ISSN:
1432-0878
Keywords:
Chromaffin cell
;
Secretion
;
Synexin
;
Annexins
;
Membrane fusion
;
Ca2+-binding proteins
;
Bovine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Synexin (annexin VII) is a Ca2+- and phospholid-binding protein which has been proposed to play a role in Ca2+-dependent membrane fusion processes. Using a monoclonal antibody against synexin, Mab 10E7, and immunogold, we carried out a semiquantitative localization study of synexin in bovine adrenal medullary chromaffin granules, and in resting and nicotine-stimulated adrenal chromaffin cells. Isolated chromaffin granules contained very little synexin, whereas chromaffin granules aggregated with synexin (24 μg/mg) and Ca2+ (1 mM) clearly showed synexin-associated immunogold particles in the vicinity of the granule membrane (1.88 gold particles per granule profile). In isolated, cultured adrenal chromaffin cells, synexin was present in the nucleus (5.5 particles/μm2) and in the cytosol (5.3 particles/μm2), but mainly around the granule membrane in the granular cell area (11.7 particles/μm2). During the active phase of cholinergically stimulated catecholamine secretion, the amount of synexin label was reduced by 33% in the nucleus, by 23% in the cytosol, and by 51% in the granule area. The plasma membrane contained a small amount of synexin, which did not significantly change upon stimulation of the cells. We conclude that synexin is involved in the secretory process in chromaffin cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00319624
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