Lipoprotein particle interaction with biomembranes

Excess, non-water soluble cholesterol from peripheral cells is
transported to the liver by High Density Lipoprotein (HDL)
particles for excretion. Thus, cholesterol has to be transferred
in the periphery from the cell membrane to HDL particles
and vice versa in the liver. It remains elusive whether
lipoprotein particle receptors like SR-B1 directly mediate
lipid flux or just keep the lipoprotein particle (LP) attached
to the plasma membrane (enhancing transfer probability).
We observed transfer of cholesterol from LPs to a lipid bilayer
upon contact without a receptor. Initial studies suggest,
that LP/membrane interactions (via specific receptor or
receptor-independent) and cargo transfer are determined by
two parameters: presence of specific apolipoproteins (major
structural compound of LPs), and local lipid environment of
the biological membrane. Hence, we plan to quantify the relative
contribution of each parameter by creation of artificial
LPs with known composition (i.e. different apolipoprotein
combinations) and to measure their interaction with varying
biomembranes using Quartz Crystal Microbalance, Fluorescence
and Atomic Force Microscopy. As comparison, we
measure native HDL particles from different donors.