Comparative Incorporation of Proenkephalin-Derived Peptides, Chromogranin A, and Dopamine β-Hydroxylase into Chromaffin Vesicles |
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Authors: | Steven P. Wilson James J. Corcoran Norman Kirshner |
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Affiliation: | Department of Pharmacology, University of South Carolina School of Medicine, Columbia 29208. |
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Abstract: | The incorporation of enkephalin-containing peptides (ECPs) derived from proenkephalin into chromaffin vesicles was examined in primary cultures of adrenal medullary chromaffin cells. Cells were pulse-labeled with [35S]methionine and chased for periods up to 24 h. Chromaffin vesicles in cell homogenates were then fractionated by density gradient centrifugation and the presence of [35S]Met-enkephalin sequences in gradient fractions determined. 35S-ECPs were incorporated into particles suggestive of immature vesicles within 1-2 h after radiolabeling. Vesicle maturation, measured by co-equilibration of 35S-ECPs and total ECPs in the gradients, was complete within 9-12 h and was unaffected by treatments that increase proenkephalin synthesis. Incorporation of [35S]chromogranin A into chromaffin vesicles followed a similar time course, but 35S-labeled dopamine beta-hydroxylase was much more slowly incorporated, possibly reflecting differences in incorporation of membrane and soluble components. In summary, the data demonstrate that ECPs are rapidly sequestered in immature chromaffin vesicles, a process unaltered by changing rates of proenkephalin synthesis. |
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Keywords: | Enkephalin Proenkephalin A Chromaffin cells Adrenal medulla Chromogranin Dopamine β-hydroxylase |
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