Biophysical Society Thematic Meeting - June 28-July 1, 2015

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.

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