title: Sorting of phosphoglucomutase to glycosomes in Trypanosoma cruzi is mediated by an internal domain.
abstract: Trypanosoma cruzi relies on highly galactosylated molecules as virulence factors and the enzymes involved in sugar biosynthesis are potential therapeutic targets. The synthesis of UDP-galactose in T. cruzi requires the activity of phosphoglucomutase (PGM), the enzyme that catalyzes the interconversion of glucose-6-phosphate and glucose-1-phosphate. Several enzymes that participate in carbohydrate metabolism in trypanosomes are confined to specialized peroxisome-like organelles called glycosomes. The majority of glycosomal proteins contain peroxisome-targeting signals (PTS) at the COOH- or at the amino-terminus, which drive their transport to glycosomes. We had previously identified the T. cruzi PGM gene (TcPGM) and demonstrated that it encodes a functional enzyme. Here, we show that, in contrast to yeast and mammalian cells, TcPGM resides in glycosomes of the parasite. However, no classical PTS1 or PTS2 motif is present in its sequence. We investigated glycosomal targeting by generating T. cruzi cell lines expressing different domains of TcPGM fused to the green fluorescent protein (GFP). The analysis of the subcellular localization of fusion proteins revealed that an internal targeting signal of TcPGM, residing between amino acid residues 260 and 380, is capable of targeting GFP to glycosomes. These results demonstrate that, in T. cruzi, PGM import into glycosomes is mediated by a novel non-PTS domain that is located internally in the protein.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Bloco G, Universidade Federal do Rio de Janeiro, 21 944 970, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ, Brazil.
authors.forename: Luciana L
authors.initials: LL
authors.lastname: Penha
authors.forename: Celso B
authors.initials: CB
authors.lastname: Sant'Anna
authors.forename: Lucia
authors.initials: L
authors.lastname: Mendonça-Previato
authors.forename: Narcisa L
authors.initials: NL
authors.lastname: Cunha-e-Silva
authors.forename: José O
authors.initials: JO
authors.lastname: Previato
authors.forename: Ana Paula C A
authors.initials: AP
authors.lastname: Lima
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D008830:Microbodies / Q000378:metabolism*; D010733:Phosphoglucomutase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D014018:Tissue Distribution; D014349:Trypanosoma cruzi / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D021382:Protein Sorting Signals; D010733:Phosphoglucomutase