Subunit composition and functional properties of G-protein heterotrimers on rat chromaffin granules.
Heterotrimeric G-proteins at the plasma membrane serve as switches between heptahelical receptors and intracellular signal cascades. Likewise endomembrane associated G-proteins may transduce signals from intracellular compartments provided they consist of a functional trimer. Using quantitative immunoelectron microscopy we found heterotrimeric G-protein subunits Galpha2, Galpha(q/11), Gbeta2 and Gbeta5 to reside on secretory granules in chromaffin cells of rat adrenal glands. Thus rat chromaffin granules are equipped with functional G-proteins that consist of a specific alpha-, beta- and probably gamma-subunit combination. Serotonin uptake into a crude rat chromaffin granule preparation was inhibited by activated Galphao2 (10 nM) to nearly the same extent as by GMppNp (50 microM) whereas GDPbetaS was ineffective. The data support the idea that vesicular G-proteins directly regulate the transmitter content of secretory vesicles. In this respect Galphao2 appears to be the main regulator of vesicular momoamine transporter activity.
Pahner
Ingrid
I
Institut für Anatomie/Neurowissenschaftliches Zentrum der Charité, Humboldt Universität zu Berlin, Germany.
Höltje
Markus
M
Winter
Sandra
S
Nürnberg
Bernd
B
Ottersen
Ole Petter
OP
Ahnert-Hilger
Gudrun
G
D000313:Adrenal Medulla / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D019439:Chromaffin Cells / Q000378:metabolism* / Q000648:ultrastructure; D002837:Chromaffin Granules / Q000378:metabolism* / Q000648:ultrastructure; D006153:Guanosine Diphosphate / Q000494:pharmacology; D006157:Guanosine Monophosphate / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D008854:Microscopy, Electron; D009479:Neuropeptides; D009638:Norepinephrine / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism*; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D012701:Serotonin / Q000378:metabolism; D050492:Vesicular Biogenic Amine Transport Proteins
D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009479:Neuropeptides; D021122:Protein Subunits; D050492:Vesicular Biogenic Amine Transport Proteins; D006153:Guanosine Diphosphate; D012701:Serotonin; D006157:Guanosine Monophosphate; D006160:Guanosine Triphosphate; D020962:Heterotrimeric GTP-Binding Proteins; D009638:Norepinephrine