Single granule pH cycling in antigen-induced mast cell secretion.
The pH cycling of individual granules in secreting (serotonin-loaded) mast cells is quantitatively examined using multicolor multiphoton fluorescence microscopy. A typical exocytosis event consists of maximal calcium rise at time zero, granule alkalization a few seconds later and, finally, complete contents release at a fraction of a second after alkalization. Membrane fusion is either transient, as indicated by subsequent granule reacidification, or 'full', as indicated by a granule disappearance with a collapse of its membrane into the plasma membrane. The relative frequency of these two coexisting behaviors (the 'kiss-to-collapse' ratio) is approximately 2:1. A typical transiently fusing granule experiences multiple alkalization/acidification cycles after addition of exogenous antigen. Between recycling granules, coalescence events are frequent, with 80% resulting in a collapse of the formed granule complex to the plasma membrane. The full dynamics of secretion encompass a complex combination of these granule activities.
Williams
R M
RM
Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA. rw36@cornell.edu
Webb
W W
WW
D000165:Acridine Orange / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis; D005089:Exocytosis; D006863:Hydrogen-Ion Concentration; D008407:Mast Cells / Q000378:metabolism*
D000165:Acridine Orange