Understanding the mechanisms of supported lipid membrane reshaping into tubular networks using quantitative DIC microscopy

Abstract

Biological membranes are known to form various structural motifs, from lipid bilayers to tubular filaments and networks facilitating e.g. adhesion and cell-cell communication. To understand the biophysical processes underpinning lipid-lipid interactions in these systems, synthetic membrane models are crucial. Here, we demonstrate the formation of tubular networks from supported lipid membranes of controlled lipid composition on glass. We quantify tube radii using quantitative differential interference contrast (qDIC) and propose a biophysical mechanism for the formation of these structures, regulated by surface tension and lipid exchange with connected supported membranes. Two lipid types are investigated, namely DOPC and DC15PC, exhibiting a liquid disordered and a solid ordered phase at room temperature, respectively. Tube formation is studied versus temperature, revealing bilamellar layers retracting and folding into tubes upon DC15PC lipids transitioning from liquid to solid phase, which is explained by lipid transfer from bilamellar to unilamellar layers. This study introduces a novel model system for bilayer tubes, allowing to elucidate the biophysics of lipid-lipid interactions governing lipid membrane reshaping into tubular structures, important for our understanding of biological membrane filaments.