Function Analysis Of Rab GTPase In Shrimp Antiviral Immunity And Interaction Between White Spot Syndrome Virus (WSSV) Envelope Proteins And Shrimp Proteins

White spot syndrome virus (WSSV) is one of the most devastating pathogens. It has spread to shrimp-farming areas around the world with a high infection and mortality rate and caused tremendous economic loss. However, up to date, there is no efficient method to control the virus. This study aimed at the mechanisms of Rab GTPase in shrimp immune and the functions of envelope proteins in WSSV infection. These works on the virus and host would be helpful for shrimp disease control.In this investigation, a Rab gene (named as PjRab gene) was obtained from Peneaus japonicus shrimp by 3'RACE and 5'RAC. The ORF of PjRab gene contained 636 bp enconding 212 amino acids. PjRab protein exhibited high homology with Rabs from other species, but was different from other Rabs in C-terminus, thereby constituting a unique member of the Rab GTPase family. This is the first Rab gene obtained from marine invertebrates. The gene was expressed in E. coli with GTP binding activity. The results of RT-PCR and Western blot indicated that PjRab gene was ubiquitously expressed in shrimp tissues. Real-time PCR revealed that the PjRab gene was up-regulated after WSSV infection suggesting that the PjRab protein might play a role in shrimp immune response against virus infection. It was found that the PjRab protein was interacted with shrimpβ-actin, tropmyosin and VP466 of WSSV as revealed by GST pull-down and mass spectrometry assays. The interaction between PjRab and actin was confirmed in vitro & in vivo. The results of antibody neutralization and RNAi assays showed that PjRab was involved in phagocytosis of shrimp hemocytes. Therefore, the regulation of hemocyte phagocytosis through interaction with actin might be a putative passway for Rab protein in antiviral immunity. This first finding of Rab involved in immune respone in animal extended the knowledge of small GTPases.Antibody neutralization showed that the virus infection could be significantly delayed or neutralized by antibodies against VP28, VP68, VP281 and VP466. These results were further confirmed by quantitative PCR. It could be concluded that the viral envelope proteins VP28, VP68, VP281 and VP466 played important roles in...