Two Distinct Modes of Exocytotic Fusion Pore Expansion in Large Astrocytic Vesicles
Year: 2013
Type: article
Abstract: Formation of the fusion pore is a central question for regulated exocytosis by which secretory cells release neurotransmitters or hormones. Here, by dynamically monitoring exocytosis of large vesicles (2–7 μm) in astrocytes with two-photon microscopy imaging, we found that the exocytotic fusion pore was generated from the SNARE-dependent fusion at a ring shape of the docked plasma-vesicular membrane and the movement of a fusion-produced membrane fragment. We observed two modes of fragment movements, 1) a shift fragment that shifted to expand the fusion pore and 2) a fall-in fragment that fell into the collapsed vesicle to expand the fusion pore. Shift and fall-in modes are associated with full and partial collapses of large vesicles, respectively. The astrocytic marker, sulforhodamine 101, stained the fusion-produced membrane fragment more brightly than FM 1-43. Sulforhodamine 101 imaging showed that double fusion pores could simultaneously occur in a single vesicle (16% of large vesicles) to accelerate discharge of vesicular contents. Electron microscopy of large astrocytic vesicles showed shift and fall-in membrane fragments. Two modes of fusion pore formation demonstrate a novel mechanism underlying fusion pore expansion and provide a new explanation for full and partial collapses of large secretory vesicles. Background: Astrocytes release glutamate and d-serine by fusion of large vesicles. Results: Fusion occurs at a ring shape of the docked membrane, and the movement of fusion-produced membrane fragment expands the fusion pore. Conclusion: Two modes of fusion pore expansion are associated with full and partial collapses of large vesicles. Significance: Two fusion modes provide a novel mechanism for full and partial collapses of large vesicles.
Source: Journal of Biological Chemistry
Authors: Hong Peng, Ning Kang, Jun Xu, Patric K. Stanton, Jian Kang
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W2151495377