Function Analysis Of Ran-myosin Complex In Shrimp Hemocytes' Phagocytosis Against Virus (WSSV) Infection

Ran GTPases,one family of small G protein superfamily,have been widely demonstrated to be involved in transport system between cytoplasm and nucleus. However the function of Ran GTPase in immunity remains unclear.In our study,it was found that the Ran GTPase(designated as PjRan) was up-regulated in virus-resistant shrimp,indicating that the PjRan might be implicated in the innate immune system against virus infection.Based on protein interactions,it was found that the PjRan was interacted with myosin,a crucial protein in the process of phagocytosis to form a protein complex.The PjRan gene knockdown by RNAi and the overexpression of PjRan assays showed that the PjRan could regulate shrimp hemocytic phagocytosis by interaction with myosin.Further data was evidenced that the depletion of PjRan by RNAi caused a significant increase of shrimp white spot syndrome virus(WSSV) copies and the overexpression of PjRan resulted in a significant decrease of WSSV copies,suggesting that the PjRan participated in the antiviral immunity by regulating phagocytosis.For the purpose of further understanding how the PjRan-myosin protein complex regulates the process of shrimp phagocytosis,the enzymatic activities of the two proteins was elementarily tested.To observe the phagocytosis process regulated by the PjRan-myosin protein complex,the phagocytosis of Drosophila S2 cells with FITC-labeled WSSV was observed by immunofluorescence staining.In this context,our study revealed a completely novel aspect of Ran GTPase in phagocytosis by the direct interaction with the cytoskeleton protein and presented a novel pathway concerning to antiviral immunity,which would help to better understand the molecular events in immune response against virus infection in invertebrates.