The Molecular Mechanisms Study Of Two Lectins Involving In Innate Immune Responses Of Red Swamp Crayfish,Procambarus Clarkii

Due to the lack of adaptive immunity,invertebrates rely mainly on the innate immune system to fight against pathogen infections.Lectins are a class of proteins that bind to specific sugar molecules and play an important role in immune responses.C-type and L-type lectins are animal lectins.Lectin plays an important role in innate immunity of crustaceans.Previous studies have focused on the typical C-type lectin in the immune response,while the immune functions of L-type lectin(LTL)and fibrinolytic protein(Ficolin-like proteins,FLPs)lectin remain to be further revealed.In this study,Procambarus clarkii was used as a model to study the roles of LTL and FLPs.The main results were as follows:1.A novel LTL was identified from the P.clarkii and named as Pc L-lectin.The Pc L-lectin had high similarity with the endoplasmic reticulum Golgi intermediate compartment-53 k Da(ERGIC-53).The expression level of Pc L-lectin was significantly down regulated in crayfish after challenged with white spot syndrome virus(WSSV).Further analysis showed that the recombinant protein of Pc L-lectin(r PcL-lectin)protein could significantly promote the replication of WSSV in P.clarkii.Knockdown the expression of Pc L-lectin in vivo could effectively inhibit the replication of WSSV in P.clarkii.The immunofluorescence results showed that Pc L-lectin was mainly localized on the membrane of hemocyte.The results of pull-down and Co-IP showed that Pc L-lectin interacted with WSSV protein VP 24.The results of this study suggest that the PcL-lectin may be involved in the replication of WSSV,and will pave a new way for the prevention of WSSV infection.2.A FLP was identified in P.clarkii and designated as PcFLP1.The PcFLP1 was present in all tested tissues,including hemocytes,heart,hepatopancreas,gill,stomach,and mid-intestine.The expression level of PcFLP1 was up-regulated in hemocytes,hepatopancreas and mid-intestines of the P.clarkii after challenged with Vibrio parahaemolyticus.The recombinant protein of PcFLP1(r PcFLP1)could protect the hepatopancreas of P.clarkii from the infection of V.parahaemolyticus.Bacterial clearance test showed that the rPcFLP1 could enhance bacterial eliminationin P.clarkii,where as the antibacterial activity was inhibited after PcFLP1 was knocked down.Furthermore,PcFLP1 showed a broad spectrum of antibacterial activity.These results demonstrated that PcFLP1 played an important role in the anti-Vibrio infection in P.clarkii.