FTIR based approach to study EnaC mechanosensory functions

ENaC gene variants and their involvement in Covid‑19 severity

Epidemiological studies report the association of diverse cardiovascular conditions with coronavirus disease 2019 (COVID-19), but the causality has remained to be established. Specific genetic factors and the extent to which they can explain variation in susceptibility or severity are largely elusive. The present study aimed to evaluate the link between 32 cardio-metabolic traits and COVID-19. A total of 60 participants were enrolled, who were categorized into the following 4 groups: A control group with no COVID-19 or any other underlying pathologies, a group of patients with a certain form of dyslipidemia and predisposition to atherosclerotic disease, a COVID-19 group with mild or no symptoms and a COVID-19 group with severe symptomatology hospitalized at the Intensive Care Unit of Sotiria Hospital (Athens, Greece). Demographic, clinical and laboratory data were recorded and genetic material was isolated, followed by simultaneous analysis of the genes related to dyslipidemia using a custom-made next-generation sequencing panel. In the COVID-19 group with mild or absent symptoms, the variant c.112C>T:p.P38S was detected in the sodium channel epithelial 1 subunit α (SCNN1A) gene, with a major allele frequency (Maf) of <0.01. In the COVID-19 group with severe symptoms, the variant c.786G>A:p.T262T was detected in the SCNN1B gene, which encodes for the β-subunit of the epithelial sodium channel ENaC, with a Maf <0.01. None of the two rare variants were detected in the control or dyslipidemia groups. In conclusion, the current study suggests that ENaC variants are likely associated with genetic susceptibility to COVID-19, supporting the rationale for the risk and protective genetic factors for the morbidity and mortality of COVID-19.

Voltage-dependent volume regulation controls epithelial cell extrusion and morphology

Epithelial cells work collectively to provide a protective barrier, yet also turn over rapidly by cell death and division. If the number of dying cells does not match those dividing, the barrier would vanish, or tumors can form. Mechanical forces and the stretch-activated ion channel (SAC) Piezo1 link both processes; stretch promotes cell division and crowding triggers cell death by initiating live cell extrusion1,2. However, it was not clear how particular cells within a crowded region are selected for extrusion. Here, we show that individual cells transiently shrink via water loss before they extrude. Artificially inducing cell shrinkage by increasing extracellular osmolarity is sufficient to induce cell extrusion. Pre-extrusion cell shrinkage requires the voltage-gated potassium channels Kv1.1 and Kv1.2 and the chloride channel SWELL1, upstream of Piezo1. Activation of these voltage-gated channels requires the mechano-sensitive Epithelial Sodium Channel, ENaC, acting as the earliest crowd-sensing step. Imaging with a voltage dye indicated that epithelial cells lose membrane potential as they become crowded and smaller, yet those selected for extrusion are markedly more depolarized than their neighbours. Loss of any of these channels in crowded conditions causes epithelial buckling, highlighting an important role for voltage and water regulation in controlling epithelial shape as well as extrusion. Thus, ENaC causes cells with similar membrane potentials to slowly shrink with compression but those with reduced membrane potentials to be eliminated by extrusion, suggesting a chief driver of cell death stems from insufficient energy to maintain cell membrane potential.

Enhanced antifouling properties of marine antimicrobial peptides by PEGylation

Covalent immobilisation of antimicrobial peptides (AMPs) on underwater surfaces to combat marine biofouling is of great interest as it is an efficient, broad-spectrum and environmentally friendly strategy. Similar to post-translational modifications of natural proteins, artificial modifications of antimicrobial peptides can introduce important impacts on their properties and functions. The present work revealed the enhanced effect of PEGylation on the antifouling properties of marine antimicrobial peptides (LWFYTMWH) through grafting the modified peptides on aluminium surfaces. PEG was coupled to the peptide by solid-phase peptide synthesis, and the PEGylated peptides were bioconjugated to the aluminium surfaces which was pre-treated by aryldiazonium salts to introduce carboxyl groups. The carboxy group has been activated through the reaction with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The successful modification was confirmed via FT-IR and XPS. Interestingly, the PEGylated peptides modified surfaces could kill 90.0% Escherichia coli (Gram-negative) and 76.1% Bacillus sp. (Gram-positive), and showed better antifouling performance than the original peptides modified surfaces. Furthermore, molecular dynamics simulations showed PEGylation could enhance the ability of peptides to destroy membrane. The PEGylated peptides inserted into the membrane and induced the change in local curvature of membrane, leading to the rupture of membrane. The presence of PEG changed the antimicrobial peptides into more flexible conformations and the high hydrophilicity of PEG hindered the settlement of bacteria. These might be the two main working mechanisms for the increased antifouling efficiency of PEGylated peptides modified surface. This study provided a feasible modification strategy of antimicrobial peptides to enhance their antifouling properties.