A Dopa Decarboxylase Modulating the Immune Response of Scallop Chlamys farreri

Zhi Zhou,Pengfei Kong,Lingling Wang,Jialong Yang,Mengqiang Wang,Linsheng Song,Huan Zhang,Limei Qiu,Yang Gao,Xiaowei Shi,Sharyn Jane Goldstien

doi:10.1371/journal.pone.0018596

Abstract

BackgroundDopa decarboxylase (DDC) is a pyridoxal 5-phosphate (PLP)-dependent enzyme that catalyzes the decarboxylation of L-Dopa to dopamine, and involved in complex neuroendocrine-immune regulatory network. The function for DDC in the immunomodulation remains unclear in invertebrate.MethodologyThe full-length cDNA encoding DDC (designated CfDDC) was cloned from mollusc scallop Chlamys farreri. It contained an open reading frame encoding a polypeptide of 560 amino acids. The CfDDC mRNA transcripts could be detected in all the tested tissues, including the immune tissues haemocytes and hepatopancreas. After scallops were treated with LPS stimulation, the mRNA expression level of CfDDC in haemocytes increased significantly (5.5-fold, P<0.05) at 3 h and reached the peak at 12 h (9.8-fold, P<0.05), and then recovered to the baseline level. The recombinant protein of CfDDC (rCfDDC) was expressed in Escherichia coli BL21 (DE3)-Transetta, and 1 mg rCfDDC could catalyze the production of 1.651±0.22 ng dopamine within 1 h in vitro. When the haemocytes were incubated with rCfDDC-coated agarose beads, the haemocyte encapsulation to the beads was increased significantly from 70% at 6 h to 93% at 24 h in vitro in comparison with that in the control (23% at 6 h to 25% at 24 h), and the increased haemocyte encapsulation was repressed by the addition of rCfDDC antibody (which is acquired via immunization 6-week old rats with rCfDDC). After the injection of DDC inhibitor methyldopa, the ROS level in haemocytes of scallops was decreased significantly to 0.41-fold (P<0.05) of blank group at 12 h and 0.47-fold (P<0.05) at 24 h, respectively.ConclusionsThese results collectively suggested that CfDDC, as a homologue of DDC in scallop, modulated the immune responses such as haemocytes encapsulation as well as the ROS level through its catalytic activity, functioning as an indispensable immunomodulating enzyme in the neuroendocrine-immune regulatory network of mollusc.

Highlights

These results collectively suggested that CfDDC, as a homologue of Dopa decarboxylase (DDC) in scallop, modulated the immune responses such as haemocytes encapsulation as well as the reactive oxygen species (ROS) level through its catalytic activity, functioning as an indispensable immunomodulating enzyme in the neuroendocrine-immune regulatory network of mollusc
L-DOPA decarboxylase (DDC) is a pyridoxal 5-phosphate (PLP)-dependent enzyme that catalyses the decarboxylation of LDopa to dopamine, one of the important catecholamines present in a wide variety of animals
Human DDC distributes in all catecholaminergic neurons of the central and peripheral nervous system [8], and it has been detected in some peripheral organs such as the liver, adrenal gland and leukocytes of rat and human [9,10]

Summary

Introduction

L-DOPA decarboxylase (DDC) is a pyridoxal 5-phosphate (PLP)-dependent enzyme that catalyses the decarboxylation of LDopa to dopamine, one of the important catecholamines present in a wide variety of animals. By catalyzing the reaction to produce dopamine, DDC is involved in many important metabolic processes and plays a central role in the complex neuroendocrineimmune regulatory network [4]. Human DDC distributes in all catecholaminergic neurons of the central and peripheral nervous system [8], and it has been detected in some peripheral organs such as the liver, adrenal gland and leukocytes of rat and human [9,10]. Dopa decarboxylase (DDC) is a pyridoxal 5-phosphate (PLP)-dependent enzyme that catalyzes the decarboxylation of L-Dopa to dopamine, and involved in complex neuroendocrine-immune regulatory network. The function for DDC in the immunomodulation remains unclear in invertebrate

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