Modulation of Ubiquitin Signaling in Innate Immune Response by Herpesviruses.

The ubiquitin proteasome system (UPS) is a protein degradation machinery that is crucial for cellular homeostasis in eukaryotes. Therefore, it is not surprising that the UPS coordinates almost all host cellular processes, including host-pathogen interactions. This protein degradation machinery acts predominantly by tagging substrate proteins designated for degradation with a ubiquitin molecule. These ubiquitin tags have been involved at various steps of the innate immune response. Hence, herpesviruses have evolved ways to antagonize the host defense mechanisms by targeting UPS components such as ubiquitin E3 ligases and deubiquitinases (DUBs) that establish a productive infection. This review delineates how herpesviruses usurp the critical roles of ubiquitin E3 ligases and DUBs in innate immune response to escape host-antiviral immune response, with particular focus on retinoic acid-inducible gene I (RIG-I)-like receptors (RLR), cyclic-GMP-AMP (cGAMP) synthase (cGAS), stimulator of interferon (IFN) genes (STING) pathways, and inflammasome signaling.

The rapid adaptation of SARS-CoV-2-rise of the variants: transmission and resistance.

The causative factor of COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is continuously mutating. Interestingly, identified mutations mainly occur in the spike (S) protein which interacts with the ACE2 receptor and is cleaved via serine protease TMPRSS2. Some mutated strains are becoming dominant in various parts of the globe because of increased transmissibility as well as cell entry efficacy. Remarkably, the neutralizing activity of monoclonal antibodies, convalescent sera, and vaccines against the variants has been reported to be significantly reduced. Therefore, the efficacy of various monoclonal antibodies therapy and vaccines against these variants is becoming a great global concern. We herein summarize the current status of SARS-CoV-2 with gears shifted towards the recent and most common genetic variants in relation to transmission, neutralizing activity, and vaccine efficacy.

The Impact on Infectivity and Neutralization Efficiency of SARS-CoV-2 Lineage B.1.351 Pseudovirus.

A new variant of SARS-CoV-2 B.1.351 lineage (first found in South Africa) has been raising global concern due to its harboring of multiple mutations in the spike that potentially increase transmissibility and yield resistance to neutralizing antibodies. We here tested infectivity and neutralization efficiency of SARS-CoV-2 spike pseudoviruses bearing particular mutations of the receptor-binding domain (RBD) derived either from the Wuhan strains (referred to as D614G or with other sites) or the B.1.351 lineage (referred to as N501Y, K417N, and E484K). The three different pseudoviruses B.1.351 lineage related significantly increased infectivity compared with other mutants that indicated Wuhan strains. Interestingly, K417N and E484K mutations dramatically enhanced cell-cell fusion than N501Y even though their infectivity were similar, suggesting that K417N and E484K mutations harboring SARS-CoV-2 variant might be more transmissible than N501Y mutation containing SARS-CoV-2 variant. We also investigated the efficacy of two different monoclonal antibodies, Casirivimab and Imdevimab that neutralized SARS-CoV-2, against several kinds of pseudoviruses which indicated Wuhan or B.1.351 lineage. Remarkably, Imdevimab effectively neutralized B.1.351 lineage pseudoviruses containing N501Y, K417N, and E484K mutations, while Casirivimab partially affected them. Overall, our results underscore the importance of B.1.351 lineage SARS-CoV-2 in the viral spread and its implication for antibody efficacy.

Enhanced microbial fuel cell (MFC) power outputs through Membrane Permeabilization using a branched polyethyleneimine.

This study demonstrates the impact outer membrane permeability has on the power densities generated by E. coli-based microbial fuel cells with neutral red as the mediator, and how increasing the permeability improves the current generation. Experiments performed with several lipopolysaccharide (LPS) mutants (ΔwaaC, ΔwaaF and ΔwaaG) of E. coli BW25113 that increase the outer membrane permeability found the power generated by two of the truncated LPS mutants, i.e., ΔwaaC and ΔwaaF, to be significantly higher (5.6 and 6.9 mW/m2, respectively) than that of the wild-type E. coli BW25113 (2.6 mW/m2). Branched polyethyleneimine (BPEI, 400 mg/L), a strong chemical permeabilizer, was more effective, however, increasing the power output from E. coli BW25113 cultures to as much as 29.7 mW/m2, or approximately 11-fold higher than the control MFC. BPEI also increased the activities of the mutant strains (to between 10.6 and 16.3 mW/m2), as well as when benzyl viologen was the mediator. Additional tests found BPEI not only enhanced membrane permeability but also increased the zeta potential of the bacterial cells from a value of -43.4 mV to -21.0 mV. This led to a significant increase in auto-aggregation of the bacterial cells and, consequently, better adherence of the cells to the anode electrode, as was demonstrated using scanning electron microscopy. In conclusion, our study demonstrates the importance of outer membrane permeabilities on MFC performances and defines two benefits that BPEI offers when used within MFCs as an outer membrane permeabilizer.

Loss of the lipopolysaccharide (LPS) inner core increases the electrocompetence of Escherichia coli.

Mutations that shorten the lipopolysaccharide (LPS) in Escherichia coli were found to significantly increase the number of transformants after electroporation. The loss of the LPS outer core increased the number of transformants with plasmid pAmCyan (3.3 kb) from 5.0 × 105 colony-forming units (CFU)/µg in the wild-type E. coli BW25113 to 3.3 × 107 CFU/µg in a ΔwaaG background, a 66.2-fold increase in efficiency. Truncation of the inner core improved this even further, with the ΔwaaF mutant exhibiting the best transformation efficiencies obtained, i.e., a 454.7-fold increase in the number of colonies over the wild-type strain. Similar results were obtained when a larger plasmid (pDA1; 11.3 kb) was used, with the ΔwaaF mutant once more giving the best transformation rates, i.e., a 73.7-fold increase. Subsequent tests proved that the enhanced transformabilities of these mutants were not due to a better survival or their surface charge properties, nor from preferential binding of these strains to the plasmid. Using N-phenyl-1-naphthylamine (NPN), we confirmed that the outer membranes of these mutant strains were more permeable. We also found that they leaked more ATP (3.4- and 2.0-fold higher for the ΔwaaF and ΔwaaG mutants, respectively, than wild-type E. coli BW25113), suggesting that the inner membrane stability is also reduced, helping to explain how the DNA enters these cells more easily. KEY POINTS: • LPS inner core gene knockouts increase the electrocompetence of E. coli. • No significant difference in survival, surface charge, or DNA binding was evident. • The LPS inner core mutants, however, exhibited higher outer membrane permeability. • Their inner membranes were also leaky, based on supernatant ATP concentrations.