Evidence for the involvement of Rab3A in Ca(2+)-dependent exocytosis from adrenal chromaffin cells.
J Biol Chem
; 269(14): 10229-34, 1994 Apr 08.
Article
in En
| MEDLINE
| ID: mdl-8144603
ABSTRACT
Bovine chromaffin cells are nondividing primary secretory cells that store and secrete catecholamine and a variety of proteins including chromogranins, opiate peptides, and opiate precursors. A transient transfection technique based upon the expression of human growth hormone as a reporter for the regulated secretory pathway was used to study the role of a Ras-like, GTP-binding protein, Rab3a, in Ca(2+)-dependent exocytosis. Immunocytochemistry and flow cytometry revealed that growth hormone and Rab proteins were coexpressed in the same cells. Overexpression of the wild type protein and expression of a mutant protein Rab3aQ81L both inhibited nicotinic agonist-stimulated exocytosis in intact cells. Expression of Rab3aQ81L also inhibited Ca(2+)-dependent secretion from permeabilized cells. Two other mutants, Rab3aN135I and Rab3aT36N, which correspond to dominant acting mutants of Ras, caused limited and no inhibition, respectively, of agonist-stimulated exocytosis. These data provide direct evidence that Rab3a plays an important role in Ca(2+)-triggered exocytosis. We suggest that Rab3a is an inhibitor of secretion, perhaps as part of a pre-fusion complex with secretory vesicles. Elevated Ca2+ may trigger exocytosis by overcoming the inhibition by Rab3a.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Calcium
/
Adrenal Glands
/
GTP-Binding Proteins
/
Exocytosis
Limits:
Animals
/
Humans
Language:
En
Journal:
J Biol Chem
Year:
1994
Document type:
Article