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  • 1
    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.
    Additional Material: 8 Ill.
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  • 2
    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.
    Additional Material: 7 Ill.
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  • 3
    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.
    Additional Material: 8 Ill.
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  • 4
    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.
    Additional Material: 3 Ill.
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