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Phospholipids undergo hop diffusion in compartmentalized cell membrane.
Takahiro Fujiwara1, Ken Ritchie, Hideji Murakoshi
1Kusumi Membrane Organizer Project, Exploratory Research for Advanced Technology Organization, Japan Science and Technology Corporation, Nagoya 460-0012, Japan. akusumi@bio.nagoya-u.ac.jp
The Journal of Cell Biology
|June 12, 2002
Summary
Cell membrane phospholipids move within nanoscale compartments, not freely diffusing. This compartmentalization, driven by the actin cytoskeleton, explains their reduced movement compared to artificial membranes.
Area of Science:
- Cell Biology
- Biophysics
- Membrane Dynamics
Background:
- Lipid diffusion in cell membranes is significantly slower (5-100x) than in artificial bilayers, a long-standing puzzle.
- Understanding lipid diffusion is crucial for cell membrane function and dynamics.
Purpose of the Study:
- To investigate the mechanism behind the reduced lateral diffusion of phospholipids in living cell membranes.
- To elucidate the role of membrane structure in regulating lipid mobility.
Main Methods:
- Single-molecule tracking of unsaturated phospholipids in rat kidney fibroblasts.
- High temporal resolution (25 microseconds) observation of phospholipid movement.
- Analysis of diffusion within distinct membrane compartments.
Main Results:
- Cell membranes exhibit compartmentalization, confining phospholipids within 230-nm compartments for ~11 ms and larger 750-nm compartments for ~0.33 s.
- Diffusion within 230-nm compartments (5.4 µm²/s) is nearly as fast as in artificial bilayers.
- Compartmentalization depends on the actin-based membrane skeleton, but not extracellular matrix, protein domains, or lipid rafts.
Conclusions:
- Cell membrane compartmentalization, not intrinsically slow diffusion, explains reduced phospholipid mobility.
- The actin-based membrane skeleton, via transmembrane proteins acting as 'pickets', creates these transient confinement zones.
- This finding provides a new mechanistic understanding of lipid diffusion regulation in biological membranes.