Two novel CYP3A isoforms in marine mussel Mytilus coruscus: Identification and response to cadmium and benzo[a]pyrene.

CYP3A enzymes play a crucial role in metabolic clearance of a variety of xenobiotics. However, their genetic information and function remain unclear in molluscs. In the present study, two novel CYP3A genes i.e. McCYP3A-1 and McCYP3A-2 were identified and characterized from the thick shell mussel Mytilus coruscus, and their tissue distribution as well as the response to cadmium (Cd) and benzo[a]pyrene (B[α]P) exposure were addressed using real time quantitative RT-PCR (qRT-PCR) and erythromycin N-demethylase (ERND) assay. McCYP3A-1 and McCYP3A-2 possess typically domains of CYP family such as helix-C, helix-I, helix-K, PERF and the heme binding domain as well as the characteristic domains of CYP3s including six SRS motifs. McCYP3A-1 and McCYP3A-2 transcripts were constitutively expressed in all examined tissues with high expression level in digestive glands, hepatopancreas and gonads. Upon B[α]P exposure, McCYP3A-1 and McCYP3A-2 mRNA expression in digestive glands showed a pattern of up-regulation followed by down-regulation, while under Cd exposure, showed a time-dependent induction profile. In addition, ERND activity, generally used as an indicator of CYP3, increased in a time-dependent manner after exposure to Cd and B[α]P. These results collectively indicated that McCYP3A-1 and McCYP3A-2 are CYP3A family member and may play a potential role in metabolic clearance of xenobiotics. Meanwhile, the current results may provide some baseline data to support McCYP3A-1 and McCYP3A-2 as candidate biomarkers for monitoring of PAHs and heavy metal pollution.