Functional analysis of SdNP; A protein of unknown function in Setaria digitata

Abstract

Lymphatic filariasis, also known as elephantiasis, is a deleterious human disease caused by the parasitic nematode Wuchereriabancrofti. If left untreated, the infection can develop into elephantiasis which can only be managed with surgical excision. Studying the parasitology of W. bancrofti is extremely challenging because there are significant complications in procuring adult parasites from the lymphatic system. Therefore, cattle filarial parasite Setariadigitata was used as a model organism as it shares homologous counterparts with W. bancrofti and can be easily cultured in the laboratory. A novel protein called SdNP (S. digitata novel protein) was identified from S. digitata that may play a significant role in pathogenesis. Recently, SiRNA inhibition studies showed that inhibiting SdNP expression severely impairs adult parasite’s locomotion, consequently leading to death of the adult worm. The research work presented here describes in vitro characterization of SdNP. Built on Bioinformatic analysis, an enzyme coupled ATPase assay was used to detect the ATPase activity of the putative kinase motifs. Our results confirmed that SdNP is a phosphor-protein that can bind and hydrolyze ATP to ADP and inorganic Pi in a substrate-independent manner. In addition, native-PAGE and gel-filtration chromatography results showed that SdNP forms a stable tetramer in vitro. The fact that SdNP is unique to parasitic nematodes and is essential for the survival of adult worm suggests that functional analysis of SdNP could pave the way to design effective clade-specific drugs against filariasis.