Comparative incorporation of proenkephalin-derived peptides, chromogranin A, and dopamine beta-hydroxylase into chromaffin vesicles.
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.
Wilson
S P
SP
Department of Pharmacology, University of South Carolina School of Medicine, Columbia 29208.
Corcoran
J J
JJ
Kirshner
N
N
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002838:Chromaffin System / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D053379:Chromogranin A; D002864:Chromogranins / Q000378:metabolism*; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism; D004745:Enkephalins / Q000032:analysis / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D011498:Protein Precursors / Q000032:analysis / Q000378:metabolism*; D013462:Sulfur Radioisotopes
D053379:Chromogranin A; D002864:Chromogranins; D004745:Enkephalins; D011498:Protein Precursors; D013462:Sulfur Radioisotopes; C029992:proenkephalin; D004744:Enkephalin, Methionine; D008715:Methionine; D004299:Dopamine beta-Hydroxylase