Apparent lack of N-glycosylation in the asexual intraerythrocytic stage of Plasmodium falciparum

Authors

  • Angela DIECKMANN-SCHUPPERT,

    Corresponding author
    1. Zentrum für Hygiene und Medizinische Mikrobiologie, University of Marburg, Federal Republic of Germany
      Correspondence to A. Dieckmann-Schuppert, Zentrum für Hygiene und Medizinische Mikrobiologie, University of Marburg, Robert-Koch-Str. 17, W-3550 Marburg, Federal Republic of Germany
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  • Stephanie BENDER,

    1. Zentrum für Hygiene und Medizinische Mikrobiologie, University of Marburg, Federal Republic of Germany
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  • Maria ODENTHAL-SCHNITTLER,

    1. Zentrum für Hygiene und Medizinische Mikrobiologie, University of Marburg, Federal Republic of Germany
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  • Ernst BAUSE,

    1. Institut für Physiologische Chemie, University of Bonn, Federal Republic of Germany
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  • Ralph T. SCHWARZ

    1. Zentrum für Hygiene und Medizinische Mikrobiologie, University of Marburg, Federal Republic of Germany
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Correspondence to A. Dieckmann-Schuppert, Zentrum für Hygiene und Medizinische Mikrobiologie, University of Marburg, Robert-Koch-Str. 17, W-3550 Marburg, Federal Republic of Germany

Abstract

This study investigates protein glycosylation in the asexual intraerythrocytic stage of the malaria parasite, Plasmodium falciparum, and the presence in the infected erythrocyte of the respective precursors.

In in vitro cultures, P. falciparum can be metabolically labeled with radioactive sugars, and its multiplication can be affected by glycosylation inhibitors, suggesting the capability of the parasite to perform protein-glycosylation reactions. Gel-filtration analysis of sugar-labeled malarial proteins before and after specific cleavage of N-glycans or O-glycans, respectively, revealed the majority of the protein-bound sugar label to be incorporated into O-glycans, but only little (7–12% of the glucosamine label) or no N-glycans were found. Analysis of the nucleotide sugar and sugar-phosphate fraction showed that radioactive galactose, glucosamine, fucose and ethanolamine were converted to their activated derivatives required for incorporation into protein. Mannose was mainly recovered as a bisphosphate, whereas the level of radiolabeled GDP-mannose was below the detection limit. The analysis of organic-solvent extracts of sugar-labeled cultures showed no evidence for the formation by the parasite of dolichol cycle intermediates, the dedicated precursors in protein N-glycosylation. Consistently, the amount of UDP-N-acetylglucosamine formed did not seem to be affected by the presence of tunicamycin in the culture. Oligosaccharyl-transferase activity was not detectable in a lysate of P. falciparum, using exogenous glycosyl donors and acceptors.

Our studies show that O-glycosylation is the major form of protein glycosylation in intraerythrocytic P. falciparum, whereas there is little or no protein N-glycosylation. A part of these studies has been published in abstract form [Dieckmann-Schuppert, A., Hensel, J. and Schwarz, R. T. (1991) Biol. Chem. Hoppe-Seyler 372, 645].

Abbreviations
glycosyl-PtdIns

glycosyl-phosphatidylinositol

HPAEC

high pH anion-exchange chromatography

PP

pyrophosphate

PNGase F

protein N-glycanase F

Enzymes
 

Calf intestinal alkaline phosphatase (EC 3.1.3.1)

 

phosphodiesterase (EC 3.1.15.1)

 

protein N-glycanase F (EC 3.2.2.18)

 

UDP-GlcNAc: dolichol-phosphate GlcNAc-phospho-transferase (EC 2.7.8.15)

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