Endocytosis of surface bound dopamine ?-hydroxylase and plasma membrane following catecholamine secretion by bovine adrenal chromaffin cells.
Cultured chromaffin cells were stimulated with either Ba(2+) or nicotine to secrete catecholamines. This resulted in the appearance of the chromaffin granule membrane protein, dopamine ?-hydroxylase (DBH), on the cell surface. The DBH exposed on the cell surface was labeled using fluorescently tagged anti-DBH Fab fragments and the cell surface was simultaneously labeled with fluorescently tagged concanavalin A. Immediately after labeling, both fluorescent markers were localized on or near the cell surface; anti-DBH fluorescence was distributed as patches, but Con A fluorescence was uniformly distributed. Approximately 30 min after labeling, anti-DBH fluorescence appeared to be almost completely internalized without apparent redistribution on the surface whereas much of the Con A fluorescence remained on the cell surface. The rate of DBH endocytosis was quantified using (125)I labeled anti-IgG to measure surface bound anti-DBH. Following stimulation of catecholamine secretion, DBH and DBH/anti-DBH complexes both disappeared from the cell surface at similar rates. The half-life on the cell surface was approximately 7 min. These results demonstrate that DBH was rapidly and selectively retrieved from the cell surface, probably from the site of exocytosis.
Lotshaw
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DP
Department of Biological Sciences and Neurobiology Research Center, State University of New York at Albany, Albany, NY 12222, U.S.A.
Ye
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Edwards
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