Transcriptional Responses of in Vivo Praziquantel Exposure in Schistosomes Identifies a Functional Role for Calcium Signalling Pathway Member CamKII

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 camkii transcription was reduced by 50-69% in s. japonicum,the subsequent effect of an ic50 dosage of praziquantel was exacerbated,reducing motility from 47% to 27% in female worms and from 61% to 23% in males. these observations indicated that camkii mitigates the effects of praziquantel,probably through stabilising ca2+ fluxes within parasite muscles and tegument. together,these studies comprehensively charted transcriptional changes upon exposure to praziquantel and,notably,identified camkii as potentially central to the,as yet undefined,mode of action of praziquantel. © 2013 you et al.