Visualization of Lipid
Raft Membrane Compartmentalization
in Living RN46A Neuronal Cells Using Single Quantum Dot Tracking
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Abstract
Lipid rafts are cholesterol-enriched subdomains in the
plasma membrane
that have been reported to act as a platform to facilitate neuronal
signaling; however, they are suspected to have a very short lifetime,
up to only a few seconds, which calls into question their roles in
biological signaling. To better understand their diffusion dynamics
and membrane compartmentalization, we labeled lipid raft constituent
ganglioside GM1 with single quantum dots through the connection of
cholera toxin B subunit, a protein that binds specifically to GM1.
Diffusion measurements revealed that single quantum dot-labeled GM1
ganglioside complexes undergo slow, confined lateral diffusion with
a diffusion coefficient of ∼7.87 × 10<sup>–2</sup> μm<sup>2</sup>/s and a confinement domain about 200 nm in
size. Further analysis of their trajectories showed lateral confinement
persisting on the order of tens of seconds, comparable to the time
scales of the majority of cellular signaling and biological reactions.
Hence, our results provide further evidence in support of the putative
function of lipid rafts as signaling platforms