Function of gC1qR in innate immunity of Chinese mitten crab, Eriocheir sinensis.

gC1qR is identified as the globular "head" binding protein of the C1q protein and performs an important function in innate immunity. A EsgC1qR gene was identified from the hepatopancreas of Eriocheir sinensis. EsgC1qR encodes a protein with 275 amino acids. Phylogenetic analysis showed that, together with crustaceans gC1qRs, EsgC1qR belongs to one group. EsgC1qR mRNA was detected in hemocytes, intestine, hepatopancreas, gills, eyestalk, heart, muscle, and nerve. The expression of the EsgC1qR transcript in the hepatopancreas could be regulated by lipopolysaccharides (LPS), peptidoglycans (PGN), Staphyloccocus aureus, or Vibrio parahaemolyticus. Recombinant EsgC1qR (rEsgC1qR) protein could bind to various bacteria, LPS, and PGN. rEsgC1qR protein also presents direct bacteria inhibitory activity. rEsgC1qR could interact with EsCnx or EsCrt. Therefore, from the results, we could speculate that EsgC1qR is involved in the innate immunity of Chinese mitten crab, E. sinensis.