Molecular cloning and characterization of a MXR-related P-glycoprotein cDNA in scallop Chlamys farreri: transcriptional response to benzo(a)pyrene, tetrabromobisphenol A and endosulfan

Abstract

ATP-binding cassette transmembrane transporters (ABC transporters) have a potential role in xenobiotic resistance. In this study, we cloned full-length cDNA encoding an important ABC transporter, P-glycoprotein (Pgp) homologue from scallop Chlamys farreri (designated Cf-Pgp). The Cf-Pgp sequence is constituted by an ORF of 4152bp encoding for 1383 amino acids (GenBank accession no. ACL80139). The predicted molecular weight is 150.7kDa. The comparison of the deduced amino acid sequences with the Pgps from vertebrates showed high conservation of the residues and domains essential to the function of Pgp, including the ATP-binding cassettes and transmembrane domains. The mRNA expression of Cf-Pgp was detected in gill, digestive gland, mantle, hemocyte, adductor muscle and mature male and female gonad. We then utilized the real-time PCR to study expression levels of the Cf-Pgp gene in response to exposure of benzo(a)pyrene (BaP), tetrabromobisphenol A (TBBPA) and endosulfan (ES) (0.05, 0.5μg/L and 5μg/L) for 96 hours. The results showed that Cf-Pgp was significantly upregulated in the gill upon exposure to TBBPA and ES, but downregulated in the gill after exposure to BaP. These results suggested that the Cf-Pgp was a constitutive and inducible acute-phase protein that perhaps involved in the xenobiotic resistance of scallop C. farreri.