P-glycoprotein and sister P-glycoprotein sequences from mummichog, Fundulus heteroclitus, liver and intestine

P-glycoproteins (Pgps) responsible for efflux of xenobiotics from drug-resistant and normal cells may also contribute to xenobiotic resistance in aquatic organisms. We recently reported elevation of Pgp in liver and liver tumors of mummichog (Fundulus heteroclitus) inhabiting a creosote-contaminated site (Cooper, P. S., Van Veld, P. A., & Vogelbein, W. K. (1999). Altered expression of the xenobiotic transporter P-glycoprotein in liver and liver tumors of mummichog (Fundulus heteroclitus) from a creosote-contaminated environment. Biomarkers, 4, 48–58). Here we provide sequence information on specific forms of Pgp in this resistant population. Reverse transcriptase-polymerase chain reaction was used to amplify overlapping cDNA fragments corresponding to the C-terminal halves of two Pgp-related sequences from liver and intestine. From liver, we amplified 3 kb of a cDNA similar to mammalian sister Pgp (Spgp). We also amplified 2.7 kb of another cDNA from mummichog intestine and liver that was similar to the mammalian Mdr Pgp. Analysis of these sequences confirms that Spgps are well conserved proteins that are closely related to but distinct from true Pgps. Features of the single mummichog Mdr sequence suggest that the initial gene duplication event producing the mammalian mdr1 and mdr2 gene lineages occurred after the separation of teleost and tetrapod vertebrates. These cDNA fragments will provide useful probes for screening fish cDNA and genomic libraries for Pgp homologs and for gene-specific analysis of Pgp expression in fish tissues.