N-glycosylation in piroplasmids: Diversity within simplicity

Authors: FLORIN-CHRISTENSEN, MONICA - Instituto De Clima Y Agua (INTA); RODRIGUEZ, ANABEL - Instituto De Clima Y Agua (INTA); Suarez, Carlos; Ueti, Massaro; DELGADO, FERNANDO - Instituto De Clima Y Agua (INTA); ECHAIDE, IGNACIO - Instituto De Clima Y Agua (INTA); SCHNITTGER, LEONHARD - Instituto De Clima Y Agua (INTA)

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2021
Publication Date: 1/8/2021
Citation: Florin-Christensen, M., Rodriguez, A.E., Suarez, C.E., Ueti, M.W., Delgado, F.O., Echaide, I., Schnittger, L. 2021. N-glycosylation in piroplasmids: Diversity within simplicity. Pathogens. 10(1). Article 50. https://doi.org/10.3390/pathogens10010050.
DOI: https://doi.org/10.3390/pathogens10010050

Interpretive Summary: Babesia bovis and other related tick borne piroplasmid parasites causes important losses to the cattle industry worldwide, and improved control is needed. The development of improved control is severely hampered by our limited knowledge of the biology of these parasites. N-glycosilation is an important biochemical process involving the modification of proteins upon the transference of sugar residues, this process results in the synthesis of glycoproteins, which may play important specific roles in cells. In this study, we used bioinformatics tools to characterize the genes involved in Babesia and other important related piroplasmid parasites. The findings of the study indicated that all piroplasmids possess the gene complement needed for the synthesis of the two N-glycosilation substrates, dolichol-phosphate and sugar nucleotides, require for the process of N-glycosilation of proteins. Importantly, the growth of Babesia bovis in in vitro cultures was significantly impaired in the presence of inhibitors of the mechanisms of N-glycosilation such as tunicamycin, underscoring the importance of N-glycoproteins for the development of blood stage parasites. In addition, the we also found that the genes involved in the mechanism of glycosilation are expressed in blood and tick stages of the life cycle of B. bovis. Understanding the biological significance of N-glycosilation will aid in the development of improved methods for the control of these important pathogens of cattle.

Technical Abstract: N-glycosylation has remained mostly unexplored in Piroplasmida, an order of tick-transmitted pathogens of veterinary and medical relevance. Analysis of eleven piroplasmid genomes revealed three distinct situations regarding this process: Babesia s.s. add one or two N-acetylglucosamine (NAcGlc) molecules to proteins; Theileria equi and Cytoauxzoon felis add (NAcGlc)2-mannose, while B. microti and Theileria s.s. synthesize dolichol-P-P-NAcGlc and dolichol-P-P-(NAcGlc)2 without subsequent transfer to proteins. All piroplasmids possess the gene complement needed for the synthesis of the two N-glycosylation substrates, dolichol-P and sugar nucleotides. The oligosaccharyl transferase of Babesia s.s., T. equi and C. felis, is predicted to be composed of only two subunits, STT3 and OST. Occurrence of short N-glycans in B. bovis merozoites was experimentally demonstrated by fluorescence microscopy using a NAcGlc-specific lectin. In vitro growth of B. bovis was significantly impaired by tunicamycin, an inhibitor of N-glycosylation, indicating a relevant role for N-glycosylation in this pathogen. Finally, genes coding for N-glycosylation enzymes and substrate biosynthesis are transcribed in B. bovis blood and tick stages, suggesting that this pathway is biologically relevant throughout the parasite life cycle. Elucidation of the role/s exerted by N-glycans will increase our understanding of these successful parasites, for which improved control measures are needed.