identified RAI1 as the first transcription factor acting downstream of OsRac1. This work will help us to understand the immune system regulated by OsRac1 in rice and its orthologs in other plant species.

DOI： 10.1093/pcp/pcs033

Interaction of alpha-taxilin Localized on Intracellular Components with the Microtubule Cytoskeleton 査読

Yukimi Horii, Satoru Nogami, Yoji Kawano, Takako Kaneko-Kawano, Natsuko Ohtomo, Tomoaki Tomiya, Hiromichi Shirataki

CELL STRUCTURE AND FUNCTION 37 ( 2 ) 111 - 126 2012年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC CELL BIOLOGY

Intracellular vesicle traffic plays an essential role in the establishment and maintenance of organelle identity and biosynthetic transport. We have identified alpha-taxilin as a binding partner of the syntaxin family, which is involved in intracellular vesicle traffic. Recently, we have found that alpha-taxilin is over-expressed in malignant tissues including hepatocellular carcinoma and renal cell carcinoma. However, a precise role of alpha-taxilin in intracellular vesicle traffic and carcinogenesis remains unclear. Then, we first investigated here the intracellular distribution of alpha-taxilin in Hela cells. Immunofluorescence studies showed that alpha-taxilin distributes throughout the cytoplasm and exhibits a tubulo-vesicular pattern. Biochemical studies showed that alpha-taxilin is abundantly localized on intracellular components as a peripheral membrane protein. Moreover, we found that alpha-taxilin distributes in microtubule-dependent and syntaxin-independent manners, that alpha-taxilin directly binds to polymerized tubulin in vitro, and that N-ethylmaleimide but not brefeldin A affects the intracellular distribution of alpha-taxilin. These results indicate that alpha-taxilin is localized on intracellular components in a syntaxin-independent manner and that the alpha-taxilin-containing intracellular components are associated with the microtubule cytoskeleton and suggest that alpha-taxilin functions as a linker protein between the alpha-taxilin-containing intracellular components and the microtubule cytoskeleton.

DOI： 10.1247/csf.12002

The Function of Rac Small GTPase and Associated Proteins in Rice Innate Immunity 査読

Yoji Kawano, Letian Chen, Ko Shimamoto

RICE 3 ( 2-3 ) 112 - 121 2010年9月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Two types of innate immune receptors, pattern recognition receptors, and resistance proteins, play crucial roles in plant innate immunity; however, the molecules activated by the receptors and how immune responses are transmitted are not well understood. Evidence has been accumulating for a decade that Rac, a small guanosine triphosphatase (GTPase; also known as Rop) belonging to the Rho-type small GTPase family, is a key regulator of innate immunity in rice, barley, and other species. Like other small GTPases, Rac GTPases function as molecular switches by cycling between GDP-bound inactive and GTP-bound active forms in cells. Rac GTPase acts as a key signaling switch downstream of the two types of immune receptors and triggers innate immunity. This review outlines the role of the Rac family small GTPase and its associated proteins in rice innate immunity.

DOI： 10.1007/s12284-010-9049-4

Activation of a Rac GTPase by the NLR Family Disease Resistance Protein Pit Plays a Critical Role in Rice Innate Immunity 査読

Yoji Kawano, Akira Akamatsu, Keiko Hayashi, Yusuke Housen, Jun Okuda, Ai Yao, Ayako Nakashima, Hiroki Takahashi, Hitoshi Yoshida, Hann Ling Wong, Tsutomu Kawasaki, Ko Shimamoto

CELL HOST & MICROBE 7 ( 5 ) 362 - 375 2010年5月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CELL PRESS

The nucleotide-binding domain and leucine-rich repeat-containing (NLR) family proteins recognize pathogen-derived molecules and trigger immune responses in both plants and animals. In plants, the direct or indirect recognition of specific pathogen effectors by NLRs culminates in a hypersensitive response (HR) and the production of reactive oxygen species (ROS), key components of the plant defense response. However, the molecules activated by NLRs and how they induce immune responses are largely unknown. We found that the rice GTPase Os-Rac1 at the plasma membrane interacts directly with Pit, an NLR protein that confers resistance to the rice blast fungus. OsRac1 contributes to Pit-mediated ROS production as well as the HR and is required for Pit-mediated disease resistance in rice. Furthermore, the active form of Pit induces the activation of OsRac1 at the plasma membrane. Thus, OsRac1 is activated by Pit during pathogen attack and plays a critical role in Pit-mediated immunity in rice.

DOI： 10.1016/j.chom.2010.04.010

Rice Guanine Nucleotide Exchange Factors for Small GTPase OsRac1 Involved in Innate Immunity of Rice 査読

Tsutomu Kawasaki, Keiko Imai, Hann Ling Wong, Yoji Kawano, Keita Nishide, Jun Okuda, Ko Shimamoto

ADVANCES IN GENETICS, GENOMICS AND CONTROL OF RICE BLAST DISEASE 179 - + 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPRINGER

Small GTPase OsRac1 is a key regulator for induction of immune responses in rice. Activation of OsRac1 induces NADPH oxidase-mediated reactive oxygen species (ROS) production, PR gene expression, production of antimicrobial compounds, and lignification, which result in enhanced resistance to Magnaporthe oryzae and Xanthomonas oryzae. Inhibition of OsRac1 function suppresses the hypersensitive response induced by avirulent M. oryzae. Thus, it is likely that OsRac1 plays important roles in R protein-mediated resistance and basal resistance. However, how OsRac1 is activated during immune response remains unknown. Recently, a new type of guanine nucleotide exchange factor (GEF) for Rac/Rop GTPase has been found in plants, termed PRONE-type GEE We found eleven PRONE-type RacGEFs in rice, which may be involved in regulation of OsRac1 in innate immunity response. Recently, the PRONE-type GEF was found to interact with receptor-like protein kinase similar to R-proteins and PAMPs receptors such as Xa-21, Pi-d2, FLS2 and EFR, suggesting that the OsRacGEFs may regulate both PAMPs- and R protein-mediated disease resistance through activation of OsRac1 in rice.

DOI： 10.1007/978-1-4020-9500-9_18

Ras regulates neuronal polarity via the PI3-kinase/Akt/GSK-3 beta/CRMP-2 pathway 査読

T Yoshimura, N Arimura, Y Kawano, S Kawabata, SJ Wang, K Kaibuchi

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 340 ( 1 ) 62 - 68 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

The establishment of a polarized morphology is an essential event in the differentiation of neurons into a single axon and dendrites. We previously showed that glycogen synthase kinase-3 beta (GSK-3 beta) is critical for specifying axon/dendrite fate by the regulation of the phosphorylation of collapsin response mediator protein-2 (CRMP-2). Here, we found that the overexpression of the small GTPase Ras induced the formation of multiple axons in cultured hippocampal neurons, whereas the ectopic expression of the dominant negative form of Ras inhibited the formation of axons. Inhibition of phosphatidylinositol-3-kinase (PI3-kinase) or extracellular signal-related kinase (ERK) kinase (MEK) suppressed the Ras-induced formation of multiple axons. The expression of the constitutively active form of PI3-kinase or Akt (also called protein kinase B) induced the formation of multiple axons. The overexpression of Ras prevented the phosphorylation of CRMP-2 by GSK-3p. Taken together, these results suggest that Ras plays critical roles in establishing neuronal polarity upstream of the PI3-kinase/Akt/GSK-3 beta/CRMP-2 pathway and mitogen-activated protein kinase cascade. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bbrc.2005.11.147

Phosphorylation by Rho kinase regulates CRMP-2 activity in growth cones 査読

N Arimura, C Menager, Y Kawano, T Yoshimura, S Kawabata, A Hattori, Y Fukata, M Amano, Y Goshima, M Inagaki, N Morone, J Usukura, K Kaibuchi

MOLECULAR AND CELLULAR BIOLOGY 25 ( 22 ) 9973 - 9984 2005年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC MICROBIOLOGY

Collapsin response mediator protein 2 (CRMP-2) enhances the advance of growth cones by regulating microtubule assembly and Numb-mediated endocytosis. We previously showed that Rho kinase phosphorylates CRMP-2 during growth cone collapse; however, the roles of phosphorylated CRMP-2 in growth cone collapse remain to be clarified. Here, we report that CRMP-2 phosphorylation by Rho kinase cancels the binding activity to the tubulin dimer, microtubules, or Numb. CRMP-2 binds to actin, but its binding is not affected by phosphorylation. Electron microscopy revealed that CRMP-2 localizes on microtubules, clathrin-coated pits, and actin filaments in dorsal root ganglion neuron growth cones, while phosphorylated CRMP-2 localizes only on actin filaments. The phosphomimic mutant of CRMP-2 has a weakened ability to enhance neurite elongation. Furthermore, ephrin-A5 induces phosphorylation of CRMP-2 via Rho kinase during growth cone collapse. Taken together, these results suggest that Rho kinase phosphorylates CRMP-2, and inactivates the ability of CRMP-2 to promote microtubule assembly and Numb-mediated endocytosis, during growth cone collapse.

DOI： 10.1128/MCB.25.22.9973-9984.2005

CRMP-2 is involved in kinesin-1-dependent transport of the Sra-1/WAVE1 complex and axon formation 査読

Y Kawano, T Yoshimura, D Tsuboi, S Kawabata, T Kaneko-Kawano, H Shirataki, T Takenawa, K Kaibuchi

MOLECULAR AND CELLULAR BIOLOGY 25 ( 22 ) 9920 - 9935 2005年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC MICROBIOLOGY

A neuron has two types of highly polarized cell processes, the single axon and multiple dendrites. One of the fundamental questions of neurobiology is how neurons acquire such specific and polarized morphologies. During neuronal development, various actin-binding proteins regulate dynamics of actin cytoskeleton in the growth cones of developing axons. The regulation of actin cytoskeleton in the growth cones is thought to be involved in axon outgrowth and axon-dendrite specification. However, it is largely unknown which actin-binding proteins are involved in axon-dendrite specification and how they are transported into the developing axons. We have previously reported that collapsin response mediator protein 2 (CRMP-2) plays a critical role in axon outgrowth and axon-dendrite specification (N. Inagald, K. Chihara, N. Arimura, C. Menager, V. Kawano, N. Matsuo, T. Nishimura, M. Amano, and K. Kaibuchi, Nat. Neurosci. 4:781-782, 2001). Here, we found that CRMP-2 interacted with the specifically Rac1-associated protein 1 (Sra-1)/WASP family verprolin-homologous protein 1 (WAVE1) complex, which is a regulator of actin cytoskeleton. The knockdown of Sra-1 and WAVE1 by RNA interference canceled CRMP-2-induced axon outgrowth and multiple-axon formation in cultured hippocampal neurons. We also found that CRMP-2 interacted with the light chain of kinesin-1 and linked kinesin-1 to the Sra-1/WAVE1 complex. The knockdown of CRMP-2 and kinesin-1 delocalized Sra-1 and WAVE1 from the growth cones of axons. These results suggest that CRMP-2 transports the Sra-1/WAVE1 complex to axons in a kinesin-1-dependent manner and thereby regulates axon outgrowth and formation.

DOI： 10.1128/MCB.25.22.9920-9935.2005

Rho mediates endocytosis of epidermal growth factor receptor through phosphorylation of endophilin A1 by Rho-kinase 査読

T Kaneko, A Maeda, M Takefuji, H Aoyama, M Nakayama, S Kawabata, Y Kawano, A Iwamatsu, M Amano, K Kaibuchi

GENES TO CELLS 10 ( 10 ) 973 - 987 2005年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：BLACKWELL PUBLISHING

After binding of epidermal growth factor (EGF), the EGF receptor is activated, internalized by endocytosis, and subsequently degraded in the lysosomal pathway. Endocytotic trafficking of the activated EGF receptor is essential for controlling EGF signaling. Upon ligand-induced activation of EGF receptors, Cbl (ubiquitin ligase) binds to the activated receptor and leads to translocation of the CIN85 (Cbl-interacting protein of 85 kDa)/endophilin complex in the vicinity of the activated EGF receptors. Endophilin is known as a key regulator of clathrin-mediated endocytosis, and the translocation of endophilin in the vicinity of active EGF receptor is thought to promote receptor internalization. The constitutively active mutant of small GTPase Rho inhibits EGF receptor endocytosis. In this study, we found that this inhibitory effect was canceled by the dominant negative form of Rho-associated kinase (Rho-kinase), which is an effector of Rho. To clarify the molecular mechanisms of endocytosis downstream of Rho/Rho-kinase signal, we searched for and identified endophilin A1 as a novel substrate of Rho-kinase. We identified the phosphorylation site of endophilin A1 at Thr-14 and made endophilin T14D (substitution of Thr-14 by Asp), which is expected to mimic the phosphorylation state of endophilin A1. Endophilin T14D inhibited EGF receptor internalization. Furthermore, phosphorylation of endophilin by Rho-kinase inhibited the binding to CIN85. Taken together, these results suggest that Rho-kinase phosphorylates endophilin downstream of Rho and regulates EGF receptor endocytosis through the inhibition of binding between endophilin and CIN85.

DOI： 10.1111/j.1365-2443.2005.00895.x

Molecular mechanisms of neuronal polarity 査読

Takeshi Yoshimura, Yoji Kawano, Nariko Arimura, Saeko Kawabata, Kozo Kaibuchi

Japanese Journal of Neuropsychopharmacology 25 ( 4 ) 169 - 174 2005年8月

記述言語：日本語

Neurons are one of the most highly polarized cells known and are comprised of two structurally and functionally distinct parts, an axon and dendrites. The specification of the axon is thought to depend on its length relative to the other minor processes, which are called immature neurites. Elongation of one of immature neurites is necessary for axon specification. We previously showed that collapsin response mediator protein-2 (CRMP-2) is critical for specifying axon/dendrite fate, possibly by promoting neurite elongation via microtubule assembly. Here, we showed that glycogen synthase kinase-3β (GSK-3β) phosphorylated CRMP-2 at Thr-514 and inactivated it. The expression of the nonphosphorylated form of CRMP-2 or inhibition of GSK-3β induced the formation of multiple axons in hippocampal neurons. The expression of constitutively active GSK-3β impaired neuronal polarization, whereas the nonphosphorylated form of CRMP-2 counteracted the inhibitory effects of GSK-3β, indicating that GSK-3β regulates neuronal polarity through the phosphorylation of CRMP-2. We here reviewed the molecular mechanisms of the axon formation.

GSK-3 beta regulates phosphorylation of CRMP-2 and neuronal polarity 査読

T Yoshimura, Y Kawano, N Arimura, S Kawabata, A Kikuchi, K Kaibuchi

CELL 120 ( 1 ) 137 - 149 2005年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CELL PRESS

Neurons are highly polarized and comprised of two structurally and functionally distinct parts, an axon and dendrites. We previously showed that collapsin response mediator protein-2 (CRMP-2) is critical for specifying axon/dendrite fate, possibly by promoting neurite elongation via microtubule assembly. Here, we showed that glycogen synthase kinase-3beta (GSK-3beta) phosphorylated CRMP-2 at Thr-514 and inactivated it. The expression of the nonphosphorylated form of CRMP-2 or inhibition of GSK-3beta induced the formation of multiple axon-like neurites in hippocampal neurons. The expression of constitutively active GSK-3beta impaired neuronal polarization, whereas the nonphosphorylated form of CRMP-2 counteracted the inhibitory effects of GSK-3beta, indicating that GSK-3beta regulates neuronal polarity through the phosphorylation of CRMP-2. Treatment of hippocampal neurons with neurotrophin-3 (NT-3) induced inactivation of GSK-3beta and dephosphorylation of CRMP-2. Knockdown of CRMP-2 inhibited NT-3-induced axon outgrowth. These results suggest that NT-3 decreases phosphorylated CRMP-2 and increases nonphosphorylated active CRMP-2, thereby promoting axon outgrowth.

DOI： 10.1016/j.cell.2004.11.012

RhoA/C and the Actin Cytoskeleton. 招待査読

Kawano Y, Kaneko-Kawano T, Yoshimura T, Kawabata S, Kaibuchi K

“Rho Family GTPases” 6 113 - 136 2005年

Smooth muscle contraction by small GTPase Rho 査読

Kawano Y, Yoshimura T, Kaibuchi K

Nagoya J Med Sci 65 ( 1-2 ) 1 - 8 2002年

CRMP-2 induces axons in cultured hippocampal neurons 査読

N Inagaki, K Chihara, N Arimura, C Menager, Y Kawano, N Matsuo, T Nishimura, M Amano, K Kaibuchi

NATURE NEUROSCIENCE 4 ( 8 ) 781 - 782 2001年8月

Inhibition of myosin phosphatase by upregulated Rho-kinase plays a key role for coronary artery spasm in a porcine model with interleukin-1 beta 査読

T Kandabashi, H Shimokawa, K Miyata, Kunihiro, I, Y Kawano, Y Fukata, T Higo, K Egashira, S Takahashi, K Kaibuchi, A Takeshita

CIRCULATION 101 ( 11 ) 1319 - 1323 2000年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：LIPPINCOTT WILLIAMS & WILKINS

Background-We recently demonstrated that the Rho-kinase-mediated pathway plays an important role for coronary artery spasm in our porcine model with interleukin-1 beta (IL-1 beta). In this study, we examined whether or not Rho-kinase is upregulated at the spastic site and if so, how it induces vascular smooth muscle hypercontraction.
Methods and Results-Segments of the left porcine coronary artery were chronically treated from the adventitia with IL-1 beta-bound microbeads. Two weeks after the operation, as reported previously, intracoronary serotonin repeatedly induced coronary hypercontractions at the IL-1 beta-treated site both in vivo and in vitro, which were. markedly inhibited by Y-27632, one of the specific inhibitors of Rho-kinase, Reverse transcription-polymerase chain reaction analysis demonstrated that the expression of Rho-kinase mRNA was significantly increased in the spastic compared with the control segment. Western blot analysis showed that during the serotonin-induced contractions, the extent of phosphorylation of the myosin-binding subunit of myosin phosphatase (MBS), one of the major substrates of Rho-kinase, was significantly greater in the spastic than in the control segment and that the increase in MBS phosphorylations was also markedly inhibited by Y-27632. There was a highly significant correlation between the extent of MBS phosphorylations and that of contractions.
Conclusions-These results indicate that Rho-kinase is upregulated at the spastic site and plays a key role in inducing vascular smooth muscle hypercontraction by inhibiting myosin phosphatase through the phosphorylation of MBS in our porcine model.

Phosphorylation of myosin-binding subunit (MBS) of myosin phosphatase by Rho-kinase in vivo 査読

Y Kawano, Y Fukata, N Oshiro, M Amano, T Nakamura, M Ito, F Matsumura, M Inagaki, K Kaibuchi

JOURNAL OF CELL BIOLOGY 147 ( 5 ) 1023 - 1037 1999年11月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROCKEFELLER UNIV PRESS

Rho-associated kinase (Rho-kinase), which is activated by the small GTPase Rho, phosphorylates myosin-binding subunit (MBS) of myosin phosphatase and thereby inactivates the phosphatase activity in vitro. Rho-kinase is thought to regulate the phosphorylation state of the substrates including myosin light chain (MLC), ERM (ezrin/radixin/moesin) family proteins and adducin by their direct phosphorylation and by the inactivation of myosin phosphatase. Here we identified the sites of phosphorylation of MBS by Rho-kinase as Thr-697, Ser-854 and several residues, and prepared antibody that specifically recognized MBS phosphorylated at Ser-854. We found by use of this antibody that the stimulation of MD CK epithelial cells with tetradecanoylphorbol-13-acetate (TPA) or hepatocyte growth factor (HGF) induced the phosphorylation of MBS at Ser-854 under the conditions in which membrane ruffling and cell migration were induced. Pretreatment of the cells with Botulinum C3 ADP-ribosyltransferase (C3),which is thought to interfere with Rho functions, or Rho-kinase inhibitors inhibited the TPA- or HGF-induced MBS phosphorylation. The TPA stimulation enhanced the immunoreactivity of phosphorylated MBS in the cytoplasm and membrane ruffling area of MDCK cells. In migrating MDCK cells, phosphorylated MBS as well as phosphorylated MLC at Ser-19 were localized in the leading edge and posterior region. Phosphorylated MBS was localized on actin stress fibers in REF52 fibroblasts. The microinjection of C3 or dominant negative Rho-kinase disrupted stress fibers and weakened the accumulation of phosphorylated MBS in REF52 cells. During cytokinesis, phosphorylated MBS, MLC and ERM family proteins accumulated at the cleavage furrow, and the phosphorylation level of MBS at Ser-854 was increased. Taken together, these results indicate that MBS is phosphorylated by Rho-kinase downstream of Rho in vivo, and suggest that myosin phosphatase and Rho-kinase spatiotemporally regulate the phosphorylation state of Rho-kinase substrates including MLC and ERM family proteins in vivo in a cooperative manner.

In vivo interaction of AF-6 with activated Ras and ZO-1 査読

T Yamamoto, N Harada, Y Kawano, S Taya, K Kaibuchi

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 259 ( 1 ) 103 - 107 1999年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC

AF-6 contains two putative Ras-associating domains (RA domains) which are seen in several Ras effecters such as RalGDS and RIN1. We previously showed that an AF-6 fragment containing the amino-terminal (N-terminal) RA domain directly binds to activated Ras and ZO-1 in vitro. In this study, we showed that a single amino acid mutation in the N-terminal RA domain of AF-6 abolished the interaction of AF-6 with activated Ras and that the sites of this critical amino acid residue were similar to those for Raf-1 and RalGDS. The overexpression of the N-terminal RA domain of AF-6 inhibited the Ras-dependent c-fos promoter/enhancer stimulation in NIH3T3 cells. Endogenous AF-6 was coimmunoprecipitated with activated Ras from Rat1 cells expressing activated Ras, Moreover, we showed that AF-6 was coimmunoprecipitated with ZO-1 from Rat1 cells. Taken together, these results indicate that the Ras-interacting region on AF-6 is structurally similar to that on Raf-l and on RalGDS and that AF-6 interacts with activated Ras and ZO-1 in vivo. (C) 1999 Academic Press.

Phosphorylation of adducin by rho-kinase plays a crucial role in cell motility 査読

Y Fukata, N Oshiro, N Kinoshita, Y Kawano, Y Matsuoka, Bennett, V, Y Matsuura, K Kaibuchi

JOURNAL OF CELL BIOLOGY 145 ( 2 ) 347 - 361 1999年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROCKEFELLER UNIV PRESS

Adducin is a membrane skeletal protein that binds to actin filaments (F-actin) and thereby promotes the association of spectrin with F-actin to form a spectrin-actin meshwork beneath plasma membranes such as ruffling membranes. Rho-associated kinase (Rho-kinase), which is activated by the small guanosine triphosphatase Rho, phosphorylates alpha-adducin and thereby enhances the F-actin-binding activity of alpha-adducin in vitro. Here we identified the sites of phosphorylation of alpha-adducin by Rho-kinase as Thr445 and Thr480. We prepared antibody that specifically recognized alpha-adducin phosphorylated at Thr445, and found by use of this antibody that Rho-kinase phosphorylated alpha-adducin at Thr445 in COS7 cells in a Rho-dependent manner. Phosphorylated alpha-adducin accumulated in the membrane ruffling area of Madin-Darby canine kidney (MDCK) epithelial cells and the leading edge of scattering cells during the action of tetradecanoylphorbol-13-acetate (TPA) or hepatocyte growth factor (HGF). The microinjection of Botulinum C3 ADP-ribosyltransferase, dominant negative Rho-kinase, or alpha-adduin(T445A,T480A) (substitution of Thr445 and Thr480 by Ala) inhibited the TPA-induced membrane ruffling in MDCK cells and wound-induced migration in NRK49F cells. alpha-Adducin(T445D,T480D) (Substitution of Thr445 and Thr480 by Asp), but not alpha-adducin(T445A,T480A), counteracted the inhibitory effect of the dominant negative Rho-kinase on the TPA-induced membrane ruffling in MDCK cells. Taken together, these results indicate that Rho-kinase phosphorylates alpha-adducin downstream of Rho in vivo, and that the phosphorylation of adducin by Rho-kinase plays a crucial role in the regulation of membrane ruffling and cell motility.

The Ras target AF-6 is a substrate of the Fam deubiquitinating enzyme 査読

S Taya, T Yamamoto, K Kano, Y Kawano, A Iwamatsu, T Tsuchiya, K Tanaka, M Kanai-Azuma, SA Wood, JS Mattick, K Kaibuchi

JOURNAL OF CELL BIOLOGY 142 ( 4 ) 1053 - 1062 1998年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROCKEFELLER UNIV PRESS

The Ras target AF-6 has been shown to serve as one of the peripheral components of cell-cell adhesions, and is thought to participate in cell-cell adhesion regulation downstream of Ras. We here purified an AF-6-interacting protein with a molecular mass of similar to 220 kD (p220) to investigate the function of AF-6 at cell-cell adhesions. The peptide sequences of p220 were identical to the amino acid sequences of mouse Fam. Fam is homologous to a deubiquitinating enzyme in Drosophila, the product of the fat facets gene. Recent genetic analyses indicate that the deubiquitinating activity of the fnr facets product plays a critical role in controlling the cell fate. We found that Fam accumulated at the cell-cell contact sites of MDCKII cells, but not at free ends of plasma membranes. Fam was partially colocalized with AF-6 and interacted with AF-6 in vivo and in vitro. We also showed that AF-6 was ubiquitinated in intact cells, and that Fam prevented the ubiquitination of AF-6.
These results indicate that AF-6 forms a complex with and serves as one of the substrates for Fam, and suggest that the degradation of peripheral components of cell-cell adhesions may be regulated by Fam.

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