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Ultrafine membrane compartments for molecular diffusion as revealed by single molecule techniques.
Kotono Murase1, Takahiro Fujiwara, Yasuhiro Umemura
1Kusumi Membrane Organizer Project, Exploratory Research for Advanced Technology Organization (ERATO/SORST), Japan Science and Technology Agency, Nagoya, Japan.
Biophysical Journal
|June 11, 2004
Summary
Plasma membranes are compartmentalized, not a fluid continuum. These compartments, observed across diverse cell types, influence molecular movement and necessitate a new model of cell membrane structure.
Area of Science:
- Cell Biology
- Membrane Biophysics
- Molecular Dynamics
Background:
- The plasma membrane's structure is debated, with models ranging from a fluid continuum to compartmentalized domains.
- Understanding membrane compartmentalization is crucial for elucidating diverse cellular functions.
Purpose of the Study:
- To investigate the existence and characteristics of plasma membrane compartments.
- To challenge the traditional fluid continuum model of the cell membrane.
Main Methods:
- Single particle tracking with high temporal resolution.
- Single fluorescent molecule video imaging of unsaturated phospholipids (DOPE).
- Analysis of molecular movement and hop diffusion across compartment boundaries in various cell types.
Main Results:
- Plasma membrane compartments were confirmed in multiple cell types (CHO, HEPA-OVA, PtK2, FRSK, HEK293, HeLa, T24, NRK).
- Compartment sizes ranged from 30 to 230 nm.
- DOPE phospholipid hop rates across boundaries varied (1-17 ms), with cell-type-dependent barrier passage probabilities.
Conclusions:
- The findings support a compartmentalized plasma membrane model over the 2D fluid continuum.
- Cellular membranes exhibit mosaicism due to these compartments, affecting molecular mobility.
- A paradigm shift towards a hop diffusion model within membrane compartments is indicated.