A Procoagulant Peptide Analog of the SARS-CoV-2 Nucleocapsid C-terminal Domain

Structural basis for the procoagulant activity of Staphylococcus aureus staphylocoagulase

3D models of the C-terminal SC region suggest that the major C-terminal domain of SC folds into a single-layer β-sheet structurally similar to the membrane occupation and recognition nexus (MORN) family of tandem repeats, which is critical for understanding SC-mediated fibrin generation.

Unraveling A4GALT Mechanism and Its Modulation With Adamantyl-Galactosylceramide Analogues: Advancing Fabry Disease Therapeutic Strategies.

Fabry disease (FD), one of the most prevalent lysosomal storage disorders in Europe, is caused by mutations in the GLA gene leading to deficient α-galactosidase A activity with lysosomal accumulation of globotriaosylceramide (Gb3). Enzyme replacement therapy (ERT) and pharmacological chaperone therapy (PCT) are used in the clinic to treat FD but are limited in efficacy, underscoring the need for alternative therapeutic strategies. Inhibiting α-1,4-galactosyltransferase (A4GALT), the glycosyltransferase responsible for Gb3 biosynthesis, represents an attractive strategy. Here, we reveal the molecular mechanism of human A4GALT at atomic detail using QM/MM simulations. We reveal a conformational rearrangement involving a 310-helix that stabilizes the donor substrate and promotes a front-face SNi-like catalytic mechanism, in which a short-lived oxocarbenium-ion intermediate forms. The simulations informed the synthesis of a panel of glycosylceramide substrate analogues. Among these, AdaGalCer (Ada = adamantyl) proved able to reduce Gb3 production in fibroblasts while simultaneously being converted by A4GALT into the galactosylated product AdaGb2. These results provide a clear path towards inhibiting A4GALT, paving the way for potential new and effective FD therapeutics.

Biomaterials and Biosystems

Novel salicylamido sulfonamides as CD73 immune checkpoint inhibitors: Synthesis and in vitro biological evaluation.

The immune checkpoint enzyme CD73 plays a crucial role in the adenosine (ADO) metabolic pathway by catalyzing the conversion of AMP to adenosine. Dysregulated CD73 activity elevates extracellular ADO in the tumor microenvironment, driving immunosuppression and tumor immune evasion, highlighting CD73 as a key immunotherapeutic target. In this study, we report the design and synthesis of a novel series of salicylamido sulfonamide-based small-molecule CD73 inhibitors. The in vitro CD73 inhibitory assay reveals that SA-41 and SA-26 exhibited potent activity with IC50 values of 2.83 ± 0.45 μM and 2.96 ± 0.46 μM, respectively. Molecular docking and dynamic simulations revealed that SA-26 maintained stable interactions with CD73 throughout a 100-ns simulation with no significant deviation. Furthermore, in silico ADME analysis indicated that both lead compounds possess favourable drug-like properties, with no Lipinski's rule-of-five violations, balanced lipophilicity, and acceptable predicted oral absorption, supporting their pharmacokinetic potential. These findings highlight SA-26 and SA-41 as promising candidates for further development as non- nucleotide-based small-molecule CD73 inhibitors.

Amantadine-induced reorganization of model SARS-CoV-2 lipid envelopes

Amantadine attracted renewed interest during the COVID-19 pandemic because of its known antiviral activity against influenza A. In this work, we investigated how amantadine affects a simplified model of the SARS-CoV-2 lipid envelope composed of DOPC : DMPS : PI (50 : 35 : 15), as well as monolayers of the individual lipids: DOPC, DMPS and PI. Langmuir experiments showed that the effect of the drug depends on the lipid type. In DOPC and PI monolayers, amantadine increased the area per molecule, suggesting its incorporation into more fluid layers. In contrast, in more compact DMPS monolayers, stronger electrostatic interactions led to different behaviour and promoted tighter packing at higher surface pressures. For the ternary model, excess area and compression–expansion hysteresis analyses pointed to drug-induced domain formation and changes in monolayer organization, which were confirmed by Brewster angle microscopy. To extend these results to 3D systems, liposomes and giant unilamellar vesicles were used as bilayer models. Dynamic light scattering revealed changes in hydrodynamic diameter and zeta potential, while fluorescence microscopy confirmed amantadine incorporation together with bilayer reorganization. Molecular dynamics simulations supported the experimental observations and showed that amantadine preferentially locates at the interface and partially inserts into the lipid layer. Overall, the results show that amantadine interactions with simplified SARS-CoV-2 lipid envelopes depend on both the net charge of the lipid headgroup and the membrane organization, which is influenced by the presence or absence of unsaturated alkyl chains in the hydrophobic region.

Expression of Active Apurinic Apyrimidinic Endodeoxyribonuclease 1 in Human Platelets

ABSTRACT The pivotal role of platelets (PLTs) in hemostasis, thrombosis, innate immunity, and tissue repair is sustained by mitochondria, whose dysfunctions can impair ATP generation and redox signaling, thus affecting optimal levels of PLTs' functionality. Maintenance of mtDNA integrity is essential for mitochondria functioning and is primarily exerted by the base excision repair (BER) pathway, never described in PLTs. Here, we provide the first evidence for the expression levels and subcellular localization of apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1), evaluated alongside cytosolic and mitochondrial markers, in resting human PLTs (huPLTs) isolated from a cohort of healthy donors. A variable expression of APE1 was detected independently of age and sex, and it was found to correlate with the specific enzymatic activity on canonical and far less on noncanonical substrates. Preliminary experiments with an APE1 enzymatic inhibitor suggest a possible involvement of APE1 in PLTs aggregation stimulated by epinephrine. Overall, our findings pave the way for understanding a novel unforeseen role of APE1 in PLTs physiology, which specifically deserves future investigation.