N-Glycosylation in Piroplasmids: Diversity within Simplicity

Area of Science:

• Molecular Parasitology
• Glycobiology
• Tick-borne Diseases

Background:

• Piroplasmida are significant tick-transmitted pathogens impacting animal and human health.
• The role of N-glycosylation, a crucial post-translational modification, remains largely uncharacterized in Piroplasmida.
• Understanding N-glycosylation is vital for developing novel control strategies against these parasites.

Purpose of the Study:

• To investigate the presence and diversity of N-glycosylation pathways in Piroplasmida.
• To determine the functional significance of N-glycosylation in the life cycle of Piroplasmida, particularly Babesia bovis.
• To identify potential targets for therapeutic intervention.

Main Methods:

• Genomic analysis of 11 Piroplasmida species to identify N-glycosylation pathway genes.
• Bioinformatic prediction of oligosaccharyl transferase (OST) complex composition.
• Experimental validation using fluorescence microscopy and a N-acetylglucosamine (NAcGlc)-specific lectin in Babesia bovis.
• In vitro growth assays of Babesia bovis treated with tunicamycin, an N-glycosylation inhibitor.
• Gene expression analysis of N-glycosylation pathway components in different life stages of Babesia bovis.

Main Results:

• Three distinct N-glycosylation patterns were identified across Piroplasmida: NAcGlc addition in Babesia s.s., (NAcGlc)2-mannose in Theileria equi and Cytauxzoon felis, and substrate synthesis without protein transfer in B. microti and Theileria s.s.
• All Piroplasmida possess genes for N-glycosylation substrate biosynthesis (dolichol-P and sugar nucleotides).
• The OST complex in Babesia, T. equi, and C. felis is predicted to consist of only two subunits (STT3 and Ost1).
• Short N-glycans were experimentally confirmed on B. bovis merozoites.
• Tunicamycin treatment significantly impaired in vitro growth of B. bovis, highlighting the importance of N-glycosylation.
• Genes involved in N-glycosylation are transcribed in both blood and tick stages of B. bovis.

Conclusions:

• N-glycosylation is a conserved but diverse pathway in Piroplasmida, playing a significant role in parasite biology.
• The functional importance of N-glycosylation in B. bovis suggests it is a critical process throughout the parasite's life cycle.
• Further research into the specific roles of N-glycans can lead to the development of improved control measures for Piroplasmida infections.