In the last decade, several monomeric and heterotrimeric @entity6370 binding proteins have been identified to associate with secretory vesicles and to be implicated in exocytosis. Vesicle volume also has been proposed to play a regulatory role in secretory vesicle fusion at the plasma membrane. However, the molecular mechanism of function of the @entity6370 binding proteins and of the regulation of secretory vesicle volume in the exocytotic process remains unclear. In this study, we report association of the secretory vesicle membrane with the alpha subunit of a heterotrimeric @entity3007 binding protein G(alpha i3) and implicate its involvement in @entity4 . Using an atomic force microscope in combination with confocal microscopy, we were able to study the dynamics of isolated zymogen granules, the secretory vesicles in exocrine pancreas. Exposure of zymogen granules to @entity3007 resulted in a 15-25% increase in vesicle height as measured by the atomic force microscope and a similar increase in vesicle diameter as determined by confocal microscopy. Mas7, an active @entity37956 analog known to stimulate Gi proteins, was found to stimulate the GTPase activity of isolated zymogen granules and cause @entity4 . Increase in vesicle size in the presence of @entity3007 , @entity7034 , and Mas7 were irreversible and KCl-sensitive. @entity141 had no effect on zymogen granule size. Taken together, the results indicate that G(alpha i3) protein localized in the secretory vesicle membrane mediates @entity4 , a potentially important prerequisite for vesicle fusion at the cell plasma membrane.

Gi regulation of secretory XXXX examined by atomic force microscopy.

@entity3007 :: ('MESH:D006160', 'Chemical') :: ['GTP'] @entity6370 :: ('CHEBI:61292', 'Chemical') :: ['guanine nucleotide'] @entity4 :: ('MESH:D004487', 'Disease') :: ['swelling', 'vesicle swelling'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+'] @entity37956 :: ('MESH:C037500', 'Chemical') :: ['mastoparan'] @entity7034 :: ('CHEBI:28741', 'Chemical') :: ['NaF']
@entity4 :: (MESH:D004487,Disease) :: ['vesicle swelling']
