TRANSCRIPTIONAL REGULATION OF ENDOTHELIAL NITRIC-OXIDE SYNTHASE BY LYSOPHOSPHATIDYLCHOLINE

We have shown that lysophosphatidylcholine (lyso-PC) increases endothe lial nitric-oxide synthase (eNOS) expression at the transcriptional le vel (Zembowicz, A., Tang, J.-L., and Wu, K. K. (1995) J. Biol. Chem. 2 70, 17006-17010). To elucidate the mechanism by which lyso-PC increase s the eNOS transcription, we identified Sp1 sites at -104 to -90 and P EA3 sites at -40 to -24 as being involved in lyso-PC-induced promoter activity. Site-directed mutagenesis of Sp1 sites resulted in a marked reduction of basal and lyso-PC-induced activity whereas PEA3 site muta tion abrogated response to lyso-PC. Band shift assays revealed that ly so-PC augmented Sp1 binding activity. Pretreatment of cells or nuclear extracts with okadaic acid reduced the Sp1 binding activity. Furtherm ore, okadaic acid treatment abrogated the lyso-PC induced promoter aug mentation. Lyse-PC increased the nuclear extract protein phosphatase 2 A (PP2A) activity, which was suppressed by okadaic acid treatment. The se results suggest that lyso-PC up-regulates eNOS transcription by a P P2A-dependent increase in Sp1 binding activity.