Mechanisms of action of hormone-sensitive lipase in mouse Leydig cells: its role in the regulation of the steroidogenic acute regulatory protein.
Hormone-sensitive lipase (HSL) catalyzes the hydrolysis of cholesteryl esters in steroidogenic tissues and, thus, facilitates cholesterol availability for steroidogenesis. The steroidogenic acute regulatory protein (StAR) controls the rate-limiting step in steroid biosynthesis. However, the modes of action of HSL in the regulation of StAR expression remain obscure. We demonstrate in MA-10 mouse Leydig cells that activation of the protein kinase A (PKA) pathway, by a cAMP analog Bt2cAMP, enhanced expression of HSL and its phosphorylation (P) at Ser-660 and Ser-563, but not at Ser-565, concomitant with increased HSL activity. Phosphorylation and activation of HSL coincided with increases in StAR, P-StAR (Ser-194), and progesterone levels. Inhibition of HSL activity by CAY10499 effectively suppressed Bt2cAMP-induced StAR expression and progesterone synthesis. Targeted silencing of endogenous HSL, with siRNAs, resulted in increased cholesteryl ester levels and decreased cholesterol content in MA-10 cells. Depletion of HSL affected lipoprotein-derived cellular cholesterol influx, diminished the supply of cholesterol to the mitochondria, and resulted in the repression of StAR and P-StAR levels. Cells overexpressing HSL increased the efficacy of liver X receptor (LXR) ligands on StAR expression and steroid synthesis, suggesting HSL-mediated steroidogenesis entails enhanced oxysterol production. Conversely, cells deficient in LXRs exhibited decreased HSL responsiveness. Furthermore, an increase in HSL was correlated with the LXR target genes, steroid receptor element-binding protein 1c and ATP binding cassette transporter A1, demonstrating HSL-dependent regulation of steroidogenesis predominantly involves LXR signaling. LXRs interact/cooperate with RXRs and result in the activation of StAR gene transcription. These findings provide novel insight and demonstrate the molecular events by which HSL acts to drive cAMP/PKA-mediated regulation of StAR expression and steroidogenesis in mouse Leydig cells.
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
Pulak R
PR
Manna
University Paris Diderot, Sorbonne Paris Cité, Physiologie de l'axe gonadotrope, Biologie Fonctionnelle et Adaptative, EAC CNRS 4413, Paris, France.
Joëlle
J
Cohen-Tannoudji
University Paris Diderot, Sorbonne Paris Cité, Physiologie de l'axe gonadotrope, Biologie Fonctionnelle et Adaptative, EAC CNRS 4413, Paris, France.
Raymond
R
Counis
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
Charles W
CW
Garner
Institute of Reproductive and Developmental Biology, Hammersmith Campus, Imperial College London, London W12 0NN, United Kingdom.
Ilpo
I
Huhtaniemi
Department of Medicine, Veterans Affairs Palo Alto Heath Care System, Palo Alto, California 94304.
Fredric B
FB
Kraemer
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430. Electronic address: doug.stocco@ttuhsc.edu.
Douglas M
DM
Stocco
D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002219:Carbamates / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000097:blood; D002788:Cholesterol Esters / Q000097:blood; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D007985:Leydig Cells / Q000201:enzymology* / Q000378:metabolism; D000071518:Liver X Receptors; D008297:Male; D051379:Mice; D009539:Nicotinic Acids / Q000494:pharmacology; D057093:Orphan Nuclear Receptors / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011374:Progesterone / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics; D047488:Retinoid X Receptors / Q000819:agonists / Q000378:metabolism; D051122:Scavenger Receptors, Class B / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems; D002787:Sterol Esterase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D000098682:Steroidogenic Acute Regulatory Protein
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; C534918:CAY 10499; D002219:Carbamates; D002352:Carrier Proteins; D002788:Cholesterol Esters; D000071518:Liver X Receptors; D009539:Nicotinic Acids; D057093:Orphan Nuclear Receptors; D010069:Oxadiazoles; D000070778:Perilipin-1; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D047488:Retinoid X Receptors; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C497388:Srebf1 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1; D013764:Tetrahydronaphthalenes; D000098682:Steroidogenic Acute Regulatory Protein; D011374:Progesterone; D003994:Bucladesine; D002784:Cholesterol; D000242:Cyclic AMP; D015096:3-Hydroxysteroid Dehydrogenases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D017868:Cyclic AMP-Dependent Protein Kinases; D002787:Sterol Esterase; C095104:LG 100268