Cryo-EM structure and polymorphic maturation of a viral transduction enhancing amyloid fibril.

Amyloid fibrils have emerged as innovative tools to enhance the transduction efficiency of retroviral vectors in gene therapy strategies. In this study, we used cryo-electron microscopy to analyze the structure of a biotechnologically engineered peptide fibril that enhances retroviral infectivity. Our findings show that the peptide undergoes a time-dependent morphological maturation into polymorphic amyloid fibril structures. The fibrils consist of mated cross-ß sheets that interact by the hydrophobic residues of the amphipathic fibril-forming peptide. The now available structural data help to explain the mechanism of retroviral infectivity enhancement, provide insights into the molecular plasticity of amyloid structures and illuminate the thermodynamic basis of their morphological maturation.

Cryo-EM structure of a catalytic amyloid fibril.

Catalytic amyloid fibrils are novel types of bioinspired, functional materials that combine the chemical and mechanical robustness of amyloids with the ability to catalyze a certain chemical reaction. In this study we used cryo-electron microcopy to analyze the amyloid fibril structure and the catalytic center of amyloid fibrils that hydrolyze ester bonds. Our findings show that catalytic amyloid fibrils are polymorphic and consist of similarly structured, zipper-like building blocks that consist of mated cross-ß sheets. These building blocks define the fibril core, which is decorated by a peripheral leaflet of peptide molecules. The observed structural arrangement differs from previously described catalytic amyloid fibrils and yielded a new model of the catalytic center.

Cryo-EM demonstrates the in vitro proliferation of an ex vivo amyloid fibril morphology by seeding.

Several studies showed that seeding of solutions of monomeric fibril proteins with ex vivo amyloid fibrils accelerated the kinetics of fibril formation in vitro but did not necessarily replicate the seed structure. In this research we use cryo-electron microscopy and other methods to analyze the ability of serum amyloid A (SAA)1.1-derived amyloid fibrils, purified from systemic AA amyloidosis tissue, to seed solutions of recombinant SAA1.1 protein. We show that 98% of the seeded fibrils remodel the full fibril structure of the main ex vivo fibril morphology, which we used for seeding, while they are notably different from unseeded in vitro fibrils. The seeded fibrils show a similar proteinase K resistance as ex vivo fibrils and are substantially more stable to proteolytic digestion than unseeded in vitro fibrils. Our data support the view that the fibril morphology contributes to determining proteolytic stability and that pathogenic amyloid fibrils arise from proteolytic selection.

Azulitox-A Pseudomonas aeruginosa P28-Derived Cancer-Cell-Specific Protein Photosensitizer.

Azulitox as a new fusion polypeptide with cancer cell specificity and phototoxicity was generated and is composed of a photosensitizer domain and the cell-penetrating peptide P28. The photosensitizer domain (EcFbFP) was derived from a bacterial blue-light receptor, which belongs to the family of light-oxygen-voltage proteins and produces reactive oxygen species (ROS) upon excitation. P28 is derived from the cupredoxin protein azurin that is known to specifically penetrate cancer cells and bind to the tumor suppressor protein p53. We show that the P28 domain specifically directs and translocates the fused photosensitizer into cancer cells. Under blue-light illumination, Azulitox significantly induced cytotoxicity. Compared to the extracellular application of EcFbFP, Azulitox caused death to about 90% of cells, as monitored by flow cytometry, which also directly correlated with the amount of ROS produced in the cells. Azulitox may open new avenues toward targeted polypeptide-photosensitizer-based photodynamic therapies with reduced systemic toxicity compared to conventional photosensitizers.

A Cerberus-Inspired Anti-Infective Multicomponent Gatekeeper Hydrogel against Infections with the Emerging "Superbug" Yeast Candida auris.

The pathogenic yeast Candida auris has received increasing attention due to its ability to cause fatal infections, its resistance toward important fungicides, and its ability to persist on surfaces including medical devices in hospitals. To brace health care systems for this considerable risk, alternative therapeutic approaches such as antifungal peptides are urgently needed. In clinical wound care, a significant focus has been directed toward novel surgical (wound) dressings as first defense lines against C. auris. Inspired by Cerberus the Greek mythological "hound of Hades" that prevents the living from entering and the dead from leaving hell, the preparation of a gatekeeper hybrid hydrogel is reported featuring lectin-mediated high-affinity immobilization of C. auris cells from a collagen gel as a model substratum in combination with a release of an antifungal peptide drug to kill the trapped cells. The vision is an efficient and safe two-layer medical composite hydrogel for the treatment of severe wound infections that typically occur in hospitals. Providing this new armament to the repertoire of possibilities for wound care in critical (intensive care) units may open new routes to shield and defend patients from infections and clinical facilities from spreading and invasion of C. auris and probably other fungal pathogens.