Lipid nanotechnologies for structural studies of membrane-associated clotting proteins by cryo-electron microscopy

Biological membranes surround all living cells, confining internal organelles and participating in a variety of essential cellular functions, such as signaling, electrolyte balance, and energy conversion. Cell membranes are structurally and chemically heterogeneous environment composed of numerous types of lipids arranged as a continuous bilayer. The assembly of protein complexes at the membrane surface is responsible for fundamental biological processes such as synaptic transmission, blood coagulation, and apoptosis. Resolving the macromolecular organization of these complexes at the membrane surface will help to understand the structural basis of their function and significance for the associated biological processes. In this review, we present our work on direct structure determination of membrane-bound clotting factors, specifically factor VIII (FVIII), by cryogenic electron microscopy (CryoEM). To resolve the FVIII membrane-bound organization, we have optimized lipid nanostructures resembling the activated platelet membrane. Combining structural CryoEM, capable of near-atomic resolution, with customized lipid nanotechnologies is a powerful approach to investigate how the cellular membrane can modulate protein function at close to physiological conditions. The outcome will open novel avenues for developing lipid nanotechnologies of diverse shapes and composition that can be optimized for various protein systems, germane for both drug delivery and macromolecular structure determination.