Transcriptional repression of the CTP:phosphocholine cytidylyltransferase gene by sphingosine.
We examined the effects of the bioactive lipid, sphingosine, on the expression of the rate-limiting enzyme involved in surfactant phosphatidylcholine synthesis, CCTalpha (CTP:phosphocholine cytidylyltransferase alpha). Sphingosine decreased phosphatidylcholine synthesis by inhibiting CCT activity in primary alveolar type II epithelia. Sphingosine decreased CCTalpha protein and mRNA levels by approx. 50% compared with control. The bioactive lipid did not alter CCTalpha mRNA stability, but significantly inhibited its transcriptional rate. In murine lung epithelia, sphingosine selectively reduced CCTalpha promoter-reporter activity when transfected with a 2 kb CCTalpha promoter/luciferase gene construct. Sphingosine also decreased transgene expression in murine type II epithelia isolated from CCTalpha promoter-reporter transgenic mice harbouring this 2 kb proximal 5'-flanking sequence. Deletional analysis revealed that sphingosine responsiveness was mapped to a negative regulatory element contained within 814 bp upstream of the coding region. The results indicate that bioactive sphingolipid metabolites suppress surfactant lipid synthesis by inhibiting gene transcription of a key surfactant biosynthetic enzyme.
Ryan
Alan J
AJ
Department of Veterans Affairs Medical Center, University of Iowa College of Medicine, Iowa City, IA 52242, USA.
Fisher
Kurt
K
Thomas
Christie P
CP
Mallampalli
Rama K
RK
D000818:Animals; D019916:Choline-Phosphate Cytidylyltransferase / Q000235:genetics*; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics; D004847:Epithelial Cells / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000235:genetics; D051379:Mice; D011650:Pulmonary Alveoli / Q000166:cytology / Q000201:enzymology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats; D020545:Respiratory Mucosa / Q000166:cytology / Q000201:enzymology; D013110:Sphingosine / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects* / Q000235:genetics
D012333:RNA, Messenger; D019916:Choline-Phosphate Cytidylyltransferase; D013110:Sphingosine