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•These studies concern blocking of the PD-1/PD-L1 complex formation.•PD-L1 amino acid sequence was used to design complex inhibitors.•The interaction of peptides with PD-1 was confirmed using SPR and ELISA.•The peptides inhibit PD-1/PD-L1 binding in cellular assays.•NMR and MD were used to confirm the peptide binding to PD-1.

The herpesvirus entry mediator (HVEM) and its ligand LIGHT play crucial roles in immune system regulation, including T-cell proliferation, B-cell differentiation, and immunoglobulin secretion. However, excessive T-cell activation can lead to chronic inflammation and autoimmune diseases. Thus, inhibiting the HVEM-LIGHT interaction emerges as a promising therapeutic strategy for these conditions and in preventing adverse reactions in organ transplantation. This study focused on designing peptide inhibitors, targeting the HVEM-LIGHT interaction, using molecular dynamics (MD) simulations of 65 peptides derived from HVEM. These peptides varied in length and disulfide-bond configurations, crucial for their interaction with the LIGHT trimer. By simulating 31 HVEM domain variants, including the full-length protein, we assessed conformational changes upon LIGHT binding to understand the influence of HVEM segments and disulfide bonds on the binding mechanism. Employing multitrajectory microsecond-scale, all-atom MD simulations and molecular mechanics with generalized Born and surface area (MM-GBSA) binding energy estimation, we identified promising CRD2 domain variants with high LIGHT affinity. Notably, point mutations in these variants led to a peptide with a single disulfide bond (C58–C73) and a K54E substitution, exhibiting the highest binding affinity. The importance of the CRD2 domain and Cys58–Cys73 disulfide bond for interrupting HVEM-LIGHT interaction was further supported by analyzing truncated CRD2 variants, demonstrating similar binding strengths and mechanisms. Further investigations into the binding mechanism utilized steered MD simulations at various pulling speeds and umbrella sampling to estimate the energy profile of HVEM-based inhibitors with LIGHT. These comprehensive analyses revealed key interactions and different binding mechanisms, highlighting the increased binding affinity of selected peptide variants. Experimental circular dichroism techniques confirmed the structural properties of these variants. This study not only advances our understanding of the molecular basis of HVEM-LIGHT interactions but also provides a foundation for developing novel therapeutic strategies for immune-related disorders. Furthermore, it sets a gold standard for peptide inhibitor design in drug development due to its systematic approach.

Amyloidoses are a group of diseases caused by the extracellular deposition of proteins forming amyloid fibrils. The amyloidosis is classified according to the main protein or peptide that constitutes the amyloid fibrils. The most effective methods for the diagnosis of amyloidosis are based on mass spectrometry. Mass spectrometry enables confirmation of the identity of the protein precursor of amyloid fibrils in biological samples with very high sensitivity and specificity, which is crucial for proper amyloid typing. Due to the fact that biological samples are very complex, mass spectrometry is usually connected with techniques such as liquid chromatography or capillary electrophoresis, which enable the separation of proteins before MS analysis. Therefore mass spectrometry constitutes an important part of the so called “hyphenated techniques” combining, preferentially in-line, different analytical methods to provide comprehensive information about the studied problem. Hyphenated methods are very useful in the discovery of biomarkers in different types of amyloidosis. In systemic forms of amyloidosis, the analysis of aggregated proteins is usually performed based on the tissues obtained during a biopsy of an affected organ or a subcutaneous adipose tissue. In some cases, when the diagnostic biopsy is not possible due to the fact that amyloid fibrils are formed in organs like the brain (Alzheimer’s disease), the study of biomarkers presented in body fluids can be carried out. Currently, large-scale studies are performed to find and validate more effective biomarkers, which can be used in diagnostic procedures. We would like to present the methods connected with mass spectrometry which are used in the diagnosis of amyloidosis based on the analysis of proteins occurring in tissues, blood and cerebrospinal fluid.