title: The protein kinase-C activation domain of the parathyroid hormone.
abstract: The PTH activates both adenylate cyclase and a mechanism that increases membrane-associated protein kinase-C (PKC) activity. To define the hormone's PKC activation domain we have used a panel of PTH fragments and ROS 17/2 rat osteosarcoma cells as the target cells. PTH equally and maximally increased PKC activity in ROS 17/2 cell membranes at physiological concentrations between 1-50 pM and 5-50 nM, but not at intermediate concentrations or concentrations above 50 nM. The PKC-stimulating picomolar concentrations of PTH did not stimulate adenylate cyclase in ROS 17/2 cells, while the PKC-stimulating nanomolar concentrations of the hormone did stimulate adenylate cyclase, with an EC50 of 1-2 nM. Very high concentrations of PTH, such as 100 nM, that did not increase membrane PKC activity were still able to maximally stimulate adenylate cyclase. PTH fragments lacking the N-terminal amino acids needed for adenylate cyclase activation increased membrane PKC activity, and the PKC activation domain was found to lie within the 28-34 region of the PTH molecule. This was confirmed by showing that optimally effective picomolar concentrations of the human PTH-(28-34) fragment itself were able to increase membrane-associated PKC activity to the same extent as the optimally effective picomolar concentrations of the intact PTH-(1-84) or the larger PTH-(1-34) or PTH-(3-34) fragments.
authors.affiliation: Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario.
authors.forename: H
authors.initials: H
authors.lastname: Jouishomme
authors.forename: J F
authors.initials: JF
authors.lastname: Whitfield
authors.forename: B
authors.initials: B
authors.lastname: Chakravarthy
authors.forename: J P
authors.initials: JP
authors.lastname: Durkin
authors.forename: L
authors.initials: L
authors.lastname: Gagnon
authors.forename: R J
authors.initials: RJ
authors.lastname: Isaacs
authors.forename: S
authors.initials: S
authors.lastname: MacLean
authors.forename: W
authors.initials: W
authors.lastname: Neugebauer
authors.forename: G
authors.initials: G
authors.lastname: Willick
authors.forename: R H
authors.initials: RH
authors.lastname: Rixon
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D012516:Osteosarcoma / Q000201:enzymology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000032:analysis
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate