Unravelling the biophysics of membrane protein-lipid interactions using coherent optical nanoscopy and molecular dynamics

The interaction between proteins and lipids on the membrane of cells is fundamental to life. This is regulated by biophysical mechanisms ranging from how proteins move/diffuse within the two-dimensional lipid bilayer to how the membrane curvature/bending is locally affected by proteins. Due to a lack of measurement techniques with sufficient spatio-temporal resolution, we still have significant knowledge gaps on these processes.

This project will combine novel optical nanoscopy technologies with molecular dynamics simulations to unravel the interaction between an important protein receptor and its lipid environment, at the nanoscale with sub-millisecond time resolution, pushing the boundary of existing methods. We will study P2X7, a receptor working as ion channel, playing important roles in inflammation and immunity [1].

Its function is thought to be linked with an association to cholesterol and liquid-ordered lipid nanodomains/rafts, but the molecular mechanisms underpinning this behaviour are poorly understood. We will exploit a unique home-built multiphoton microscope [2] and a cell line expressing P2X7 tagged with the green fluorescent protein (GFP). The microscope features chemical sensing of lipids (including cholesterol) via coherent Raman scattering, correlatively with P2X7-GFP-fluorescence.

Sensitivity to lipid nanodomains will be achieved via the local enhancement of light occurring in the nanoscale region near a gold nano-antenna [3], following pioneering advances recently implemented in our laboratory. The experiments will be supported by molecular dynamics simulations, defining cholesterol binding sites and developing a molecular-level understanding of P2X7-lipid interactions.

This work is poised to transform our understanding of protein-lipid interactions in living cell membranes.