title: Phosphorylation of the ribosomal protein S6 during agonist-induced exocytosis in exocrine glands is catalyzed by calcium-phospholipid-dependent protein kinase (protein kinase C). Experiments with guinea pig parotid glands.
abstract: The ribosomal protein S6 in exocrine cells is phosphorylated during stimulation of exocytosis by cAMP-dependent or calcium-dependent agonists. Under both conditions the same tryptic S6 phosphopeptides (termed A, B, and C) were found [Padel, Kruppa, Jahn & Söling (1983) FEBS Lett. 159, 112-118]. Studies have now been made of the phosphorylation pattern of protein S6 from purified guinea pig parotid ribosomes following in vitro phosphorylation with calmodulin-dependent, phospholipid-dependent, and cAMP-dependent protein kinases. Only the phospholipid-dependent enzyme led to the phosphorylation of peptides A, B, and C, while the cAMP-dependent enzyme phosphorylated only peptides A and C, and the calmodulin-dependent enzyme did not phosphorylate any of the phosphopeptides found in S6 from unstimulated or stimulated intact cells. Guinea pig parotid microsomes contain substantial phospholipid-dependent protein kinase activity. Stimulation of intact parotid glands with tetradecanoylphorbol acetate led to a significant phosphorylation of S6 and a similar tryptic S6 phosphopeptide pattern as seen with carbamoylcholine. It is concluded that activation of phospholipid-dependent protein kinase is responsible for the phosphorylation of protein S6 during stimulation with calcium-dependent and cAMP-dependent secretagogues.
authors.forename: U
authors.initials: U
authors.lastname: Padel
authors.forename: H D
authors.initials: HD
authors.lastname: Söling
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002384:Catalysis; D000242:Cyclic AMP / Q000502:physiology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000201:enzymology; D010306:Parotid Gland / Q000201:enzymology / Q000378:metabolism*; D010743:Phospholipids / Q000502:physiology; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism*; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins / Q000378:metabolism*
chemical_list: D010743:Phospholipids; D010748:Phosphopeptides; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D002118:Calcium