CAREER: Mechanisms controlling spatial patterning of PIP lipids in eukaryotic cell polarity

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The ability of cells to regulate the localization of molecules in both time and space is a hallmark of cellular organization. In eukaryotic cells, phosphatidylinositol phosphate (PIP) lipids function as master regulators of cellular organization by selectively recruiting proteins to intracellular membranes and locally controlling their activity. Using a multidisciplinary biochemistry approach, this project will help decipher mechanisms that regulate communication between signaling molecules that control cellular organization. In long-term, this project will provide a molecular understanding of tissue organization, asymmetric cell division, and cell polarity. Integrated with this research strategy, the education plan seeks to improve how early career scientists communicate their research using art and scientific imagery as a tool for promoting inquiry-based learning. Undergraduate researchers will receive training in visual arts to improve their ability to communicate science. The education plan will support career development in scientific illustration and molecular visualization that bridges science, art, and design.The goal of the proposed research is to determine how biochemical reactions spontaneously self-organize on the plasma membrane to drive cell polarity. To achieve this goal, this project will use a bottom-up approach to biochemically reconstitute the communication between several important signaling elements, including (1) phosphatidylinositol phosphate (PIP) lipids, (2) Rho-GTPases, and (3) the actin cytoskeleton on membrane surfaces. Measurements, implemented in this project, will span several length scales beginning with single molecule biophysical measurements of PIP lipid modifying enzymes on supported membranes using Total Internal Reflection Fluorescence (TIRF) microscopy. Individual biochemical reactions will be combined to generate reaction diffusion systems that exhibit emergent properties, including bistability and polarization on membranes. This research will establish methods to directly visualize interactions between polarized signaling domains and the actin cytoskeleton using micropatterned supported bilayers and membrane encapsulation. Deterministic and stochastic kinetic modeling will be used to create a theoretical framework that describes the enzymology and spatial patterning mechanisms investigated. Overall, the proposed research will identify principles and signaling network architectures that are important for establishing communication between different classes of membrane signaling reactions that control cell polarity. This project is supported by the Molecular Biophysics and Cellular Dynamics and Function Clusters of the Molecular and Cellular Biosciences Division in the Directorate for Biological Sciences.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.