title: Glucosylceramide transferase activity is critical for encystation and viable cyst production by an intestinal protozoan, Giardia lamblia.
abstract: The production of viable cysts by Giardia is essential for its survival in the environment and for spreading the infection via contaminated food and water. The hallmark of cyst production (also known as encystation) is the biogenesis of encystation-specific vesicles (ESVs) that transport cyst wall proteins to the plasma membrane of the trophozoite before laying down the protective cyst wall. However, the molecules that regulate ESV biogenesis and maintain cyst viability have never before been identified. Here, we report that giardial glucosylceramide transferase-1 (gGlcT1), an enzyme of sphingolipid biosynthesis, plays a key role in ESV biogenesis and maintaining cyst viability. We find that overexpression of this enzyme induced the formation of aggregated/enlarged ESVs and generated clustered cysts with reduced viability. The silencing of gGlcT1 synthesis by antisense morpholino oligonucleotide abolished ESV production and generated mostly nonviable cysts. Interestingly, when gGlcT1-overexpressed Giardia was transfected with anti-gGlcT1 morpholino, the enzyme activity, vesicle biogenesis, and cyst viability returned to normal, suggesting that the regulated expression of gGlcT1 is important for encystation and viable cyst production. Furthermore, the overexpression of gGlcT1 increased the influx of membrane lipids and fatty acids without altering the fluidity of plasma membranes, indicating that the expression of gGlcT1 activity is linked to lipid internalization and maintaining the overall lipid balance in this parasite. Taken together, our results suggest that gGlcT1 is a key player of ESV biogenesis and cyst viability and therefore could be targeted for developing new anti-giardial therapies.
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Tavis L
authors.initials: TL
authors.lastname: Mendez
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Atasi
authors.initials: A
authors.lastname: De Chatterjee
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Trevor T
authors.initials: TT
authors.lastname: Duarte
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Felipe
authors.initials: F
authors.lastname: Gazos-Lopes
authors.affiliation: From Infectious Disease and Immunology; Neuroscience and Metabolic Disorder Clusters, Border Biomedical Research Center, El Paso, Texas 79968-5808.
authors.forename: Leobarda
authors.initials: L
authors.lastname: Robles-Martinez
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Debarshi
authors.initials: D
authors.lastname: Roy
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Sun
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Rosa A
authors.initials: RA
authors.lastname: Maldonado
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808; Neuroscience and Metabolic Disorder Clusters, Border Biomedical Research Center, El Paso, Texas 79968-5808.
authors.forename: Sukla
authors.initials: S
authors.lastname: Roychowdhury
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808.
authors.forename: Igor C
authors.initials: IC
authors.lastname: Almeida
authors.affiliation: From Infectious Disease and Immunology; Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas 79968-5808. Electronic address: sdas@utep.edu.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Das
mesh_terms: D016829:Giardia lamblia / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D013107:Sphingolipids / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D015800:Protozoan Proteins; D013107:Sphingolipids; D016695:Glycosyltransferases
keywords: Giardia; Glucosylceramide; Glycolipids; Lipid Metabolism; Lipids; Parasite; Parasite Metabolism; Sphingolipid; Transferase