ABSTRACT
The first encoded SARS-CoV-2 protein (Nsp1) binds to the human 40S ribosome and blocks synthesis of host proteins, thereby inhibiting critical elements of the innate immune response. The final 33 residues of the natively unstructured Nsp1 C-terminus adopt a helix-turn-helix geometry upon binding to the ribosome. We have characterized the fluctuating conformations of this peptide using circular dichroism spectroscopy along with measurements of tryptophan fluorescence and energy transfer. Tryptophan fluorescence decay kinetics reveal that copper(II) binds to the peptide at micromolar concentrations, and electron paramagnetic resonance spectroscopy indicates that the metal ion coordinates to the lone histidine residue.
Subject(s)
COVID-19 , SARS-CoV-2 , Viral Nonstructural Proteins/metabolism , Circular Dichroism , Copper/chemistry , Humans , Peptides/chemistry , Tryptophan/chemistry , Viral Nonstructural Proteins/chemistry , Virulence FactorsABSTRACT
Skeletal muscle has an extraordinary regenerative capacity reflecting the rapid activation and effective differentiation of muscle stem cells (MuSCs). In the course of muscle regeneration, MuSCs are reprogrammed by immune cells. In turn, MuSCs confer immune cells anti-inflammatory properties to resolve inflammation and facilitate tissue repair. Indeed, MuSCs can exert therapeutic effects on various degenerative and inflammatory disorders based on their immunoregulatory ability, including effects primed by interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). At the molecular level, the tryptophan metabolites, kynurenine or kynurenic acid, produced by indoleamine 2,3-dioxygenase (IDO), augment the expression of TNF-stimulated gene 6 (TSG6) through the activation of the aryl hydrocarbon receptor (AHR). In addition, insulin growth factor 2 (IGF2) produced by MuSCs can endow maturing macrophages oxidative phosphorylation (OXPHOS)-dependent anti-inflammatory functions. Herein, we summarize the current understanding of the immunomodulatory characteristics of MuSCs and the issues related to their potential applications in pathological conditions, including COVID-19.
Subject(s)
COVID-19/therapy , Immune System/physiology , Muscles/physiology , Regeneration/physiology , Stem Cells/cytology , Animals , COVID-19/immunology , Cell Adhesion Molecules/metabolism , Cell Differentiation , Cell Proliferation , Humans , Indoleamine-Pyrrole 2,3,-Dioxygenase/metabolism , Inflammation , Insulin-Like Growth Factor II/metabolism , Interferon-gamma/metabolism , Kynurenic Acid/metabolism , Kynurenine/metabolism , Macrophages/metabolism , Mice , Muscles/metabolism , Oxidative Phosphorylation , Receptors, Aryl Hydrocarbon/metabolism , Tryptophan/chemistry , Tumor Necrosis Factor-alpha/metabolismABSTRACT
The interactions at the atomic level between small molecules and the main components of cellular plasma membranes are crucial for elucidating the mechanisms allowing for the entrance of such small species inside the cell. We have performed molecular dynamics and metadynamics simulations of tryptophan, serotonin, and melatonin at the interface of zwitterionic phospholipid bilayers. In this work, we will review recent computer simulation developments and report microscopic properties, such as the area per lipid and thickness of the membranes, atomic radial distribution functions, angular orientations, and free energy landscapes of small molecule binding to the membrane. Cholesterol affects the behaviour of the small molecules, which are mainly buried in the interfacial regions. We have observed a competition between the binding of small molecules to phospholipids and cholesterol through lipidic hydrogen-bonds. Free energy barriers that are associated to translational and orientational changes of melatonin have been found to be between 10-20 kJ/mol for distances of 1 nm between melatonin and the center of the membrane. Corresponding barriers for tryptophan and serotonin that are obtained from reversible work methods are of the order of 10 kJ/mol and reveal strong hydrogen bonding between such species and specific phospholipid sites. The diffusion of tryptophan and melatonin is of the order of 10-7 cm2/s for the cholesterol-free and cholesterol-rich setups.
Subject(s)
1,2-Dipalmitoylphosphatidylcholine/chemistry , Cholesterol/chemistry , Dimyristoylphosphatidylcholine/chemistry , Melatonin/chemistry , Serotonin/chemistry , Tryptophan/chemistry , 1,2-Dipalmitoylphosphatidylcholine/metabolism , Cholesterol/metabolism , Dimyristoylphosphatidylcholine/metabolism , Hydrogen Bonding , Lipid Bilayers/chemistry , Lipid Bilayers/metabolism , Melatonin/metabolism , Molecular Dynamics Simulation , Serotonin/metabolism , Solutions , Static Electricity , Thermodynamics , Tryptophan/metabolism , Water/chemistryABSTRACT
Coronavirus disease 2019 (COVID-19) has been a pandemic disease of which the termination is not yet predictable. Currently, researches to develop vaccines and treatments is going on globally to cope with this disastrous disease. Main protease (3CLpro) from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the good targets to find antiviral agents before vaccines are available. Some flavonoids are known to inhibit 3CLpro from SARS-CoV which causes SARS. Since their sequence identity is 96%, a similar approach was performed with a flavonoid library. Baicalin, herbacetin, and pectolinarin have been discovered to block the proteolytic activity of SARS-CoV-2 3CLpro. An in silico docking study showed that the binding modes of herbacetin and pectolinarin are similar to those obtained from the catalytic domain of SARS-CoV 3CLpro. However, their binding affinities are different due to the usage of whole SARS-CoV-2 3CLpro in this study. Baicalin showed an effective inhibitory activity against SARS-CoV-2 3CLpro and its docking mode is different from those of herbacetin and pectolinarin. This study suggests important scaffolds to design 3CLpro inhibitors to develop antiviral agents or health-foods and dietary supplements to cope with SARS-CoV-2.
Subject(s)
Coronavirus Infections/drug therapy , Flavonoids/chemistry , Pneumonia, Viral/drug therapy , Viral Proteins/antagonists & inhibitors , Viral Proteins/chemistry , Antiviral Agents/chemistry , Betacoronavirus , COVID-19 , Drug Design , Fluorescence Resonance Energy Transfer , Humans , Molecular Docking Simulation , Pandemics , Polyproteins , Protease Inhibitors/chemistry , Protein Binding , Protein Conformation , SARS-CoV-2 , Spectrophotometry , Tryptophan/chemistry , COVID-19 Drug TreatmentABSTRACT
SARS-CoV and SARS-CoV-2 do not appear to have functions of a hemagglutinin and neuraminidase. This is a mystery, because sugar binding activities appear essential to many other viruses including influenza and even most other coronaviruses in order to bind to and escape from the glycans (sugars, oligosaccharides or polysaccharides) characteristic of cell surfaces and saliva and mucin. The S1 N terminal Domains (S1-NTD) of the spike protein, largely responsible for the bulk of the characteristic knobs at the end of the spikes of SARS-CoV and SARS-CoV-2, are here predicted to be "hiding" sites for recognizing and binding glycans containing sialic acid. This may be important for infection and the ability of the virus to locate ACE2 as its known main host cell surface receptor, and if so it becomes a pharmaceutical target. It might even open up the possibility of an alternative receptor to ACE2. The prediction method developed, which uses amino acid residue sequence alone to predict domains or proteins that bind to sialic acids, is naïve, and will be advanced in future work. Nonetheless, it was surprising that such a very simple approach was so useful, and it can easily be reproduced in a very few lines of computer program to help make quick comparisons between SARS-CoV-2 sequences and to consider the effects of viral mutations.