A dopamine beta hydroxylase from Chlamys farreri and its induced mRNA expression in the haemocytes after LPS stimulation

Dopamine beta hydroxylase (DBH) is a critical enzyme in the biosynthesis of catecholamines, and also plays an important role in complex neuroendocrine-immune regulatory network. In the present study, the cDNA encoding dopamine beta hydroxylase (designated CfDBH) was cloned from Chlamys farreri by using rapid amplification of cDNA ends (RACE) approaches and expression sequence tag (EST) analysis. The full-length cDNA of CfDBH was of 2302 bp, containing a 5' untranslated region (UTR) of 32 bp, a 3' UTR of 461 bp with a poly (A) tail, and an open reading frame (ORF) of 1809 bp encoding a polypeptide of 603 amino acids. The deduced amino acid sequence of CfDBH contained a signal peptide, a DOMON domain and a Cu2_monooxygen domain, and it shared 39.4%-42.9% similarity with other reported DBHs. The conserved domains in CfDBH and the amino acid sequence similarity with other DBHs strongly suggested that it was a homologue of DBH in C. farreri. The mRNA expression of CfDBH in various tissues and its temporal expression in haemocytes of scallops stimulated with LPS were ascertained by Quantitative real-time RT-PCR. The mRNA transcripts of CfDBH were detected in all the examined tissues with the highest expression level in hepatopancreas. The expression level of CfDBH in haemocytes was up-regulated after LPS stimulation and increased to hundreds fold higher than that of the control group at 12 h, and then decrease significantly to 0.36-fold and 0.31-fold at 24 h and 48 h respectively. The results suggested pathogen infections significantly induced the expression level of CfDBH, and the activation of DBH could influence the immune response of scallop C. farreri through changing the concentration of catecholamines.