Journal article
Two farnesoid X receptor alpha isoforms in Japanese medaka (Oryzias latipes) are differentially activated in vitro
Aquatic toxicology, Vol.98(3), pp.245-255
07/01/2010
DOI: 10.1016/j.aquatox.2010.02.020
PMCID: PMC2874645
PMID: 20430454
Abstract
The nuclear receptor farnesoid X receptor alpha (FXRα, NR1H4) is activated by bile acids in multiple species including mouse, rat, and human and in this study we have identified two isoforms of Fxrα in Japanese medaka (Oryzias latipes), a small freshwater teleost. Both isoforms share a high amino acid sequence identity to mammalian FXRα (∼70% in the ligand-binding domain). Fxrα1 and Fxrα2 differ within the AF1 domain due to alternative splicing at the fourth intron-exon boundary. This process results in Fxrα1 having an extended N-terminus compared to Fxrα2. A Gal4DBD-FxrαLBD fusion construct was activated by chenodeoxycholic, cholic, deoxycholic and lithocholic acids, and the synthetic agonist GW4064 in transient transactivation assays. Activation of the Gal4DBD-FxrαLBD fusion construct was enhanced by addition of PGC-1α, as demonstrated through titration assays. Surprisingly, when the full-length versions of the two Fxrα isoforms were compared in transient transfection assays, Fxrα2 was activated by C24 bile acids and GW4064, while Fxrα1 was not significantly activated by any of the compounds tested. Since the only significant difference between the full-length constructs was sequence in the AF1 domain, these experiments highlight a key functional region in the Fxrα AF1 domain. Furthermore, mammalian two-hybrid studies demonstrated the ability of Fxrα2, but not Fxrα1, to interact with PGC-1α and SRC-1, and supported our results from the transient transfection reporter gene activation assays. These data demonstrate that both mammalian and teleost FXR (Fxrα2 isoform) are activated by primary and secondary bile acids.
Details
- Title: Subtitle
- Two farnesoid X receptor alpha isoforms in Japanese medaka (Oryzias latipes) are differentially activated in vitro
- Creators
- Deanna L Howarth - Integrated Toxicology and Environmental Health Program and Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USALee R Hagey - Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USASheran H.W Law - Department of Environmental and Molecular Toxicology, North Carolina State University, Raleigh, NC 27695, USANi Ai - Department of Pharmacology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USAMatthew D Krasowski - Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA, USASean Ekins - Department of Pharmacology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USAJohn T Moore - GlaxoSmithKline Discovery Research, Research Triangle Park, NC 27709, USAErin M Kollitz - Department of Environmental and Molecular Toxicology, North Carolina State University, Raleigh, NC 27695, USADavid E Hinton - Integrated Toxicology and Environmental Health Program and Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USASeth W Kullman - Department of Environmental and Molecular Toxicology, North Carolina State University, Raleigh, NC 27695, USA
- Resource Type
- Journal article
- Publication Details
- Aquatic toxicology, Vol.98(3), pp.245-255
- DOI
- 10.1016/j.aquatox.2010.02.020
- PMID
- 20430454
- PMCID
- PMC2874645
- NLM abbreviation
- Aquat Toxicol
- ISSN
- 0166-445X
- eISSN
- 1879-1514
- Publisher
- Elsevier B.V
- Language
- English
- Date published
- 07/01/2010
- Academic Unit
- Pathology
- Record Identifier
- 9984047742202771
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