Fusion pore expansion is a slow, discontinuous, and Ca2+-dependent processregulating secretion from alveolar type II cells

Citation
T. Haller et al., Fusion pore expansion is a slow, discontinuous, and Ca2+-dependent processregulating secretion from alveolar type II cells, J CELL BIOL, 155(2), 2001, pp. 279-289
Citations number
48
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell & Developmental Biology
Journal title
JOURNAL OF CELL BIOLOGY
ISSN journal
0021-9525 → ACNP
Volume
155
Issue
2
Year of publication
2001
Pages
279 - 289
Database
ISI
SICI code
0021-9525(20011015)155:2<279:FPEIAS>2.0.ZU;2-R
Abstract
In alveolar type II cells, the release of surfactant is considerably delaye d after the formation of exocytotic fusion pores, suggesting that content d ispersal may be limited by fusion pore diameter and subject to regulation a t a postfusion level. To address this issue, we used confocal FRAP and N-(3 -triethylammoniumpropyl)-4-(4-[dibutylamino]styryl) pyridinium dibromide (F M 1-43), a dye yielding intense localized fluorescence of surfactant when e ntering the vesicle lumen through the fusion pore (Haller, T., J. Ortmayr, F. Friedrich, H. Volkl, and F. Died. 1998. Proc. Nad. Acad Sci. USA. 95:157 9-1584). Thus, we have been able to monitor the dynamics of individual fusi on pores up to hours in intact cells, and to calculate pore diameters using a diffusion model derived from Fick's law. After formation, fusion pores w ere arrested in a state impeding the release of vesicle contents, and expan ded at irregular times thereafter. The expansion rate of initial pores and the probability of late expansions were increased by elevation of the cytop lasmic Ca2+ concentration. Consistently, content release correlated with th e occurrence of Ca2+ oscillations in ATP-treated cells, and expanded fusion pores were detectable by EM. This study supports a new concept in exocytos is, implicating fusion pores in the regulation of content release for exten ded periods after initial formation.