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Formation and Characterization of Supported Lipid Bilayers Containing Phosphatidylinositol-4,5-bisphosphate and Cholesterol as Functional Surfaces
journal contribution
posted on 2014-12-16, 00:00 authored by Patrick Drücker, David Grill, Volker Gerke, Hans-Joachim GallaSolid-supported lipid bilayers (SLBs)
mimicking a biological membrane are commonly used to investigate lipid–lipid
or lipid–protein interactions. Simple binary or ternary lipid
systems are well established, whereas more complex model membranes
containing biologically important signaling lipids such as phosphatidylinositol-4,5-bisphosphate
(PI(4,5)P2) and cholesterol have not been extensively described
yet. Here we report the generation of such bilayers and their relevant
biophysical properties and in particular the accessibility of PI(4,5)P2 for protein binding. Ternary mixtures of POPC with 20% cholesterol
and either 3 or 5 mol % dioleoyl-phosphatidylinositol-4,5-bisphosphate
were probed by employing the quartz crystal microbalance and atomic
force microscopy. We show that these mixtures form homogeneous solid-supported
bilayers that exhibit no intrinsic phase separation and are characterized
by long-term stability (>8 h). Bilayers were formed in a pH-dependent
manner and were characterized by the accessibility of PI(4,5)P2 on the SLB surface as shown by the interaction with the PI(4,5)P2 binding domain of the cortical membrane-cytoskeleton linker
protein ezrin. A time-dependent reduction of PI(4,5)P2 levels
in the upper leaflet of SLBs was observed, which could be effectively
inhibited by the incorporation of a negatively charged lipid such
as phosphatidylserine. Furthermore, quartz crystal microbalance measurements
revealed that cholesterol affects bilayer adsorption to the solid
support.