scholarly journals Critical Negatively Charged Residues Are Important for the Activity of SARS-CoV-1 and SARS-CoV-2 Fusion Peptides

2021 ◽  
Author(s):  
Alex L. Lai ◽  
Jack H. Freed
Keyword(s):  
Critical Role ◽  
Binding Energies ◽  
Host Cells ◽  
Topological Model ◽  
Pseudotyped Virus ◽  
Fusion Peptides ◽  
Human Pathogens ◽  
Charged Residues ◽  
The Difference

AbstractCoronaviruses are a major infectious disease threat, and include the human pathogens of zoonotic origin SARS-CoV (“SARS-1”), SARS-CoV-2 (“SARS-2”) and MERS-CoV (“MERS”). Entry of coronaviruses into host cells is mediated by the viral spike (S) protein. Previously, we identified that the domain immediately downstream of the S2’ cleavage site is the bona fide FP (amino acids 798-835) for SARS-1 using ESR spectroscopy technology. We also found that the SARS-1 FP induces membrane ordering in a Ca2+ dependent fashion. In this study, we want to know which residues are involved in this Ca2+ binding, to build a topological model and to understand the role of the Ca2+. We performed a systematic mutation study on the negatively charged residues on the SARS-1 FP. While all six negatively charged residues contributes to the membrane ordering activity of the FP to some extent, D812 is the most important residue. We provided a topological model of how the FP binds Ca2+ ions: both FP1 and FP2 bind one Ca2+ ion, and there are two binding sites in FP1 and three in FP2. We also found that the corresponding residue D830 in the SARS-2 FP plays a similar critical role. ITC experiments show that the binding energies between the FP and Ca2+ as well as between the FP and membranes also decreases for all mutants. The binding of Ca2+, the folding of FP and the ordering activity correlated very well across the mutants, suggesting that the function of the Ca2+ is to help to folding of FP in membranes to enhance its activity. Using a novel pseudotyped virus particle (PP)-liposome methodology, we monitored the membrane ordering induced by the FPs in the whole S proteins in its trimer form in real time. We found that the SARS-1 and SARS-2 PPs also induce membrane ordering as the separate FPs do, and the mutations of the negatively charged residues also greatly reduce the membrane ordering activity. However, the difference in kinetic between the PP and FP indicates a possible role of FP trimerization. This finding could lead to therapeutic solutions that either target the FP-calcium interaction or block the Ca2+ channel to combat the ongoing COVID-19 pandemic.

scholarly journals Toll-like receptor-mediated innate immunity against herpesviridae infection: a current perspective on viral infection signaling pathways

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Wenjin Zheng ◽  
Qing Xu ◽  
Yiyuan Zhang ◽  
Xiaofei E ◽  
Wei Gao ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Immune System ◽  
Signaling Pathways ◽  
Critical Role ◽  
Innate Immune ◽  
Host Cells ◽  
Main Body ◽  
Current Perspective ◽  
Viral Components

Abstract Background In the past decades, researchers have demonstrated the critical role of Toll-like receptors (TLRs) in the innate immune system. They recognize viral components and trigger immune signal cascades to subsequently promote the activation of the immune system. Main body Herpesviridae family members trigger TLRs to elicit cytokines in the process of infection to activate antiviral innate immune responses in host cells. This review aims to clarify the role of TLRs in the innate immunity defense against herpesviridae, and systematically describes the processes of TLR actions and herpesviridae recognition as well as the signal transduction pathways involved. Conclusions Future studies of the interactions between TLRs and herpesviridae infections, especially the subsequent signaling pathways, will not only contribute to the planning of effective antiviral therapies but also provide new molecular targets for the development of antiviral drugs.

scholarly journals The Regulation of Flavivirus Infection by Hijacking Exosome-Mediated Cell–Cell Communication: New Insights on Virus–Host Interactions

Viruses ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 765
Author(s):  
José Manuel Reyes-Ruiz ◽  
Juan Fidel Osuna-Ramos ◽  
Luis Adrián De Jesús-González ◽  
Selvin Noé Palacios-Rápalo ◽  
Carlos Daniel Cordero-Rivera ◽  
...  
Keyword(s):  
Viral Infections ◽  
Cell Communication ◽  
Cell Interaction ◽  
Host Cells ◽  
Human Pathogens ◽  
Cellular Functions ◽  
Cellular Targets ◽  
Host Interaction ◽  
Flavivirus Infection

The arthropod-borne flaviviruses are important human pathogens, and a deeper understanding of the virus–host cell interaction is required to identify cellular targets that can be used as therapeutic candidates. It is well reported that the flaviviruses hijack several cellular functions, such as exosome-mediated cell communication during infection, which is modulated by the delivery of the exosomal cargo of pro- or antiviral molecules to the receiving host cells. Therefore, to study the role of exosomes during flavivirus infections is essential, not only to understand its relevance in virus–host interaction, but also to identify molecular factors that may contribute to the development of new strategies to block these viral infections. This review explores the implications of exosomes in flavivirus dissemination and transmission from the vector to human host cells, as well as their involvement in the host immune response. The hypothesis about exosomes as a transplacental infection route of ZIKV and the paradox effect or the dual role of exosomes released during flavivirus infection are also discussed here. Although several studies have been performed in order to identify and characterize cellular and viral molecules released in exosomes, it is not clear how all of these components participate in viral pathogenesis. Further studies will determine the balance between protective and harmful exosomes secreted by flavivirus infected cells, the characteristics and components that distinguish them both, and how they could be a factor that determines the infection outcome.

Implementing the Team Approach in Higher Education

2008 ◽  
Vol 22 (4) ◽  
pp. 245-251 ◽  
Author(s):  
Tracy M. Lara ◽  
Aaron W. Hughey
Keyword(s):  
Higher Education ◽  
Needs Assessment ◽  
Higher Education Administration ◽  
Critical Role ◽  
Education Administration ◽  
Team Approach ◽  
Academic Environment ◽  
Team Efficacy ◽  
The Difference

Many companies have implemented the team approach as a way to empower their employees in an effort to enhance productivity, quality and overall profitability. While application of the concept to higher education administration has been limited, colleges and universities could benefit from the team approach if implemented appropriately and conscientiously. The authors discuss some of the issues and concerns that are relevant to implementing the team approach in an academic environment. Suggestions for implementing teams in higher education are provided, including the difference between the team approach and traditional administration, the importance of a preliminary needs assessment, the development of an implementation plan, the critical role of leadership, dealing with issues of assessment and accountability, and the concept of team efficacy.

scholarly journals Interleukin-5 Is Essential for Vaccine-Mediated Immunity but Not Innate Resistance to a Filarial Parasite

2000 ◽  
Vol 68 (5) ◽  
pp. 2513-2517 ◽  
Author(s):  
Laetitia Le Goff ◽  
P'ng Loke ◽  
H. Fahimeda Ali ◽  
David W. Taylor ◽  
Judith E. Allen
Keyword(s):  
Critical Role ◽  
Human Pathogens ◽  
Filarial Infection ◽  
Innate Resistance ◽  
Interleukin 5 ◽  
Filarial Nematodes ◽  
Third Stage ◽  
Parasite Survival ◽  
Patent Infection

ABSTRACT The study of protective immune mechanisms effective against filarial nematodes has been hampered by the inability of these important human pathogens to infect laboratory mice. Recently,Litomosoides sigmodontis, a natural parasite of rats, has been developed as a valuable model for the study of filarial infection. BALB/c mice are fully susceptible to infection with L. sigmodontis third-stage larvae and develop patent infection. In contrast, mice on the C57BL background are resistant, and parasites undergo only a single molt and do not mature to adulthood. We used interleukin-5 (IL-5)-deficient mice on the C57BL/6 background to address the role of IL-5 and eosinophils in the innate resistance of C57BL/6 mice. We found no differences in parasite survival between IL-5-deficient and C57BL/6 mice. However, when these mice were used for the analysis of vaccine-mediated immunity, a critical role for IL-5 was elucidated. Mice genetically deficient in IL-5 were unable to generate a protective immune response when vaccinated with irradiated larvae, whereas C57BL/6 mice were fully protected from challenge infection. These studies help to clarify the highly controversial role of eosinophils in filarial infection.

scholarly journals Role of astroglial Connexin 43 in pneumolysin cytotoxicity and during pneumococcal meningitis

2020 ◽  
Vol 16 (12) ◽  
pp. e1009152
Author(s):  
Chakir Bello ◽  
Yasmine Smail ◽  
Vincent Sainte-Rose ◽  
Isabelle Podglajen ◽  
Alice Gilbert ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Connexin 43 ◽  
Critical Role ◽  
Neurovascular Unit ◽  
Brain Slices ◽  
Host Cells ◽  
Intermediate Filament Protein ◽  
Young Infants ◽  
The Brain

Streptococcus pneumoniae or pneumococcus (PN) is a major causative agent of bacterial meningitis with high mortality in young infants and elderly people worldwide. The mechanism underlying PN crossing of the blood brain barrier (BBB) and specifically, the role of non-endothelial cells of the neurovascular unit that control the BBB function, remains poorly understood. Here, we show that the astroglial connexin 43 (aCx43), a major gap junctional component expressed in astrocytes, plays a predominant role during PN meningitis. Following intravenous PN challenge, mice deficient for aCx43 developed milder symptoms and showed severely reduced bacterial counts in the brain. Immunofluorescence analysis of brain slices indicated that PN induces the aCx43–dependent destruction of the network of glial fibrillary acid protein (GFAP), an intermediate filament protein specifically expressed in astrocytes and up-regulated in response to brain injury. PN also induced nuclear shrinkage in astrocytes associated with the loss of BBB integrity, bacterial translocation across endothelial vessels and replication in the brain cortex. We found that aCx4-dependent astrocyte damages could be recapitulated using in vitro cultured cells upon challenge with wild-type PN but not with a ply mutant deficient for the pore-forming toxin pneumolysin (Ply). Consistently, we showed that purified Ply requires Cx43 to promote host cell plasma membrane permeabilization in a process involving the Cx43-dependent release of extracellular ATP and prolonged increase of cytosolic Ca2+ in host cells. These results point to a critical role for astrocytes during PN meningitis and suggest that the cytolytic activity of the major virulence factor Ply at concentrations relevant to bacterial infection requires co-opting of connexin plasma membrane channels.

scholarly journals Cathepsins: innate immune proteases that regulate viral entry into host cells

2018 ◽  
Vol 72 ◽  
pp. 253-263 ◽  
Author(s):  
Magdalena Bossowska-Nowicka ◽  
Felix N. Toka ◽  
Matylda Mielcarska ◽  
Lidia Szulc-Dąbrowska
Keyword(s):  
Viral Entry ◽  
Antigen Processing ◽  
Viral Infections ◽  
Innate Immune ◽  
Host Cells ◽  
Human Pathogens ◽  
Cellular Mechanisms ◽  
Cathepsin Proteases ◽  
Cell Adhesion And Migration

Cathepsins are group of endolysosomal proteases that regulate the mechanisms of innate and adaptive immunity, including cell adhesion and migration, antigen processing and presentation and resistance to several viral infections. Some cathepsins are required for Toll-like receptor (TLR)3, TLR7 and TLR9 cleavage and the formation of functional receptors that participate in sensing viral nucleic acids. Moreover, cathepsins directly stimulate or inhibit cytokine secretion involved in the regulation of antiviral innate immune response. Recent findings underline the important role of cathepsins in the entry of filoviruses, reoviruses, retroviruses and other types of viruses into the host cell. Many enveloped viruses require the presence of cathepsins for efficient fusion with membranes of infected cells, and the inhibition of their activity results in a significant reduction of virus replication. In addition, many viruses utilize conserved cellular mechanisms, such as endocytosis or low pH within the endosome, for efficient penetration into the cell interior, disassembly of viral capsid, and other stages of productive viral replication cycle. Therefore, a better understanding of the functional role of cathepsin proteases in the pathogenesis of viral infections should lead to the development of novel therapeutics for a variety of particularly dangerous human pathogens.

scholarly journals Updated SARS-CoV-2 Single Nucleotide Variants and Mortality Association

2021 ◽  
Author(s):  
Shuyi Fang ◽  
Sheng Liu ◽  
Jikui Shen ◽  
Alex Z Lu ◽  
Yucheng Zhang ◽  
...  
Keyword(s):  
Protein Structure ◽  
Critical Role ◽  
Single Nucleotide Variants ◽  
Protein Structure Analysis ◽  
Single Nucleotide ◽  
Synonymous Mutations ◽  
Conformation Changes ◽  
The Difference ◽  
Distinct Distribution

AbstractSince its outbreak in December 2019, COVID-19 has caused 100,5844,555 cases and 2,167,313 deaths as of Jan 27, 2021. Comparing our previous study of SARS-CoV-2 single nucleotide variants (SNVs) before June 2020, we found out that the SNV clustering had changed considerably since June 2020. Apart from that the group SNVs represented by two non-synonymous mutations A23403G (S: D614G) and C14408T (ORF1ab: P4715L) became dominant and carried by over 95% genomes, a few emerging groups of SNVs were recognized with sharply increased monthly occurrence ratios up to 70% in November 2020. Further investigation revealed that several SNVs were strongly associated with the mortality, but they presented distinct distribution in specific countries, e.g., Brazil, USA, Saudi Arabia, India, and Italy. SNVs including G25088T, T25A, G29861T and G29864A were adopted in a regularized logistic regression model to predict the mortality status in Brazil with the AUC of 0.84. Protein structure analysis showed that the emerging subgroups of non-synonymous SNVs and those mortality-related ones in Brazil were located on protein surface area. The clashes in protein structure introduced by these mutations might in turn affect virus pathogenesis through conformation changes, leading to the difference in transmission and virulence. Particularly, we found that SNVs tended to occur in intrinsic disordered regions (IDRs) of Spike (S) and ORF1ab, suggesting a critical role of SNVs in protein IDRs to determine protein folding and immune evasion.

scholarly journals Critical role of toll-like receptors and nucleotide oligomerisation domain in the regulation of health and disease

2007 ◽  
Vol 193 (3) ◽  
pp. 323-330 ◽  
Author(s):  
Jane A Mitchell ◽  
Mark J Paul-Clark ◽  
Graham W Clarke ◽  
Shaun K McMaster ◽  
Neil Cartwright
Keyword(s):  
Germ Line ◽  
Critical Role ◽  
Adaptor Proteins ◽  
Lipoteichoic Acid ◽  
Host Cells ◽  
Toll Like Receptors ◽  
Specific Pathogen ◽  
Toll Receptor ◽  
Leucine Rich Repeats

Pathogens are sensed by pattern recognition receptors (PRRs), which are germ line-encoded receptors, including transmembrane Toll-like receptors (TLRs) and cytosolic nucleotide oligomerisation domain (NOD) proteins, containing leucine-rich repeats (NLRs). Activation of PRRs by specific pathogen-associated molecular patterns (PAMPs) results in genomic responses in host cells involving activation transcription factors and the induction of genes. There are now at least 10 TLRs in humans and 13 in mice, and 2 NLRs (NOD1 and NOD2). TLR signalling is via interactions with adaptor proteins including MyD88 and toll-receptor associated activator of interferon (TRIF). NOD signalling is via the inflammasome and involves activation of Rip-like interactive clarp kinase (RICK). Bacterial lipopolysaccharide (LPS) from Gram-negative bacteria is the best-studied PAMP and is activated by or ‘sensed’ by TLR4. Lipoteichoic acid (LTA) from Gram-positive bacteria is sensed by TLR2. TLR4 and TLR2 have different signalling cascades, although activation of either results in symptoms of sepsis and shock. This review describes the rapidly expanding field of pathogen-sensing receptors and uses LPS and LTA as examples of how these pathways parallel and diverge from each other. The role of pathogen-sensing pathways in disease is also discussed.

scholarly journals A Critical Role of Non-active Site Residues on Cyclooxygenase Helices 5 and 6 in the Control of Prostaglandin Stereochemistry at Carbon 15

2007 ◽  
Vol 282 (38) ◽  
pp. 28157-28163 ◽  
Author(s):  
Karin Valmsen ◽  
William E. Boeglin ◽  
Reet Järving ◽  
Ivar Järving ◽  
Külliki Varvas ◽  
...  
Keyword(s):  
Amino Acid ◽  
Active Site ◽  
Amino Acid Sequence Identity ◽  
Critical Role ◽  
Site Directed Mutagenesis ◽  
Single Amino Acid ◽  
Active Site Residues ◽  
The Core ◽  
The Difference

The correct stereochemistry of prostaglandins is a prerequisite of their biological activity and thus is under a strict enzymatic control. Recently, we cloned and characterized two cyclooxygenase (COX) isoforms in the coral Plexaura homomalla that share 97% amino acid sequence identity, yet form prostaglandins with opposite stereochemistry at carbon 15. The difference in oxygenation specificity is only partially accounted for by the single amino acid substitution in the active site (Ile or Val at position 349). For further elucidation of residues involved in the C-15 stereocontrol, a series of sequence swapping and site-directed mutagenesis experiments between 15R- and 15S-COX were performed. Our results show that the change in stereochemistry at carbon 15 of prostaglandins relates mainly to five amino acid substitutions on helices 5 and 6 of the coral COX. In COX proteins, these helices form a helix-turn-helix motif that traverses through the entire protein, contributing to the second shell of residues around the oxygenase active site; it constitutes the most highly conserved region where even slight changes result in loss of catalytic activity. The finding that this region is among the least conserved between the P. homomalla 15S- and 15R-specific COX further supports its significance in maintaining the desired prostaglandin stereochemistry at C-15. The results are particularly remarkable because, based on its strong conservation, the conserved middle of helix 5 is considered as central to the core structure of peroxidases, of which COX proteins are derivatives. Now we show that the same parts of the protein are involved in the control of oxygenation with 15R or 15S stereospecificity in the dioxygenase active site.

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