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Staurosporine and calphostin-C inhibit the phorbol ester-induced decrease of protein kinase C activity in rat
J A García-Sáinz1, F J López-Gómez, M Robles-Flores
1Departamento de Bioenergética, Facultad de Medicina, Universidad Nacional Autónoma de México, D.F.
Biochemistry International
|December 1, 1992
Summary
Protein kinase C (PKC) activity in rat hepatocytes decreases after phorbol myristate acetate (PMA) treatment. This decrease is dose-dependently blocked by PKC inhibitors, indicating PKC activation precedes the activity reduction.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Protein Kinase C (PKC) is a family of enzymes involved in cell signaling.
- Phorbol myristate acetate (PMA) is a potent activator of PKC.
- Understanding PKC regulation is crucial for comprehending cellular responses.
Purpose of the Study:
- To investigate the effect of phorbol myristate acetate (PMA) on protein kinase C (PKC) activity in rat hepatocytes.
- To elucidate the role of PKC activation in the observed decrease in its own activity.
Main Methods:
- Detection of PKC 1 and PKC 2 in rat hepatocyte homogenates using DEAE-cellulose column chromatography.
- In vivo treatment of rats with PMA.
- Administration of PKC inhibitors (staurosporine, calphostin-C) to assess their effect on PMA-induced activity changes.
Main Results:
- Two main forms of PKC (PKC 1 and PKC 2) were identified in rat hepatocytes.
- PMA treatment paradoxically led to a rapid decrease in the activity of both PKC forms.
- PKC inhibitors, staurosporine and calphostin-C, shifted the dose-response curves for PMA-induced activity decrease, and blocked the effect dose-dependently.
Conclusions:
- PKC activation is a necessary event that precedes the decrease in PKC activity induced by PMA.
- This suggests a feedback mechanism where activated PKC leads to its own downregulation.