Sphingosine regulates the transcription of CYP17 by binding to steroidogenic factor-1.
Steroidogenic factor (SF1, Ad4BP, NR5A1) is a nuclear receptor that is essential for steroid hormone biosynthesis and endocrine development. Recent crystallographic studies have found that phospholipids are ligands for SF1. In the present study, our aim was to identify endogenous ligands for SF1 and characterize their functional significance in mediating cAMP-dependent transcription of human CYP17. Using tandem mass spectrometry, we show that in H295R adrenocortical cells, SF1 is bound to sphingosine (SPH) and lyso-sphingomyelin (lysoSM) under basal conditions and that cAMP stimulation decreases the amount of SPH and lysoSM bound to the receptor. Silencing both acid and neutral ceramidases using small interfering RNA induces CYP17 mRNA expression, suggesting that SPH acts as an inhibitory ligand. SPH antagonized the ability of cAMP and the coactivator steroid receptor coactivator-1 to increase CYP17 reporter gene activity. These studies demonstrate that SPH is a bonafide endogenous ligand for SF1 and a negative regulator of CYP17 gene expression.
Urs
Aarti N
AN
School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, Georgia 30332-0230, USA.
Dammer
Eric
E
Sewer
Marion B
MB
D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism*; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics*; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
D018398:Homeodomain Proteins; C515057:NR5A1 protein, human; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; D000242:Cyclic AMP; D013254:Steroid 17-alpha-Hydroxylase; D013110:Sphingosine