Towards understanding how lipid variations and membrane proteins may influence the biophysical chemistry of biomembranes

Abstract

Biomembranes in living cells are complex, heterogeneous and dynamic systems that regulate numerous biological processes such as cell signaling, endocytosis and exocytosis, and protein trafficking. Cholesterol‐rich lipid domains have been hypothesized to exist in a liquid‐ordered phase and play an important role in cellular functions. Yet, these direct observations of these lipid domains in the plasma membrane of living cell remain elusive. In addition, the relevance of model membranes to elucidate the structure‐function relationship of cellular membranes has been debated recently. Here, we test the hypothesis that cholesterol diffuses as a complex with other lipids in membranes, both model and natural ones. We also examine the role of lipid variation and proteins on the biophysical properties on biomembranes using comparative studies on giant unilamellar vesicles (GUVs) and plasma membrane vesicles (GPMVs) isolated from Hs578Bst living cells using newly developed Bodipy‐cholesterol derivatives. The fluorescence dynamics assay used here includes two‐photon fluorescence lifetime imaging, fluorescence resonance energy transfer, and fluorescence polarization as well as correlation spectroscopy. Our comparative studies on GUVs and GPMVs serve as a platform to test our understanding of lipid‐lipid and lipid‐protein interactions in the plasma membrane.