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Bilayers merge even when exocytosis is transient.
Justin W Taraska1, Wolfhard Almers
1Vollum Institute, Oregon Health and Sciences University, 3181 Southwest Sam Jackson Park Road, Portland, OR 97239, USA.
Summary
Neuroendocrine granules release contents during exocytosis, losing lipids but retaining proteins. Even after resealing, lipid bilayer fusion with the plasma membrane occurs during transient exocytosis.
Area of Science:
- Cell Biology
- Neuroscience
- Biochemistry
Background:
- Exocytosis involves secretory vesicle fusion with the plasma membrane.
- Transient exocytosis models, like kiss-and-run, propose minimal membrane mixing.
- The extent of lipid and protein exchange during neuroendocrine granule exocytosis remains unclear.
Purpose of the Study:
- To investigate lipid and protein exchange between dense core granules and the plasma membrane during exocytosis.
- To determine if neuroendocrine granules follow the kiss-and-run model.
Main Methods:
- Utilized two-color evanescent field microscopy to image single dense core granules.
- Employed the lipid probe FM4-64 and fluorescent proteins (GFP-phogrin) to track membrane dynamics.
Main Results:
- Granules lost the lipid probe FM4-64 to the plasma membrane within fractions of a second during exocytosis.
- The membrane protein GFP-phogrin remained within the granule.
- FM4-64 loss was observed even in granules that subsequently resealed.
Conclusions:
- Neuroendocrine granules exhibit lipid bilayer continuity with the plasma membrane during exocytosis.
- This lipid exchange occurs even when exocytosis is transient and the granule reseals.