Spatial regulation of membrane receptor signaling using DNA origami

Abstract: Juxtracrine signaling between apposing membrane receptors and ligands is an important class of intercellular communication. Much focus has been directed towards studying the biochemical interactions between receptors and ligands, their surface expression levels and signaling activities for driving downstream signaling processes. However, the lateral distribution of receptors/ligands on the membrane has been gaining increasing significance in modulating intercellular signaling. Nevertheless, little is known about the cellular mechanisms of interpreting this biophysical factor during ligand/receptor signaling. The work in thesis is based on the hypothesis that cells use information from the spatial organization of their surface ligands/receptors to direct intracellular signaling. To address this, we have employed the power of DNA origami technology to manipulate ligand spatial distances with nanometer precision and constrain their cognate receptors into defined configurations in ephrin/Eph signaling and the T-cell negative regulators PD-L1/PD-1 on T cell signaling. With this approach, we demonstrated that modulating the nanoscale organization of ephrin-A5 ligands contributed to divergent transcriptional profiles in human glioblastoma cells (paper I). We also showed that the nanoscale organization of PD-L1 regulates T-cell activation and sizes of PD-1 clusters (paper II). In summary, this work describes that the spatial organization of ligands/receptors at the nanoscale can serve as an important physical guidance cue that tunes the overall cellular response.