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Biology 2015, 4(1), 200-215; doi:10.3390/biology4010200

StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells

Department of Biochemistry and Molecular Biology, Center for Genetics and Molecular Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USA
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Author to whom correspondence should be addressed.
Academic Editor: Annette Graham
Received: 1 December 2014 / Revised: 13 January 2015 / Accepted: 20 February 2015 / Published: 4 March 2015
(This article belongs to the Special Issue Lipid Metabolism)
View Full-Text   |   Download PDF [573 KB, uploaded 4 March 2015]   |  

Abstract

The steroidogenic acute regulatory protein (STAR) protein expression is required for cholesterol transport into mitochondria to initiate steroidogenesis in the adrenal and gonads. STAR is synthesized as a 37 kDa precursor protein which is targeted to the mitochondria and imported and processed to an intra-mitochondrial 30 kDa protein. Tropic hormone stimulation of the cAMP-dependent protein kinase A (PKA) signaling pathway is the major contributor to the transcriptional and post-transcriptional regulation of STAR synthesis. Many studies have focused on the mechanisms of cAMP-PKA mediated control of STAR synthesis while there are few reports on STAR degradation pathways. The objective of this study was to determine the effect of cAMP-PKA-dependent signaling on STAR protein stability. We have used the cAMP-PKA responsive Y1 mouse adrenocortical cells and the PKA-deficient Kin-8 cells to measure STAR phosphorylation and protein half-life. Western blot analysis and standard radiolabeled pulse-chase experiments were used to determine STAR phosphorylation status and protein half-life, respectively. Our data demonstrate that PKA-dependent STAR phosphorylation does not contribute to 30 kDa STAR protein stability in the mitochondria. We further show that inhibition of the 26S proteasome does not block precursor STAR phosphorylation or steroid production in Y1 cells. These data suggest STAR can maintain function and promote steroidogenesis under conditions of proteasome inhibition. View Full-Text
Keywords: STAR; phosphorylation; protein stability; proteasome STAR; phosphorylation; protein stability; proteasome
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Clark, B.J.; Hudson, E.A. StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells. Biology 2015, 4, 200-215.

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