title: Addition of α-O-GlcNAc to threonine residues define the post-translational modification of mucin-like molecules in Trypanosoma cruzi.
abstract: Trypanosoma cruzi, an intracellular protozoan etiologic agent of Chagas disease is covered by a dense coat of mucin-type glycoproteins, which is important to promote the parasite entry and persistence in the mammalian host cells. The O-glycosylation of T. cruzi mucins (Tc-mucins) is initiated by enzymatic addition of α-O-N-acetylglucosamine (GlcNAc) to threonine (Thr) by the UDP-GlcNAc:polypeptide α-N-acetylglucosaminyltransferase (pp-α-GlcNAcT) in the Golgi. The Tc-mucin is characterized by the presence of a high structural diversity of O-linked oligosaccharides found among different parasite strains, comprising two O-glycan Cores. In the Core 1, from strains principally associated with the domestic transmission cycle of Chagas disease, the GlcNAc O-4 is substituted with a β-galactopyranose (βGalp) unit, and in the most complex oligosaccharides the GlcNAc O-6 is further processed by the addition of β1 → 2-linked Galp residues creating a short linear Galp-containing chain. In the Core 2 structures, expressed by strains isolated from T. cruzi sylvatic hosts, the GlcNAc O-4 carries a β-galactofuranose (βGalf) unit and the GlcNAc O-6 can carry a branched Galpβ1 → 3[Galpβ1 → 2]Galpβ1 → 6 motif. The O-glycans carrying nonreducing terminal βGalp are available for sialylation by a surface T. cruzi trans-sialidase activity. Based on structural results, this review summarizes available data on the highly conserved process, which adds the GlcNAc unit in α-linkage to Thr residues the basis of the post-translational modification system in T. cruzi mucins. In addition, a mechanism unique employed by the parasite to transfer exogenous sialic acid residues to Tc-mucins is presented.
authors: Laboratório de Glicobiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21 941 902, Ilha do Fundão, Cidade Universitária, Rio de Janeiro, RJ, Brazil, luciamp@biof.ufrj.br.
authors: Lucia
authors: L
authors: Mendonça-Previato
authors: Luciana
authors: L
authors: Penha
authors: Tatiana Cortes
authors: TC
authors: Garcez
authors: Christopher
authors: C
authors: Jones
authors: Jose Osvaldo
authors: JO
authors: Previato
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D006031:Glycosylation; D009077:Mucins / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000378:metabolism*
chemical_list: D009077:Mucins; D015800:Protozoan Proteins; D013912:Threonine; D000117:Acetylglucosamine