Identification of GPCR-neuropeptide interactions and their functional analyses in Schistosoma mansoni

Abstract text

Introduction

Schistosomes are parasitic flatworms that cause schistosomiasis. Standard treatment of schistosomiasis relies on a single drug, praziquantel. Neuropeptides are important messenger molecules that act via G protein-coupled receptors (GPCRs) as neurotransmitters, or hormones in the nervous system. Due to their pharmacological importance and proven druggability, GPCRs represent promising targets for new anthelmintics. Comparative transcriptomics of paired and unpaired worms and their gonads revealed 59 differentially regulated GPCR genes putatively involved in Schistosoma mansoni neuronal processes. Furthermore, 23 of 27 S. mansoni neuropeptide precursor (Sm_npp) genes of adult S. mansoni exhibited higher transcript levels in males (paired or unpaired) and unpaired females.

Objectives

Our knowledge of S. mansoni GPCRs and their ligands are still fragmentary. Goal of this study was to confirm rhodopsin-like orphan GPCR (SmGPCR20)-Sm_npp interactions by biochemical methods and to characterize the appropriate partners at the molecular level including functional analyses.

Materials & methods

To characterize SmGPCR20, we employed the MALAR-Y2H system. We examined the transcript profiles by quantitative real-time PCR (qRT-PCR) and localized their transcripts by whole mount in situ hybridization (WISH). To unravel the function of the receptor/ligand pairs, we performed RNA interference (RNAi) in adult S. mansoni in vitro with subsequent phenotype analysis. Confocal laser scanning microscopy (CLSM) was used for morphological analyses.

Results

We identified specific interactions between SmGPCR20/SmNPP26 and SmGPCR20/SmNPP40 and co-localized SmGPCR20/SmNPP26 and SmGPCR20/SmNPP40 expression in the head region and along the worm body in particular patterns. SmGPCR20, SmNPP26, and SmNPP40 were found to be preferentially transcribed in bM and sM but also in sF. Phenotype analyses following RNAi against these molecules indicated a substantial decline in egg production compared with the untreated control group. Consistent with the decreased egg production, CLSM analyses revealed morphologic changes in the female gonads.

Conclusion

The obtained results suggest that SmNPP26 and SmNPP40 are ligands of SmGPCR20, and that these molecules are involved in the molecular communication of male and female S. mansoni influencing egg production. Furthermore, GPCRs and neuropeptides may play important roles for male-female interaction and the control of reproduction.