The protein kinase-C activation domain of the parathyroid hormone.
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.
Jouishomme
H
H
Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario.
Whitfield
J F
JF
Chakravarthy
B
B
Durkin
J P
JP
Gagnon
L
L
Isaacs
R J
RJ
MacLean
S
S
Neugebauer
W
W
Willick
G
G
Rixon
R H
RH
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
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate