Efficient Replication Of AcMNPV Is Dependent On Cellular Fatty Acid Synthesis Pathway

Autographa californica multiple nucleopolyhedrovirus(AcMNPV)is the prototype species of baculoviruses.In the infection cycle of AcMNPV,the energy required for virions trafficking,palmitation modification of virus proteins,the remodeling of plasma and nuclear membranes induced by the envelopement of viral capsid and the formation of large amounts of intranuclear microvesicles are closely related with the cellular fatty acid synthesis pathway.However,the molecular roles of host fatty acid synthesis pathway in AcMNPV infection are not clear.In this study,to uncover the dependence of AcMNPV infection on cellular fatty acid synthesis pathway,we initially retrieved the transcriptome data from AcMNPV-infected cells and analyzed the transcription level for acetyl-CoA carboxylase(ACC)and fatty acid synthase(FASN)which catalyze the formation of long-chain fatty acids.In AcMNPV-infected Tnm42 cells,the transcription level for ACC is significantly down-regulated,however,the transcription level for FASN is up-regulated about 2 folds at the early stage of infection(0-6 hours post-infection).Using 5-25 uM C75,the specific inhibitor of FASN,to inhibit the activity of cellular FASN did not cause a detectable toxicity to Sf9 cells,but these treatments significantly decreased the production of infectious budded virions of AcMNPV.These results suggest that cellular fatty acid synthesis pathway is involved in efficient replication of AcMNPV.Further analysis revealed that,inhibition of FASN activity by using 20 ?M C75 after inoculation of AcMNPV dramatically decreased the expression level for beta-galactosidase and beta-glucuronidase that separately directed by the early or late promoter of AcMNPV.Similarly,in C75-treated cells,the expression of viral major envelope glycoprotein GP64 and the replication of viral genomic DNA are also reduced.Further analysis revealed that,inhibition of FASN activity before virus infection or at the time of inoculation of AcMNPV did not result in the significant reduction of infectious BV production.However,the infectious BV titirs were dramatically decreased when the infected cells were treated with C75 at 1,3 or 6 hours post-infection.These results indicated that cellular FASN activity is required for the early stage of viral infection,but it might be not necessary for AcMNPV entry into Sf9 cells.In conclusion,our results clearly demonstrated that cellular fatty acid synthesis pathway is involved in efficient replication of AcMNPV.Further studies will be focused on identifying the potential roles of fatty acid synthesis pathway in providing energy and phospholipids for viral genes expression and the envelopement of capsids.