Pathways of dephosphorylation of 1-D-myo-inositol 1,4,5-trisphosphate in GH3 pituitary tumor cells.
Previous work in [3H]inositol-labelled GH3 pituitary tumor cells stimulated with thyrotropin-releasing hormone (TRH) reported the existence of at least ten distinct [3H]inositol-containing substances which were identified as different inositol mono-, bis- and tris-phosphate isomers [1]. Here a complete kinetic study of the dephosphorylation pathways of the second messenger Ins(1,4,5)P3 is reported in GH3 cell homogenates, identifying a new intermediate, Ins(4,5)P2, in the metabolism of the second messenger. in vitro results obtained with exogenous substrates are compared with in vivo results obtained measuring levels of the endogenous [3H]inositol-labelled isomers that participate in the dephosphorylation pathways of Ins(1,4,5)P3 in resting and TRH-stimulated GH3 cells. The effect of Li+ on the activity of the different phosphatases involved in these pathways is studied as well.
Ruiz-Larrea
F
F
National Centre of Biotechnology, Cantoblanco, Madrid, Spain.
Drummond
A H
AH
D000818:Animals; D002460:Cell Line; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D000072181:Inositol Polyphosphate 5-Phosphatases; D007700:Kinetics; D008094:Lithium / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D010911:Pituitary Neoplasms / Q000378:metabolism; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000378:metabolism
D007295:Inositol Phosphates; D014316:Tritium; D013973:Thyrotropin-Releasing Hormone; D015544:Inositol 1,4,5-Trisphosphate; C066454:inositol 4,5-bisphosphate; D008094:Lithium; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D000072181:Inositol Polyphosphate 5-Phosphatases; C053087:inositol-1,4-bisphosphate 1-phosphatase