Structure and composition of the fusion pore.
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, alpha-fodrin and the calcium channels alpha1c and beta3 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.
Jena
Bhanu P
BP
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. bjena@med.wayne.edu
Cho
Sang-Joon
SJ
Jeremic
Aleksandar
A
Stromer
Marvin H
MH
Abu-Hamdah
Rania
R
D000199:Actins / Q000032:analysis; D000818:Animals; D015220:Calcium Channels / Q000032:analysis; D002352:Carrier Proteins / Q000032:analysis; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D002478:Cells, Cultured; D003034:Coated Pits, Cell-Membrane / Q000737:chemistry / Q000648:ultrastructure; D005089:Exocytosis; D008297:Male; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000032:analysis*; D008840:Microfilament Proteins / Q000032:analysis; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D052066:N-Ethylmaleimide-Sensitive Proteins; D020799:Pancrelipase / Q000737:chemistry* / Q000648:ultrastructure*; D050765:Qa-SNARE Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D022142:Secretory Vesicles / Q000737:chemistry* / Q000648:ultrastructure*; D013329:Structure-Activity Relationship; D033921:Vesicular Transport Proteins; D014746:Vimentin / Q000032:analysis; D013049:Spectrin
D000199:Actins; D015220:Calcium Channels; D002352:Carrier Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins; D020799:Pancrelipase; D050765:Qa-SNARE Proteins; D033921:Vesicular Transport Proteins; D014746:Vimentin; D013049:Spectrin; C498737:Nsf protein, rat