Background: Amyloid ␤ peptide plays a role in Alzheimer disease. Results: Interaction of amyloid ␤ peptides with 40 and 42 amino acids has consequences for oligomer formation. Conclusion: Increased production of amyloid ␤ peptide with 42 amino acids affects the behavior of the entire amyloid ␤ peptide pool. Significance: This might explain the synaptotoxic effect observed with a shift in amyloid ␤ peptide production.

The pro-inflammatory cytokine thymic stromal lymphopoietin (TSLP) is pivotal to the pathophysiology of widespread allergic diseases mediated by type 2 helper T cell (Th2) responses, including asthma and atopic dermatitis. The emergence of human TSLP as a clinical target against asthma calls for maximally harnessing its therapeutic potential via structural and mechanistic considerations. Here we employ an integrative experimental approach focusing on productive and antagonized TSLP complexes and free cytokine. We reveal how cognate receptor TSLPR allosterically activates TSLP to potentiate the recruitment of the shared interleukin 7 receptor α-chain (IL-7Rα) by leveraging the flexibility, conformational heterogeneity and electrostatics of the cytokine. We further show that the monoclonal antibody Tezepelumab partly exploits these principles to neutralize TSLP activity. Finally, we introduce a fusion protein comprising a tandem of the TSLPR and IL-7Rα extracellular domains, which harnesses the mechanistic intricacies of the TSLP-driven receptor complex to manifest high antagonistic potency.

Aggregation and misfolding of the prion protein (PrP) are thought to be the cause of a family of lethal neurodegenerative diseases affecting humans and other animals. Although the structures of PrP from several species have been solved, still little is known about the mechanisms that lead to the misfolded species. Here, we show that the region of PrP comprising the hairpin formed by the helices H2 and H3 is a stable independently folded unit able to retain its secondary and tertiary structure also in the absence of the rest of the sequence. We also prove that the isolated H2H3 is highly fibrillogenic and forms amyloid fibers morphologically similar to those obtained for the full-length protein. Fibrillization of H2H3 but not of full-length PrP is concomitant with formation of aggregates. These observations suggest a "banana-peeling" mechanism for misfolding of PrP in which H2H3 is the aggregation seed that needs to be first exposed to promote conversion from a helical to a ␤-rich structure.Transmissible spongiform encephalopathies are fatal neurodegenerative pathologies that affect humans as well as several other mammalian species. They are thought to be caused by the aggregation and misfolding of the prion protein (PrP).7 According to the "protein-only" hypothesis (1-3), PrP undergoes an ␣-to-␤ transition from its native state (PrP c ) to a misfolded species (PrP sc ), which is believed to act as a template to "infect" and misfold other PrP copies. As in other misfolding pathologies such as Alzheimer and Parkinson diseases, the neurotoxicity of PrP Sc is thought to be associated to an oligomeric form of the protein rather than to the mature aggregates (4).One of the crucial questions that remains unanswered concerns which region(s) of PrP promotes the polymerization process; this information would be both the key for understanding cross-species infectivity and help in decoding the bases of the aggregation process. Different regions have been proposed to be the fibrillogenic seed. PrP c consists of an unstructured N-terminal tail and a folded C-terminal domain formed by three helices (H1, H2, and H3) and a short-stranded ␤-sheet (formed by S1 and S2). H2 and H3 are connected through a disulfide bridge (5). A common view suggests the S1H1S2 region is crucial for ␤-sheet seeding and PrP Sc formation (6, 7). H1 has been implicated as a primary interaction site between PrP Sc and PrP c (8, 9), whereas the loop between S2 and H2, a rigid loop stabilized by its long range interactions with H3 (10), and the C terminus of H3 has been suggested to be recognized by a "Protein-X" that would affect the conversion of PrP c into PrP Sc (11). A study based on intrachain distance estimation performed on tagged PrP amyloid fibrils obtained under chaotropic treatment suggests the involvement of the H2H3 domain of PrP in amyloid formation (12). H/D exchange studies of the amyloid fibrils from human PrP reveal that the ␤-sheet core of PrP amyloids is formed by H2, the major part of H3, and the loop between them (13, 14).We have fol...

We provide a validated and rapid protocol for the solubilization of amyloid β-peptide (Aβ). This procedure involves sequential solubilization using structure-breaking organic solvents hexafluoroisopropanol and DMSO followed by column purification. The low solubility and tendency of Aβ to aggregate considerably impede the in vitro handling and biophysical or biological investigation of Aβ, despite the interest in this peptide because of its implication in Alzheimer's disease. The main advantage of the proposed protocol over others is that it results in standardized aggregate-free Aβ peptide samples that are biocompatible for cell culture studies and yield reproducible aggregation kinetics and cytotoxicities. This three-step protocol also enables the co-solubilization of the longer Aβ42 variant with Aβ40 in ratios relevant to Alzheimer's disease.