Induction of early growth response-1 gene expression by calmodulin antagonist trifluoperazine through the activation of Elk-1 in human fibrosarcoma HT1080 cells.
The early growth response gene-1 (Egr-1) is a transcription factor that plays an important role in cell growth and differentiation. It has been known that Egr-1 expression is down-regulated in many types of tumor tissues, including human fibrosarcoma HT1080 cells, and introduction of the Egr-1 gene into HT1080 cells inhibits cell growth and tumorigenic potential. Trifluoperazine (TFP), a phenothiazine class calmodulin antagonist, is known to inhibit DNA synthesis and cell proliferation and potentially important in antitumor activities. To understand the regulatory mechanism of Egr-1, we investigated the effect of TFP on expression of Egr-1 in HT1080 cells. Herein, we report that Egr-1 expression was increased by TFP in synergy with serum at the transcriptional level. Both the Ca(2+)/calmodulin-dependent protein kinase II inhibitor KN62 and the calcineurin inhibitor cyclosporin A enhanced TFP-dependent increase of Egr-1, suggesting that the Ca(2+)/calmodulindependent pathway plays a role in regulation of Egr-1 expression in HT1080 cells. The TFP-stimulated increase of the Egr-1 protein was preferentially inhibited by the MEK-specific inhibitor PD98059. In addition, activation of human Egr-1 promoter and the transcriptional activation of the ternary complex factor Elk-1 induced by TFP were inhibited both by pretreatment of PD98059 and by expression of the dominant-negative RasN17. These results indicate that the Ras/MEK/Erk/Elk-1 pathway is necessary for TFP-induced Egr-1 expression. We propose that the calmodulin antagonist TFP stimulates Egr-1 gene expression by modulating Ras/MEK/Erk and activation of the Elk-1 pathway in human fibrosarcoma HT1080 cells.
Shin
S Y
SY
Department of Biochemistry and Molecular Biology, College of Medicine, Yeungnam University, Daegu 705-717, South Korea.
Kim
S Y
SY
Kim
J H
JH
Min
D S
DS
Ko
J
J
Kang
U G
UG
Kim
Y S
YS
Kwon
T K
TK
Han
M Y
MY
Kim
Y H
YH
Lee
Y H
YH
D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002746:Chlorpromazine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics*; D051766:Early Growth Response Protein 1; D005354:Fibrosarcoma / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D017874:Immediate-Early Proteins; D048728:MAP Kinase Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics*; D014268:Trifluoperazine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D050807:ets-Domain Protein Elk-1
D002147:Calmodulin; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; C494112:ELK1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D014268:Trifluoperazine; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D002746:Chlorpromazine