Biology subjects

Frickel, E.

Publications and source records attributed to Frickel, E..

8 recordsLinked to original sources

bioRxiv2023

p97/VCP targets Toxoplasma gondii vacuoles for parasite restriction in interferon-stimulated human cells

Infection with the parasite Toxoplasma gondii leads to production of interferon gamma (IFN{gamma}) that stimulates cells to upregulate defence proteins targeting the parasite for cell intrinsic elimination or growth restriction. Various host defence mechanisms operate at the parasitophorous vacuole (PV) in different human cell types leading to PV disruption, acidification, or membrane envelopment. Ubiquitin and p62 are players in all human host control mechanisms of Toxoplasma, but other unifying proteins have not been identified. Here, we show that p97/valosin-containing protein (VCP), as well as its associated proteins ANKRD13A and UBXD1 control Toxoplasma infection while recruited to the PV in IFN{gamma}-stimulated endothelial cells. Convergent deposition of ANKRD13A, p97/VCP and UBXD1 onto the same vacuole is dependent on vacuolar ubiquitination and observed within 2h post-infection. ANKRD13A, p97/VCP and UBXD1 all drive the acidification mechanism of the vacuole, which is the IFN{gamma}-dependent control pathway of Toxoplasma in endothelial cells. We assessed p97/VCP in Toxoplasma control in various human cells and demonstrate that p97/VCP is a universal IFN{gamma}-dependent host restriction factor targeting the Toxoplasma PV in epithelial (HeLa) and endothelial cells (HUVEC), fibroblasts (HFF) and macrophages (THP1).

immunology↗

bioRxiv2022

Molecular autism research in Africa: a scoping review comparing publication outputs to Brazil, India, the UK, and the USA.

The increased awareness of autism spectrum disorders (ASD) is accompanied by burgeoning ASD research, and concerted research efforts are trying to elucidate the molecular ASD aetiology. However, much of this research is concentrated in the Global North, with recent reviews of research in Sub-Saharan Africa (SSA) highlighting the significant shortage of ASD publications from this region. The most limited focus area was molecular research with only two molecular studies ever published from SSA, both being from South Africa (SA). We examine the molecular ASD research publications from 2016 to 2021 from all African countries, with a special focus on SA. The SSA publications are compared to Brazil and India, two non-African, low-to-middle-income countries (LMICs), and to the UK and USA, two high-income countries (HICs). There were 228 publications across all regions of interest; only three publications were from SA. Brazil (n=29) and India (n=27) had almost 10 times more publications than SA. The HICs had more publications than the LMICs, with the UK (n=62) and the USA (n=74) having approximately 20 to 25 times more publications than SA, respectively. Given that SA has substantial research capacity as demonstrated by its recent research on SARS-CoV-2, we explore potential reasons for this deficit in molecular ASD publications from SA. We compare mental health research outputs, GDP per capita, research and development expenditure, and the number of psychiatrists and child psychiatrists per 100,000 people across all regions. The UK and the USA had significantly higher numbers for all these indicators, consistent with their higher publication output. Among the LMICs, SA can potentially produce more molecular ASD research, however, there are numerous barriers that need to be addressed to facilitate increased research capacity. These include cultural stigmas, challenges in accessing mental healthcare, shortages of specialists in the public sector, and the unreliability of ASD diagnostic tools across the 11 official SA languages. The unique genetic architecture of African populations presents an untapped reservoir for finding novel genetic loci associated with ASD. Therefore, addressing the disparity in molecular ASD research between the Global North and SSA is integral to global advancements in ASD research.

molecular biology↗

bioRxiv2021

Toxoplasma-proximal and distal control by GBPs in human macrophages

Human guanylate-binding proteins (GBPs) are key players of interferon-gamma (IFN{gamma})-induced cell intrinsic defense mechanisms targeting intracellular pathogens. In this study we combine the well-established Toxoplasma gondii infection model with three in vitro macrophage culture systems to delineate the contribution of individual GBP family members to control this apicomplexan parasite. Use of high-throughput imaging assays and genome engineering allowed us to define a role for GBP1, 2 and 5 in parasite infection control. While GBP1 performs a pathogen-proximal, parasiticidal and growth-restricting function through accumulation at the parasitophorous vacuole of intracellular Toxoplasma, GBP2 and 5 perform a pathogen-distal, growth-restricting role. We further find that mutants of the GTPase or isoprenylation site of GBP1/2/5 affect their normal function in Toxoplasma control by leading to mis-localization of the proteins.

microbiology↗

bioRxiv2019

In vivo control of Toxoplasma gondii by zebrafish macrophages

Toxoplasma gondii is an obligate intracellular parasite capable of invading any nucleated cell. Three main clonal lineages (type I, II, III) exist and murine models have driven the understanding of general and strain-specific immune mechanisms underlying Toxoplasma infection. However, murine models are limited for studying parasite-leukocyte interactions in vivo, and discrepancies exist between cellular immune responses observed in mouse versus human cells. Here, we develop a zebrafish infection model to study the innate immune response to Toxoplasma in vivo. By infecting the zebrafish hindbrain ventricle, and using high-resolution microscopy techniques coupled with computer vision driven automated image analysis, we reveal that Toxoplasma invades and replicates inside a parasitophorous vacuole to which type I and III parasites recruit host cell mitochondria. We show that type II and III strains maintain a higher infectious burden than type I strains. To understand how parasites are being cleared in vivo, we analyzed Toxoplasma-macrophage interactions using time-lapse and correlative light and electron microscopy. Strikingly, macrophages are recruited to the infection site and play a key role in Toxoplasma control. These results highlight in vivo control of Toxoplasma by macrophages, and illuminate the possibility to exploit zebrafish for discoveries within the field of parasite immunity.

microbiology↗

bioRxiv2019

Mimicry embedding for advanced neuralnetwork training of 3D biomedical micrographs

The use of deep neural networks (DNNs) for analysis of complex biomedical images shows great promise but is hampered by a lack of large verified datasets for rapid network evolution. Here we present a novel \"mimicry embedding\" strategy for rapid application of neural network architecture-based analysis of biomedical imaging datasets. Embedding of a novel biological dataset, such that it mimics a verified dataset, enables efficient deep learning and seamless architecture switching. We apply this strategy across various microbiological phenotypes; from super-resolved viruses to in vivo parasitic infections. We demonstrate that mimicry embedding enables efficient and accurate analysis of three-dimensional microscopy datasets. The results suggest that transfer learning from pre-trained network data may be a powerful general strategy for analysis of heterogeneous biomedical imaging datasets.

bioinformatics↗

bioRxiv2018

TCR-MHC Interaction Strength Defines Trafficking and Resident Memory Status of CD8 T cells in the Brain

T cell receptor-Major histocompatibility complex (TCR-MHC) affinities span a wide range in a polyclonal T cell response, yet it is undefined how affinity shapes long-term properties of CD8 T cells during chronic infection with persistent antigen. Here, we investigate how the affinity of the TCR-MHC interaction shapes the phenotype of memory CD8 T cells in the chronically Toxoplasma gondii-infected brain. We employed CD8 T cells from three lines of transnuclear (TN) mice that harbour in their endogenous loci different T cell receptors specific for the same Toxoplasma antigenic epitope ROP7. The three TN CD8 T cell clones span a wide range of affinities to MHCI-ROP7. These three CD8 T cell clones have a distinct and fixed hierarchy in terms of effector function in response to the antigen measured as proliferation capacity, trafficking, T cell maintenance and memory formation. In particular, the T cell clone of lowest affinity does not home to the brain. The two higher affinity T cell clones show differences in establishing resident memory populations (CD103+) in the brain with the higher affinity clone persisting longer in the host during chronic infection. Transcriptional profiling of naive and activated ROP7-specific CD8 T cells revealed that Klf2 encoding a transcription factor that is known to be a negative marker for T cell trafficking is upregulated in the activated lowest affinity ROP7 clone. Our data thus suggest that TCR-MHC affinity dictates memory CD8 T cell fate at the site of infection.

immunology↗

bioRxiv2017

Detection of cytosolic Shigella flexneri via a C-terminal triple-arginine motif of GBP1 inhibits actin-based motility

Dynamin-like guanylate binding proteins (GBPs) are gamma interferon (IFN{gamma})-inducible host defense proteins that can associate with cytosol-invading bacterial pathogens. Mouse GBPs promote the lytic destruction of targeted bacteria in the host cell cytosol but the antimicrobial function of human GBPs and the mechanism by which these proteins associate with cytosolic bacteria are poorly understood. Here, we demonstrate that human GBP1 is unique amongst the seven human GBP paralogs in its ability to associate with at least two cytosolic Gram-negative bacteria, Burkholderia thailandensis and Shigella flexneri. Rough lipopolysaccharide (LPS) mutants of S. flexneri co-localize with GBP1 less frequently than wildtype S. flexneri, suggesting that host recognition of O-antigen promotes GBP1 targeting to Gram-negative bacteria. The targeting of GBP1 to cytosolic bacteria, via a unique triple-arginine motif present in its C-terminus, promotes the co-recruitment of four additional GBP paralogs (GBP2, GBP3, GBP4 and GBP6). GBP1-decorated Shigella replicate but fail to form actin tails leading to their intracellular aggregation. Consequentially, wildtype but not the triple-arginine GBP1 mutant restricts S. flexneri cell-to-cell spread. Furthermore, human-adapted S. flexneri, through the action of one its secreted effectors, IpaH9.8, is more resistant to GBP1 targeting than the non-human-adapted bacillus B. thailandensis. These studies reveal that human GBP1 uniquely functions as an intracellular glue trap inhibiting the cytosolic movement of normally actin-propelled Gram-negative bacteria. In response to this powerful human defense program S. flexneri has evolved an effective counter-defense to restrict GBP1 recruitment.\n\nImportanceSeveral pathogenic bacterial species evolved to invade, reside and replicate inside the cytosol of their host cells. One adaptation common to most cytosolic bacterial pathogens is the ability to co-opt the hosts actin polymerization machinery, in order to generate force for intracellular movement. This actin-based motility enables Gram-negative bacteria such as Shigella to propel themselves into neighboring cells thereby spreading from host cell to host cell without exiting the intracellular environment. Here, we show that the human protein GBP1 acts as a cytosolic glue trap capturing cytosolic Gram-negative bacteria through a unique protein motif and preventing disseminated infections in cell culture models. To escape from this GBP1-mediated host defense, Shigella employs a virulence factor that prevents or dislodges the association of GBP1 with cytosolic bacteria. Thus, therapeutic strategies to restore GBP1 binding to Shigella may lead to novel treatment options for shigellosis in the future.

microbiology↗

bioRxiv2017

Free ISG15 as a dimer generates IL-1β-producing CD8α+ dendritic cells at the site of infection

ISG15 is strongly induced after type I IFN stimulation producing a protein comprised of two ubiquitin-like domains. Intracellularly, ISG15 can be covalently linked and modify the function of target proteins (ISGylation). In addition, free unconjugated ISG15 can be released from cells. We found that ISG15 is released in the serum of Toxoplasma gondii infected mice early after infection in a type-I IFN independent manner. Once in the extracellular space, free ISG15 forms dimers and enhances the release of key cytokines involved in the immune response to the parasite: IL-12, IFN-{gamma}, and IL-1{beta}. Its action is dependent on an actively invading and replicating live parasite. ISG15 induces an increase of IL-1{beta} later during infection by leading to increased IL-1{beta} producing CD8+ dendritic cells at the site of infection. Here, we define for the first time the molecular determinants of active free ISG15 and link ISG15 to IL-1{beta} production by CD8+ dendritic cells. Thus we define ISG15 as a novel secreted modulator of the cytokine response during Toxoplasma infection.

immunology↗