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- Title
Development of a yeast reporter gene assay to detect ligands of freshwater cladoceran Daphnia magna ultraspiracle, a homolog of vertebrate retinoid X receptors.
- Authors
Ito‐Harashima, Sayoko; Tsubouchi, Yumiko; Takada, Eiji; Kawanishi, Masanobu; Yagi, Takashi
- Abstract
Endocrine‐disrupting chemicals (EDCs) often affect homeostatic regulation in living organisms by directly acting on nuclear receptors (NRs). Retinoid X receptors (RXRs), the most highly conserved members of the NR superfamily during evolution, function as partners to form heterodimers with other NRs, such as retinoic acid, thyroid hormone, and vitamin D3 receptors. RXRs also homodimerize and induce the expression of target genes upon binding with their natural ligand, 9‐cis‐retinoic acid (9cRA), and typical EDCs organotin compounds, such as tributyltin and triphenyltin. In the present study, we established a new yeast reporter gene assay (RGA) to detect the ligands of freshwater cladoceran Daphnia magna ultraspiracle (Dapma‐USP), a homolog of vertebrate RXRs. D. magna has been used as a representative crustacean species for aquatic EDC assessments in the Organization for Economic Corporation and Development test guidelines. Dapma‐USP was expressed along with the Drosophila melanogaster steroid receptor coactivator Taiman in yeast cells carrying the lacZ reporter plasmid. The RGA for detecting agonist activity of organotins and o‐butylphenol was improved by use of mutant yeast strains lacking genes encoding cell wall mannoproteins and/or plasma membrane drug efflux pumps as hosts. We also showed that a number of other human RXR ligands, phenol and bisphenol A derivatives, and terpenoid compounds such as 9c‐RA exhibited antagonist activity on Dapma‐USP. Our newly established yeast‐based RGA system is valuable as the first screening tool to detect ligand substances for Dapma‐USP and for evaluating the evolutionary divergence of the ligand responses of RXR homologs between humans and D. magna. The freshwater cladoceran Daphnia magna has been used as a representative crustacean species for aquatic assessments of endocrine‐disrupting chemicals (EDCs) in the Organization for Economic Corporation and Development test guidelines. The typical EDCs, organotin compounds, which include tributyltin and triphenyltin, exhibit ligand activities for nuclear receptor retinoid X receptors (RXRs). In the present study, a new reporter gene assay to detect ligands of D. magna ultraspiracle, a homolog of vertebrate RXRs, was established in the yeast Saccharomyces cerevisiae.
- Subjects
RETINOID X receptors; DAPHNIA magna; REPORTER genes; THYROID hormones; FUNGAL cell walls; LIGANDS (Biochemistry); ORGANOTIN compounds
- Publication
Journal of Applied Toxicology, 2023, Vol 43, Issue 10, p1447
- ISSN
0260-437X
- Publication type
Article
- DOI
10.1002/jat.4476