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

摘要

Alpha-2 macroglobulin ( alpha ₂M), a broad-spectrum protease inhibitor, exists widely in vertebrates and invertebrates, but little information is available to date regarding alpha ₂M in amphioxus, an animal bridging from invertebrates to vertebrates. Here we first show that the full alpha ₂M cDNA of Branchiostoma japonicum (Bj alpha ₂m) 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 pI of mature Bj alpha ₂M were 164.2 kDa and 4.6 respectively. Bj alpha ₂m was mainly expressed in the hepatic caecum and hind-gut in a tissue-specific manner, contrasting to the primary expression of alpha ₂M in vertebrate liver. Following challenge with lipopolysaccharide (LPS), Bj alpha ₂m 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 ₂M is an immune-relevant molecule possibly involved in the acute phase response via the digestive organs.