Subcellular fractionation studies on the post-translational processing of pro-adrenocorticotropic hormone/endorphin in rat intermediate pituitary.
The subcellular localization of the post-translational processing steps which occur in the conversion of pro-adrenocorticotropic hormone (ACTH)/endorphin into beta-endorphin-sized molecules in rat intermediate pituitary has been studied. Primary cell cultures were incubated in radioactively labeled amino acids, and a subcellular fraction containing secretory granules was separated from a subcellular fraction containing rough endoplasmic reticulum and Golgi apparatus by centrifugation of homogenates on gradients on Percoll (Pharmacia Fine Chemicals). The radiolabeled beta-endorphin-related material in the granule and rough endoplasmic reticulum/Golgi apparatus fractions was quantitated by immunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis. A pulse-chase labeling experiment demonstrated that newly synthesized beta-endorphin-related material first appeared in the rough endoplasmic reticulum/Golgi apparatus fraction and after longer incubations (chase) appeared in the secretory granule fraction. After 2 h of chase incubation, about 85% of the beta-endorphin-related material synthesized during the 30-min pulse incubation had been transferred from the rough endoplasmic reticulum/Golgi apparatus to the secretory granule fraction. The conversion of most of the newly synthesized pro-ACTH/endorphin into beta-lipotropin occurred in the rough endoplasmic reticulum/Golgi apparatus fraction, whereas the conversion of most of the beta-lipotropin into beta-endorphin-sized molecules occurred in the secretory granule fraction.
D000324:Adrenocorticotropic Hormone / Q000096:biosynthesis* / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004723:Endorphins / Q000096:biosynthesis* / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism*; D011333:Pro-Opiomelanocortin; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D013462:Sulfur Radioisotopes
D004723:Endorphins; D011498:Protein Precursors; D013462:Sulfur Radioisotopes; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone