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Tracking chromaffin granules on their way through the actin cortex.
1Max-Planck Institute for Experimental Medicine, Molecular Biology of Neuronal Signals, Göttingen, Germany. martin.oheim@espci.fr
European Biophysics Journal : EBJ
|July 6, 2000
Summary
Chromaffin granule trafficking near the plasma membrane is constrained by the actin cortex. Exocytosis stimulation recruits distant granules, while actin polymerization changes affect mobility and release rates.
Area of Science:
- Cell Biology
- Biophysics
Background:
- Chromaffin granules store and release hormones via exocytosis.
- Understanding granule dynamics is crucial for exocytosis regulation.
Purpose of the Study:
- To quantitatively analyze chromaffin granule trafficking kinetics near the plasma membrane.
- To investigate the role of the actin cytoskeleton in granule mobility and exocytosis.
Main Methods:
- Quantitative time-lapse evanescent-wave imaging of fluorescently labeled chromaffin granules.
- Analysis of mean squared displacement (MSD) to determine the 3D diffusion coefficient (D(3)).
- Calculation of granule speed, displacement, direction, and autocorrelation.
Main Results:
- Granule diffusion (D(3)) was ~10,000 times lower than free diffusion.
- Near-membrane granules exhibited random motion with reversals before docking.
- Docking involved a rapid decrease in mobility (<100 ms).
- Actin polymerization inhibitors altered granule mobility and reduced release rates.
Conclusions:
- Chromaffin granule mobility is significantly constrained by the filamentous actin meshwork.
- Changes in actin viscosity influence granule transport and exocytosis.
- Exocytosis stimulation dynamically alters granule distribution and mobility near the plasma membrane.