Journal of Biological Chemistry
Volume 278, Issue 35, 29 August 2003, Pages 32987-32993
Journal home page for Journal of Biological Chemistry

Mechanisms of Signal Transduction
Roles of Glycosylphosphatidylinositols of Toxoplasma gondii: INDUCTION OF TUMOR NECROSIS FACTOR-α PRODUCTION IN MACROPHAGES*

https://doi.org/10.1074/jbc.M304791200Get rights and content
Under a Creative Commons license
open access

Toxoplasma gondii is a ubiquitous parasitic protozoan, which causes congenital infectious diseases as well as severe encephalitis, a major cause of death among immune-deficient persons, such as AIDS patients. T. gondii is normally controlled by the immune system of healthy individuals, leading to an asymptomatic infection. T. gondii triggers early cytokine production, which, to a certain extent, protects the host against replication of tachyzoites, the infective form of the parasite. Glycosylphosphatidylinositols (GPIs) constitute a class of glycolipids that have various functions, the most fundamental being to link proteins to eucaryotic cell membranes. GPIs are involved in the pathogenicity of other protozoan parasites and are known to induce tumor necrosis factor-α (TNFα) production. We show that GPIs highly purified from T. gondii tachyzoites, as well as their core glycans, induce TNFα production in macrophages. A chemically synthesized GPI of T. gondii lacking its lipid moiety, GPIa, has the same effect as the natural GPIs, whereas a chemically synthesized molecule with dialkylglycerol instead of diacylglycerol as lipid moiety, GPIb, does not induce TNFα production. Moreover, GPIb inhibits the TNFα production induced by T. gondii GPI or by GPIa. The core glycan prepared from the two chemically synthesized molecules activates macrophages, showing that the lipid moiety may regulate signaling. Stimulation of macrophages with GPIs of T. gondii results in activation of the transcription factor NF-κB, which is inhibited by the chemically synthesized GPIb, suggesting the involvement of NF-κB in TNFα gene expression. Our results support the idea that T. gondii GPIs are bioactive factors that participate in the production of TNFα during toxoplasmal pathogenesis.

Cited by (0)

*

This work was supported by the Deutsche Forschungsgemeinschaft, Fonds der Chemischen Industrie, Stiftung P. E. Kempkes, Hessisches Ministerium für Wissenschaft und Kunst, and by the French Ministry of Research Grant AOPRFMMIP1A123C, and Fondation pour la Recherche Médicale (to J. F. D.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.