The ABCG2 efflux transporter from rabbit placenta: Cloning and functional characterization

Area of Science:

• Pharmacology
• Toxicology
• Molecular Biology

Background:

• The ATP-binding cassette efflux transporter ABCG2 is vital for placental drug and toxin excretion, contributing to fetoprotection.
• Developmental toxicity studies often utilize rabbits, but functional ABCG2 expression in this species was previously unknown.

Purpose of the Study:

• To clone and characterize the functional expression of ABCG2 in rabbit placenta.
• To compare the substrate spectrum of rabbit ABCG2 with human ABCG2.

Main Methods:

• Cloning of rabbit ABCG2 (rbABCG2) from placental tissue.
• Expression of rbABCG2 in MDCKII cells, confirmed by RT-PCR and Western blot.
• Functional assessment using Hoechst H33342 efflux assay and inhibition studies with known ABCG2 substrates.

Main Results:

• Rabbit ABCG2 shares 84-86% amino acid identity with human, rat, and mouse orthologues.
• Stable expression and functional efflux activity of rbABCG2 were demonstrated in MDCKII cells.
• Rabbit and human ABCG2 exhibited comparable inhibition by established drug substrates, suggesting a similar substrate spectrum.

Conclusions:

• This study provides the first evidence of functional ABCG2 expression in the rabbit placenta.
• Rabbit and human ABCG2 transporters display similar drug substrate profiles, which is significant for extrapolating toxicity data.