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New Biological Frontiers Illuminated by Molecular Sensors and Actuators
Poster Abstracts
12-POS
Board 12
Probing the Dynamics of Raft Lipids Induced by Receptor-Mediated Signaling in Living
Cells
Chia-Fen Hsieh
1
, Yii-Lih Lin
1,2
, Chia-Fu Chou
1
.
1
Academia Sinica, Taipei, Taiwan,
2
National Taiwan University, Taipei, Taiwan.
Lipid rafts, the relatively ordered and tightly packed membrane microdomains with enriched
cholesterol and glycosphingolipids, play an important role in compartmentalizing cellular
processes through assembling of signaling molecules and regulating membrane protein
trafficking. However, the direct dynamics of lipid rafts involving signaling pathways remains
unclear.
In this study, we directly investigated the dynamics of lipid rafts with the lipid molecules
conjugated with single fluorescent dyes. Sphingomyelin (SM) was used as the lipid raft marker
while phosphoglycerolipid (DPPE) was used as the non-lipid raft marker. The whole process of
signaling was slowed down from few minutes to hours by controlling the ligand-binding area
within tens of nanometers. The movements of receptors were also recorded with nano-sized
particles.
We believe this is the first direct observation of the dynamics of lipid raft following the ligand-
binding receptor. The raft lipids are not just concentrated in the ligand-receptor binding area, but
also moved along with the receptor on cell membrane. During the floating process of lipid raft
with receptor, the concentration of raft lipids increases 2.8-fold in average in an area of 1 µm
2
.
Increment in the concentration of raft lipids in a fixed area correlates to a slower movement of
the receptors. The diffusion coefficient of receptors can vary from 0.004 to 0.5 µm
2
/s. In this
study, we observed the early events of lipid raft aggregation induced by receptor-mediated
signaling in living cells.