Functional motif analysis for glycosyltransferases in apicomplexan genomes (608.5)

Abstract

Parasitic protozoa of the Phylum Apicomplexa include the genus Plasmodium (causative agents of malaria) and Toxoplasma gondii which causes toxoplasmosis. Little is known about glycosylation pathways and their contributions to pathogenesis. Increased glycosylation is known to be a feature of the chronic infection with Toxoplasma defined by the formation of the tissue cyst. Lectin reactivity and biochemical identification indicate that Toxoplasma tissue cysts contain diverse glycan modifications that are hypothesized to originate from both the parasite and the host. In order to establish the potential extent of host derived glycan modifications we have undertaken a comprehensive survey of the encoded potential in the toxoplasma genome (www.toxodb.org) by conducting a rigorous bioinformatics survey for predicted glycosyltransferases (GT). In addition to the identification of a truncated pathway for the synthesis of N‐linked glycans predicting simple (ConA positive) but not complex (LCA positive) labeling we find a complete absence of any of the machinery to permit modification with sialic acid. The presence in tissue cysts of both complex N‐linked glycans and sialic acid (SNA, MALII, Limax agglutinin and anti Sia‐Tn antigen) implicates host cell involvement. In order to understand the full extent of the novel form of parasitism, the hijacking of host glycan modifying enzymes, we are now investigating whether the Toxoplasma genome encodes other classes of glycosyltransferases. We hypothesize that the absence of a specific GT encoded in the parasite genome coupled with its phenotypic detection implicates thievery from the host cell. The current interrogation is being extended to other parasitic protozoa for which the genomes are now available (www.eupathdb.org). Such a broad survey across Apicomplexa and other parasitic Phyla may reveal insights into the evolution of the glycosylation machinery in these early branching eukaryotes and provide insights into infection and immunity.Grant Funding Source: NIHR21 AI099509 (to APS)