巻号一覧
24 巻 (1999)
- 6 号 p. 425-
- 5 号 p. 237-
- 4 号 p. 171-
- 3 号 p. 111-
- 2 号 p. 59-
- 1 号 p. 1-
24 巻, 6 号
選択された号の論文の6件中1～6を表示しています
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REVIEW
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Yoshihiro Yoneda, Miki Hieda, Emi Nagoshi, Yoichi Miyamoto1999 年 24 巻 6 号 p. 425-433
発行日: 1999年
公開日: 2000/03/27
ジャーナル フリーThe active transport of proteins into and out of the nucleus is mediated by specific signals, the nuclear localzation signal (NLS) and nuclear export signal (NES), respectively. The best characterized NLS is that of the SV40 large T antigen, which contains a cluster of basic amino acids. The NESs were first identified in the protein kinase inhibitor (PKI) and HIV Rev protein, which are rich in leucine residues. The SV40 T-NLS containing transport substrates are carried into the nucleus by an importin α/β heterodimer. Importin α recognizes the NLS and acts as an adapter between the NLS and importin β, whereas importin β interacts with importin α bound to the NLS, and acts as a carrier of the NLS/importin α/β trimer. It is generally thought that importin α and β are part of a large protein family. The leucine rich NES-containing proteins are exported from the nucleus by one of the importin β family molecules, CRM1/exportin 1. A Ras-like small GTPase Ran plays a crucial role in both import/export pathways and determines the directionality of nuclear transport. It has recently been demonstrated in living cells that Ran actually shuttles between the nucleus and the cytoplasm and that the recycling of Ran is essential for the nuclear transport. Furthernore, it has been shown that nuclear transport factor 2 (NTF2) mediates the nuclear import of RanGDP. This review largely focuses on the issue concerning the functional divergence of importin α family molecules and the role of Ran in nucleocytoplasmic protein transport.抄録全体を表示PDF形式でダウンロード (653K)
REGULAR ARTICLES
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Takashi Kojima, Miduturu Srinivas, Alfredo Fort, Mathew Hopperstad, Ma ...1999 年 24 巻 6 号 p. 435-441
発行日: 1999年
公開日: 2000/03/27
ジャーナル フリーConnexin 26 (Cx26) has been proposed to be a tumor suppressor gene and its expression may modulate development, cell growth and differentination in various tissues, including the brain. 12-O-tetradecanoylphorbol-13-acetate (TPA) may serve as either tumor promoter (in mammary gland and skin) or as a differentiating agent (in neuroblastoma and leukemic cells) and may also modulate expression, function and phosphorylation of gap junctions. In this study, to determine the effects of TPA on Cx26 expression and its function in neuroblastoma, we transfected N2A mouse neuroblastoma cells (which are gap junction deficient) with the coding region of human Cx26 gene (which lacks TPA response elements) and examined the changes of expression and function of Cx26 following 10 nM TPA treatment. Individual clones of transfectants stably expressed distinct levels of exogenous Cx26 as judged by Northern and Western blots, immunocytochemistry and electrophysiological recordings. Cx26 channels displayed unitary conductances of about 140-155 pS. Increase of Cx26 expression following TPA treatment was markedly ohserved using immunocytochemistry and Western blots of membrane fractions although it was not detected in Northern or Western blots of whole cells. This increase in Cx26 expression in the plasma membrane was accompanied by an increase of function as evidenced in measurements of junctional conductance. These results suggest that induction of exogenous Cx26 in neuroblastoma cells by TPA treatment is controlled by post-translational mechanisms.抄録全体を表示PDF形式でダウンロード (540K) -
Atsuyki Okuda, Masumi Ohtsu, Genki Kimura1999 年 24 巻 6 号 p. 443-449
発行日: 1999年
公開日: 2000/03/27
ジャーナル フリーA temperature-sensitive mutant of 3Y1, 3Y1tsD123, reversibly arrested in G1 phase of cell cycle at the restrictive temperature of 39.8°C, shows a single amino acid exchange in the D123 protein. In this study, we found that the D123 protein level in 3Y1tsD123, which was 1/8 of that in 3Y1 compared at the permissive temperature of 33.9°C, lowered to 1/4 after a shift to the restrictive temperature. During inhibition of protein synthesis with cycloheximide, the D123 protein level in 3Y1tsD123 decreased markedly depending on the incubation temperature, compared with that in 3Y1, indicating that the lowered levels of D123 protein in 3Y1tsD123 are due to its degradation. Unexpectedly, 2 stably temperature-resistant clones were isolated after transfection of SV-3Y1tsD123 (SV40-transformed 3Y1tSD123, which shows cell death instead of G1 arrest at the restrictive temperature) with the cDNA of the mutant-type (3Y1tsD123-derived) D123 protein. The D123 protein in both clones degraded extensively at both temperatures, suggesting that the overexpression of the mutant-type D123 protein exceeds its degradation. Both temperature-resistant clones contained higher levels of D123 protein at the restrictive temperature than did SV-3Y1tsD123 at the permissive temperature. We concluded that the lowered D123 protein level at the restrictive temperature induces the temperature-sensitive characteristics of 3Y1tsD123 and SV-3Y1tSD123.抄録全体を表示PDF形式でダウンロード (590K) -
Masanori Nakata, Nobue Uto, Ikuro Maruyama, Toshihiko Yada1999 年 24 巻 6 号 p. 451-455
発行日: 1999年
公開日: 2000/03/27
ジャーナル フリーAn excessive production of nitric oxide (NO) in response to cytokines has been shown to be the major cause of the destruction of islet β-cells associated with type 1 (insulin-dependent) diabetes mellitus. The NO-induced β-cell death is the typical apoptosis. In the present study, we show evidcnce that supports a tight link between NO, Ca2+, protease and apoptosis in β-cells. Three different NO donors, SNAP, NOR3 and NOC7, induced apoptosis in a β-cell line, MIN6 cells, in a concentration-dependent manner. SNAP at 200 μM increased cytosolic Ca2+ concentration ([Ca2+]i) and induced apoptosis. The SNAP-induced apoptosis was blocked by a Ca2+ chelator, BAPTA-AM, and by an inhibitor of a Ca2+-dependent protease, calpain. In conclusion, an excessive NO production induces apoptosis, wherein an increase in [Ca2+]i and resultant activation of calpain play a key role.抄録全体を表示PDF形式でダウンロード (292K) -
Zhi-ping Zong, Kohzaburo Fujikawa-Yamamoto, Ai-li Li, Nobuo Yamaguchi, ...1999 年 24 巻 6 号 p. 457-463
発行日: 1999年
公開日: 2000/03/27
ジャーナル フリーStaurosporine has been reported to cause arrest of cells in G1 phase at low concentration and in G2 phase at high concentration. This raises the question of why the effects of staurosporine on the cell cycle depend on the applied concentration. In order to verify these multiple functions of staurosporine in Meth-A cells, we used cyclin E as a landmark of G1/S transition, cyclin B as a landmark of G2/M transition and MPM2 as a hallmark of M phase. We found that staurosporine arrested cells in G1 phase at a low concentration (20 nM) and in G2/M phase at a high concentration (200 nM). However, 200 nM staurosporine increased the expression of cyclin B and cdc2 proteins, suggesting that the cells progressed through the G2/M transition, and increased the expression of MPM2 protein, indicating that the cells entered M phase. Moreover, 200 nM staurosporine increased the expression of p53 and p21 proteins and inhibited the expression of cyclin E and cdk2 proteins, suggesting that the cells were arrested in the G1 phase of the next cycle. Morphological observation showed similar results as well. These data suggest that the G2/M accumulation induced by 200 nM staurosporine does not reflect G2 arrest, but rather results from M phase arrest, followed by progression from M phase to the G1 phase of the next cycle without cytokinesis, and finally arrest of the cells in G1 phase.抄録全体を表示PDF形式でダウンロード (855K) -
Rumi Ishisaka, Toshihiko Utsumi, Tomoko Kanno, Kayo Arita, Nobuhiko Ka ...1999 年 24 巻 6 号 p. 465-470
発行日: 1999年
公開日: 2000/03/27
ジャーナル フリーA previous paper from this laboratory reported the activation of a caspase-3-like protease by a digitonin-treated lysosomal fraction [FEBS Lett. 435, 233-236, 1998]. In this study, we examined the effects of specific inhibitors of lysosomal cysteine proteases, such as cathepsins B, S, and L, on the activation of caspase-3 to find out which cathepsin is responsible for the activation. Pro-caspase-3 in the cytosol was cleaved by a lysosomal protease(s) contained in the supernatant of a digitonin-treated crude mitochondrial fraction containing lysosomes (ML) and the cleaved product was detected by Western blotting using anti-caspase-3 antibody. The activation of caspase-3 by the lysosomal protease(s) was pH dependent and the optimun pH for activation was pH 6.6-6.8. This activation was not inhibited by CA-074, a specific inhibitor of cathepsin B, but was strongly inhibited by CLIK-066 and CLIK-181, specific inhibitors of cathepsin L. The inhibitory effect of CLIK-060, a specific inhibitor of cathepsin S, was very weak. Furthermore, the activation of caspase-3 was enhanced by addition of purified cathepsin L only in the presence of the supernatant of the digitonin-treated ML. These results suggested that a cathepsin L-type protease activity might participate in the activation mechanism of caspase-3 in the presence of the supernatnat from the ML.抄録全体を表示PDF形式でダウンロード (429K)
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