A novel protein with a fibrinogen-like domain involved in the innate immune response of Marsupenaeus japonicus

Fibrinogen-related proteins play important roles in innate immunity. We isolated a fibrinogen-related protein gene (MjFREP1) in kuruma shrimp Marsupenaeus japonicus. MjFREP1 encoded a protein of 270 amino acids, including a 223 amino acid fibrinogen-like domain. Quantitative real-time polymerase chain reaction analysis shows that MjFREP1 is mainly expressed in the gills and the expression is significantly upregulated by Vibrio anguillarum, Staphylococcus aureus, or white spot syndrome virus (WSSV) challenge. Recombinant MjFREP1 fibrinogen-like domain agglutinates Gram-positive bacteria Bacillus subtilis, Bacillus thuringiensis, Bacillus megaterium, and S. aureus in the presence of calcium ions. The fibrinogen-like domain of MjFREP1 binds peptidoglycans, LPS, bacteria, and the VP28 of WSSV. These results suggest that the MjFREP1 may play an important role in the shrimp immune response against different pathogens.