Cloning, distribution and primary immune characteristics of amphioxus alpha-2 macroglobulin

Alpha-2 macroglobulin (alpha M-2), a broad-spectrum protease inhibitor, exists widely in vertebrates and invertebrates, but little information is available to date regarding alpha M-2 in amphioxus, an animal bridging from invertebrates to vertebrates. Here we first show that the full alpha M-2 cDNA of Branchiostoma japonicum (Bj alpha M-2) contained 5545 bp with an open reading frame of 4593 bp encoding signal sequence of 16 amino acid residues and a mature protein of 1514 residues. The calculated molecular mass and pl of mature Bj alpha M-2 were 164.2 kDa and 4.6 respectively. Bj alpha M-2 was mainly expressed in the hepatic caecum and hindgut in a tissue-specific manner, contrasting to the primary expression of alpha M-2 in vertebrate liver. Following challenge with lipopolysaccharide (LPS), Bj alpha M-2 expression was significantly up-regulated (7-folds) at 8 h and then declined to the base line at 16 h. Taken together, it is suggested that Bj alpha M-2 is an immune-relevant molecule possibly involved in the acute phase response via the digestive organs. (C) 2011 Elsevier Ltd. All rights reserved.