Engineering nuclear pore complex function on biological interfaces

Nuclear pore complexes (NPCs) are the sole gateways that regulate the bidirectional exchange of macromolecules across the nuclear envelope (NE). In spite of bearing a ~40 nm wide aqueous channel, each NPC controls this fundamental nucleocytoplasmic transport (NCT) with unprecedented selectivity and efficiency. It is well established that soluble nuclear transport receptors (NTRs) such as Karyopherinβ1 (Kapβ1), regulate the traffic of specific cargoes by their multivalent interactions with intrinsically disordered, phenylalanine-glycine-rich protein (FG Nucleoporins or FG Nups) domains within the NPC. Nevertheless, how the FG Nups reject non-specific macromolecules while promoting the traffic of cargo-carrying NTRs remains elusive.
Recent in vitro studies on intrinsically disordered, end-grafted FG Nup domain brushes suggest that Kapβ1 is a bona fide constituent of the FG Nup permeability barrier and plays an integral role in regulating NPC transport selectivity and speed. However, these studies were performed directly on planar Au or SiO2 surfaces and are lacking a nanoconfined pore geometry as one of the key characteristics of the NPC.
This thesis provides a route to engineer biomimetic NPCs for the ex vivo investigation of the FG Nup permeability barrier at biological interfaces under spatial confinement. NTA – Histidine affinity mediated immobilization of FG Nup domain brushes on supported lipid layers formed by spontaneous liposome spreading proved to be a versatile tool to impart NPC functionality on Au and SiO2 substrates. A hallmark of minimal NPC models engineered by this approach is that the FG Nups are exposed to a consistent biointerface regardless of the underlying support. This allows one to investigate pristine FG Nup brushes and brushes interacting with Kapβ1 formed on lipid layers in a holistic manner by different techniques.