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B. Plochberger, M. Axmann, C. Röhrl, J. Weghuber, M. Brameshuber, B. Rossboth, S. Mayr, R. Ros, R. Bittman, H. Stangl, G. Schütz:
"Direct observation of cargo transfer from HDL particles to the plasma membrane";
Atherosclerosis, 277 (2018), 53 - 59.

Background and aims: Exchange of cholesterol between high-density lipoprotein (HDL) particles and cells is a key
process for maintaining cellular cholesterol homeostasis. Recently, we have shown that amphiphilic cargo derived
from HDL can be transferred directly to lipid bilayers. Here we pursued this work using a fluorescencebased
method to directly follow cargo transfer from HDL particles to the cell membrane.
Methods: HDL was either immobilized on surfaces or added directly to cells, while transfer of fluorescent cargo
was visualized via fluorescence imaging.
Results: In Chinese hamster ovary (CHO) cells expressing the scavenger receptor class B type 1 (SR-B1), transfer
of amphiphilic cargo from HDL particles to the plasma membrane was observed immediately after contact,
whereas hydrophobic cargo remained associated with the particles; about 60% of the amphiphilic cargo of
surface-bound HDL was transferred to the plasma membrane. Essentially no cargo transfer was observed in cells
with low endogenous SR-B1 expression. Interestingly, transfer of fluorescently-labeled cholesterol was also facilitated
by using an artificial linker to bind HDL to the cell surface.
Conclusions: Our data hence indicate that the tethering function of SR-B1 is sufficient for efficient transfer of free
cholesterol to the plasma membrane.

Single molecule microscopy HDL Cholesterol transfer