Intersection of endocytic and exocytic systems in Toxoplasma gondii

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143628/1/tra12556.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143628/2/tra12556-sup-0001-EditorialProcess.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143628/3/tra12556_am.pd

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Toxoplasma gondii Exploits the Host ESCRT Machinery for Parasite Uptake of Host Cytosolic Proteins

A variety of pathogens, from viruses to bacteria, have developed mechanisms to exploit the host endosomal sorting complex required for transport (ESCRT) machinery for intracellular subsistence and replication. Here, we elucidate the mechanism for host ESCRT recruitment to the replicative compartment of the obligate intracellular parasite Toxoplasma gondii. We discovered that this eukaryotic microorganism exploits the host ESCRT machinery for the uptake of host cytosolic proteins that are thought to be a source of nutrients for the parasite. Furthermore, we have identified the parasite dense granule protein GRA14, which contains motifs homologous to the ESCRT-interacting late domain motifs of the HIV-1 Gag and is necessary for uptake of host cytosolic proteins, as an ESCRT-interacting parasite effector protein. GRA14 contributes to the recruitment of early- and late-acting ESCRT components such as TSG101 and VPS4B via its late domain motifs. Thus, as our working model we propose that host ESCRT components interact with GRA14 to trigger the formation of vesicles across the PV membrane (PVM) that contain host-derived resources. This work shed light on the first described mechanisms for ESCRT exploitation by a eukaryotic microorganism and provides evidence for a conserved role of the late domain, first described to be important in retroviral budding, in this process.PHDMicrobiology & ImmunologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/172718/1/ryoly_1.pd

The multifaceted interactions between pathogens and host ESCRT machinery.

The Endosomal Sorting Complex Required for Transport (ESCRT) machinery consists of multiple protein complexes that coordinate vesicle budding away from the host cytosol. ESCRTs function in many fundamental cellular processes including the biogenesis of multivesicular bodies and exosomes, membrane repair and restoration, and cell abscission during cytokinesis. Work over the past 2 decades has shown that a diverse cohort of viruses critically rely upon host ESCRT machinery for virus replication and envelopment. More recent studies reported that intracellular bacteria and the intracellular parasite Toxoplasma gondii benefit from, antagonize, or exploit host ESCRT machinery to preserve their intracellular niche, gain resources, or egress from infected cells. Here, we review how intracellular pathogens interact with the ESCRT machinery of their hosts, highlighting the variety of strategies they use to bind ESCRT complexes using short linear amino acid motifs like those used by ESCRTs to sequentially assemble on target membranes. Future work exposing new mechanisms of this molecular mimicry will yield novel insight of how pathogens exploit host ESCRT machinery and how ESCRTs facilitate key cellular processes

Emerging Mechanisms of Endocytosis in Toxoplasma gondii

Eukaryotes critically rely on endocytosis of autologous and heterologous material to maintain homeostasis and to proliferate. Although mechanisms of endocytosis have been extensively identified in mammalian and plant systems along with model systems including budding yeast, relatively little is known about endocytosis in protozoan parasites including those belonging to the phylum Apicomplexa. Whereas it has been long established that the apicomplexan agents of malaria (Plasmodium spp.) internalize and degrade hemoglobin from infected red blood cells to acquire amino acids for growth, that the related and pervasive parasite Toxoplasma gondii has a functional and active endocytic system was only recently discovered. Here we discuss emerging and hypothesized mechanisms of endocytosis in Toxoplasma gondii with reference to model systems and malaria parasites. Establishing a framework for potential mechanisms of endocytosis in Toxoplasma gondii will help guide future research aimed at defining the molecular basis and biological relevance of endocytosis in this tractable and versatile parasite

Toxoplasma gondii exploits the host ESCRT machinery for parasite uptake of host cytosolic proteins.

Toxoplasma gondii is a master manipulator capable of effectively siphoning the resources from the host cell for its intracellular subsistence. However, the molecular underpinnings of how the parasite gains resources from its host remain largely unknown. Residing within a non-fusogenic parasitophorous vacuole (PV), the parasite must acquire resources across the limiting membrane of its replicative niche, which is decorated with parasite proteins including those secreted from dense granules. We discovered a role for the host Endosomal Sorting Complex Required for Transport (ESCRT) machinery in host cytosolic protein uptake by T. gondii by disrupting host ESCRT function. We identified the transmembrane dense granule protein TgGRA14, which contains motifs homologous to the late domain motifs of HIV-1 Gag, as a candidate for the recruitment of the host ESCRT machinery to the PV membrane. Using an HIV-1 virus-like particle (VLP) release assay, we found that the motif-containing portion of TgGRA14 is sufficient to substitute for HIV-1 Gag late domain to mediate ESCRT-dependent VLP budding. We also show that TgGRA14 is proximal to and interacts with host ESCRT components and other dense granule proteins during infection. Furthermore, analysis of TgGRA14-deficient parasites revealed a marked reduction in ingestion of a host cytosolic protein compared to WT parasites. Thus, we propose a model in which T. gondii recruits the host ESCRT machinery to the PV where it can interact with TgGRA14 for the internalization of host cytosolic proteins across the PV membrane (PVM). These findings provide new insight into how T. gondii accesses contents of the host cytosol by exploiting a key pathway for vesicular budding and membrane scission

Stable endocytic structures navigate the complex pellicle of apicomplexan parasites.

Apicomplexan parasites have immense impacts on humanity, but their basic cellular processes are often poorly understood. Where endocytosis occurs in these cells, how conserved this process is with other eukaryotes, and what the functions of endocytosis are across this phylum are major unanswered questions. Using the apicomplexan model Toxoplasma, we identified the molecular composition and behavior of unusual, fixed endocytic structures. Here, stable complexes of endocytic proteins differ markedly from the dynamic assembly/disassembly of these machineries in other eukaryotes. We identify that these endocytic structures correspond to the 'micropore' that has been observed throughout the Apicomplexa. Moreover, conserved molecular adaptation of this structure is seen in apicomplexans including the kelch-domain protein K13 that is central to malarial drug-resistance. We determine that a dominant function of endocytosis in Toxoplasma is plasma membrane homeostasis, rather than parasite nutrition, and that these specialized endocytic structures originated early in infrakingdom Alveolata likely in response to the complex cell pellicle that defines this medically and ecologically important ancient eukaryotic lineage

Stable endocytic structures navigate the complex pellicle of apicomplexan parasites

Acknowledgements: This work was supported by the Wellcome Trust, United Kingdom, Investigator award 214298/Z/18/Z to R.F.W., a Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) grant 464878930 to S.G., and a DFG Equipment grant INST 86/1831-1 to Prof. Markus Meissner. B.N.M.S. was supported by a Gates Cambridge Scholarship, and K.B. was supported by the Leverhulme Early Career Fellowship (ECF-2015-562) provided jointly by the Isaac Newton Trust and the Leverhulme Trust. M.S.R. and J.H. was supported by Wellcome Trust grants 086598 and 214272 to M.S.R. and a Wellcome Trust Strategic Award 100140 to the Cambridge Institute for Medical Research (CIMR). N.R.Z. was supported by Wellcome Trust grant WT 207455/Z/17/Z. C.M.K. was supported by a Canada Vanier Graduate Scholarship and J.B.D. is supported by the Canada Research Chair (Tier II) in Evolutionary Cell Biology and by the Natural Sciences and Engineering Research Council of Canada (RES0043758, RES0046091). Y.R-C. was supported by NIH awards F31AI152297 and T32AI007528. We thank VEuPathDB for their invaluable Informatics Resources, and Markus Meissner, Christine Hopp, Nicola Hodson, Julian Rayner, Mirko Singer and David Warhurst for useful discussions, and Cornelia Niemann and Karin Müller for assistance with electron microscopy.AbstractApicomplexan parasites have immense impacts on humanity, but their basic cellular processes are often poorly understood. Where endocytosis occurs in these cells, how conserved this process is with other eukaryotes, and what the functions of endocytosis are across this phylum are major unanswered questions. Using the apicomplexan model Toxoplasma, we identified the molecular composition and behavior of unusual, fixed endocytic structures. Here, stable complexes of endocytic proteins differ markedly from the dynamic assembly/disassembly of these machineries in other eukaryotes. We identify that these endocytic structures correspond to the ‘micropore’ that has been observed throughout the Apicomplexa. Moreover, conserved molecular adaptation of this structure is seen in apicomplexans including the kelch-domain protein K13 that is central to malarial drug-resistance. We determine that a dominant function of endocytosis in Toxoplasma is plasma membrane homeostasis, rather than parasite nutrition, and that these specialized endocytic structures originated early in infrakingdom Alveolata likely in response to the complex cell pellicle that defines this medically and ecologically important ancient eukaryotic lineage.</jats:p

Memoria del primer simposium sobre historia, sociedad y cultura de México y América Latina

El presente volumen reúne 21 ponencias de las 25 que se presentaron en el “Primer simposium sobre historia, sociedad y cultura de México y América Latina”, realizado el 27 y el 28 de octubre de 2005, en el Centro de Investigación en Ciencias Sociales y Humanidades (CICSyH) de la Universidad Autónoma del Estado de México (UAEM), en Toluca, Estado de México