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Metal-induced metallothionein gene expression can be inactivated by protein kinase C inhibitor
1Institute of Radiation Biology, National Tsing Hua University, Hsinchu Taiwan, ROC.
Abstract:
The effects of protein kinase C (PKC) inhibitors on the metallothionein (MT) gene expression induced by metals were investigated. When PKC inhibitor (H7 or chelerythrine) was administered to Cd resistant, MT gene-amplified Chinese hamster ovary (CdR) cells, the induction of MT mRNA by Cd or Zn was blocked. Treating the CdR cells with a PKA-specific inhibitor, HA1004, did not cause an inhibition of metal-induced MT gene transcription. The inhibitory effect was effectuated by adding inhibitors within 40 min of exposing the cells to Cd. Apparently, AP1 was not involved in this down-regulatory effect of PKC inhibitor on MT gene expression since the inducibility of MT promoter was blocked by H7 even in the absence of the AP1-binding sequence. For Cd-treated cells, Cd accumulation in the cell was similar with or without H7 treatment. However, H7 markedly reduced cellular Zn accumulation when the cells were treated with Zn. Cycloheximide treatment increased the level of MT mRNA. This elevation can also be blocked by treating the cell with PKC inhibitor. Results in this study suggest that PKC participates in the process of metal-induced MT gene expression.
Insights
Protein kinase C (PKC) inhibitors block metal-induced metallothionein (MT) gene expression by inhibiting transcription. This suggests PKC plays a role in regulating MT gene expression in response to metals.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Metallothioneins (MTs) are crucial proteins involved in metal detoxification and homeostasis.
- Metal-induced MT gene expression is a complex process regulated by various signaling pathways.
- Protein Kinase C (PKC) is a family of enzymes implicated in diverse cellular functions, including gene regulation.
Purpose of the Study:
- To investigate the role of Protein Kinase C (PKC) in the regulation of metallothionein (MT) gene expression induced by heavy metals.
- To determine if PKC inhibition affects metal-induced MT mRNA and protein levels.
Main Methods:
- Chinese hamster ovary (CdR) cells with MT gene amplification were treated with metal ions (Cadmium, Zinc) and PKC inhibitors (H7, chelerythrine).
- Messenger RNA (mRNA) levels of MT were quantified using molecular biology techniques.
- Cellular metal accumulation was measured to assess the impact of inhibitors on metal uptake.
Main Results:
- PKC inhibitors (H7, chelerythrine) significantly blocked the induction of MT mRNA by Cadmium (Cd) and Zinc (Zn).
- A PKA-specific inhibitor (HA1004) did not affect metal-induced MT gene transcription, indicating a specific role for PKC.
- PKC inhibition reduced cellular Zinc (Zn) accumulation but not Cadmium (Cd) accumulation.
- PKC inhibition also blocked the increase in MT mRNA induced by cycloheximide, suggesting involvement in protein synthesis regulation.
Conclusions:
- Protein Kinase C (PKC) is involved in the signaling pathway that mediates metal-induced metallothionein (MT) gene expression.
- PKC acts as a positive regulator in the induction of MT gene expression by metals.
- The findings highlight PKC as a potential therapeutic target for modulating MT levels in metal-related conditions.