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Eukaryotic Cell, August 2006, p. 1430-1440, Vol. 5, No. 8
1535-9778/06/$08.00+0     doi:10.1128/EC.00067-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Trypanosoma congolense Procyclins: Unmasking Cryptic Major Surface Glycoproteins in Procyclic Forms

Silvia Utz,1 Isabel Roditi,2 Christina Kunz Renggli,3 Igor C. Almeida,4,{dagger} Alvaro Acosta-Serrano,5 and Peter Bütikofer1*

Institute of Biochemistry & Molecular Medicine, University of Bern, Bern, Switzerland,1 Institute of Cell Biology, University of Bern, Bern, Switzerland,2 Swiss Tropical Institute, Basel, Switzerland,3 Department of Parasitology, University of Sao Paulo, Sao Paulo, Brazil,4 Wellcome Centre for Molecular Parasitology, University of Glasgow, Scotland, United Kingdom5

Received 9 March 2006/ Accepted 20 June 2006

In the tsetse fly, the protozoan parasite Trypanosoma congolense is covered by a dense layer of glycosylphosphatidylinositol (GPI)-anchored molecules. These include a protease-resistant surface molecule (PRS), which is expressed by procyclic forms early in infection, and a glutamic acid- and alanine-rich protein (GARP), which appears at later stages. Since neither of these surface antigens is expressed at intermediate stages, we investigated whether a GPI-anchored protein of 50 to 58 kDa, previously detected in procyclic culture forms, might constitute the coat of these parasites. We therefore partially purified the protein from T. congolense Kilifi procyclic forms, obtained an N-terminal amino acid sequence, and identified its gene. Detailed analyses showed that the mature protein consists almost exclusively of 13 heptapeptide repeats (EPGENGT). The protein is densely N glycosylated, with up to 13 high-mannose oligosaccharides ranging from Man5GlcNAc2 to Man9GlcNAc2 linked to the peptide repeats. The lipid moiety of the glycosylphosphatidylinositol is composed of sn-1-stearoyl-2-lyso-glycerol-3-HPO4-1-(2-O-acyl)-D-myo-inositol. Heavily glycosylated proteins with similar repeats were subsequently identified in T. congolense Savannah procyclic forms. Collectively, this group of proteins was named T. congolense procyclins to reflect their relationship to the EP and GPEET procyclins of T. brucei. Using an antiserum raised against the EPGENGT repeat, we show that T. congolense procyclins are expressed continuously in the fly midgut and thus form the surface coat of cells that are negative for both PRS and GARP.

* Corresponding author. Mailing address: Institute of Biochemistry & Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland. Phone: 41 31 631 41 13. Fax: 41 31 631 37 37. E-mail: peter.buetikofer{at}mci.unibe.ch.

{dagger} Present address: Department of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968.

Eukaryotic Cell, August 2006, p. 1430-1440, Vol. 5, No. 8
1535-9778/06/$08.00+0     doi:10.1128/EC.00067-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.





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