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Glucosylceramide synthesis inhibition affects cell cycle progression, membrane trafficking, and stage differentiation in Giardia lamblia


Stefanic, S; Spycher, C; Morf, L; Fabriàs, G; Casas, J; Schraner, E; Wild, P; Hehl, A B; Sonda, S (2010). Glucosylceramide synthesis inhibition affects cell cycle progression, membrane trafficking, and stage differentiation in Giardia lamblia. Journal of Lipid Research, 51(9):2527-2545.

Abstract

Synthesis of glucosylceramide via glucosylceramide synthase (GCS) is a crucial event in higher eukaryotes, both for the production of complex glycosphingolipids and for regulating cellular levels of ceramide, a potent antiproliferative second messenger. In this study, we explored the dependence of the early branching eukaryote Giardia lamblia on GCS activity. Biochemical analyses revealed that the parasite has a GCS located in endoplasmic reticulum (ER) membranes that is active in proliferating and encysting trophozoites. Pharmacological inhibition of GCS induced aberrant cell division, characterized by arrest of cytokinesis, incomplete cleavage furrow formation, and consequent block of replication. Importantly, we showed that increased ceramide levels were responsible for the cytokinesis arrest. In addition, GCS inhibition resulted in prominent ultrastructural abnormalities, including accumulation of cytosolic vesicles, enlarged lysosomes, and clathrin disorganization. Moreover, anterograde trafficking of the encystations-specific protein CWP1 was severely compromised and resulted in inhibition of stage differentiation. Our results reveal novel aspects of lipid metabolism in G. lamblia and specifically highlight the vital role of GCS in regulating cell cycle progression, membrane trafficking events, and stage differentiation in this parasite. In addition, we identified ceramide as a potent bioactive molecule, underscoring the universal conservation of ceramide signaling in eukaryotes.

Synthesis of glucosylceramide via glucosylceramide synthase (GCS) is a crucial event in higher eukaryotes, both for the production of complex glycosphingolipids and for regulating cellular levels of ceramide, a potent antiproliferative second messenger. In this study, we explored the dependence of the early branching eukaryote Giardia lamblia on GCS activity. Biochemical analyses revealed that the parasite has a GCS located in endoplasmic reticulum (ER) membranes that is active in proliferating and encysting trophozoites. Pharmacological inhibition of GCS induced aberrant cell division, characterized by arrest of cytokinesis, incomplete cleavage furrow formation, and consequent block of replication. Importantly, we showed that increased ceramide levels were responsible for the cytokinesis arrest. In addition, GCS inhibition resulted in prominent ultrastructural abnormalities, including accumulation of cytosolic vesicles, enlarged lysosomes, and clathrin disorganization. Moreover, anterograde trafficking of the encystations-specific protein CWP1 was severely compromised and resulted in inhibition of stage differentiation. Our results reveal novel aspects of lipid metabolism in G. lamblia and specifically highlight the vital role of GCS in regulating cell cycle progression, membrane trafficking events, and stage differentiation in this parasite. In addition, we identified ceramide as a potent bioactive molecule, underscoring the universal conservation of ceramide signaling in eukaryotes.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Veterinary Anatomy
05 Vetsuisse Faculty > Institute of Parasitology
04 Faculty of Medicine > Institute of Parasitology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
600 Technology
Language:English
Date:2010
Deposited On:03 Feb 2011 11:51
Last Modified:05 Apr 2016 14:42
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0022-2275
Additional Information:This research was originally published in: Stefanic, S; Spycher, C; Morf, L; Fabriàs, G; Casas, J; Schraner, E; Wild, P; Hehl, A B; Sonda, S (2010). Glucosylceramide synthesis inhibition affects cell cycle progression, membrane trafficking, and stage differentiation in Giardia lamblia. Journal of Lipid Research, 51(9):2527-2545. © the American Society for Biochemistry and Molecular Biology.
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:10.1194/jlr.M003392
PubMed ID:20335568
Permanent URL: http://doi.org/10.5167/uzh-44337

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