engleski

Interaction of zebrafish Organic anion transporters (Oats) with endo- and xenobiotics

Objectives: OATS/Oats are transmembrane proteins that transport a variety of compounds including drugs, environmental toxins and endogenous metabolites into the cell. Zebrafish (Danio rerio) has seven Oat orthologs: Oat1, Oat2a-e and Oat3. In this study we specifically address Oat2 (gene symbol Slc22a7 subfamily, by cloning, heterologous expression and development of transport activity assays that can be used for a detailed analyses of Oat2 transporters and their interactors. Materials and methods: HEK293-T cells transiently transfected with Oat2a-e genes were used in transport assays. Various anionic fluorescent dyes were tested to identify model fluorescent substrates of zebrafish Oats which were used in subsequent inhibition assays. Inhibition measurements were based on the co- exposure of transfected cells and mock control with the determined model substrate and potential interactor. Various endo- and xenobiotics, including cyanotoxins, were tested for their interaction with zebrafish Oats. Results: Our initial testing of anionic fluorescent dyes revealed two model fluorescent substrates of three studied Oats: Oat2a (lucifer yellow, LY) , Oat2b (6- carboxyfluorescein, 6-CF) and Oat2d (LY and 6- CF), while Oat2c and Oat2e showed no activity with any of tested dyes. Oat2a, b and d showed interaction with numerous endo- and xenobiotics. However, they showed no interaction with tested microcystins, suggesting that MCs are probably transported by other specific anion transporters from Oatp family. Conclusion: We have identified new model substrates for three zebrafish Oat2 proteins and standardized high throughput assays for their functional characterization. The interaction screening assay revealed interaction of Oat2a, b and d with numerous endo- and xenobiotics confirming their polyspecific properties. The lack of interaction with microcystins could be due to their size (≈1000 Da), as Oat substrates are characterized by a small size (<500 Daltons), unlike Oatps which mediate transport of large amphipatic organic anions.

Organic anion transporters ; zebrafish ; cellular detoxification ; xenobiotics ; cyanotoxins

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