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Glycobiology Advance Access originally published online on August 20, 2009
Glycobiology 2009 19(12):1462-1472; doi:10.1093/glycob/cwp121
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© The Author 2009. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Sorting of phosphoglucomutase to glycosomes in Trypanosoma cruzi is mediated by an internal domain

Luciana L Penha, Celso B Sant’Anna, Lucia Mendonça-Previato, Narcisa L Cunha-e-Silva, José O Previato and Ana Paula C A Lima1

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

1 To whom correspondence should be addressed: Tel: +55-21-2209-6591; Fax: +55-21-2280-8193; e-mail: anapaula{at}biof.ufrj.br

Received on June 24, 2009; revised on August 11, 2009; accepted on August 11, 2009

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.

Key words: glycosome / green fluorescent protein / phosphoglucomutase / targeting signal / Trypanosoma


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