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

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

doi:10.1002/(sici)1097-4644(19960501)61:2<255::aid-jcb9>3.0.co;2-t

“…1 C). This synergistic increase in Grp78 mRNA was consistent with the observation of greater-than-additive increase in Grp78 protein which was seen on western blot and [35S]methionine-labeling analysis of cells treated with the OA-HS treatment [9].…”

Section: Resultssupporting

confidence: 88%

“…Our previous studies showed that treatment with okadaic acid before but not after can aggravate as well as alter the kinetics of stress protein expression in heat-shocked 9L cells [9]. The regulation of Grp78 has been studied extensively and shown to involve a complex signal transduction cascade that relays information from the cytosol into the nucleus under this sequentially combined treatment of OA and heat-shock.…”

Section: Discussionmentioning

confidence: 99%

“…It has been demonstrated that OA can markedly enhance the synthesis of Grp78 [6] and potentiate the heat-induced hsp70 promoter activity [I@. Recently, we have demonstrated that treatment with OA can enhance the phosphorylation of vimentin and markedly potentiate the expression of Grp78 in heatshocked 9L rat brain tumor cells [9]. When followed by heat shock (US), the induction of Grp78 requires only 60 rnin treatment eith OA at relatively low dose (200 nM) instead of several hours of continuous treatment.…”

mentioning

confidence: 97%

See 1 more Smart Citation

Rapid Induction of the Grp78 Gene by Cooperative Actions of Okadaic Acid and Heat‐Shock in 9L Rat Brain Tumor Cells

Chen

¹

,

Hung

²

,

Huang

³

et al. 1997

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

We have demonstrated that treatment with 200 nM okadaic acid (OA) for 1 h followed by a 15-min heat shock (HS) at 45°C (termed OA-HS treatment) leads to a rapid transactivation of grp78, the gene for the 78-kDa glucose-regulated protein, in 9L rat brain tumor cells. The level of Grp78 mRNA rose 15-fold in 60 inin after the combined treatment. Nuclear extracts from cells subjected to OA-HS treatment, compared to those of treatment with OA or HS alone, exhibited an increased binding activity toward an oligonucleotide probe containing the CAMP-responsive element-like (CRE-like, TGACGTGA) regulatory element in electrophoretic mobility shift assays (EMSA). The binding resulted in the formation of two protein-EMSA probe complexes exhibiting different association and dissociation rates in kinetic studies. The protein factors in the upper band (complex I) and lower band (complex 11) were identified as the activating transcription factor-2 (ATF-2) and the CRE binding factor 1 (CREB-I), respectively, by antibody interference assays. In addition, the identity of CREB-1 was confirmed by supershift analysis. The binding activity, as well as the transactivation of the grp78 gene, can be abolished by a I-h treatment with the CAMP-dependent protein kinase (PKA) inhibitor but not with protein kinase C or Ca'+/calmodulin-dependent protein kinase I1 inhibitors. Accumulation of steady-state level of ATF-2 was observed and was also modulated by treatment with H-89, a PKA inhibitor. From these results, we conclude that the CRE-like element plays an important role in the rapid transactivation of the grp78 gene and that the PKA signaling pathway is involved. In addition, PKA-mediated transcriptional regulation of grp78 in OA-HS treatment is through regulation of protein phosphorylation as well as de novo synthesis of ATF-2.

show abstract

“…The present study investigates the alterations of vimentin phosphorylation and IF organization in taxol-treated 9L rat brain tumor cells (RBT cells). Vimentin has been shown as the major IF component to be phosphorylated and reorganized in cells subjected to a variety of external stimuli [Lee et al, 1992;1993;Cheng and Lai, 1994;Chen et al, 1996]. In this communication, we demonstrate that vimentin IFs are hyperphosphorylated in cells treated with taxol and the effect is both concentration and time dependent.…”

mentioning

confidence: 54%

Taxol induces concomitant hyperphosphorylation and reorganization of vimentin intermediate filaments in 9l rat brain tumor cells

Chu

¹

,

Chen

²

,

Lin

³

et al. 1998

View full text Add to dashboard Cite

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.

show abstract

Taxol induces concomitant hyperphosphorylation and reorganization of vimentin intermediate filaments in 9l rat brain tumor cells

Chu

¹

,

Chen

²

,

Lin

³

et al. 1998

View full text Add to dashboard Cite

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.

show abstract

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

Cited by 11 publications

References 35 publications

Rapid Induction of the Grp78 Gene by Cooperative Actions of Okadaic Acid and Heat‐Shock in 9L Rat Brain Tumor Cells

Rapid Induction of the Grp78 Gene by Cooperative Actions of Okadaic Acid and Heat‐Shock in 9L Rat Brain Tumor Cells

Taxol induces concomitant hyperphosphorylation and reorganization of vimentin intermediate filaments in 9l rat brain tumor cells

Taxol induces concomitant hyperphosphorylation and reorganization of vimentin intermediate filaments in 9l rat brain tumor cells

Contact Info

Product

Resources

About