[PhD Thesis Presentation_Zoom] - Xunwu Hu - "Developing Integrin-targeted Peptide Assemblies to Direct Cancer Cell migration"

Presenter: Xunwu Hu

Supervisor: Prof. Ye Zhang 

Unit: Bioinspired Soft Matter Unit

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Title: Developing Integrin-targeted Peptide Assemblies to Direct Cancer Cell migration

Abstract: 

Advances in mechanistic understanding of integrin-mediated adhesion highlight the importance of precise control of ligand presentation in directing cell migration. The development of top-down nanofabrication techniques, such as polymer blending and nanolithography, achieved control over the spatial presentation of integrin ligand at the sub-micron resolution, which promoted the mechanistic study of integrin-mediated adhesions and inspired biomaterial innovations. We sought to enhance the spatial resolution beyond sub-micron resolution to understand the subsequent cellular response at the molecular level. To address this challenge, we developed a bottom-up nanofabrication strategy, reaching by far the highest spatial resolution of ligand presentation (48 ligands/100 nm2), which is beyond the submicron limit of the top-down technique. Via simple molecular engineering, we transformed a natural ECM-derived ligand into an assembling ligand. Co-assembly of the assembling ligand with non-functional motifs at various proportions, forms biocompatible nanofilaments presenting different ligand densities. Peptide assemblies possessing various ligand densities exert biphasic effects on cell migration, with fast migration occurring at low density because of promotion of nascent adhesion and lamellipodia formation, and inhibition occurring at high density due to the prevention of integrin and actin filament disassembly at the cell rear. Meanwhile, we illustrated the cellular response to extracellular super high-density ligands. When the cells are exposed to super high-density ligands, the stress-fiber-associated focal adhesions (FAs) slide inward, while the actin cytoskeleton together with the integrin receptors and adaptor proteins were stabilized at the cell rear, restricting the cell retraction and protrusion. By expressing vin 258, a mutant that possesses vinculin D1 domain exhibiting high affinity to talin and paxillin but lack of actin-binding domain, the cells successfully maintained the FA on the periphery but failed to preserve the actomyosin network and could not resume protrusion nor trailing edge retraction. Extra Rho activation preserves FAs at the cell edge and is associated with actomyosin bundles and eased the full disassembly of FAs facilitating trailing edge retraction but failed to resume the cell protrusion. By contrast, the constant activation of Tiam1/Rac1 signaling effectively rescued the cell migration restricted by the excessive binding interactions between integrins and the super high-density ligands. Together, this strategy may provide new insights in material design for manipulating and further understanding in ligand-density-dependent-modulation for manipulating and further understanding in ligand-density-dependent-modulation.