Biophysical mechanisms for bidirectional coupling between mechanotransduction and cell morphology

About This Grant

This project explores the mechanisms by which cells respond and adapt to biochemical and physical cues from their environment. A particular focus is placed on mechanotransduction signaling in response to the material properties of a cell’s environment, leading to the nuclear translocation of important transcription regulatory proteins such as yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). The project aims to quantify cell response to substrate nanotopography (i.e., nanoscale surface features) and to molecules that activate G protein-coupled receptors (GPCRs). It is hypothesized that cells integrate physical and chemical environmental cues through intracellular signaling events at the cell and nuclear surfaces, leading to distinct changes in YAP/TAZ localization and in cellular morphology. Throughout, this work utilizes a productive cycle of biophysical experiments and simulations. The K99 phase of this project examines cell and nuclear deformation on substrates with nanoscale topographical features, in the presence or absence of the GPCR agonist angiotensin II. Experiments will quantify the response of a human cell line (U2OS) to substrates with nanopillars. Mechanotransduction signaling will be quantified by immunofluorescence imaging of cytoskeletal activation, nuclear deformation, and YAP/TAZ localization in fixed cells, while biosensor-based fluorescence imaging will be used to monitor GPCR activation and downstream signaling events in live cells. These data will constrain a computational model that considers spatiotemporal dynamics of biochemical signaling within the cell coupled to curvature of the plasma membrane and deformation of the nucleus. Such simulations leverage recent advances in finite-element-based software packages used for spatial models of cell signaling and cell mechanics. This work will be conducted at the University of California, San Diego, supported by state-of-the-art experimental and computational resources and a strong team of scientific advisors including co-mentors Profs. Padmini Rangamani (primary) and Jin Zhang. This team will support training in biophysical experiments and computation. The candidate’s career goal is obtaining a tenure-track faculty position to lead research using both experimental and computational approaches to understand the biophysics of mechanotransduction. The associated R00 research will use human neutrophils as a model cell. Cell spreading and associated signaling events will be monitored in the presence or absence of the GPCR agonist CXCL8 on flat substrates of varying stiffness to assess how substrate deformability influences spreading efficacy. These results will be leveraged against predictions of a fluid-mechanics-based model of neutrophil motility coupled to a biochemical model of integrin-mediated signaling in neutrophils. Finally, deformation of the lobed and flexible neutrophil nucleus will be measured on nanopillar substrates and compared to that of rigid nuclei. Coupled mechanochemical simulations will be used to assess the implications of nuclear deformability for mechanosensitive signaling.