SARS-CoV-2 spike L452R variant evades cellular immunity and increases infectivity

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The GAR/RGG motif defines a family of nuclear alarmins

The nucleus is the target of autoantibodies in many diseases, which suggests intrinsic nuclear adjuvants that confer its high autoimmunogenicity. Nucleolin (NCL) is one abundant nucleolar autoantigen in systemic lupus erythematosus (SLE) patients and, in lupus-prone mice, it elicits autoantibodies early. With purified NCL, we observed that it was a potent alarmin that activated monocytes, macrophages and dendritic cells and it was a ligand for TLR2 and TLR4. NCL released by necrotic cells also exhibited alarmin activity. The NCL alarmin activity resides in its glycine/arginine-rich (GAR/RGG) motif and can be displayed by synthetic GAR/RGG peptides. Two more GAR/RGG-containing nucleolar proteins, fibrillarin (FBRL) and GAR1, were also confirmed to be novel alarmins. Therefore, the GAR/RGG alarmin motif predicts a family of nucleolar alarmins. The apparent prevalence of nucleolar alarmins suggests their positive contribution to tissue homeostasis by inducing self-limiting tissue inflammation with autoimmunity only occurring when surveillance is broken down.Subject terms: Cell death and immune response, Systemic lupus erythematosus     

Structure of the flavin site of Chromatium flavocytochrome c -552

Two flavin peptides have been isolated from $\text{Chromatium}$ cytochrome $\text{c}{}_{552}$ by digestion with pepsin and with trypsin-chymotrypsin, respectively. Acid hydrolysis and aminopeptidase digestion of the peptic peptide shows the presence of 1 mole each of threonine and cysteine and 2 of tyrosine, per mole of FAD. Edman degradation gives the sequence: tyr-thr-cys (flavin)-tyr. Tryptic-chymotryptic digestion yields a flavin tripeptide of the structure: thr-cys (flavin)-tyr. The N-terminal tyrosine in the peptic tetrapeptide shows a strong interaction with the flavin, as judged by CD spectra, and this may account for the resistance of the bridge sulfur to oxidation by cold performic acid. Both peptides show abnormally low fluorescence in the pure state (1 to 5% relative to riboflavin) and positive iodoplatinic test; the peptic peptide yields a positive, the trypticchymotryptic peptide negative ninhydrin reaction. The electrophoretic mobility of the major product of aminopeptidase digestion (presumably the thiazolidine form of cysteinyl-8α-FAD thiohemiacetal) and other properties of the two peptides are in accord with previous suggestions that the linkage of the flavin to the peptide is a thiohemiacetal.     

In Vitro Activities of Fourteen Antimicrobial Agents Against Drug Susceptible and Resistant Clinical Isolates of Mycobacterium tuberculosis and Comparative Intracellular Activities Against the Virulent H37Rv Strain in Human Macrophages

Minimal inhibitory concentrations (MICs) of 14 first and second-line antituberculous drugs against drug-susceptible and drug-resistant clinical isolates of Mycobacterium tuberculosis (including the multiple drug-resistant or MDR-TB isolates), as well as the type strain H37Rv, were determined radiometrically by the Bactec 460-TB methodols. MICs (μg/ml) of all the fourteen drugs were within an extremely narrow range in case of susceptible strains; isoniazid (0.02–0.04), rifampin (0.2–0.4), ethambutol and streptomycin (0.5–2.0), ethionamide (0.25–0.5), D-cycloserine (25–75), capreomycin (1–2), kanamycin (2–4), amikacin (0.5–1.0), clofazimine (0.1–0.4), ofloxacin (0.5–1.0), ciprofloxacin (0.25–1.0), and sparfloxacin (0.1–0.4). The activity of second-line drugs remained unaltered against MDR-TB isolates resistant to routine first-line drugs. With peak serum level concentrations (Cmax), the intracellular killing of the virulent H37Rv strain was studied in detail in cultured human macrophages. Based on an decreasing order of bactericidal activity, our results showed the following spectrum of intracellular drug action: among the first-line drugs, rifampin > ethionamide = isoniazid > ethambutol > streptomycin > D-cycloserine; among second-line drugs, clofazimine = amikacin > kanamycin = capreomycin; among fluoroquinolones, sparfloxacin > ofloxacin > ciprofloxacin. On the other hand, contrary to atypical mycobacteria, the macrolide drug clarithromycin was inactive against both extracellular and intracellular M. tuberculosis. Received: 23 January 1996 / Accepted: 5 April 1996