Identification and characterization of a protein G-binding intelectin in Japanese lamprey

Intelectins are recently identified extracellular animal lectins. They are glycan-binding receptors recognizing glycan epitopes on foreign pathogens and in the host system. In the present study, we report the identification of a new type of serum lectin from Japanese lamprey (Lampetra japonica). Gene expression analysis and Western blots demonstrated that the lamprey intelectin was expressed in blood, intestine, kidney, heart, gill, liver, medulla, and gonad. The recombinant lamprey intelectin protein (Lj-intelectin) appeared as ~34kD, ~44kD, and ~65kD bands on non-reducing SDS-PAGE gels, suggesting that it is consisted of monomers, dimmers and trimers. In addition, direct binding assays demonstrated that Lj-intelectin bind to protein G. Furthermore, Li-intelectin induced by in vivo bacterial stimulation showed agglutination activity against pathogenic Gram-positive and Gram-negative bacteria, indicating that it may play an important role in self-defense against bacteria in the internal circulation system of lamprey. The Lj-intelectin also exhibited a calcium-dependent agglutination to human red blood cells. These results demonstrate that lamprey intelectin plays an important role in immune response.