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

被引:82
作者
Haller, T
Dietl, P
Pfaller, K
Frick, M
Mair, N
Paulmichl, M
Hess, MW
Fürst, J
Maly, K
机构
[1] Univ Innsbruck, Dept Physiol, A-6020 Innsbruck, Austria
[2] Univ Innsbruck, Dept Anat & Histol, A-6020 Innsbruck, Austria
[3] Univ Innsbruck, Dept Med Chem & Biochem, A-6020 Innsbruck, Austria
[4] Univ Helsinki, Inst Biotechnol, FIN-00014 Helsinki, Finland
关键词
alveolus; exocytosis; lamellar bodies; lung; surfactant secretion;
D O I
10.1083/jcb.200102106
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
In alveolar type II cells, the release of surfactant is considerably delayed after the formation of exocytotic fusion pores, suggesting that content dispersal may be limited by fusion pore diameter and subject to regulation at a postfusion level. To address this issue, we used confocal FRAP and N-(3-triethylammoniumpropyl)-4-(4-[dibutylamino]styryl) pyridinium dibromide (FM 1-43), a dye yielding intense localized fluorescence of surfactant when entering the vesicle lumen through the fusion pore (Haller, T., J. Ortmayr, F. Friedrich, H. Volkl, and F. Died. 1998. Proc. Nad. Acad Sci. USA. 95:1579-1584). Thus, we have been able to monitor the dynamics of individual fusion 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 were arrested in a state impeding the release of vesicle contents, and expanded at irregular times thereafter. The expansion rate of initial pores and the probability of late expansions were increased by elevation of the cytoplasmic Ca2+ concentration. Consistently, content release correlated with the occurrence of Ca2+ oscillations in ATP-treated cells, and expanded fusion pores were detectable by EM. This study supports a new concept in exocytosis, implicating fusion pores in the regulation of content release for extended periods after initial formation.
引用
收藏
页码:279 / 289
页数:11
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