Functional genomics characterisation of a α-N-acetylgalactosaminidase (α-NAGAL) in the parasitic blood fluke Schistosoma mansoni

Abstract

Amongst parasitic infections of humans, schistosomiasis causes the second highest number of deaths behind malaria. Schistosoma mansoni, the major causative species of intestinal schistosomiasis, is primarily controlled by praziquantel treatment. However, there is major concern on the sustainability of this control method. The parasite glycan machinery has been shown to play an important functional role in S. mansoni biology and more specifically in hostparasite interaction mechanisms. α-N-acetylgalactosaminidases (α-NAGAL) and αgalactosidases (α-GAL) are glycosyl hydrolases responsible for maintaining normal cellular homeostasis by regulating glycan substrates. Defiencies in human α-NAGAL and α-GAL lead to Schindler/Kanzaki disease and Fabry disease, which are characterised by neurological/neuromuscular impairments. This study investigates whether S. mansoni possesses enzymatically active α-NAGAL and α-GAL proteins. Sequence and phylogenetic analyses of putative α-NAGAL/α-GAL protein types showed that Smp_089290 to be the only S. mansoni protein to contain all functional amino acid residues necessary for enzymatic activity. Both α-NAGAL and α-GAL enzymatic activities were higher in females compared to males, which was consistent with smp_089290’s female-biased expression. Spatial localisation of smp_089290 in adult schistosomes revealed accumulation in neuronal cells, parenchymal cells, the vitellaria and mature vitellocytes. siRNA-mediated knockdown of smp_089290 in adult worms significantly inhibited α-NAGAL activity and led to significant reductions in adult worm motility and egg production. Smp_089290, therefore, acts predominantly as a α-NAGAL (hereafter termed SmNAGAL) and participates in coordinating movement and oviposition processes. The CRISPR-Cas9 system was used to introduce indels/substitutions in targeted smnagal genomic sequences. Low levels of genome editing were observed, which is consistent with other targeted S. mansoni genomic loci. Despite this, smnagal-edited worms showed significant reductions in transcript abundance and egg production. This work is the first to characterise α-NAGALs within Schistosoma and provides further clarity on the functional importance of the parasitic glycan machinery.

Date of Award	2020
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Karl Hoffmann (Supervisor)