Transcriptional responses of in vivo praziquantel exposure in schistosomes identifies a functional role for calcium signalling pathway member CamKII. PLoS Pathog

Treatment for clinical schistosomiasis has relied centrally on the broad spectrum anthelmintic praziquantel; however, there is limited information on its mode of action or the molecular response of the parasite. This paper presents a transcriptional and functional approach to defining the molecular responses of schistosomes to praziquantel. Differential gene expression in Schistosoma japonicum was investigated by transcriptome-wide microarray analysis of adult worms perfused from infected mice after 0.5 to 24 hours after oral administration of sub-lethal doses of praziquantel. Genes up-regulated initially in male parasites were associated with ‘‘Tegument/Muscle Repair’ ’ and ‘‘Lipid/Ion Regulation’ ’ functions and were followed by ‘‘Drug Resistance’ ’ and ‘‘Ion Regulation’ ’ associated genes. Prominent responses induced in female worms included up-regulation of ‘‘Ca2+ Regulation’ ’ and ‘‘Drug Resistance’ ’ genes and later by transcripts of ‘‘Detoxification’ ’ and ‘‘Pathogen Defense’ ’ mechanisms. A subset of highly over-expressed genes, with putative drug resistance/detoxification roles or Ca2+-dependant/modulatory functions, were validated by qPCR. The leading candidate among these was CamKII, a putative calcium/calmodulin-dependent protein kinase type II delta chain. RNA interference was employed to knockdown CamKII in S. japonicum to determine the role of CamKII in the response to praziquantel. After partial-knockdown, schistosomes were analysed using IC50 concentrations (50 % worm motility) and quantitative monitoring of parasite movement. When CamKI