A Library-Based Screening Strategy for the Identification of DARPins as Ligands for Receptor-Targeted AAV and Lentiviral Vectors
Delivering genes selectively to the therapeutically relevant cell type is among the prime goals of vector development. Here, we present a high-throughput selection and screening process that identifies designed ankyrin repeat proteins (DARPins) optimally suited for receptor-targeted gene delivery using adeno-associated viral (AAV) and lentiviral (LV) vectors. In particular, the process includes expression, purification, and in situ biotinylation of the extracellular domains of target receptors as Fc fusion proteins in mammalian cells and the selection of high-affinity binders by ribosome display from DARPin libraries each covering more than 1012 variants. This way, DARPins specific for the …
The Stalk Domain of NKp30 Contributes to Ligand Binding and Signaling of a Preassembled NKp30-CD3ζ Complex
The natural cytotoxicity receptor (NCR) NKp30 (CD337) is a key player for NK cell immunosurveillance of infections and cancer. The molecular details of ligand recognition and its connection to CD3ζ signaling remain unsolved. Here, we show that the stalk domain (129KEHPQLGAGTVLLLR143) of NKp30 is very sensitive to sequence alterations, as mutations lead to impaired ligand binding and/or signaling capacity. Surprisingly, the stalk domains of NKp30 and NKp46, another NCR employing CD3ζ for signaling, were not exchangeable without drastic deficiencies in folding, plasma membrane targeting, and/or ligand-induced receptor signaling. Further mutational studies, N-glycosylation mapping, and plasma …