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Multiple trimeric G‐proteins on the trans‐Golgi network exert stimulatory and inhibitory effects on secretory vesicle formation.
Author(s) -
Leyte A.,
Barr F.A.,
Kehlenbach R.H.,
Huttner W.B.
Publication year - 1992
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1992.tb05585.x
Subject(s) - heterotrimeric g protein , biology , golgi apparatus , secretory vesicle , neuroscience , vesicle , microbiology and biotechnology , g protein , biochemistry , signal transduction , endoplasmic reticulum , membrane
The role of heterotrimeric G‐proteins on the formation of constitutive secretory vesicles (CSVs) and immature secretory granules (ISGs) from the trans‐Golgi network (TGN) of PC12 cells was investigated. Using immunofluorescence and subcellular fractionation in conjunction with immunoblotting or ADP‐ribosylation by either pertussis toxin or cholera toxin, TGN membranes were found to contain not only several alpha i/alpha o G‐protein subunits including apparently alpha i3, but also alpha s. Pertussis toxin treatment of cells, which resulted in the stoichiometric ADP‐ribosylation of alpha i/alpha o, a modification known to prevent their coupling to receptors, led to the stimulation of cell‐free CSV and ISG formation, suggesting the presence of a guanine nucleotide exchange factor for alpha i/alpha o on the TGN. Mastoparan‐7, a peptide known to mimic an activated receptor and to stimulate nucleotide exchange on alpha i/alpha o, inhibited cell‐free vesicle formation, an effect abolished by pertussis toxin. In contrast, activation of alpha s by cholera toxin treatment of cells resulted in a stimulation of cell‐free CSV and ISG formation. This stimulation could be reversed when the alpha subunits not activated by cholera toxin, i.e. alpha i/alpha o, were activated by GTP gamma S and [AIF4]‐. Our results show that both inhibitory and stimulatory trimeric G‐proteins on the TGN participate in the regulation of secretory vesicle formation.