Abstract
BackgroundAcetycholinesterase (AChE; EC 3.1.1.7) is an essential hydrolytic enzyme in the cholinergic nervous system, which plays an important role during immunomodulation in vertebrates. Though AChEs have been identified in most invertebrates, the knowledge about immunomodulation function of AChE is still quite meagre in invertebrates.MethodologyA scallop AChE gene was identified from Chlamys farreri (designed as CfAChE), and its open reading frame encoded a polypeptide of 522 amino acids. A signal peptide, an active site triad, the choline binding site and the peripheral anionic sites (PAS) were identified in CfAChE. The recombinant mature polypeptide of CfAChE (rCfAChE) was expressed in Pichia pastoris GS115, and its activity was 71.3±1.3 U mg−1 to catalyze the hydrolysis of acetylthiocholine iodide. The mRNA transcripts of CfAChE were detected in haemocytes, hepatopancreas, adductor muscle, mantle, gill, kidney and gonad, with the highest expression level in hepatopancreas. The relative expression level of CfAChE mRNA in haemocytes was both up-regulated after LPS (0.5 mg mL−1) and human TNF-α (50 ng mL−1) stimulations, and it reached the highest level at 12 h (10.4-fold, P<0.05) and 1 h (3.2-fold, P<0.05), respectively. After Dichlorvos (DDVP) (50 mg L−1) stimulation, the CfAChE activity in the supernatant of haemolymph decreased significantly from 0.16 U mg−1 at 0 h to 0.03 U mg−1 at 3 h, while the expression level of lysozyme in the haemocytes was up-regulated and reached the highest level at 6 h, which was 3.0-fold (P<0.05) of that in the blank group.ConclusionsThe results collectively indicated that CfAChE had the acetylcholine-hydrolyzing activity, which was in line with the potential roles of AChE in the neuroimmune system of vertebrates which may help to re-balance the immune system after immune response.
Highlights
Acetycholinesterase (AChE; EC 3.1.1.7) is an essential hydrolytic enzyme in the cholinergic nervous system, and responsible for catalyzing the degradation of acetylcholine (ACh) into acetate and choline [1]
The results collectively indicated that CfAChE had the acetylcholine-hydrolyzing activity, which was in line with the potential roles of AChE in the neuroimmune system of vertebrates which may help to re-balance the immune system after immune response
Because AChE is capable of altering the acetylcholine level in the synaptic cleft and blood plasma, it plays a crucial role in the physiological activity adjustment of the cholinergic nervous system [2,3,4,5]
Summary
Acetycholinesterase (AChE; EC 3.1.1.7) is an essential hydrolytic enzyme in the cholinergic nervous system, and responsible for catalyzing the degradation of acetylcholine (ACh) into acetate and choline [1]. Except for conserved amino acid residues, there are usually two or three conserved intramolecular disulfide bonds in AChEs to keep these crucial sites in a correct spatial structure [2]. These conserved sites and disulfides bonds provide the essential structural elements for the catalytic function of AChE and conformational positions for some AChE inhibitors [24]. Acetycholinesterase (AChE; EC 3.1.1.7) is an essential hydrolytic enzyme in the cholinergic nervous system, which plays an important role during immunomodulation in vertebrates. Though AChEs have been identified in most invertebrates, the knowledge about immunomodulation function of AChE is still quite meagre in invertebrates
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