StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells
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...
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doaj-69a9717d53474cca83460b161c3b988e2020-11-24T23:06:23ZengMDPI AGBiology2079-77372015-03-014120021510.3390/biology4010200biology4010200StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical CellsBarbara J. Clark0Elizabeth A. Hudson1Department of Biochemistry and Molecular Biology, Center for Genetics and Molecular Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USADepartment of Biochemistry and Molecular Biology, Center for Genetics and Molecular Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USAThe 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.http://www.mdpi.com/2079-7737/4/1/200STARphosphorylationprotein stabilityproteasome |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Barbara J. Clark Elizabeth A. Hudson |
spellingShingle |
Barbara J. Clark Elizabeth A. Hudson StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells Biology STAR phosphorylation protein stability proteasome |
author_facet |
Barbara J. Clark Elizabeth A. Hudson |
author_sort |
Barbara J. Clark |
title |
StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells |
title_short |
StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells |
title_full |
StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells |
title_fullStr |
StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells |
title_full_unstemmed |
StAR Protein Stability in Y1 and Kin-8 Mouse Adrenocortical Cells |
title_sort |
star protein stability in y1 and kin-8 mouse adrenocortical cells |
publisher |
MDPI AG |
series |
Biology |
issn |
2079-7737 |
publishDate |
2015-03-01 |
description |
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. |
topic |
STAR phosphorylation protein stability proteasome |
url |
http://www.mdpi.com/2079-7737/4/1/200 |
work_keys_str_mv |
AT barbarajclark starproteinstabilityiny1andkin8mouseadrenocorticalcells AT elizabethahudson starproteinstabilityiny1andkin8mouseadrenocorticalcells |
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