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Spot Variation Fluorescence Correlation Spectroscopy for Analysis of Molecular Diffusion at the Plasma Membrane of Living Cells
Published on: November 12, 2020
Modulation of lateral diffusion in the plasma membrane by protein density
Manfred Frick1, Katja Schmidt, Benjamin J Nichols
1Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
Current Biology : CB
|March 3, 2007
Summary
Lateral protein diffusion in mammalian plasma membranes (PM) is slow. Protein density, not cortical factors, primarily dictates diffusion rates, suggesting an intrinsic membrane property.
Area of Science:
- Cell Biology
- Biophysics
- Membrane Protein Dynamics
Background:
- Lateral diffusion of proteins in the plasma membrane (PM) of mammalian cells is significantly slower than in artificial membranes.
- Existing models propose explanations such as increased membrane viscosity due to protein crowding or the influence of cortical factors like actin and spectrin filaments.
Purpose of the Study:
- To experimentally test the predictions of models explaining slow protein diffusion in the PM.
- To elucidate the factors governing the rate of lateral protein diffusion over micron-scale distances.
Main Methods:
- Utilized photobleaching techniques to measure protein diffusion rates.
- Manipulated cortical actin levels and spectrin expression.
- Disrupted the PM structure through ventral membrane sheet formation and permeabilization.
- Altered the total protein content of the PM in live cells.
Main Results:
- Loss of cortical actin or spectrin knockdown did not affect protein diffusion rates.
- PM disruption led to protein aggregation and increased diffusion rates for the non-aggregated fraction.
- Increasing or decreasing PM protein content reciprocally altered lateral diffusion rates.
Conclusions:
- Slow lateral diffusion over micron-scale distances appears to be an intrinsic property of the cell membrane itself.
- The density of proteins within the plasma membrane is a critical determinant of lateral diffusion rates.
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