Alteration of a Single Amino Acid in Peroxisome Proliferator-Activated Receptor-α (PPARα) Generates a PPARδ Phenotype

• Published in: Molecular endocrinology (Baltimore, Md.) Vol. 14; no. 5; pp. 733 - 740
• Main Authors: Takada, Ichiro, Yu, Ruth T, Xu, H. Eric, Lambert, Millard H, Montana, Valerie G, Kliewer, Steven A, Evans, Ronald M, Umesono, Kazuhiko
• Format: Journal Article
• Language: English
• Published: United States Endocrine Society 01-05-2000; Oxford University Press
• Subjects: Amino Acid Substitution; Animals; Cell Line; Chickens; Crystallography, X-Ray; DNA, Complementary - genetics; Evolution, Molecular; Haplorhini; Humans; Kidney; Male; Mammals; Methionine - chemistry; Models, Molecular; Mutagenesis, Site-Directed; Peroxisome Proliferators - pharmacology; Phenotype; Protein Conformation; Receptors, Cytoplasmic and Nuclear - chemistry; Receptors, Cytoplasmic and Nuclear - drug effects; Receptors, Cytoplasmic and Nuclear - genetics; Species Specificity; Transcription Factors - chemistry; Transcription Factors - drug effects; Transcription Factors - genetics; Transfection; Valine - chemistry; Xenopus laevis
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/mend.14.5.0456

Three pharmacologically important nuclear
receptors, the peroxisome proliferator-activated receptors (PPARs α,γ
, and δ), mediate key transcriptional responses involved in lipid
homeostasis. The PPARα and γ subtypes are well conserved from
Xenopus to man, but the β/δ subtypes display
substantial species variations in both structure and ligand activation
profiles. Characterization of the avian cognates revealed a close
relationship between chick (c) α and γ subtypes to their mammalian
counterparts, whereas the third chicken subtype was intermediate to
Xenopus (x) β and mammalian δ, establishing that β
and δ are orthologs. Like xPPARβ, cPPARβ responded efficiently to
hypolipidemic compounds that fail to activate the human counterpart.
This provided the opportunity to address the pharmacological problem as
to how drug selectivity is achieved and the more global evolutionary
question as to the minimal changes needed to generate a new class of
receptor. X-ray crystallography and chimeric analyses combined with
site-directed mutagenesis of avian and mammalian cognates revealed that
a Met to Val change at residue 417 was sufficient to switch the human
and chick phenotype. These results establish that the genetic drive to
evolve a novel and functionally selectable receptor can be modulated by
a single amino acid change and suggest how nuclear receptors can
accommodate natural variation in species physiology.