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Structure and composition of the fusion pore
Bhanu P Jena1, Sang-Joon Cho, Aleksandar Jeremic
1Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. bjena@med.wayne.edu
Biophysical Journal
|January 28, 2003
Summary
This study reveals the fusion pore, a stable structure on the cell membrane, as a cup-shaped lipoprotein complex. This complex, involving SNAREs, facilitates the docking and release of secretory vesicles in pancreatic acinar cells.
Area of Science:
- Cell Biology
- Membrane Biology
- Biophysics
Background:
- Fusion pores are dynamic structures at the cell plasma membrane involved in vesicle fusion and content release.
- Previous studies utilized atomic force microscopy (AFM) to visualize fusion pore dynamics in live secretory cells.
Purpose of the Study:
- To confirm and detail the structure and molecular composition of fusion pores in pancreatic acinar cells.
- To elucidate the role of specific proteins, including SNAREs, in the fusion pore complex.
Main Methods:
- Transmission electron microscopy (TEM) for ultrastructural analysis.
- Immunochemical studies to identify associated proteins.
- Combined AFM, immunoAFM, and electrophysiological measurements to map protein localization.
Main Results:
- TEM confirmed fusion pores as stable, cup-shaped structures associated with secretory vesicles in pancreatic acinar cells.
- t-SNAREs, NSF, actin, vimentin, alpha-fodrin, and calcium channels (alpha1c, beta3) were identified as components of the fusion complex.
- AFM and immunoAFM revealed the arrangement of SNAREs at the base of the fusion pore, facilitating vesicle docking and secretion.
Conclusions:
- The fusion pore, also termed the porosome, is a lipoprotein structure crucial for regulated exocytosis.
- Specific protein interactions at the fusion pore mediate the docking and fusion of secretory vesicles for content release.