The constantly evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOC) fuel the worldwide coronavirus disease (COVID-19) pandemic. The spike protein is essential for the SARS-CoV-2 viral entry and thus has been extensively targeted by therapeutic antibodies. However, mutations along the spike in SARS-CoV-2 VOC and Omicron subvariants have caused more rapid spread and strong antigenic drifts, rendering most of the current antibodies ineffective. Hence, understanding and targeting the molecular mechanism of spike activation is of great interest in curbing the spread and development of new therapeutic approaches. In this review, we summarize the conserved features of spike-mediated viral entry in various SARS-CoV-2 VOC and highlight the converging proteolytic processes involved in priming and activating the spike. We also summarize the roles of innate immune factors in preventing spike-driven membrane fusion and provide outlines for the identification of novel therapeutics against coronavirus infections.

Cancer cells exhibit accelerated protein production to accommodate their high rates of growth and proliferation. Elevated protein synthesis creates a dependency on endoplasmic reticulum (ER)-resident proteins and chaperones, which are required to maintain proteostasis. In this study, we identified the protein disulfide isomerases (PDIs) PDIA1 and PDIA5, which play a critical role in folding of client proteins in the ER, as important regulators of prostate cancer growth and response to therapy. PDIA1 and PDIA5 are upregulated in prostate cancer and induced by the androgen receptor (AR) signaling axis. Genetic or pharmacological disabling of PDIA1/PDIA5 caused redox stress, mitochondrial dysfunction, growth inhibition, and death of prostate cancer cells in vitro and in vivo. The critical functions of these enzymes in redox homeostasis and cell survival were observed in both AR-driven and AR-independent models of prostate cancer. Loss of PDIA1/PDIA5 activity led to ubiquitination and degradation of the AR, revealing a feedback loop between these chaperones and the AR pathway. Mechanistically, PDIA1/PDIA5 regulated AR stability by mediating disulfide bond formation, an activity that required cysteines 669 and 844 in AR’s ligand-binding domain. Importantly, targeting PDIAs sensitized prostate cancer cells to the AR antagonist, enzalutamide. This study reveals a mechanism governing AR proteostasis in prostate cancer and positions PDIA1/5 as viable therapeutic targets.

To improve the oxidation resistance of Cu nanoparticles chemically, silica-coated Cu nanoparticles were obtained by a multi-step process. First, Cu nanoparticles were produced by reducing copper inorganic salts in the presence of citrate acid in aqueous solution. Then these particles were undergone an in-situ surface modification treatment with 3-aminopropyl-trimethoxysilane (APS). And then they were coated subsequently with a silica layer by adding tetraethyl orthosilicate (TEOS) ethanol solution into the above solution. The molar ratio of citrate: Cu²⁺: hydrazine is 1:1:10, which can guarantee the basic environment of aqueous solution, in which the preparation of Cu particles and the latter coating of silica can be carried out simultaneously and controllably. The stability of Cu particles through coating was improved. Citrate acid and APS had essential effects on the antioxidation of Cu nanoparticles during their synthesis and coating with silica, respectively.

Introduction: The persistent evolution of SARS-CoV-2 has diminished the efficacy of existing vaccines and antibodies, increasing the risks of reinfection and Long COVID. There is a significant need for the development of convenient, broad-spectrum antiviral agents that target the early stage of viral infection. Traditional Chinese Medicine (TCM) volatile oils, with their diverse components and suitability for nasal delivery, demonstrate potential against respiratory viruses. This study aimed to screen bioactive compounds from TCM volatile oils for their ability to inhibit the interaction between the SARS-CoV-2 spike (S) protein and its host receptor, ACE2. Methods: A virtual screening of 47 structurally diverse TCM volatile compounds was performed to identify potential inhibitors of the Spike-ACE2 interaction. The top candidate, dibutyl phthalate (DBP), was further evaluated using in vitro assays including Spike-mediated membrane fusion and pseudovirus infection. Its mechanism was investigated through ELISA, surface plasmon resonance (SPR), ACE2 enzymatic activity assays, molecular docking. To evaluate its broad-spectrum potential, membrane fusion assays were further performed using spike proteins from the wild-type (WT), Delta, and Omicron XBB.1.5 variants. Critical binding residues were identified through molecular docking and subsequently confirmed by site-directed mutagenesis of the Spike receptor-binding domain (RBD). Results: Virtual screening identified ten potential inhibitors, with dibutyl phthalate (DBP) showing the strongest activity. DBP effectively inhibited S protein-mediated membrane fusion ( IC ₅₀ = 64.53 μM) and pseudovirus infection ( IC ₅₀ = 73.06 μM) with specificity. SPR analysis confirmed that DBP competitively inhibited the binding between the S trimer and ACE2 (increasing the K _D from 8.28 nM to 86.7 nM). Mechanistic studies revealed that DBP disrupts the S-ACE2 interaction by targeting the receptor-binding domain (RBD) without affecting ACE2 enzymatic activity. Furthermore, DBP exhibited broad-spectrum inhibitory activity against membrane fusion mediated by the Delta ( IC ₅₀ = 49.22 μM) and Omicron XBB.1.5 ( IC ₅₀ = 53.70 μM) spike variants. Molecular docking and subsequent site-directed mutagenesis identified Tyr453 and Tyr495 as critical residues for DBP binding and its inhibitory function. Discussion: This study elucidates for the first time that DBP functions as a broad-spectrum RBD inhibitor. It binds to the RBD-ACE2 interface, dependent on conserved residues Tyr453 and Tyr495, and acts primarily through steric hindrance to block the Spike-ACE2 interaction. Notably, DBP shares critical aromatic and ester groups with other active-site inhibitors. Structure-activity relationship analysis of its derivatives revealed that introducing additional hydrogen-bond acceptors significantly enhances inhibitory activity, providing a clear structure optimization strategy. While DBP has known toxicity, its antiviral potential may be harnessed through strategic delivery approaches or SAR-guided optimization to advance its development against SARS-CoV-2 variants.

The innate immune response involves interferons (IFNs), antiviral cytokines that upregulate numerous IFN-stimulated genes, many of which have uncharacterized functions and mechanisms. Here we performed transcriptomic profiling of lung tissues from wild-type and IFNAR^−/− mice infected with SARS-CoV-2 and single-cell RNA sequencing of bronchoalveolar lavage fluid and peripheral blood mononuclear cells from patients with COVID-19. We identified O-GalNAc transferase 2 (GALNT2), an N-acetylgalactosaminyltransferase, as an antiviral IFN-stimulated gene restricting the replication of multiple coronaviruses and influenza A viruses in vitro and in vivo, contributing to viral clearance and reducing disease severity. Mechanistically, GALNT2-dependent O-linked glycosylation may regulate viral glycoprotein proteolytic processing and impair viral growth by blocking virus–cell fusion. In addition, we found that serine residues at 810/813 in the viral spike protein undergo O-glycosylation and function as the primary genetic determinants of sensitivity or evasion towards GALNT2. Human genetic data analysis revealed that individuals with GALNT2 variants that lost antiviral function had elevated risk of hospitalization following SARS-CoV-2 infection. This study establishes GALNT2 as an antiviral factor against some respiratory virus infections.