PTH elevates inositol polyphosphates and diacylglycerol in a rat osteoblast-like cell line.
Parathyroid hormone (PTH)-stimulated signal transduction through mechanisms alternate to adenosine 3',5'-cyclic monophosphate (cAMP) production were studied in UMR 106-01 cells, a cell line with an osteoblastic phenotype. PTH produced transient, dose-related increases in cytosolic calcium [( Ca2+]i), inositol trisphosphates, and diacylglycerol (DAG). Both inositol 1,4,5-trisphosphate (Ins-1,4,5P3) and inositol 1,3,4-trisphosphate (Ins-1,3,4P3) production were rapidly stimulated by PTH. Consistent with the production of Ins-1,3,4P3, rapid stimulation of late eluting inositol tetrakisphosphate was observed. The effects on the inositol phosphates were induced rapidly, consistent with roles as signals for changes in [Ca2+]i. In saponin-permeabilized UMR 106-01 cells, Ins-1,4,5P3 stimulated 45Ca release from a nonmitochondrial intracellular pool. Thus the hypothesis that PTH-stimulated Ins-1,4,5P3 production initiates Ca2+ release and contributes to transient elevations of [Ca2+]i is supported. Pretreatment of UMR 106-01 cells with pertussis toxin had no effect on PTH stimulation of inositol phosphates. Pertussis toxin reduced PTH-stimulated elevations of [Ca2+]i, but cAMP analogues had an even greater effect than pertussis toxin. These data suggest that stimulation of cAMP production during PTH stimulation may negatively affect production of rises in [Ca2+]i during PTH stimulation. The inactivation of the inhibitory G protein of adenylate cyclase by pertussis toxin could explain its action similar to cAMP analogues. Cyclic nucleotides diminish the effects of PTH on [Ca2+]i, probably interacting on a biochemical step subsequent to or independent of Ins-1,4,5P3 release.
Civitelli
R
R
Department of Medicine, Jewish Hospital of St. Louis, Missouri 63110.
Reid
I R
IR
Westbrook
S
S
Avioli
L V
LV
Hruska
K A
KA
D037361:Adenylate Cyclase Toxin; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism*; D005989:Glycerides / Q000378:metabolism*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D037342:Pertussis Toxin; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013268:Stimulation, Chemical; D013403:Sugar Phosphates / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D004075:Diglycerides; D005989:Glycerides; D007295:Inositol Phosphates; D010281:Parathyroid Hormone; D013403:Sugar Phosphates; D010566:Virulence Factors, Bordetella; D015544:Inositol 1,4,5-Trisphosphate; D037342:Pertussis Toxin; D002118:Calcium