Calcium-stimulated parathyroid hormone-like protein secretion: potentiation through a protein kinase-C pathway.
The effect of altering intracellular calcium levels on PTH-like protein (PLP) secretion was assessed in the NCI-H727 cell line. Ionomycin stimulated PLP secretion in a dose- and time-dependent manner, with a maximum rate of secretion occurring within minutes. Phorbol esters (phorbol 12-myristate 13-acetate and phorbol 12,13-didecanoate) stimulated PLP secretion at 10(-7)-10(-5) M, whereas forskolin treatment had no effect. When cells were treated initially with phorbol esters, ionomycin-stimulated PLP secretion was potentiated. The kinetics of this effect were rapid (t1/2, less than 1 min), and pretreatment with cycloheximide or actinomycin-D before phorbol ester and ionomycin treatment did not alter PLP secretion. Pretreatment for 24 h with phorbol 12-myristate 13-acetate to desensitize the cells or use of inactive phorbol ester isomer 4 alpha-phorbol 12,13-didecanoate did not potentiate the ionomycin-stimulated PLP secretion. Treatment with exogenously added phospholipase-C caused a dose-dependent increase in PLP secretion. These data indicate that PLP secretion can be stimulated through a phospholipase-C-mediated mechanism.
Brandt
D W
DW
Department of Medicine, University of California-San Diego.
Pandol
S J
SJ
Deftos
L J
LJ
D002118:Calcium / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D003609:Dactinomycin; D015759:Ionomycin; D003513:Cycloheximide; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium