Recent advances in the Giardia–host relationship reveal danger lurking behind the smile

Coelho, Camila H.; Singer, Steven M.

doi:10.1371/journal.pntd.0006625

Cited by 8 publications

(7 citation statements)

References 20 publications

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“…However, although Giardia may secrete non-exosomal and non-MVB-derived extracellular vesicles, the absence of key ESCRT machinery (e.g. TOM1-esc, ESCRT-I, and VPS36 GRAM domain), along with a lack of specific exosomal markers and limited proteomics data (Ma’ayeh et al, 2017; Coelho et al, 2018) keeps the status of PV-associated vesicles in some doubt. An alternate interpretation is the PVs as a form of reduced and functionally limited MVB-like compartments in a similarly reduced Giardia endomembrane system which evolved via a process of merging organelle identity and distribution of endocytic function.…”

Section: Discussionmentioning

confidence: 99%

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

Pipaliya

Santos

Salas‐Leiva

et al. 2021

Preprint

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Comparing a parasitic lineage to its free-living relatives is a powerful way to understand how the evolutionary transition to parasitism occurred. Giardia intestinalis (Fornicata) is a leading cause of gastrointestinal disease world-wide and is famous for its unusual complement of cellular compartments, such as having peripheral vacuoles instead of typical endosomal compartments. Endocytosis plays an important role in Giardia's pathogenesis. Endosomal sorting complexes required for transport (ESCRT) are membrane-deforming proteins associated with the late endosome/multivesicular body (MVB). MVBs are ill-defined in G. intestinalis and roles for identified ESCRT-related proteins are not fully understood in the context of its unique endocytic system. Furthermore, components thought to be required for full ESCRT functionality have not yet been documented in this species. We used genomic and transcriptomic data from several Fornicata species to clarify the evolutionary genome streamlining observed in Giardia, as well as to detect any divergent orthologs of the Fornicata ESCRT subunits. We observed differences in the ESCRT machinery complement between Giardia strains. Microscopy-based investigations of key components of ESCRT machinery such as GiVPS36and GiVPS25 link them to peripheral vacuoles, highlighting these organelles as simplified MVB equivalents. Unexpectedly, we show ESCRT components associated with the Endoplasmic Reticulum, and for the first time, mitosomes. Finally, we identified the rare ESCRT component CHMP7 in several fornicate representatives, including Giardia, and show that contrary to current understanding, CHMP7 evolved from a gene fusion of VPS25 and SNF7 domains, prior to the last eukaryotic common ancestor, over 1.5 billion years ago. Our findings show that ESCRT machinery in G. intestinalis is far more varied and complete than previously thought, and associating to multiple cellular locations and presenting changes in ESCRT complement which pre-date adoption of a parasitic lifestyle.

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Section: Discussionmentioning

confidence: 99%

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

Pipaliya

Santos

Salas‐Leiva

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Complement factor H is a large, soluble glycoprotein found in serum that suppresses reactions of the alternative pathway of the complement system to host cells (Parente et al, 2017). The complement system has been shown to be important in the immune defense against of Giardia in mice (Li et al, 2016;Coelho and Singer, 2018) and it is possible that this protein is used by the parasite to prevent complement-mediated immune mechanisms. Another gene, ORF5800, that earlier was annotated to encode a hypothetical protein, has been shown to be similar to lipid transporters in the StART family (Ansell et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

High Cysteine Membrane Proteins (HCMPs) Are Up-Regulated During Giardia-Host Cell Interactions

Peirasmaki

Ma’ayeh

et al. 2020

Front. Genet.

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Giardia intestinalis colonizes the upper small intestine of humans and animals, causing the diarrheal disease giardiasis. This unicellular eukaryotic parasite is not invasive but it attaches to the surface of small intestinal epithelial cells (IECs), disrupting the epithelial barrier. Here, we used an in vitro model of the parasite's interaction with host IECs (differentiated Caco-2 cells) and RNA sequencing (RNAseq) to identify differentially expressed genes (DEGs) in Giardia, which might relate to the establishment of infection and disease induction. Giardia trophozoites interacted with differentiated Caco-2 cells for 1.5, 3, and 4.5 h and at each time point, 61, 89, and 148 parasite genes were up-regulated more than twofold, whereas 209, 265, and 313 parasite genes were down-regulated more than twofold. The most abundant DEGs encode hypothetical proteins and members of the High Cysteine Membrane Protein (HCMP) family. Among the up-regulated genes we also observed proteins associated with proteolysis, cellular redox balance, as well as lipid and nucleic acid metabolic pathways. In contrast, genes encoding kinases, regulators of the cell cycle and arginine metabolism and cytoskeletal proteins were down-regulated. Immunofluorescence imaging of selected, up-regulated HCMPs, using C-terminal HA-tagging, showed localization to the plasma membrane and peripheral vesicles (PVs). The expression of the HCMPs was affected by histone acetylation and free iron-levels. In fact, the latter was shown to regulate the expression of many putative giardial virulence factors in subsequent RNAseq experiments. We suggest that the plasma membrane localized and differentially expressed HCMPs play important roles during Giardia-host cell interactions.

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“…It could thus be speculated that, during Giardia infection, transfer of some virulence proteins into the host cells might occur to initiate the mitochondrial pathway of apoptosis. A recent review has addressed the effects of ESPs released from Giardia on host cell signaling and immune regulation [ 43 ]. ESPs have also been shown to function during the trophozoite attachment process [ 44 , 45 ].…”

Section: Discussionmentioning

confidence: 99%

Giardia duodenalis Induces Apoptosis in Intestinal Epithelial Cells via Reactive Oxygen Species-Mediated Mitochondrial Pathway In Vitro

et al. 2020

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The intestinal protozoan parasite, Giardia duodenalis, infects a large number of people in the world annually. Giardia infection has been considered a negative effect on intestinal epithelial cell growth, while the underlying mechanisms remain to be explored. Here we evaluated reactive oxygen species (ROS) production and apoptotic events in Giardia trophozoites-stimulated Caco-2 cells via fluorescence microscopy, transmission electron microscopy, flow cytometry, western blot, and cell counting kit-8 analyses. The results showed that Giardia trophozoite treatment could induce lactate dehydrogenase release and Caco-2 cell apoptosis. The ROS levels were increased post treatment. The observed typical characteristics of mitochondria damage include significant swelling and degeneration of matrix and cristae. After trophozoite treatment, the level of Bax protein expression was increased, while Bcl-2 protein decreased. Trophozoite stimulation also led to reduction of mitochondrial membrane potential and release of cytochrome c from the mitochondria to the cytoplasm, and this process was accompanied by activation of caspase-9 and caspase-3 and poly (ADP-ribose) polymerase 1 cleavage. Pretreatment with N-acetyl-L-cysteine, a ROS inhibitor, reversed G. duodenalis-induced Caco-2 cell apoptosis. Taken together, we indicated that G. duodenalis could induce Caco-2 cell apoptosis through a ROS- and mitochondria-mediated caspase-dependent pathway. This study furthers our understanding of the cellular mechanism of the interaction between Giardia trophozoites and host cells.

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Recent advances in the Giardia–host relationship reveal danger lurking behind the smile

Cited by 8 publications

References 20 publications

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

High Cysteine Membrane Proteins (HCMPs) Are Up-Regulated During Giardia-Host Cell Interactions

Giardia duodenalis Induces Apoptosis in Intestinal Epithelial Cells via Reactive Oxygen Species-Mediated Mitochondrial Pathway In Vitro

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