scholarly journals EXP1 is required for organization of the intraerythrocytic malaria parasite vacuole

2019 ◽  
Author(s):  
Timothy Nessel ◽  
John M. Beck ◽  
Shima Rayatpisheh ◽  
Yasaman Jami-Alahmadi ◽  
James A. Wohlschlegel ◽  
...  
Keyword(s):  
Genome Editing ◽  
Translational Control ◽  
Protein Identification ◽  
Parasitophorous Vacuole ◽  
Critical Role ◽  
Transferase Activity ◽  
Glutathione S Transferase ◽  
Malaria Parasites ◽  
Vacuole Membrane

AbstractIntraerythrocytic malaria parasites reside within a parasitophorous vacuole membrane (PVM) that closely overlays the parasite plasma membrane (PPM) and constitutes the barrier between parasite and host compartments. The PVM is the site of several essential transport activities but the basis for organization of this membrane system is unknown. We utilized the second-generation promiscuous biotin ligase BioID2 fused to EXP2 or HSP101 to probe the content of the PVM, identifying known and novel candidate PVM proteins. Among the best represented hits were members of a group of single-pass integral membrane proteins that constitute a major component of the PVM proteome but whose function remains unclear. We investigated the function of EXP1, the longest known member of this group, by adapting a CRISPR/Cpf1 genome editing system to install the TetR-DOZI-aptamers system for conditional translational control. EXP1 knockdown was essential for intraerythrocytic development and accompanied by profound changes in vacuole ultrastructure, including increased separation of the PVM and PPM and formation of abnormal membrane structures in the enlarged vacuole lumen. While previous in vitro studies indicated EXP1 possesses glutathione S-transferase activity, a mutant version of EXP1 lacking a residue important for this activity in vitro still provides substantial rescue of endogenous exp1 knockdown in vivo. Intriguingly, while activity of the Plasmodium translocon of exported proteins was not impacted by depletion of EXP1, the distribution of the translocon pore-forming protein EXP2 was substantially altered. Collectively, our results reveal a novel PVM defect that indicates a critical role for EXP1 in maintaining proper PVM organization.ImportanceLike other obligate intracellular apicomplexans, blood-stage malaria parasites reside within a membrane-bound compartment inside the erythrocyte known as the parasitophorous vacuole. Although the vacuole is the site of several transport activities essential to parasite survival, little is known about its organization. To explore vacuole biology, we adopted recently developed proteomic (BioID2) and genetic (CRISPR/Cpf1) tools for use in Plasmodium falciparum, which allowed us to query the function of the prototypical vacuole membrane protein EXP1.Knockdown of EXP1 showed that a previously reported glutathione S-transferase activity cannot fully account for the essential function(s) of EXP1 and revealed a novel role for this protein in maintaining normal vacuole morphology and PVM protein arrangement. Our results provide new insight into vacuole organization and illustrate the power of BioID2 and Cpf1 (which utilizes a T-rich PAM uniquely suited to the P. falciparum genome) for proximity protein identification and genome editing in P. falciparum.

scholarly journals EXP1 is critical for nutrient uptake across the parasitophorous vacuole membrane of malaria parasites

PLoS Biology ◽  
2019 ◽  
Vol 17 (9) ◽  
pp. e3000473 ◽  
Author(s):  
Paolo Mesén-Ramírez ◽  
Bärbel Bergmann ◽  
Thuy Tuyen Tran ◽  
Matthias Garten ◽  
Jan Stäcker ◽  
...  
Keyword(s):  
Nutrient Uptake ◽  
Parasitophorous Vacuole ◽  
Parasitophorous Vacuole Membrane ◽  
Malaria Parasites ◽  
Vacuole Membrane

scholarly journals Stages of in vitro phagocytosis of Plasmodium falciparum-infected erythrocytes by human monocytes

2009 ◽  
Vol 42 (2) ◽  
pp. 103-106 ◽  
Author(s):  
Maria Imaculada Muniz-Junqueira ◽  
Carlos Eduardo Tosta
Keyword(s):  
Plasmodium Falciparum ◽  
Blood Circulation ◽  
Defense Mechanisms ◽  
Healthy Adult ◽  
Critical Role ◽  
Immune Serum ◽  
Human Monocytes ◽  
Malaria Parasites

Monocytes/macrophages play a critical role in the defense mechanisms against malaria parasites, and are the main cells responsible for the elimination of malaria parasites from the blood circulation. We carried out a microscope-aided evaluation of the stages of in vitro phagocytosis of Plasmodium falciparum-infected erythrocytes, by human monocytes. These cells were obtained from healthy adult individuals by means of centrifugation through a cushion of Percoll density medium and were incubated with erythrocytes infected with Plasmodium falciparum that had previously been incubated with a pool of anti-plasmodial immune serum. We described the stages of phagocytosis, starting from adherence of infected erythrocytes to the phagocyte membrane and ending with their destruction within the phagolisosomes of the monocytes. We observed that the different erythrocytic forms of the parasite were ingested by monocytes, and that the process of phagocytosis may be completed in around 30 minutes. Furthermore, we showed that phagocytosis may occur continuously, such that different phases of the process were observed in the same phagocyte.

Effect of inhibitors of glutathione S-transferase on glyceryl trinitrate activity in isolated rat aorta

1993 ◽  
Vol 71 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Rita Nigam ◽  
Tracy Whiting ◽  
Brian M. Bennett
Keyword(s):  
Glyceryl Trinitrate ◽  
Cyclic Gmp ◽  
Guanylyl Cyclase ◽  
Rat Aorta ◽  
Supernatant Fraction ◽  
Organic Nitrates ◽  
Transferase Activity ◽  
Glutathione S Transferase ◽  
Glutathione S Transferases

We investigated the role of glutathione S-transferases (enzymes known to biotransform organic nitrates) in the vascular action of glyceryl trinitrate (GTN). Relaxation of phenylephrine-contracted rat aortic strips was assessed in the presence or absence of the glutathione S-transferase inhibitors Basilen Blue, bromosulfophthalein, Rose Bengal, hematin, chlorotriphenyltin, and (octyloxy)benzoylvinylglutathione. Whereas none of the inhibitors increased the EC50 for GTN relaxation, glutathione S-transferase activity in the 100 000 × g supernatant fraction of rat aorta was inhibited markedly by most of the inhibitors. In addition, GTN-stimulated activation of aortic guanylyl cyclase in broken-cell preparations was attenuated by all of the glutathione S-transferase inhibitors, suggesting a direct inhibitory action on guanylyl cyclase. In other experiments using aortic strips preexposed to phenylephrine, the inhibitors had no effect on GTN-induced cyclic GMP accumulation or on vascular biotransformation of GTN. In contrast, both Basilen Blue and bromosulfophthalein significantly inhibited GTN-induced relaxation of K+-contracted aortic strips, and Basilen Blue significantly inhibited GTN biotransformation in aortic strips preexposed to 25 mM K+. This may be due to a more favourable electrochemical gradient for entry of the inhibitors into membrane-depolarized tissues. We conclude that vascular glutathione S-transferases play a role in mediating the vasodilator actions of GTN in intact tissues in vitro, but that this appears to depend upon the nature of the contractile agent used in such studies.Key words: glyceryl trinitrate, glutathione S-transferase, cyclic GMP, vascular smooth muscle, biotransformation.

scholarly journals Toxoplasma gondii PPM3C, a secreted protein phosphatase, affects parasitophorous vacuole effector export

2020 ◽  
Author(s):  
Joshua A. Mayoral ◽  
Tadakimi Tomita ◽  
Vincent Tu ◽  
Jennifer T. Aguilan ◽  
Simone Sidoli ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Parasitophorous Vacuole ◽  
Acute Infection ◽  
Critical Role ◽  
Cell Types ◽  
Effector Proteins ◽  
Secreted Proteins ◽  
Growth Defect ◽  
Label Free

ABSTRACTToxoplasma gondii is a highly successful parasite that infects a significant portion of the human population. As an intracellular parasite, T. gondii thrives within many different cell types due to its residence in the parasitophorous vacuole, a specialized and heavily modified compartment in which parasites divide. Within this vacuole, numerous secreted proteins facilitate functions that optimize intracellular survival. We characterized one such protein, TgPPM3C, which is predicted to contain a domain belonging to the PP2C class of serine/threonine phosphatases and is secreted by both tachyzoites and differentiating bradyzoites into the vacuolar lumen. Genetic deletion of TgPPM3C established that parasites lacking this predicted phosphatase exhibit a minor growth defect in vitro, are avirulent during acute infection in mice, and form fewer cysts in mouse brain during chronic infection. A label-free phosphoproteomic approach was utilized to identify putative TgPPM3C substrates and demonstrated several secreted proteins with altered phosphorylation status in the absence of TgPPM3C. Altered phosphorylation status was seen in MYR1, a protein essential to the process of protein effector export from the parasitophorous vacuole into the host cell, and in GRA16 and GRA28, two exported effector proteins. Defects were seen in the export of GRA16 and GRA28, but not the effector TgIST, in the TgPPM3C knockout strain. Parasites lacking TgPPM3C also exhibited defects in host c-Myc induction, a process influenced by effector export. Phosphomimetic mutations of GRA16 serine residues recapitulated export defects, implicating de-phosphorylation as an important process in facilitating the export of GRA16. These findings provide an example of the emerging critical role that phosphatases play in regulating the complex environment of the T. gondii parasitophorous vacuole.

Possible role of blood insulin levels on glutathione S-transferase activities from different tissues of male rats

1990 ◽  
Vol 68 (2) ◽  
pp. 170-173 ◽  
Author(s):  
Cristina E. Carnovale ◽  
Juan A. Monti ◽  
Viviana A. Catania ◽  
Maria C. Carrillo
Keyword(s):  
Diabetic Rats ◽  
Male Rats ◽  
Blood Levels ◽  
Transferase Activity ◽  
Glutathione S Transferase ◽  
Insulin Levels ◽  
Blood Insulin ◽  
Glucose Levels

The activity of in vitro glutathione S-transferase towards 1-chloro-2,4-dinitrobenzene was examined in liver, renal cortex, and small intestine (duodenum, jejunum, ileum) after the in vivo treatment of male Wistar rats with streptozotocin or alloxan. The studies were performed at 2, 10, 24, and 48 h and 7 and 15 days after streptozotocin treatment or 24 and 48 h after alloxan treatment. The results indicated that while the blood levels of insulin–glucose did not show variations, there were no alterations of the glutathione S-transferase activity in the tissues tested. On the other hand, when the treatments caused modifications on blood insulin–glucose levels, there were changes of glutathione S-transferase activity in all tissues (except in the ileum) in such a way that a direct relationship between plasma insulin levels and glutathione S-transferase activity could be demonstrated. These results were also confirmed through insulin administration to control and diabetic rats. The data demonstrate a possible regulation of glutathione S-transferase activity by blood insulin and (or) glucose levels in the tissues tested.Key words: insulin, glutathione S-transferase, streptozotocin, alloxan.

Effect of Temperature and Safeners on Glutathione Levels and Glutathione S-Transferase Activity in Maize

1991 ◽  
Vol 46 (9-10) ◽  
pp. 856-860 ◽  
Author(s):  
Daniel L. Kunkel ◽  
John C. Steffens ◽  
Robin R. Bellinder
Keyword(s):  
Low Temperatures ◽  
Herbicide Tolerance ◽  
Effect Of Temperature ◽  
Transferase Activity ◽  
Glutathione S Transferase ◽  
Different Temperatures ◽  
Maize Plants ◽  
Incubation Temperatures ◽  
Gst Activity

Abstract Studies were conducted to determine the biochemical aspects of chloroacetamide injury to maize and the mechanism by which safeners maintain herbicide tolerance, even at reduced temperatures. The objectives of these studies were threefold: one, determine whether gluta­thione (GSH) content varies in maize plants grown at three different temperatures in safener-treated and non-treated plants; two, determine whether glutathione S-transferase (GST) activ­ity varies in plants grown at different temperatures; and three, determine if GSH activity is sensitive to low temperatures in vitro. The herbicide safeners CGA -154281 [4-(dichloroacetyl)-3,4-dihydro-3-methyl-2 H-1 ,4-benzoxazine] and dichlormid [2,2-dichloro-N,N-di-2-propenylacetamide] were used with metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-n-(2-methoxy-1-methyl)acetamide] or acetochlor [2-chloro-N-(ethoxymethyl)-N-2-ethyl-6-methylphenyl)-acetamide], respectively, to determine the mechanisms of maize tolerance. CGA -154281 signifi­cantly increased GSH levels in maize seedlings grown at 27 °C compared to non-safened seed­lings, however significant differences were not seen at 17 or 37 °C. Dichlormid increased GSH levels by 1.6-fold at all growth temperatures. Both CGA -154281 and dichlormid increased GST activity significantly at all growth temperatures. The safener-induced GST activity was main­tained at in vitro incubation temperatures of 5 and 15 °C for acetochlor and metolachlor, re­spectively. In contrast, GST activity from non-safened tissue was essentially absent at these temperatures. Therefore, greater GST activity following safener treatment may result in higher levels of herbicide metabolism, even at low temperatures.

scholarly journals Novel Antimalarial Inhibitors That Specifically Target the Invasion Motor Protein Myosin A in Malaria Parasites

Proceedings ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 9
Author(s):  
Janna Ehlert ◽  
Arne Alder ◽  
Viola Introini ◽  
Julia Weder ◽  
Pietro Cicuta ◽  
...  
Keyword(s):  
Covalent Binding ◽  
Critical Role ◽  
Resistance Mechanisms ◽  
Myosin Isoforms ◽  
Malaria Parasites ◽  
Wide Range ◽  
Reversible Covalent ◽  
Parasite Motility ◽  
Vitro Analysis

Malaria remains a devastating disease with nearly half a million deaths per year. The WHO reports a stagnating number of new infections every year without a significant decline, as a result of insufficient access to antimalarials in endemic regions as well as complex resistance mechanisms of the parasites against current treatments. Due to its critical role during the parasite’s life cycle, the invasion motor myosin A is a promising target, which has not yet been considered in drug discovery. Myosins appeared to be undruggable since they are ubiquitously expressed and involved in a wide range of cellular processes. In total, the protein superfamily of myosins comprises 35 known subclasses. However, recent studies highlighted the possibility to modulate the myosin motor activity of specific myosin isoforms and classes using small allosteric effector molecules. Exploiting the concept of reversible covalent binding, we show the development of highly potent and specific inhibitors of the key motor myosin A of the glideosome—a sophisticated motor machinery involved in parasite motility and host cell invasion. Combining chemical synthesis with biophysical in vitro analysis confirmed the preferential inhibition of the target protein in the submicromolar range. The developed compounds show significant antiparasitic activities and block efficiently glideosome-associated processes, parasite proliferation, and parasitemia of the malaria parasites. Our findings demonstrate the high potential of our approach using reversible covalent binding to develop new allosteric inhibitors, targeting specifically the key invasion motor as a novel drug target to treat infections caused by malaria parasites.

scholarly journals An ER CREC family protein regulates the egress proteolytic cascade in malaria parasites

2018 ◽  
Author(s):  
Manuel A. Fierro ◽  
Beejan Asady ◽  
Carrie F. Brooks ◽  
David W. Cobb ◽  
Alejandra Villegas ◽  
...  
Keyword(s):  
Protein Trafficking ◽  
Double Mutant ◽  
Essential Role ◽  
Parasitophorous Vacuole ◽  
Parasitophorous Vacuole Membrane ◽  
Malaria Parasites ◽  
Vacuole Membrane ◽  
Proteolytic Cascade ◽  
Family Protein ◽  
Parasite Egress

AbstractThe endoplasmic reticulum (ER) is thought to play an essential role during egress of malaria parasites because the ER is assumed to be the calcium (Ca2+) signaling hub and required for biogenesis of egress-related organelles. However, no proteins localized to the parasite ER have been shown to play a role in egress of malaria parasites. In this study, we generated conditional mutants of the Plasmodium falciparumEndoplasmic Reticulum-resident Calcium-binding protein (PfERC), a member of the CREC family. Knockdown of PfERC shows that this gene is essential for asexual growth of P. falciparum. Analysis of the intraerythrocytic lifecycle revealed that PfERC is essential for parasite egress but not required for protein trafficking or Ca2+ storage. We found that PfERC knockdown prevents the rupture of the parasitophorous vacuole membrane. This is because PfERC knockdown inhibited the proteolytic maturation of the subtilisin-like serine protease, SUB1. Using double mutant parasites, we show that PfERC is required for the proteolytic maturation of the essential aspartic protease, Plasmepsin X, which cleaves SUB1. Further, we show that processing of substrates downstream of the proteolytic cascade is inhibited by PfERC knockdown. Thus, these data establish the ER-resident CREC family protein, PfERC, as a key early regulator of the egress proteolytic cascade of malaria parasites.

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