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Anti-proliferative effects of protein kinase C inhibitors in human keratinocytes
L Hegemann1, B Bonnekoh, L A van Rooijen
1Department of Dermatology, University of Cologne, Germany.
Abstract:
Various lines of evidence indicate that protein kinase C, a key enzyme in transmembraneous signal transduction, is involved in the regulation of keratinocyte proliferation. In the present study we have investigated the effects of various structurally unrelated protein kinase C inhibitors on the proliferation of HaCa T cells, a non-tumorigenic human keratinocyte cell line. All protein kinase C inhibitors dose-dependently inhibited cell proliferation as assessed by the incorporation of radioactively labelled thymidine and amino acids as well as the increase in total protein content in keratinocytes. The potencies of the drugs to inhibit cell proliferation were strongly correlated to their inhibitory potency on purified protein kinase C, displaying a correlation coefficient of 0.97. Methotrexate, an anti-proliferative drug, was found not to inhibit protein kinase C. Therefore, our data provide evidence that protein kinase C is crucially involved in the regulation of keratinocyte proliferation but is not the only target of anti-proliferative drug action.
Insights
Protein kinase C (PKC) regulates keratinocyte proliferation. Various PKC inhibitors demonstrated dose-dependent inhibition of HaCaT cell proliferation, correlating with their PKC inhibitory potency. Methotrexate did not inhibit PKC.
Area of Science:
- Cell Biology
- Biochemistry
- Dermatology
Background:
- Protein kinase C (PKC) is a key enzyme in transmembraneous signal transduction.
- Evidence suggests PKC's involvement in regulating keratinocyte proliferation.
Purpose of the Study:
- To investigate the effects of structurally unrelated PKC inhibitors on HaCaT cell proliferation.
- To determine the correlation between PKC inhibition and anti-proliferative effects.
Main Methods:
- HaCaT cells were treated with various PKC inhibitors.
- Cell proliferation was assessed by measuring radioactively labeled thymidine and amino acid incorporation.
- Total protein content increase was measured.
- Inhibitory potency on purified PKC was determined.
Main Results:
- All tested PKC inhibitors dose-dependently inhibited HaCaT cell proliferation.
- A strong correlation (r=0.97) was observed between the potency of drugs to inhibit cell proliferation and their potency to inhibit purified PKC.
- Methotrexate, an anti-proliferative drug, did not inhibit PKC activity.
Conclusions:
- PKC plays a crucial role in regulating keratinocyte proliferation.
- PKC is a significant, but not the sole, target for anti-proliferative drug action in keratinocytes.