Misc - KOJIMA Takashi

A close relation of occludin to actin cytoskeleton in endothelial cells

Cell struct. Funct   26   101 - 108  2001

慢性肝炎から肝癌へ：その分子生物学機序

日本臨床   59   89 - 94  2001

ギャップ結合と細胞分化：ギャップ結合蛋白（Cx32）によるタイト結合の誘導およびアクチン構築の変化

肝サイトスケルトン研究会誌   11   17 - 22  2001

Cx32 formation and/or Cx32 mediated intercellular communication induce tight junctions in hepatocytes

T Kojima, Y Kokai, H Chiba, M Yamamoto, D Spray, Y Mochizuki, N Sawada

MOLECULAR BIOLOGY OF THE CELL ( AMER SOC CELL BIOLOGY )  11   330A - 330A  2000.12

Research paper, summary (international conference)  

ギャップ結合と細胞分化 ギャップ結合によるタイト結合の誘導

小島 隆, 千葉 英樹, 小海 康夫, 望月 洋一, 澤田 典均

日本癌学会総会記事 ( (一社)日本癌学会 )  59回   36 - 36  2000.09

ギャップ結合とタイト結合の形成過程における相互関係

山本 正夫, 小島 隆

日本臨床電子顕微鏡学会誌 ( 日本臨床分子形態学会 )  33 ( 増刊 ) S81 - S81  2000.08

培養肝細胞におけるギャップ結合蛋白(C×32)によるタイト結合の誘導

小島 隆, 望月 洋一, 澤田 典均, 小海 康夫, 千葉 英樹

日本病理学会会誌 ( (一社)日本病理学会 )  89 ( 1 ) 174 - 174  2000.03

Uncoupling of gate and fence functions of MDCK cells by the actin depolymerizing reagent mycalolide B

Exp. Cell Res   257 ( 2 ) 238 - 244  2000

DOI PubMed CiNii

"Negative" physiology: What connexin-deficient mice reveal about the functional roles of individual gap junction proteins

DC Spray, T Kojima, E Scemes, SO Suadicani, Y Gao, S Zhao, A Fort

GAP JUNCTIONS ( ELSEVIER ACADEMIC PRESS INC )  49   509 - 533  2000

Book review, literature introduction, etc.  

DOI

Induction of tight junctions in human connexin 32 (hCx32)-transfected mouse hepatocytes: Connexin 32 interacts with occludin

T Kojima, N Sawada, H Chiba, Y Kokai, M Yamamoto, M Urban, GH Lee, EL Hertzberg, Y Mochizuki, DC Spray

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS ( ACADEMIC PRESS INC )  266 ( 1 ) 222 - 229  1999.12

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Small gap junction plaques are associated with tight junction strands in some cell types including hepatocytes and it is thought that they may be closely related to tight junctions and the establishment of cell polarity. In order to examine roles of gap junctions in regulating expression and structure of tight junctions, we transfected human Cx32 cDNA into immortalized mouse hepatocytes (CHST8 cells) which lack endogenous Cx32 and Cx26. Immunocytochemistry revealed that endogenous integral tight junction protein occludin was strongly localized and was colocalized with Cx32 at cell borders in transfectants, whereas neither was detected in parental cells. In Northern blots, mRNAs encoding occludin and the other integral tight junction proteins, claudin-1 and -2, were induced in the transfectants compared to parental cells. In Western blots, occludin protein was increased in the transfectants compared to parental cells, and binding of occludin to Cx32 protein was demonstrated by immunoprecipitation. In freeze fracture of the transfectants, tight junction strands were more numerous and complex compared to parental cells, and small gap junction plaques appeared within induced tight junction strands. Nevertheless, no change in barrier function of tight junctions was observed. These results indicate that in hepatocytes, gap junction, and tight junction expression are closely coordinated, and that Cx32 may play a role in regulating occludin expression. (C) 1999 Academic Press.

DOI PubMed CiNii

Functional properties of channels formed by the neuronal gap junction protein connexin36

M Srinivas, R Rozental, T Kojima, R Dermietzel, M Mehler, DF Condorelli, JA Kessler, DC Spray

JOURNAL OF NEUROSCIENCE ( SOC NEUROSCIENCE )  19 ( 22 ) 9848 - 9855  1999.11

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The expression and functional properties of connexin36 (Cx36) were examined in two communication-deficient cell lines (N2A-neuroblastoma and PC-12 cells) transfected with Cx36 and in hippocampal neurons that express the connexin endogenously. Transfected cells expressed the expected 2.9 kb Cx36 transcript and Cx36 immunoreactivity, whereas nontransfected cells were devoid of Cx36. The relationship between steady-state junctional conductance (g(j)) and transjunctional voltage was well described by a two-state Boltzmann equation. The half-inactivation voltage (V-0), the ratio of minimal to maximal g(j) (g(min)/g(max)), and the equivalent gating charge were +/- 75 mV, 0.55, and 1.75, respectively, indicating that Cx36 exhibits very low voltage sensitivity. Conductance of single Cx36 channels measured with patch pipettes containing 130 mM CsCl was 10-15 pS (n = 15 cell pairs); despite this low unitary conductance, Cx36 channels were permeable to the dye Lucifer yellow. Hippocampal neurons expressed Cx36 both in vivo and in culture. The electrophysiological properties of channels in cultured hippocampal neurons were similar to those of the channels expressed by the transfected cell lines, and the neuronal channels were similarly permeable to Lucifer yellow. The unique combination of weak voltage sensitivity, small unitary conductance, and permeation by anions as large as second messenger molecules endows Cx36 gap junction channels with properties well suited for mediating flexible electrical and biochemical interactions between neurons.

Knockdown of AMPA receptor GluR2 expression causes delayed neurodegeneration and increases damage by sublethal ischemia in hippocampal CA1 and CA3 neurons

K Oguro, N Oguro, T Kojima, SY Grooms, A Calderone, Zheng, X, MVL Bennett, RS Zukin

JOURNAL OF NEUROSCIENCE ( SOC NEUROSCIENCE )  19 ( 21 ) 9218 - 9227  1999.11

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Considerable evidence suggests that Ca2+-permeable AMPA receptors are critical mediators of the delayed, selective neuronal death associated with transient global ischemia and sustained seizures. Global ischemia suppresses mRNA and protein expression of the glutamate receptor subunit GluR2 and increases AMPA receptor-mediated Ca2+ influx into vulnerable neurons of the hippocampal CA1 before the onset of neurodegeneration. Status epilepticus suppresses GluR2 mRNA and protein in CA3 before neurodegeneration in this region. To examine whether acute downregulation of the GluR2 subunit, even in the absence of a neurological insult, can cause neuronal cell death, we performed GluR2 "knockdown" experiments. Intracerebral injection of antisense oligodeoxynucleotides targeted to GluR2 mRNA induced delayed death of pyramidal neurons in CA1 and CA3. Antisense-induced neurodegeneration was preceded by a reduction in GluR2 mRNA, as indicated by in situ hybridization, and in GluR2 protein, as indicated by Western blot analysis. GluR2 antisense suppressed GluR2 mRNA in the dentate gyrus but did not cause cell death. The AMPA receptor antagonist 6-cyano-7-nitroquinoxiline-2,3-dione (CNQX) and the Ca2+-permeable AMPA receptor channel blocker 1-naphthyl acetyl spermine protected against antisense-induced cell death. This result indicates that antisense-induced cell death is mediated by Ca2+-permeable AMPA receptors. GluR2 antisense and brief sublethal global ischemia acted synergistically to cause degeneration of pyramidal neurons, consistent with action by a common mechanism. These findings demonstrate that downregulation of GluR2 is sufficient to induce delayed death of specific neuronal populations.

肝ギャップ結合蛋白(Cx32)によるタイト結合の誘導

小島 隆, 澤田 典均, 森 道夫, 望月 洋一

日本臨床電子顕微鏡学会誌 ( 日本臨床分子形態学会 )  32 ( 増刊 ) S110 - S110  1999.10

Disruption of circumferential actin filament causes disappearance of occludin from the cell borders of rat hepatocytes in primary culture without distinct changes of tight junction strands

T Kojima, N Sawada, M Yamamoto, Y Kokai, M Mori, Y Mochizuki

CELL STRUCTURE AND FUNCTION ( JAPAN SOC CELL BIOLOGY )  24 ( 1 ) 11 - 17  1999.02

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We investigated the relationship of actin filament organization to occludin and tight junction strands in primary cultured rat hepatocytes using an actin depolymerizing agent, mycalolide B. In control cultures, well-developed circumferential actin filaments and occludin immunoreactivity were observed on the most subapical plasma membrane of the cells, and tight junction strands formed well-developed networks in freeze-fracture replicas. In hepatocytes treated with 3 mu M mycalolide B for 6 h, circumferential actin filaments and occludin immunoreactivity disappeared from the cell borders, However, there were no marked abnormalities of tight junction strands in freeze fracture replicas. Similar results were obtained from cells cultured in medium with 0.05 mM Ca2+ for 6 h. The close association of occludin with actin and the existence of intact tight junction strands that are virtually free of both occludin and actin suggest a physiological role of occludin, but not the other proteins forming the tight junction strands, in the linkage between actin cytoskeleton and tight junction.

DOI PubMed CiNii

Spontaneous appearance of circular actin bands in cultured hepatocytes of adult rats.

MINAMITSUJI-MOCHIZUKI Chihiro, MITAKA Toshihiro, KOJIMA Takashi, NIITSU Yoshiro, MOCHIZUKI Yohichi

Med Electron Microsc   32 ( 2 ) 114 - 121  1999

DOI PubMed CiNii

細胞接着装置 タイト結合とギャップ結合の機能測定法

新培養細胞実験法    1999

Expression and function of the human liver gap junction protein, Cx26 in transfected cells.

T Kojima, M Srinivas, A Fort, G Lee, DC Spray

HEPATOLOGY ( W B SAUNDERS CO )  28 ( 4 ) 594A - 594A  1998.10

Research paper, summary (international conference)  

Gap junction expression and function in primary cultures of CX32 deficient (KO) mouse hepatocytes.

T Kojima, M Tao, A Fort, Z Huang, DC Spray

HEPATOLOGY ( W B SAUNDERS CO )  28 ( 4 ) 176A - 176A  1998.10

Research paper, summary (international conference)  

Occludin expression and tight junction strand formation during replicative DNA synthesis in primary cultures of rat hepatocytes

KOJIMA T

Med. Electron Microsc   31 ( 4 ) 169 - 176  1998

DOI CiNii

Effects of the protein phosphatase inhibitors, okadaic acid and vanadate, on localization of occludin in primary cultures of rat hepatocytes

Kojima, Takashi Sawada, Norimasa Takakuwa, Yasunari

Tumor Res ( Sapporo Medical University )  33   15 - 26  1998

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To elucidate whether protein phosphorylation is associated with the loca-lization of the tight junction protein occludin, we determined the changes of occludin protein expression in primary cultures of rat hepatocytes after treat-ment with the protein phosphatase inhibitors okadaic acid and vanadate. After 2 h of treatment with 1myu M okadaic acid or 5 mM vanadate, occludin immunoreactivity showing continuous lines in non-treated cells changed to a few spots on the plasma membrane. In western blots, broad bands above the occludin protein (65 kD) became conspicuous after treatment with okadaic acid and vanadate. We treated the same samples with alkaline phosphatase to examine whether the broad bands depended on the changes in the phos-phorylation states of occludin protein. The broad bands disappeared and the occludin was observed as a narrow band corresponding to 65 kD. Neither a significant change in the mRNA of occludin nor a change in the immunoreac-tivity of the tight junction associated protein, ZO-1, was observed after treatment with okadaic acid or vanadate. These results suggested that the phosphorylation of occludin is closely associated with localization of the protein in cultured hepatocytes and that protein phosphatase inhibitors affect the loca-lization of occludin but not ZO-1 on the plasma membrane.

DOI CiNii