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07:54
Cholesterol Efflux Assay
Published on: March 6, 2012
Elevated levels of protein kinase C in Y1 cells which express apolipoprotein E decrease basal steroidogenesis by
M E Reyland1, M M Prack, D L Williams
1Department of Pharmacological Sciences, State University of New York, Stony Brook 11794.
The Journal of Biological Chemistry
|September 5, 1992
Summary
Apolipoprotein E expression in Y1-E cells increases protein kinase C (PKC) activity, suppressing steroidogenesis by reducing P450-cholesterol side chain cleavage mRNA. PKC inhibition partially restores steroidogenesis but not cAMP-stimulated pathways.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- Apolipoprotein E (ApoE) expression in mouse Y1 adrenocortical cells (Y1-E cells) previously shown to reduce steroidogenesis.
- This suppression is partly due to inhibited cAMP-mediated events.
Purpose of the Study:
- To investigate the role of protein kinase C (PKC) in ApoE-mediated suppression of steroidogenesis in Y1-E cells.
- To determine if elevated PKC activity contributes to the Y1-E cell phenotype.
Main Methods:
- Assessed total cellular PKC activity, mRNA, and protein levels in Y1-E cells.
- Measured diacylglycerol levels, an in vivo activator of PKC.
- Utilized PKC inhibitors (staurosporine, calphostin C) to assess their impact on steroidogenesis and gene expression.
Main Results:
- Y1-E cells exhibited a 3-5 fold increase in total cellular PKC activity, mRNA, and protein levels.
- Diacylglycerol levels were elevated 2-3 fold in Y1-E cells.
- PKC inhibition with staurosporine or calphostin C increased P450-cholesterol side chain cleavage mRNA expression and partially restored basal steroidogenesis.
Conclusions:
- Increased PKC expression in Y1-E cells contributes to reduced basal steroidogenesis by suppressing P450-cholesterol side chain cleavage mRNA.
- PKC inhibition does not fully reverse the block in cAMP-stimulated steroidogenesis, indicating ApoE's pleiotropic effects are not solely mediated by PKC.
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