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  • 1
    ISSN: 1573-4943
    Keywords: Autophosphorylation-dependent protein kinase ; vimentin ; assembly ; phosphorylation sites ; cytoskeletal intermediate filament
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The autophosphorylation-dependent protein kinase has been identified as a potent vimentin kinase that incorporates 2 mol of phosphates per mol of protein and generates five major phosphorylation sites in vimentin. Tryptic phosphopeptide mapping by high-performance liquid chromatography followed by sequential manual Edman degradation and direct peptide sequence analysis revealed that Ser-25, Ser-38, Ser-65, and Ser-71 in the amino-terminal domain and Ser-411 in the carboxyl-terminal domain are the phosphorylation sites in vimentin phosphorylated by this kinase, indicating that autophosphorylation-dependent protein kinase is a potent and unique vimentin kinase. Functional study further revealed that phosphorylation of vimentin by autophosphorylation-dependent protein kinase can completely inhibit polymerization and assembly of the cytoskeletal intermediate filament as demonstrated by electron microscopic analysis. Taken together, the results provide initial evidence that the autophosphorylation-dependent protein kinase may function as a vimentin kinase involved in the structure-function regulation of the cytoskeletal system. The results also support the notion that this cyclic nucleotide- and calcium-independent protein kinase may function as a multisubstrate/multifunctional protein kinase involved in the regulation of diverse cell functions.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 57 (1995), S. 150-162 
    ISSN: 0730-2312
    Keywords: thermotolerance ; heat-shock response ; cytoskeletal systems ; vimentin ; HSC70 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Withangulatin A (WA), a newly discovered withanolide isolated from an antitumor Chinese herb, has been shown to be a vimentin intermediate filament-targeting drug by using immunofluorescence microscopy. Together with cytochalasin D and colchicine, these drugs were employed to investigate the importance of vimentin intermediate filaments, actin filaments, and microtubules in the development of acquired thermotolerance in 9L rat brain tumor cells treated at 45°C for 15 min (priming heat-shock). Acquired thermotolerance was abrogated in cells incubated with WA before the priming heat-shock but it could be detected in cells treated with WA after the priming heat-shock. In contrast, cytochalasin D and colchicine do not interfere with the development of thermotolerance at all. The intracellular localizations of vimentin and the constitutive heat-shock protein70 (HSC70) in treated cells were examined by using immunofluorescence microscopy and detergent-extractability studies. In cells treated with WA before the priming heat-shock, vimentin IFs were tightly aggregated around the nucleus and unable to return to their normal organization after a recovery under normal growing conditions. In contrast, the IF network in cells treated with WA after the priming heat-shock was able to reorganize into filamentous form after a recovery period, a behavior similar to that of the cells treated with heat-shock only. HSC70 was found to be co-localized with vimentin during these changes. It is suggested that the integrity of intermediate filaments is important for the development of thermotolerance and that HSC70 may be involved in this process by stabilizing the intermediate filaments through direct or indirect binding.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 52 (1993), S. 253-265 
    ISSN: 0730-2312
    Keywords: heat-shock proteins ; stress response ; vimentin ; intermediate filament ; withangulatin A ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Withangulatin A induced cell rounding up and the morphological alteration resulted from the reorganization of all of the major cytoskeletal components, i.e., vimentin, tubulin, and actin, as revealed by immunofluorescence techniques. When the withangulatin A-treated cells changed to a round-up morphology, vimentin intermediate filaments were found to be collapsed and clustered around the nucleus. The alteration was accompanied by characteristic changes of vimentin molecules, including augmentation of phosphorylation, retardation of electrophoretic mobility, and decrease in detergent extractability. The levels of vimentin phosphorylation were augmented by 2.5- and 1.8-fold in cells incubated with 50 μM withangulatin A for 1 and 3 h, respectively. The electrophoretic mobility of vimentin was partially retarded in cells treated with withangulatin A for 1 h at 10 μM and a completely upshift mobility was observed after 5 h treatment at 50 μM. In addition, vimentin molecules became less extractable by nonident P-40 after the cells were treated with withangulatin A and this effect was dose dependent. The decrease in solubility of vimentin was accompanied by the redistribution of HSP72 into the detergent nonextractable fraction and these two events were well correlated. Our results suggest that withangulatin A induced the modification of vimentin, which resulted in the alteration of cell morphology and redistribution of intracellular HSP72, an event that may play an important role in the induction of heat-shock response.
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 54 (1994), S. 100-109 
    ISSN: 0730-2312
    Keywords: heat-shock genes ; HSC70 ; vimentin ; protein phosphorylation ; intermediate filaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Characteristic changes in vimentin were studied in 9L rat brain tumor cells treated at 45°C. During heat-shock treatment, vimentin molecules were rapidly phosphorylated and reorganized from a filamentous form into a perinuclear higher-order structure that was less extractable by nonionic detergent. These effects were found to be highly transient, peaked at 30 min after the onset of heat-shock treatment, and subsided thereafter. Simultaneously, the solubility of the constitutively expressed heat-shock protein70 (HSC70) was also temporarily decreased and the kinetics was identical to that of vimentin. The results indicated that HSC70 and vimentin were co-insolubilized during the heat-shock treatment. We propose that the reorganization of the intermediate filaments resulted from enhanced phosphorylation of vimentin leads to the concurrent association of HSC70 to the intermediate filaments. This process may play an essential role in regulating heat-shock genes.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 61 (1996), S. 255-265 
    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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  • 7
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 53 (1993), S. 161-168 
    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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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 169-181 
    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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