Cortical Actin Networks Induce Spatio-temporal Confinement of Phospholipids in the Plasma Membrane – A Minimally Invasive Investigation by STED-FCS

July 24, 2015

Important discoveries in the last decades have changed our view of the plasma membrane organisation. Specifically, the cortical cytoskeleton has emerged as a key modulator of the lateral diffusion of membrane proteins. Cytoskeleton-dependent compartmentalised lipid diffusion has been proposed, but this concept remains controversial because this phenomenon has thus far only been observed with artefact-prone probes in combination with a single technique: single particle tracking. In this paper, we report the first direct observation of compartmentalised phospholipid diffusion in the plasma membrane of living cells using a minimally invasive, fluorescent dye labelled lipid analogue. These observations were made using optical STED nanoscopy in combination with fluorescence correlation spectroscopy (STED-FCS), a technique which allows the study of membrane dynamics on a sub-millisecond time-scale and with a spatial resolution of down to 40 nm. Specifically, we find that compartmentalised phospholipid diffusion depends on the cortical actin cytoskeleton, and that this constrained diffusion is directly dependent on the F-actin branching nucleator Arp2/3. These findings provide solid evidence that the Arp2/3-dependent cortical actin cytoskeleton plays a pivotal role in the dynamic organisation of the plasma membrane, potentially regulating fundamental cellular processes.

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Andrade DM, Clausen MP, Keller J, Mueller V, Wu C, Bear JE, Hell SW, Lagerholm BC, and Eggeling C:
Cortical Actin Networks Induce Spatio-temporal Confinement of Phospholipids in the Plasma Membrane – A Minimally Invasive Investigation by STED-FCS

Scientific Reports 5: 11454 (2015); doi: 10.1038/srep11454

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