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11

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Vimentin serves as a phosphate sink during the apparent activation of protein kinases by okadaic acid in mammalian cells (1993)

Lai, Yiu-Kay ; Lee, Wen-Chuan ; Chen, Kuang-Den

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 53 (1993), S. 161-168

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ISSN: 0730-2312

Keywords: vimentin ; intermediate filament ; protein phosphorylation ; immunoblotting ; scanning densitometry ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: The vimentin contents of four mammalian cell lines originating from rat and human tissues were determined by immunoblotting and scanning densitometry. On per cell volume basis, vimentin content in 9L, KD, and HeLa cells was found to be 206.6, 151.6, and 19.1 ng/μl, respectively. A431 cells were devoid of vimentin. Protein phosphorylation was augmented by treatment of 600 nM okadaic acid for 1 h in these cells. During the apparent activation of protein kinases, vimentin became hyperphosphorylated and the phosphorylation level of other nonvimentin phosphoproteins was relatively little affected in 9L and KD cells. In contrast, cytokeratins and other nonvimentin proteins were heavily phosphorylated in OA-treated HeLa and A431 cells. Regression analysis indicated that the relative increase in phosphorylation level of nonvimentin phosphoproteins was inversely correlated to the contents of vimentin in the four cell lines [r2 = -0.985]. These observations strongly suggest that vimentin acts as a phosphate sink by which the effects of “excess kinase activity” inflicted by phosphatases inhibition was attenuated.

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Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jcb.240530209

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12

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Okadaic acid as an inducer of the 78-kDa glucose-regulated protein in 9L rat brain tumor cells (1993)

Hou, Ming-Chin ; Shen, Chi-Hsiu ; Lee, Wen-Chuan ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 51 (1993), S. 91-101

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ISSN: 0730-2312

Keywords: okadaic acid ; 78-kDa glucose-regulated proteins ; brain tumor cells ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Okadaic acid (OA), a potent inhibitor of protein phosphatases 1 and 2A, has been widely used as a tool for unravelling the regulation of cellular metabolic processes involving protein phosphorylation/dephosphorylation. It has recently been found that OA can induce reversible hyperphosphorylation of vimentin and reorganization of intermediate filaments [Lee et al., J. Cell. Biochem. 49: 378-393, 1992]. We report here that OA specifically induced the synthesis of a 78-kDa protein, which was identified as the 78-kDa glucose-regulated protein (GRP78) by two-dimensional sodium dodecylsulfate-polyacrylamide gel electrophoresis and peptide mapping. The induction of GRP78 by OA was dose-dependent and reversible. For 7 h treatments, GRP78 synthesis was initially enhanced under 50 nM OA and became the highest (about 6-fold) under 200 nM OA. Meanwhile, under 200 nM OA, GRP78 synthesis was initially enhanced after 4 h and reached its maximal level (about 8-fold) after 15 h of treatment. Subsequently, upon removal of OA, the level of OA-induced GRP78 was reduced to basal level after 12 h of recovery. Induction of GRP78 synthesis by OA was abolished in cells pretreated with actinomycin D and cycloheximide, indicating that it was regulated at the transcriptional level and its induction required de novo protein synthesis. Furthermore, OA suppressed protein glycosylation, and the result lent support to the hypothesis that suppression of protein glycosylation may correlate with induction of GRP78 synthesis. © 1993 Wiley-Liss, Inc.

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URL: http://dx.doi.org/10.1002/jcb.240510116

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13

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Modulation of protein phosphorylation and stress protein expression by okadaic acid on heat shock cells (1996)

Chen, Kuang-Den ; Chu, Jao-Jia ; Lai, Yiu-Kay

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 61 (1996), S. 255-265

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ISSN: 0730-2312

Keywords: glucose-regulated proteins ; heat shock proteins ; heat shock ; okadaic acid ; protein phosphorylation ; vimentin ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: We have demonstrated that pretreatment but not post-treatment with okadaic acid (OA) can aggravate cytotoxicity as well as alter the kinetics of stress protein expression and protein phosphorylation in heat shocked cells. Compared to heat shock, cells recovering from 1 hr pretreatment of OA at 200 nM and cotreated with heat shock at 45°C for the last 15 min of incubation (OA→HS treatment) exhibited enhanced induction of heat shock proteins (HSPs) 70 and 110. In addition to enhanced expression, the attenuation of HSC70 and HSP90 after the induction peaks was also delayed in OA→HS-treated cells. The above treatment also resulted in the rapid induction of the 78 kDa glucose-regulated protein (GRP78), which expression remained constant in cells recovering from treatment with 200 nM OA for 1 hr, heat shocked at 45°C for 15 min, or in combined treatment in reversed order (HS→OA treatment). Enhanced phosphorylation of vimentin and proteins with molecular weights of 65, 40, and 33 kDa and decreased phosphorylation of a protein with a molecular weight of 29 kDa were also observed in cells recovering from OA→HS treatment. Again, protein phosphorylation in cells recovering from HS→OA treatment did not differ from those in cells treated only with heat shock. Since the alteration in the kinetics of stress protein expression and protein phosphorylation was tightly correlated, we concluded that there is a critical link between induction of the stress proteins and phosphorylation of specific proteins. Furthermore, the rapid induction of GRP78 under the experimental condition offered a novel avenue for studying the regulation of its expression. © 1996 Wiley-Liss, Inc.

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14

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Taxol induces concomitant hyperphosphorylation and reorganization of vimentin intermediate filaments in 9l rat brain tumor cellsIn Memory of Dr. Chi-Shuen Tsou. (1998)

Chu, Jao-Jia ; Chen, Kuang-Den ; Lin, Yi-Liang ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 68 (1998), S. 472-483

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ISSN: 0730-2312

Keywords: taxol ; microtubules ; vimentin ; intermediate filaments ; protein phosphorylation ; protein kinases ; inhibitors ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Taxol, a microtubule stabilizing agent, has been extensively investigated for its antitumor activity. The cytotoxic effect of taxol is generally attributed to its antimicrotubule activity and is believed to be cell cycle dependent. Herein, we report that taxol induces hyperphosphorylation and reorganization of the vimentin intermediate filament in 9L rat brain tumor cells, in concentration- and time-dependent manner. Phosphorylation of vimentin was maximum at 10-6 M of taxol treatment for 8 h and diminished at higher (10-5 M) concentration. Enhanced phosphorylation of vimentin was detectable at 2 h treatment with 10-6 M taxol and was maximum after 12 h of treatment. Taxol-induced phosphorylation of vimentin was largely abolished in cells pretreated with staurosporine and bisindolymaleimide but was unaffected by H-89, KT-5926, SB203580, genistein, and olomoucine. Thus, protein kinase C may be involved in this process. Hyperphosphorylation of vimentin was accompanied by rounding up of cells as revealed by scanning electron microscopy. Moreover, there was a concomitant reorganization of the vimentin intermediate filament in the taxol-treated cells, whereas the microtubules and the actin microfilaments were less affected. Taken together, our data demonstrate that taxol induces hyperphosphorylation of vimentin with concomitant reorganization of the vimentin intermediate filament and that this process may be mediated via a protein kinase C signaling pathway. J. Cell Biochem. 68:472-483, 1998. © 1998 Wiley-Liss, Inc.

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15

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Induction of stress response and differential expression of 70 kDa stress proteins by sodium fluoride in hela and rat brain tumor 9l cells (1998)

Cheng, Ting-Jen ; Chen, Tzu-Mei ; Chen, Chi-Hau ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 69 (1998), S. 221-231

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ISSN: 0730-2312

Keywords: sodium fluoride ; stress response ; stress proteins ; heat shock proteins ; rat brain tumor 9L cells ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: We herein demonstrate that sodium fluoride (NaF) acts as a stress response inducer on HeLa and 9L rat brain tumor cells. NaF is only slightly cytotoxic, and inhibitory to Ser/Thr-phosphatases but not to Tyr-phosphatases in both cell lines. After treatment with 5 mM NaF for 2 h, the phosphorylation levels of vimentin and an alkali-resistant 65-kDa phosphoprotein were enhanced, a common phenomenon detected in cells under a variety of stress conditions. Under an identical treatment protocol, in which the cells were treated with 5 mM NaF for 2 h and then allowed to recover under normal growing conditions for up to 12 h, NaF differentially induced the cytoplasmic/nuclear heat-shock protein70s (including both the inducible and the constitutively expressed members of this protein family) in HeLa cells and the endoplasmic reticulum residing heat-shock protein70 (the glucose-regulated protein with an apparent molecular weight of 78 kDa) in 9L cells. Electrophoretic mobility shift assays (EMSA) using probes containing well-characterized regulatory elements revealed the activation of the heat-shock factor in HeLa but not in 9L cells; this is in good agreement with the stress protein induction pattern. Additional differential induction of binding activities toward EMSA probes individually containing NF-κB, AP-2, and CRE-like elements were detected in NaF-treated cells. The possible involvement of these binding sites as well as the corresponding factors in the stress response are discussed. J. Cell. Biochem. 69:221-231, 1998. © 1998 Wiley-Liss, Inc.

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16

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Involvement of heat shock elements and basal transcription elements in the differential induction of the 70-kDa heat shock protein and its cognate by cadmium chloride in 9L rat brain tumor cells (1998)

Hung, Jan-Jong ; Cheng, Ting-Jen ; Dah-Tsyr Chang, Margaret ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 71 (1998), S. 21-35

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ISSN: 0730-2312

Keywords: heat shock protein ; heat shock genes ; heat shock element ; heat shock factor ; basal transcription elements ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Exposure of 9L rat brain tumor cells to 40-100 μM CdCl2 for 2 h leads to an induction of a wide spectrum of heat shock proteins (HSPs). We have demonstrated that induction of the 70-kDa HSP (HSP70) and enhanced expression of its cognate (HSC70) by cadmium are concentration dependent and that the induction kinetics of these HSP70s are different. The increased synthesis of the HSP70s is accompanied by the increase in hsp70 and hsc70 mRNA levels, indicative of transcriptional regulation of the heat shock genes. Electrophoretic mobility shift assay (EMSA) using probes encompassing heat shock element (HSE), TATA, GC, and CCAAT boxes derived from the promoter regions of the heat shock genes shows distinguished binding patterns between hsp70 and hsc70 genes in both control and cadmium-treated cells. The results indicate that, in addition to the HSEs, the basal transcription elements are important in the regulation of the heat shock genes. The binding patterns of the corresponding transcription factors of these elements are examined by EMSA by using extended promoter fragments from respective heat shock genes with sequential addition of excess oligonucleotides encompassing individual transcription elements. Taken together, our results show that the differential induction of hsp70 and hsc70 involves multiple transcription factors that interact with HSE, TATA, GC, and CCAAT boxes. J. Cell. Biochem. 71:21-35, 1998. © 1998 Wiley-Liss, Inc.

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17

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Identification of mitogen-activated protein kinase-activated protein kinase-2 as a vimentin kinase activated by okadaic acid in 9L rat brain tumor cells (1998)

Cheng, Ting-Jen ; Lai, Yiu-Kay

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 71 (1998), S. 169-181

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ISSN: 0730-2312

Keywords: intermediate filaments ; mitogen-activated protein ; kinase-activated protein kinase-2 ; vimentin ; okadaic acid ; phosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Organization of intermediate filament, a major component of cytoskeleton, is regulated by protein phosphorylation/dephosphorylation, which is a dynamic process governed by a balance between the activities of involved protein kinases and phosphatases. Blocking dephosphorylation by protein phosphatase inhibitors such as okadaic acid (OA) leads to an apparent activation of protein kinase(s) and to genuine activation of phosphatase-regulated protein kinase(s). Treatment of 9L rat brain tumor cells with OA results in a drastically increased phosphorylation of vimentin, an intermediate filament protein. In-gel renaturing assays and in vitro kinase assays using vimentin as the exogenous substrate indicate that certain protein kinase(s) is activated in OA-treated cells. With specific protein kinase inhibitors, we show the possible involvement of the cdc2 kinase- and p38 mitogen-activated protein kinase (p38MAPK)-mediated pathways in this process. Subsequent in vitro assays demonstrate that vimentin may serve as an excellent substrate for MAPK-activated protein kinase-2 (MAPKAPK-2), the downstream effector of p38MAPK, and that MAPKAPK-2 is activated with OA treatment. Comparative analysis of tryptic phosphopeptide maps also indicates that corresponding phosphopeptides emerged in vimentin from OA-treated cells and were phosphorylated by MAPKAPK-2. Taken together, the results clearly demonstrate that MAPKAPK-2 may function as a vimentin kinase in vitro and in vivo. These findings shed new light on the possible involvement of the p38MAPK signaling cascade, via MAPKAPK-2, in the maintenance of integrity and possible physiological regulation of intermediate filaments. J. Cell. Biochem. 71:169-181, 1998. © 1998 Wiley-Liss, Inc.

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18

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Induction of heat-shock response and alterations of protein phosphorylation by a novel topoisomerase ii inhibitor, withangulatin A, in 9L rat brain tumor cells (1991)

Lee, Wen-Chuan ; Lin, Kae-Yuan ; Chen, Chiu-Ming ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 149 (1991), S. 66-76

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ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Withangulatin A is a newly identified in vitro topoisomerase II inhibitor isolated from the Chinese antitumor herb Physalis angulata. In vivo, it was found to be cytotoxic, capable of suppressing general protein synthesis and of inducing the synthesis of a small set of proteins including those generated by heat-shock treatment. The 70 kDa protein generated by withangulatin A was unequivocally identified as the heat-shock protein70 (HSP70) since both proteins migrated to the same position on two-dimensional polyacrylamide gels, could be recognized by a monoclonal antibody to human HSP70, and exhibited identical peptide maps. The induction of protein synthesis by withangulatin A was regulated at the transcriptional level since it was aborted in cells pre-treated with actinomycin D. However, the initiation of this process did not require de novo protein synthesis since it was not affected by cycloheximide. Other cellular effect of withangulatin A was alterations of protein phosphorylation including an enhancement of phosphorylation of a 32 kDa protein which was also detected in the heat-shocked cells. Morevoer, this process was observed within 7.5 min after the initial heat treatment which is much faster than the onset of HSP synthesis. Therefore, increased phosphorylation of the 65 kDa protein may represent on of the earliest signals generated by both heat-shock and withangulatin A and may be involved in the upstream regulation of heat-shock response in cells.

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Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jcp.1041490110

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