Coupling Force, Tension and Cell Plasma Membrane Plasticity at the Nanoscale Functional Roles of Caveolin Nanodomains

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Mechanical forces exerted at the cell plasma membrane (PM) direct many important cellular and tissue processes, including cell adhesion, migration and invasiveness. In these processes, the membrane curving protein caveolin 1 (cav1) and the different types of nano-scale domains it forms at the PM are emerging as critical mechano-transducing hubs and tension buffering structures of mammalian cells. Yet, the structural plasticity of cav1 nano-scale domains and their functional coupling to the local mechanical and tension states of the PM are still enigmatic. Consequently, some of the fundamental mechanisms by which the cell membrane adapts to varying forces at the nano-scale remain undefined. This project aims at understanding how cav1 nano-scale domains modulate the PM structure in response to mechanical cues and at defining the core physical principles that govern PM plasticity, maintenance of membrane tension and proper cell response to forces. This project will be implemented through a multidisciplinary approach that integrates super-resolution (SR) microscopy imaging, optical force sensing, engineering of bio-materials for cell mechano-biology, quantitative biophysics and modeling. It will (i) define, quantitatively, the nano-scale organization of cav1 nano-scale domains at the cell PM, (ii) establish their plasticity in response to specific PM forces, (iii) determine how they locally regulate PM tension and (iv) provide physical models of their functions as key PM tension modulators. By its original and multidisciplinary nature, the project engages its participants in highly interdisciplinary research. It will provide them with skills that match the current convergence between cell biology, physics and engineering research. The proposed activities also provide a platform integrating modern technology and cross-pollination science for traditionally underrepresented students at the undergraduate and high school levels, through (i) hands-on experimentation with imaging probes, cell culture and microscopy imaging, (ii) outreach projects and (iii) educational activities. Economically disadvantaged undergraduate and high school students will be recruited via established programs at USC and through outreach to high schools in the Greater Los Angeles Area. In particular, an 8-weeks Summer Internship organized by the PI and Co-PI together with the Mathematics, Engineering, Science Achievement (MESA) program at USC will be offered to high-school students over the course of the project. Experience and knowledge gained by actively taking part in the project will attract this younger generation of scholars to the field of Biophysics and will provide them with strong scientific foundationsThe functional influence of cellular adhesion forces on the 3D plasticity of cav1 nano-domains and their spatial coupling to sub-membranous actin fibers and focal adhesions (FAs) will first be established by correlative 3D SR microscopy, robust spatial correlation analyses and modulation of adhesion geometry for micro-patterned cells. This will provide new understanding of the homeostatic PM functions of cav1 nano-domains as cells respond to specific mechanical constraints. The plasticity of cav1 nano-domains will then be quantitatively correlated with extra- and intracellular picoNewton forces developed along the PM at FAs by combining optical force sensor measurements, SR microscopy and cell micropatterning. This will shed new light on the role of cav1 as a mechano-transducer of extra/intracellular forces at the cell surface. Using quantum dot tracking of curvature- and non-curvature-coupled PM receptors together with 3D SR microscopy of cav1 nano-domains in live cells, the functional roles of cav1 nano-domains as local modulators of PM tension will then be established. This will reveal how they participate in adaptive coupling between local PM tension and cellular force generation on substrates. Finally, physical models describing the plasticity of cav1 nano-domains as a function of local membrane tension will be conceived and tested quantitatively to define some of the core physical principles that govern the adaptation of the cell PM to forces. Beyond offering new optical tools and original methodologies to study the function of PM nano-structures in cells, this work will bring novel insights into the physics of living systems by providing a mechanistic understanding of the physical principles that dictate PM plasticity and adaptation to forces at the nano-scale. This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Cellular Dynamics and Function Program in the Division of Molecular and Cellular Biosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.