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  • Fusion-activated Ca2+ entry : an "active zone" of elevated Ca2+ during the postfusion stage of lamellar body exocytosis in rat type II pneumocytes
    Miklavc, Pika ...
    Background: Ca2+ is essential for vesicle fusion with the plasma membrane in virtually all types of regulated exocytoses. However, in contrast to the well-known effects of a high cytoplasmic Ca2+ ... concentration ([Ca2+]c) in the prefusion phase, the occurrence and significance of Ca2+ signals in the postfusion phase have not been described before. Methodology/Principal Findings: We studied isolated rat alveolar type II cells using previously developed imaging techniques. These cells release pulmonary surfactant, a complex of lipids and proteins, from secretory vesicles (lamellar bodies) in an exceptionally slow, Ca2+- and actin-dependent process. Measurements of fusion pore formation by darkfield scattered light intensity decrease or FM 1-43 fluorescence intensity increase were combined with analysis of [Ca2+]c byratiometric Fura-2 or Fluo-4 fluorescence measurements. We found that the majority of single lamellar body fusion events were followed by a transient (t1/2 of decay = 3.2 s) rise of localized [Ca2+]c originating at the site of lamellar body fusion. [Ca2+]c increase followed with a delay of ~0.2-0.5 s (method-dependent) and in the majority of cases this signal propagated throughout the cell (at ~10 m/s). Removal of Ca2+ from, or addition of Ni2+ to the extracellular solution, strongly inhibited these [Ca2+]c transients, whereas Ca2+ store depletion with thapsigargin had no effect. Actin-GFP fluorescence around fused LBs increased several seconds after the rise of [Ca2+]c. Both effects were reduced by the non-specific Ca2+ channel blocker SKF96365. Conclusions/Significance: Fusion-activated Ca2+ entry (FACE) is a new mechanism that leads to [Ca2+]c transients at the site of vesicle fusion. Substantial evidence from this and previous studies indicates that fusion-activated Ca2+ entry enhances localized surfactant release from type IIcells, but it may also play a role for compensatory endocytosis and other cellular functions.
    Vir: PloS one [Elektronski vir]. - ISSN 1932-6203 (Vol. 5, iss. 6, June 2010, str. 1-10)
    Vrsta gradiva - e-članek
    Leto - 2010
    Jezik - angleški
    COBISS.SI-ID - 65208577

    Povezava(-e):

    http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010982
    DOI

vir: PloS one [Elektronski vir]. - ISSN 1932-6203 (Vol. 5, iss. 6, June 2010, str. 1-10)

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