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Protein kinase C activation down-regulates natriuretic peptide receptor C expression via transcriptional and
N Yanaka1, H Akatsuka, K Omori
1Lead Generation Research Laboratory, Tanabe Seiyaku Co., Ltd., Osaka, Japan.
Abstract:
Natriuretic peptide receptor C (NPR-C) mRNA expression and ANP-binding activity via NPR-C are significantly down-regulated in HeLa cells with phorbol myristate acetate (PMA) treatment. Stabilization of the NPR-C mRNA by PMA indicated that down-regulation of its mRNA was mediated through negative transcriptional regulation. Despite the significant loss of the mRNA, reduction of NPR-C-specific ANP-binding activity after PMA exposure (4 h) was accompanied by a slight decrease in total NPR-C protein (with a 5% loss) and was also produced in the presence of actinomycin D or cycloheximide. The inhibitory effect of a long PMA exposure (18 h) paralleled with a decrease in total NPR-C protein is suggested to be dependent on reduction of de novo NPR-C synthesis. PMA-induced transcriptional and post-translational down-regulation of NPR-C was effectively reversible in the presence of the protein kinase C inhibitor GF109203X. These findings demonstrate that protein kinase C activation down-regulated NPR-C expression through transcriptional and post-translational pathways and that immediate functional receptor loss was mediated via a post-translational mechanism, such as enhanced receptor internalization.
Insights
Phorbol myristate acetate (PMA) treatment down-regulates natriuretic peptide receptor C (NPR-C) via transcriptional and post-translational mechanisms. Protein kinase C activation mediates this NPR-C expression reduction, reversible with inhibitors.
Area of Science:
- Molecular Biology
- Cell Biology
Background:
- Natriuretic peptide receptor C (NPR-C) plays a role in regulating blood pressure and fluid balance.
- Understanding NPR-C regulation is crucial for developing therapies targeting cardiovascular diseases.
Purpose of the Study:
- To investigate the molecular mechanisms underlying NPR-C down-regulation induced by phorbol myristate acetate (PMA).
- To elucidate the role of protein kinase C (PKC) in PMA-mediated NPR-C regulation.
Main Methods:
- HeLa cells were treated with PMA to assess NPR-C mRNA and protein levels.
- Experiments were conducted in the presence of actinomycin D, cycloheximide, and the PKC inhibitor GF109203X.
- ANP-binding activity was measured to evaluate NPR-C function.
Main Results:
- PMA treatment significantly down-regulated NPR-C mRNA and ANP-binding activity.
- NPR-C mRNA down-regulation was mediated by negative transcriptional regulation.
- Short-term PMA exposure led to functional receptor loss via post-translational mechanisms, possibly enhanced internalization.
- Long-term PMA exposure reduced NPR-C protein synthesis, and PMA-induced down-regulation was reversible with GF109203X.
Conclusions:
- PKC activation by PMA down-regulates NPR-C expression through both transcriptional and post-translational pathways.
- Immediate functional NPR-C loss is primarily mediated by post-translational events.
- PKC inhibition can reverse PMA-induced NPR-C down-regulation, suggesting therapeutic potential.