Encystation commitment in<i>Giardia duodenalis</i>: a long and winding road

Argüello-García, Raúl; Ortega‐Pierres, Guadalupe

doi:10.1051/parasite/2009164247

Cited by 23 publications

(19 citation statements)

References 59 publications

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“…We speculate that at the onset of encystation, encystation stimuli activate proteins/molecules that are partitioned in microdomains and initiate the encystation process. It is possible that once the encystation is initiated, rafts are no longer required and encystation may continue without cholesterol (under cholesterol-starved conditions), as observed previously (35,36).…”

Section: Discussionmentioning

confidence: 63%

The Assembly of GM1 Glycolipid- and Cholesterol-Enriched Raft-Like Membrane Microdomains Is Important for Giardial Encystation

et al. 2015

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Although encystation (or cyst formation) is an important step of the life cycle of Giardia, the cellular events that trigger encystation are poorly understood. Because membrane microdomains are involved in inducing growth and differentiation in many eukaryotes, we wondered if these raft-like domains are assembled by this parasite and participate in the encystation process. Since the GM1 ganglioside is a major constituent of mammalian lipid rafts (LRs) and known to react with cholera toxin B (CTXB), we used Alexa Fluor-conjugated CTXB and GM1 antibodies to detect giardial LRs. Raft-like structures in trophozoites are located in the plasma membranes and on the periphery of ventral discs. In cysts, however, they are localized in the membranes beneath the cyst wall. Nystatin and filipin III, two cholesterol-binding agents, and oseltamivir (Tamiflu), a viral neuraminidase inhibitor, disassembled the microdomains, as evidenced by reduced staining of trophozoites with CTXB and GM1 antibodies. GM1-and cholesterol-enriched LRs were isolated from Giardia by density gradient centrifugation and found to be sensitive to nystatin and oseltamivir. The involvement of LRs in encystation could be supported by the observation that raft inhibitors interrupted the biogenesis of encystation-specific vesicles and cyst production. Furthermore, culturing of trophozoites in dialyzed medium containing fetal bovine serum (which is low in cholesterol) reduced raft assembly and encystation, which could be rescued by adding cholesterol from the outside. Our results suggest that Giardia is able to form GM1-and cholesterol-enriched lipid rafts and these raft domains are important for encystation.

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Section: Discussionmentioning

confidence: 63%

The Assembly of GM1 Glycolipid- and Cholesterol-Enriched Raft-Like Membrane Microdomains Is Important for Giardial Encystation

et al. 2015

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“…Invasion of mammalian host by Giardia is marked by conversion of the parasite from environmentally resistant, latent cysts to actively growing trophozoites that causes pathogenesis of the disease. The excystation and encystation events in the parasite life cycle have been established in vitro through manipulation of pH and bile concentration in the growth medium; however, the molecular mechanism and triggers effecting these transitions have not been fully understood [22], [45]. Analysis of GlHsp90 transcript and protein levels during trophozoite to cyst transition suggest that GlHsp90 may be involved in triggering this transition.…”

Section: Discussionmentioning

confidence: 99%

“…These trophozoites colonize the colon of the intestine where they adhere to the epithelial cells and are thus well nourished in a nutrient rich milieu [21]. Some of these trophozoites undergo encystation upon environmental cues that are only partially understood [22]. The precise molecular triggers and mechanism underlining these transitions remain unclear [23].…”

Section: Introductionmentioning

confidence: 99%

Trans-spliced Heat Shock Protein 90 Modulates Encystation in Giardia lamblia

et al. 2014

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BackgroundHsp90 from Giardia lamblia is expressed by splicing of two independently transcribed RNA molecules, coded by genes named HspN and HspC located 777 kb apart. The reasons underlying such unique trans-splicing based generation of GlHsp90 remain unclear.Principle FindingIn this study using mass-spectrometry we identify the sequence of the unique, junctional peptide contributed by the 5′ UTR of HspC ORF. This peptide is critical for the catalytic function of Hsp90 as it harbours an essential “Arg” in its sequence. We also show that full length GlHsp90 possesses all the functional hall marks of a canonical Hsp90 including its ability to bind and hydrolyze ATP. Using qRT-PCR as well as western blotting approach we find the reconstructed Hsp90 to be induced in response to heat shock. On the contrary we find GlHsp90 to be down regulated during transition from proliferative trophozoites to environmentally resistant cysts. This down regulation of GlHsp90 appears to be mechanistically linked to the encystation process as we find pharmacological inhibition of GlHsp90 function to specifically induce encystation.SignificanceOur results implicate the trans-spliced GlHsp90 from Giardia lamblia to regulate an essential stage transition in the life cycle of this important human parasite.

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“…low pH, cholesterol, and bile components) and carries out stage conversions (ex-and encystation) with intermediate entities (excyzoite and encyzoite, respectively) resulting in the establishment of the parasite inside and dissemination outside the infected host Gillin et al, 1988;Argüello-García et al, 2009). Owing to these interactions the parasite responds to host stimuli (i.e.…”

Section: Introductionmentioning

confidence: 99%

Giardia

2011

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This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifi cally those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machines or similar means, and storage in data banks.Product Liability: The publisher can give no guarantee for all the information contained in this book. This does also refer to information about drug dosage and application thereof. In every individual case the respective user must check its accuracy by consulting other pharmaceutical literature.The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specifi c statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

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Encystation commitment inGiardia duodenalis: a long and winding road

Cited by 23 publications

References 59 publications

The Assembly of GM1 Glycolipid- and Cholesterol-Enriched Raft-Like Membrane Microdomains Is Important for Giardial Encystation

The Assembly of GM1 Glycolipid- and Cholesterol-Enriched Raft-Like Membrane Microdomains Is Important for Giardial Encystation

Trans-spliced Heat Shock Protein 90 Modulates Encystation in Giardia lamblia

Giardia

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