<i>Giardia intestinalis</i> can interact, change its shape and internalize large particles and microorganisms

Benchimol, Marlene

doi:10.1017/s0031182020002292

Cited by 8 publications

(11 citation statements)

References 39 publications

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“…Furthermore, GlActin-depleted cells have defects in cell polarity and cell shape (6). Another possible role for GlActin interactors localized to the plasma membrane is in phagocytosis, a process previously unrecorded in Giardia, but for which evidence has recently been published (60); if further research shows Giardia to be capable of phagocyotis, GlActin is likely to be involved (60,61), given its role in phagocytosis in other organisms.…”

Section: Discussionmentioning

confidence: 99%

Identification of Actin Filament Interactors in Giardia lamblia

Steele-Ogus

Johnson

MacCoss

et al. 2021

Preprint

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The deep-branching protozoan parasite Giardia lamblia is the causative agent of the intestinal disease giardiasis. Consistent with its proposed evolutionary position, many pathways are minimalistic or divergent, including its actin cytoskeleton. Giardia is the only eukaryote known to lack all canonical actin-binding proteins. Previously, our lab identified a number of non-canonical Giardia lamblia actin (GlActin) interactors; however, these proteins appeared to interact only with monomeric or globular actin (G-actin), rather than filamentous actin (F-actin). To identify interactors, we used a chemical crosslinker to preserve native interactions, followed by an anti-GlActin antibody, Protein A affinity chromatography, and liquid chromatography coupled to mass spectrometry. We found 46 putative actin interactors enriched in the conditions favoring F-actin. None of the proteins identified contain known actin-interacting motifs, and many lacked conserved domains. Each potential interactor was then tagged with the fluorescent protein mNeonGreen and visualized in live cells. We categorized the proteins based on their primary localization; localizations included ventral disc, marginal plate, nuclei, flagella, plasma membrane, and internal membranes. One protein from each category was co-localized with GlActin using immunofluorescence microscopy. We also co-immunoprecipitated one protein from each category and confirmed three interactions. Most of the localization patterns are consistent with previously demonstrated GlActin functions, but the ventral disc represents a new category of actin interactor localization. These results suggest a role for GlActin in ventral disc function, which has previously been controversial.

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Section: Discussionmentioning

confidence: 99%

Identification of Actin Filament Interactors in Giardia lamblia

Steele-Ogus

Johnson

MacCoss

et al. 2021

Preprint

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“…Furthermore, Gl Actin-depleted cells have defects in cell polarity and cell shape ( 6 ). Another possible role for Gl Actin interactors localized to the plasma membrane is in phagocytosis; evidence for this process taking place in Giardia has recently been published ( 61 ). If further research shows Giardia to be capable of phagocytosis, Gl Actin is likely to be involved ( 61 , 62 ), given its role in phagocytosis in other organisms.…”

Section: Discussionmentioning

confidence: 99%

Identification of Actin Filament-Associated Proteins in Giardia lamblia

et al. 2021

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Giardia lamblia is an intestinal parasite that colonizes the small intestine and causes diarrhea, which can lead to dehydration and malnutrition. Giardia actin ( Gl Actin) has a conserved role in Giardia cells, despite being a highly divergent protein with none of the conserved regulators found in model organisms. Here, we identify and localize 46 interactors of polymerized actin.

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“…Although Giardia is missing proteins involved in cell motility, the protrusion rate is on the same order of magnitude as cells using lamellipodia dependent mesenchymal motility (32, 33), suggesting that the Gl Actin cytoskeleton remains fully functional. Indeed recent observations unexpectedly demonstrated that Giardia may be capable of phagocytosis, which is an actin-dependent process that requires the formation of large membrane protrusions (48).…”

Section: Discussionmentioning

confidence: 99%

TheGiardialamellipodium-like ventrolateral flange supports attachment and rapid cytokinesis

Gcm

Taparia

et al. 2021

Preprint

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Attachment to the intestinal epithelium is critical to the lifestyle of the ubiquitous parasite Giardia lamblia. The microtubule cytoskeleton plays a well characterized role in attachment via the ventral adhesive disc, whereas the role of the unconventional actin cytoskeleton is controversial. We identified a novel actin associated protein with putative WH2-like actin binding domains we named Flangin. Flangin complexes with Giardia actin and is enriched in the ventrolateral flange (VLF), a lamellipodium-like membrane protrusion at the interface between parasites and attached surfaces. Live imaging revealed that the VLF grows to ~1 μm in width after cytokinesis, then remains size-uniform in interphase, grows during mitosis, and is resorbed during cytokinesis. A Flangin truncation mutant stabilizes the VLF and blocks cytokinesis, indicating that the VLF is a membrane reservoir supporting rapid myosin-independent cytokinesis in Giardia. Rho family GTPases are important regulators of membrane protrusions, GlRac, the sole Rho family GTPase in Giardia, was localized to the VLF. Knockdown of Flangin, actin, and GlRac result in VLF formation defects indicating a conserved role for GlRac and actin in forming membrane protrusions, despite the absence of canonical actin binding proteins that link Rho GTPase signaling to lamellipodia formation. Flangin-depleted parasites challenged with fluid shear force in flow chambers had a reduced ability to remain attached, indicating a role for the VLF in attachment. This secondary attachment mechanism complements the microtubule based adhesive ventral disc, a feature that is particularly important during mitosis when the parental ventral disc begins disassembly in preparation for cytokinesis.ImportanceThe ventrolateral flange (VLF) is a lamellipodium-like structure found at the host-parasite interface that has long been thought to be involved in parasite attachment. The proteins responsible for building the VLF have remained unidentified precluding manipulation of the VLF to determine its role in Giardia biology. We identified Flangin, a novel actin associated protein that localizes to the VLF, implicating Giardia actin in VLF formation. We demonstrate that: 1.) Flangin, actin, and GlRac are required for VLF formation, 2.) the VLF serves as a membrane reservoir to support Giardia’s incredibly fast cytokinesis, and 3) the VLF augments attachment, which is critical to parasitism. The microtubule-based adhesive ventral disc and the actin-based ventrolateral flange represent redundant means of maintaining attachment, the presence of redundant systems illustrate the importance of attachment to the lifestyle of this ubiquitous parasite.

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Giardia intestinalis can interact, change its shape and internalize large particles and microorganisms

Cited by 8 publications

References 39 publications

Identification of Actin Filament Interactors in Giardia lamblia

Identification of Actin Filament Interactors in Giardia lamblia

Identification of Actin Filament-Associated Proteins in Giardia lamblia

TheGiardialamellipodium-like ventrolateral flange supports attachment and rapid cytokinesis

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