Highly flexible ligand binding pocket of ecdysone receptor: a single amino acid change leads to discrimination between two groups of nonsteroidal ecdysone agonists.
The insect steroid hormone 20-hydroxyecdysone works through a ligand-activated nuclear receptor, the ecdysone receptor (EcR), which plays critical roles in insect development and reproduction. The EcR has been exploited to develop insecticides to control pests and gene switches for gene regulation. Recently reported crystal structures of the EcR protein show different but partially overlapping binding cavities for ecdysteroid (ECD) and diacylhydrazine (DAH) ligands, providing an explanation for the differential activity of DAH ligands in insects. 1-Aroyl-4-(arylamino)-1,2,3,4-tetrahydroquinoline (THQ) ligands were recently discovered as ecdysone agonists. Mutagenesis of the EcR (from Choristoneura fumiferana, CfEcR) ligand binding domain followed by screening in a reporter assay led to the identification of CfEcR mutants, which responded well to THQ ligands but poorly to both ECD and DAH ligands. These mutants were further improved by introducing a second mutation, A110P, which was previously reported to cause ECD insensitivity. Testing of these V128F/A110P and V128Y/A110P mutants in a C57BL/6 mouse model coactivator interaction assay and in insect cells showed that this mutant EcR is activated by THQ ligands but not by ECD or DAH ligands. The CfEcR and its V128F/A110P mutant were used to demonstrate simultaneous regulation of two reporter genes using THQ and DAH ligands.
Kumar
Mohan B
MB
RheoGene Inc., Norristown, Pennsylvania 19403, USA.
Potter
David W
DW
Hormann
Robert E
RE
Edwards
Angela
A
Tice
Colin M
CM
Smith
Howard C
HC
Dipietro
Martha A
MA
Polley
Mitch
M
Lawless
Michael
M
Wolohan
Philippa R N
PR
Kethidi
Damodhar R
DR
Palli
Subba R
SR
D016475:3T3 Cells; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000634:Aminoquinolines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D004440:Ecdysone / Q000819:agonists; D026461:Ecdysteroids / Q000494:pharmacology; D017930:Genes, Reporter / Q000235:genetics; D006834:Hydrazines / Q000737:chemistry / Q000494:pharmacology; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D009036:Moths / Q000201:enzymology / Q000235:genetics; D011987:Receptors, Steroid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015533:Transcriptional Activation; D014162:Transfection
D000634:Aminoquinolines; D026461:Ecdysteroids; D006834:Hydrazines; D008024:Ligands; D011987:Receptors, Steroid; D011994:Recombinant Proteins; C055469:ecdysone receptor; C029424:hydrazine; D004440:Ecdysone