A chemical, genetic, and structural analysis of the nuclear bile acid receptor FXR.
The farnesoid X receptor (FXR) functions as a bile acid (BA) sensor coordinating cholesterol metabolism, lipid homeostasis, and absorption of dietary fats and vitamins. However, BAs are poor reagents for characterizing FXR functions due to multiple receptor independent properties. Accordingly, using combinatorial chemistry we evolved a small molecule agonist termed fexaramine with 100-fold increased affinity relative to natural compounds. Gene-profiling experiments conducted in hepatocytes with FXR-specific fexaramine versus the primary BA chenodeoxycholic acid (CDCA) produced remarkably distinct genomic targets. Highly diffracting cocrystals (1.78 A) of fexaramine bound to the ligand binding domain of FXR revealed the agonist sequestered in a 726 A(3) hydrophobic cavity and suggest a mechanistic basis for the initial step in the BA signaling pathway. The discovery of fexaramine will allow us to unravel the FXR genetic network from the BA network and selectively manipulate components of the cholesterol pathway that may be useful in treating cholesterol-related human diseases.
Downes
Michael
M
Howard Hughes Medical Institute, Gene Expression Laboratory, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
Verdecia
Mark A
MA
Roecker
A J
AJ
Hughes
Robert
R
Hogenesch
John B
JB
Kast-Woelbern
Heidi R
HR
Bowman
Marianne E
ME
Ferrer
Jean-Luc
JL
Anisfeld
Andrew M
AM
Edwards
Peter A
PA
Rosenfeld
John M
JM
Alvarez
Jacqueline G A
JG
Noel
Joseph P
JP
Nicolaou
K C
KC
Evans
Ronald M
RM
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001555:Benzene Derivatives / Q000138:chemical synthesis / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D002635:Chenodeoxycholic Acid / Q000819:agonists* / Q000031:analogs & derivatives* / Q000378:metabolism; D003106:Colon / Q000378:metabolism; D003429:Cross Reactions / Q000235:genetics; D004268:DNA-Binding Proteins / Q000819:agonists / Q000737:chemistry* / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000235:genetics; D018390:Gene Targeting; D015698:Genomic Library; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism; D008968:Molecular Conformation; D015394:Molecular Structure; D020411:Oligonucleotide Array Sequence Analysis; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014157:Transcription Factors / Q000819:agonists / Q000737:chemistry* / Q000235:genetics; D000099150:Receptor, Farnesoid X-Activated
D001555:Benzene Derivatives; D002635:Chenodeoxycholic Acid; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D000099150:Receptor, Farnesoid X-Activated; C474615:fexaramine