Structure and Composition of the Fusion Pore
Bhanu P. Jena*, Sang-Joon Cho*, Aleksandar Jeremic*, Marvin H. Stromer
and Rania Abu-Hamdah*
* Departments of Physiology and Pharmacology, Wayne State University School of Medicine, Detroit, Michigan 48201 USA; and Department of Animal Science, Biochemistry and Biophysics, Iowa State University, Ames, Iowa 50011 USA
Correspondence: Address reprint requests to Prof. Bhanu P. Jena, Ph.D., Depts. of Physiology and Pharmacology, Wayne State University School of Medicine, 5239 Scott Hall, 540 E. Canfield Ave., Detroit, MI 48201-4177. Tel.: 313-577-1532; Fax: 313-993-4177; E-mail: bjena@med.wayne.edu .
Earlier studies using atomic force microscopy (AFM) demonstrated the presence of fusion pores at the cell plasma membrane in a number of live secretory cells, revealing their morphology and dynamics at nm resolution and in real time. Fusion pores were stable structures at the cell plasma membrane where secretory vesicles dock and fuse to release vesicular contents. In the present study, transmission electron microscopy confirms the presence of fusion pores and reveals their detailed structure and association with membrane-bound secretory vesicles in pancreatic acinar cells. Immunochemical studies demonstrated that t-SNAREs, NSF, actin, vimentin, 
-fodrin and the calcium channels 1c and ß3 are associated with the fusion complex. The localization and possible arrangement of SNAREs at the fusion pore are further demonstrated from combined AFM, immunoAFM, and electrophysiological measurements. These studies reveal the fusion pore or porosome to be a cup-shaped lipoprotein structure, the base of which has t-SNAREs and allows for docking and release of secretory products from membrane-bound vesicles.
Source: Biophysical Journal 84:1337-1343 (2003).
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