Mechanistic analysis of VDR-mediated renin suppression.
BACKGROUND
The vitamin D receptor (VDR) is involved in the regulation of renin expression and vitamin D analogs down-regulated renin mRNA expression in As4.1 cells.


METHODS
Microarray analysis was used to assess the VDR-mediated gene expression profile in As4.1 cells treated with paricalcitol, followed by real-time RT-PCR. Mechanistic analyses were done using siRNA, electrophoretic mobility shift assay (EMSA) and Western blotting.


RESULTS
Microarray analysis shows that 709 target genes were affected by paricalcitol with 286 up- and 423 downregulated. A number of major pathways were impacted including transcription factors. Real-time RT-PCR confirmed the microarray results. Treatment of the cells with siRNA against nuclear receptor co-repressor (NCOR1) eliminated VDR-mediated renin suppression. Using EMSA, paricalcitol treatment reduced the level of protein complex binding to the cyclic AMP-responsive element (CRE)-like domain in the renin distal enhancer region. VDR, CRE-binding protein (CREB1) and NCOR1 were identified in the complex binding to the CRE-like domain by Western blot in the paricalcitol-treated cells. Paricalcitol treatment resulted in an increase in the VDR level, but no significant change in the CREB1 and NCOR1 levels.


CONCLUSIONS
These results suggest that VDR-mediated renin suppression likely acts through a transcriptional regulatory complex including CREB1, NCOR1 and VDR that binds to the CRE-like domain in the renin enhancer region.
Abbott Laboratories, Abbott Park, IL, USA. nakane475@earthlink.net
Masaki
M
Nakane
Junli
J
Ma
Xiaoan
X
Ruan
Paul E
PE
Kroeger
Ruth
R
Wu-Wong
D000595:Amino Acid Sequence; D000818:Animals; D002117:Calcitriol / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000502:physiology; D020869:Gene Expression Profiling; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018167:Receptors, Calcitriol / Q000235:genetics / Q000502:physiology*; D012083:Renin / Q000096:biosynthesis / Q000235:genetics; D000092502:Renin Inhibitors
D002117:Calcitriol; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D012083:Renin; D000092502:Renin Inhibitors