Molecular diversity of the Trypanosoma cruzi TcSMUG family of mucin genes and proteins

The surface of the protozoan Trypanosoma cruzi is covered by a dense coat of mucin-type glycoconjugates, which make a pivotal contribution to parasite protection and host immune evasion. Their importance is further underscored by the presence of >1000 mucin-like genes in the parasite genome. In the present study we demonstrate that one such group of genes, termed TcSMUG L, codes for previously unrecognized mucintype glycoconjugates anchored to and secreted from the surface of insect-dwelling epimastigotes. These features are supported by the in vivo tracing and characterization of endogenous TcSMUG L products and recombinant tagged molecules expressed by transfected parasites. Besides displaying substantial homology to TcSMUG S products, which provide the scaffold for the major Gp35/50 mucins also present in insect-dwelling stages of the T. cruzi lifecycle, TcSMUG L products display unique structural and functional features, including being completely refractory to sialylation by parasite trans-sialidases. Although quantitative real time-PCR and gene sequencing analyses indicate a high degree of genomic conservation across the T. cruzi species, TcSMUG L product expression and processing is quite variable among different parasite isolates.