An alpha-2 macroglobulin in the pearl oyster Pinctada fucata: Characterization and function in hemocyte phagocytosis of Vibrio alginolyticus. (August 2016)

• Record Type: Journal Article
• Authors: Wang, Zhongliang; Wang, Bei; Chen, Gang; Lu, Yishan; Jian, Jichang; Wu, Zaohe
• Is Part Of: Fish & shellfish immunology. Volume 55(2016:Aug.)
• Page Start: 585
• Page End: 594
• Publication Date: 2016-08
• Subjects: Alpha-2 macroglobulin -- Phagocytosis -- Pinctada fucata -- RNAi -- Innate immunity; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2016.06.037
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: Alpha-2 macroglobulin (α2M) is a ubiquitous protease inhibitor and considered to be an evolutionarily conserved constituent of innate host defence system. Here, an α2M gene (designated as Pfα2M ) was obtained from the pearl oyster Pinctada fucata by RT-PCR, PCR walking and rapid amplification of cDNA ends (RACE). The Pfα2M cDNA consists of 6394 bp with an open reading frame (ORF) of 5745 bp encoding a protein of 1914 amino acids with a 19 residues signal peptide. Pfα2M sequence contains three putative functional domains, including a bait region, a thiol ester domain and a receptor-binding domain. Phylogenetic analysis revealed that Pfα2M is closely related to the α2Ms from other molluscs. Pfα2M was expressed in all tested tissues including digestive gland, gill, adductor muscle, mantle and foot, while the highest expression was found in hemocytes. Following challenge with Vibrio alginolyticus, Pfα2M expression in hemocytes was significantly up-regulated at 2 h and then returned to the original level at 48 h. Knockdown of Pfα2M by RNA interference significantly reduced the phagocytosis of V. alginolyticus by hemocytes in vivo, and similar results were obtained upon chemical inactivation of the reactive thioester bond in Pfα2M by methylamine treatment. Taken together, it is suggested that Pfα2M is an immune-relevant molecule and involved in phagocytosis of V. alginolyticus by P. fucata hemocytes, and the function of Pfα2M in phagocytosis is dependent on the active thioester bond. Highlights: An α2M gene (designated as Pfα2M ) was obtained from Pinctada fucata. Pfα2M contains a bait region, a thiol ester domain and a receptor-binding domain. Pfα2M expression in hemocytes was significantly up-regulated by bacterial challenge. Hemocyte phagocytosis was significantly reduced by RNAi and methylamine treatment. Pfα2M is involved in phagocytosis of Vibrio alginolyticus by P. fucata hemocytes.