scholarly journals Wnt5a promotes hippocampal postsynaptic development and GluN2B-induced expression via the eIF2α HRI kinase

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eva Ramos-Fernández ◽  
Macarena S. Arrázola ◽  
Carolina A. Oliva ◽  
Sebastián B. Arredondo ◽  
Lorena Varela-Nallar ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Ex Vivo ◽  
Initiation Factor ◽  
Glutamatergic Neurotransmission ◽  
Reading Frame ◽  
Molecular Pathway ◽  
Nmda Receptor Function ◽  
Translational Mechanisms ◽  
Phosphorylated Eif2α

AbstractWnt signaling plays a key role in neurodevelopment and neuronal maturation. Specifically, Wnt5a stimulates postsynaptic assemblies, increases glutamatergic neurotransmission and, through calcium signaling, generates nitric oxide (NO). Trying to unveil the molecular pathway triggering these postsynaptic effects, we found that Wnt5a treatment induces a time-dependent increases in the length of the postsynaptic density (PSD), elicits novel synaptic contacts and facilitates F-actin flow both in in vitro and ex vivo models. These effects were partially abolished by the inhibition of the Heme-regulated eukaryotic initiation factor 2α (HRI) kinase, a kinase which phosphorylates the initiation translational factor eIF2α. When phosphorylated, eIF2α normally avoids the translation of proteins not needed during stress conditions, in order to avoid unnecessary energetic expenses. However, phosphorylated eIF2α promotes the translation of some proteins with more than one open reading frame in its 5′ untranslated region. One of these proteins targeted by Wnt-HRI-eIF2α mediated translation is the GluN2B subunit of the NMDA receptor. The identified increase in GluN2B expression correlated with increased NMDA receptor function. Considering that NMDA receptors are crucial for excitatory synaptic transmission, the molecular pathway described here contributes to the understanding of the fast and plastic translational mechanisms activated during learning and memory processes.

scholarly journals The rocaglate CR-31-B (-) inhibits SARS-CoV-2 replication at non-cytotoxic, low nanomolar concentrations in vitro and ex vivo

2020 ◽  
Author(s):  
Christin Müller ◽  
Wiebke Obermann ◽  
Nadja Karl ◽  
Hans-Guido Wendel ◽  
Gaspar Taroncher-Oldenburg ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Ex Vivo ◽  
Rna Virus ◽  
Mrna Translation ◽  
Hemorrhagic Fever ◽  
Airway Epithelial Cells ◽  
Initiation Factor ◽  
Protein Accumulation ◽  
Hemorrhagic Fever Virus

AbstractSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a betacoronavirus in the subgenus Sarbecovirus causes a respiratory disease with varying symptoms referred to as coronavirus disease 2019 (COVID-19) and is responsible for a pandemic that started in early 2020. With no vaccines or effective antiviral treatments available, and infection and fatality numbers continuing to increase globally, the quest for novel therapeutic solutions remains an urgent priority. Rocaglates, a class of plant-derived cyclopenta[b]benzofurans, exhibit broad-spectrum antiviral activity against positive- and negative-sense RNA viruses. This compound class inhibits eukaryotic initiation factor 4A (eIF4A)-dependent mRNA translation initiation, resulting in strongly reduced viral RNA translation. The synthetic rocaglate CR-31-B (-) has previously been shown to inhibit the replication of human coronaviruses, such as HCoV-229E and MERS-CoV, as well as Zika-, Lassa-, Crimean Congo hemorrhagic fever virus in primary cells. Here, we assessed the antiviral activity of CR-31-B (-) against SARS-CoV-2 using both in vitro and ex vivo cell culture models. In African green monkey Vero E6 cells, CR-31-B (-) inhibited SARS-CoV-2 replication with an EC50 of ~1.8 nM. In line with this, viral protein accumulation and replication/transcription complex formation were found to be strongly reduced by this compound. In an ex vivo infection system using human airway epithelial cells, CR-31-B (-) was found to cause a massive reduction of SARS-CoV-2 titers by about 4 logs to nearly non-detectable levels. The data reveal a potent anti-SARS-CoV-2 activity by CR-31-B (-), corroborating previous results obtained for other coronaviruses and supporting the idea that rocaglates may be used in first-line antiviral intervention strategies against novel and emerging RNA virus outbreaks.

scholarly journals The Interaction between the Ribosomal Stalk Proteins and Translation Initiation Factor 5B Promotes Translation Initiation

2018 ◽  
Vol 38 (16) ◽  
Author(s):  
Ryo Murakami ◽  
Chingakham Ranjit Singh ◽  
Jacob Morris ◽  
Leiming Tang ◽  
Ian Harmon ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Yeast Cells ◽  
Upstream Open Reading Frame ◽  
Initiation Factor ◽  
Hydrophobic Pocket ◽  
Reading Frame ◽  
Ribosomal Stalk

ABSTRACTRibosomal stalk proteins recruit translation elongation GTPases to the factor-binding center of the ribosome. Initiation factor 5B (eIF5B in eukaryotes and aIF5B in archaea) is a universally conserved GTPase that promotes the joining of the large and small ribosomal subunits during translation initiation. Here we show that aIF5B binds to the C-terminal tail of the stalk protein. In the cocrystal structure, the interaction occurs between the hydrophobic amino acids of the stalk C-terminal tail and a small hydrophobic pocket on the surface of the GTP-binding domain (domain I) of aIF5B. A substitution mutation altering the hydrophobic pocket of yeast eIF5B resulted in a marked reduction in ribosome-dependent eIF5B GTPase activityin vitro. In yeast cells, the eIF5B mutation affected growth and impairedGCN4expression during amino acid starvation via a defect in start site selection for the first upstream open reading frame inGCN4mRNA, as observed with the eIF5B deletion mutant. The deletion of two of the four stalk proteins diminished polyribosome levels (indicating defective translation initiation) and starvation-inducedGCN4expression, both of which were suppressible by eIF5B overexpression. Thus, the mutual interaction between a/eIF5B and the ribosomal stalk plays an important role in subunit joining during translation initiationin vivo.

scholarly journals Rocaglates as dual-targeting agents for experimental cerebral malaria

2018 ◽  
Vol 115 (10) ◽  
pp. E2366-E2375 ◽  
Author(s):  
David Langlais ◽  
Regina Cencic ◽  
Neda Moradin ◽  
James M. Kennedy ◽  
Kodjo Ayi ◽  
...  
Keyword(s):  
Inflammatory Response ◽  
Cerebral Malaria ◽  
Ex Vivo ◽  
Myeloid Cells ◽  
Initiation Factor ◽  
Proinflammatory Response ◽  
Experimental Cerebral Malaria ◽  
Mortality And Morbidity

Cerebral malaria (CM) is a severe and rapidly progressing complication of infection by Plasmodium parasites that is associated with high rates of mortality and morbidity. Treatment options are currently few, and intervention with artemisinin (Art) has limited efficacy, a problem that is compounded by the emergence of resistance to Art in Plasmodium parasites. Rocaglates are a class of natural products derived from plants of the Aglaia genus that have been shown to interfere with eukaryotic initiation factor 4A (eIF4A), ultimately blocking initiation of protein synthesis. Here, we show that the rocaglate CR-1-31B perturbs association of Plasmodium falciparum eIF4A (PfeIF4A) with RNA. CR-1-31B shows potent prophylactic and therapeutic antiplasmodial activity in vivo in mouse models of infection with Plasmodium berghei (CM) and Plasmodium chabaudi (blood-stage malaria), and can also block replication of different clinical isolates of P. falciparum in human erythrocytes infected ex vivo, including drug-resistant P. falciparum isolates. In vivo, a single dosing of CR-1-31B in P. berghei-infected animals is sufficient to provide protection against lethality. CR-1-31B is shown to dampen expression of the early proinflammatory response in myeloid cells in vitro and dampens the inflammatory response in vivo in P. berghei-infected mice. The dual activity of CR-1-31B as an antiplasmodial and as an inhibitor of the inflammatory response in myeloid cells should prove extremely valuable for therapeutic intervention in human cases of CM.

scholarly journals Threshold to N-methyl-D-aspartate-induced seizures in mice undergoing chronic nutritional magnesium deprivation is lowered in a way partly responsive to acute magnesium and antioxidant administrations

2008 ◽  
Vol 101 (3) ◽  
pp. 317-321 ◽  
Author(s):  
Pierre Maurois ◽  
Nicole Pages ◽  
Pierre Bac ◽  
Michèle German-Fattal ◽  
Geneviève Agnani ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Magnesium Deficiency ◽  
Ex Vivo ◽  
Receptor Activation ◽  
Audiogenic Seizures ◽  
Seizure Threshold ◽  
Nutritional Deficit ◽  
Chloride Hexahydrate

Magnesium deficiency may be induced by a diet impoverished in magnesium. This nutritional deficit promotes chronic inflammatory and oxidative stresses, hyperexcitability and, in mice, susceptibility to audiogenic seizures. Potentiation by low-magnesium concentrations of the opening of N-methyl-d-aspartate (NMDA) receptor/calcium channel in in vitro and ex vivo studies, and responsiveness to magnesium of in vivo brain injury states are now well established. By contrast, little or no specific attention has been, however, paid to the in vivo NMDA receptor function/excitability in magnesium deficiency. The present work reports for the first time that, in mice undergoing chronic nutritional deprivation in magnesium (35 v. 930 parts per million for 27 d in OF1 mice), NMDA-induced seizure threshold is significantly decreased (38 % of normal values). The attenuation in the drop of NMDA seizure threshold (percentage of reversal) was 58 and 20 % upon acute intraperitoneal administrations of magnesium chloride hexahydrate (28 mg magnesium/kg) and the antioxidant ebselen (20 mg/kg), respectively. In nutritionally magnesium-deprived animals, audiogenic seizures are completely prevented by these compound doses. Taken as a whole, our data emphasise that chronic magnesium deprivation in mice is a nutritional in vivo model for a lowered NMDA receptor activation threshold. This nutritional model responds remarkably to acute magnesium supply and moderately to acute antioxidant administration.

scholarly journals In vivo NMDA receptor function in people with NMDA receptor antibody encephalitis

2021 ◽  
Author(s):  
Marian Galovic ◽  
Adam Al-Diwani ◽  
Umesh Vivekananda ◽  
Francisco Torrealdea ◽  
Kjell Erlandsson ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Neuropsychiatric Symptoms ◽  
Supporting Evidence ◽  
Normal Density ◽  
Residual Symptoms ◽  
Receptor Antibody ◽  
Positron Emission ◽  
Nmda Receptor Function

AbstractIn N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis, NMDAR-autoantibodies are hypothesised to cause prominent neuropsychiatric symptoms by internalizing NMDARs. However, supporting evidence comes chiefly from in vitro and rodent data with scant direct evidence from affected humans. Here, we used in vivo positron emission tomography (PET) with [18F]GE-179 to show a mean 30% reduction of the density of open, activated NMDARs in grey matter of persistently NMDAR-autoantibody seropositive patients following NMDAR-antibody encephalitis compared to healthy controls. The reduction was most prominent in the anterior temporal and superior parietal cortices. These patients had normal structural MRIs and mild residual symptoms. In contrast, one symptom-free patient who recovered from NMDAR-antibody encephalitis and was not NMDAR-autoantibody seropositive had normal density of active NMDARs. These findings reveal a functional deficit of open, activated NMDARs in humans with NMDAR-autoantibodies. Moreover, we observed a functional NMDAR deficit for up to 8 months following the disease peak, despite only mild residual symptoms, highlighting the considerable compensatory capacity of the human brain.One Sentence SummaryReductions of activated NMDA receptors detected in vivo in female patients following NMDA-receptor-antibody encephalitis.

scholarly journals Detection of immunogenic cell death and its relevance for cancer therapy

2020 ◽  
Vol 11 (11) ◽  
Author(s):  
Jitka Fucikova ◽  
Oliver Kepp ◽  
Lenka Kasikova ◽  
Giulia Petroni ◽  
Takahiro Yamazaki ◽  
...  
Keyword(s):  
Cell Death ◽  
Anticancer Agents ◽  
Ex Vivo ◽  
High Mobility ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Immunogenic Cell Death ◽  
Type I ◽  
Eukaryotic Translation

AbstractChemotherapy, radiation therapy, as well as targeted anticancer agents can induce clinically relevant tumor-targeting immune responses, which critically rely on the antigenicity of malignant cells and their capacity to generate adjuvant signals. In particular, immunogenic cell death (ICD) is accompanied by the exposure and release of numerous damage-associated molecular patterns (DAMPs), which altogether confer a robust adjuvanticity to dying cancer cells, as they favor the recruitment and activation of antigen-presenting cells. ICD-associated DAMPs include surface-exposed calreticulin (CALR) as well as secreted ATP, annexin A1 (ANXA1), type I interferon, and high-mobility group box 1 (HMGB1). Additional hallmarks of ICD encompass the phosphorylation of eukaryotic translation initiation factor 2 subunit-α (EIF2S1, better known as eIF2α), the activation of autophagy, and a global arrest in transcription and translation. Here, we outline methodological approaches for measuring ICD markers in vitro and ex vivo for the discovery of next-generation antineoplastic agents, the development of personalized anticancer regimens, and the identification of optimal therapeutic combinations for the clinical management of cancer.

scholarly journals eIF5B gates the transition from translation initiation to elongation

2019 ◽  
Author(s):  
Jinfan Wang ◽  
Alex G. Johnson ◽  
Christopher P. Lapointe ◽  
Junhong Choi ◽  
Arjun Prabhakar ◽  
...  
Keyword(s):  
Single Molecule ◽  
Translation Initiation ◽  
Protein Product ◽  
Initiation Factor ◽  
Translation System ◽  
80S Ribosome ◽  
Reading Frame ◽  
Initiation Factors ◽  
Translation Initiation Factors

Translation initiation determines both the quantity and identity of the protein product by establishing the reading frame for protein synthesis. In eukaryotic cells, numerous translation initiation factors (eIFs) prepare ribosomes for polypeptide elongation, yet the underlying dynamics of this process remain enigmatic1–4. A central question is how eukaryotic ribosomes transition from translation initiation to elongation. Here, we applied in vitro single-molecule fluorescence microscopy approaches to monitor directly in real time the pathways of late translation initiation and the transition to elongation using a purified yeast Saccharomyces cerevisiae translation system. This transition was remarkably slower in our eukaryotic system than that reported for Escherichia coli5–7. The slow entry to elongation was defined by a long residence time of eIF5B on the 80S ribosome after joining of individual ribosomal subunits, which is catalyzed by this universally conserved initiation factor. Inhibition of eIF5B GTPase activity following subunit joining prevented eIF5B dissociation from the 80S complex, thereby preventing elongation. Our findings illustrate how eIF5B dissociation serves as a kinetic checkpoint for the transition from initiation to elongation, and its release may be governed by a conformation of the ribosome complex that triggers GTP hydrolysis.

Effects of the Tibetan herbal preparation PADMA 28 on blood lipids and lipid oxidisability in subjects with mild hypercholesterolaemia

VASA ◽  
2005 ◽  
Vol 34 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Brunner-La Rocca ◽  
Schindler ◽  
Schlumpf ◽  
Saller ◽  
Suter
Keyword(s):  
Endothelial Dysfunction ◽  
Blood Lipids ◽  
Ex Vivo ◽  
Hdl Cholesterol ◽  
Blood Lipid ◽  
Tibetan Medicine ◽  
Double Blind ◽  
Intraarterial Infusion ◽  
Padma 28

Background: Previous studies showed an anti-atherosclerotic effect of PADMA 28, an herbal formula based on Tibetan medicine. As the mechanisms of action are not fully understood, we investigated whether PADMA 28 may lower blood lipids and lipid oxidisability, and affect early endothelial dysfunction. Patients and methods: Sixty otherwise healthy subjects with total cholesterol ≥5.2 mmol/l and < 8.0 mmol/l were randomly assigned to placebo or PADMA 28, 3 x 2 capsules daily, for 4 weeks (double-blind). Blood lipids (total, LDL-, and HDL-cholesterol, triglycerides, Apo-lipoprotein A1 and B) and ex vivo lipid oxidisability were measured before and after treatment. In a subset of 24 subjects, endothelial function was assessed using venous occlusion plethysmography with intraarterial infusion of acetylcholine. Isolated LDL and plasma both untreated and pre-treated with PADMA 28 extract were oxidised by the radical generator AAPH. Conjugated diene formation was measured at 245 nm. Results: Blood lipids did not change during the study in both groups. In contrast to previous reports in mild hypercholesterolaemia, no endothelial dysfunction was seen and, consequently, was not influenced by therapy. Ex vivo blood lipid oxidisability was significantly reduced with PADMA 28 (area under curve: 5.29 ± 1.62 to 4.99 ± 1.46, p = 0.01), and remained unchanged in the placebo group (5.33 ± 1.88 to 5.18 ± 1.78, p > 0.1). This effect persisted one week after cessation of medication. In vitro experiments confirmed the prevention of lipid peroxidation in the presence of PADMA 28 extracts. Persistent protection was also seen for LDL isolated from PADMA 28-pretreated blood after being subjected to rigorous purification. Conclusions: This study suggests that the inhibition of blood lipid oxidisability by PADMA 28 may play a role in its anti-atherosclerotic effect.

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

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