Phorbol ester inhibits polyphosphoinositide phosphodiesterase activity stimulated by either Ca2+, fluoride or GTP analogue in HL60 membranes and in permeabilized HL60 cells.
The effect of PMA (phorbol 12-myristate, 13-acetate) on PPI-pde (polyphosphoinositide phosphodiesterase) activity in the promyelocytic cell-line HL60 was examined. HL60 cells were pretreated with PMA in a time- and concentration-dependent manner and PPI-pde activity was monitored both in streptolysin O-permeabilized cells and in membranes. PPI-pde activity was stimulated by either GTP gamma S (guanosine 5'-[gamma-thio]triphosphate), fluoride or Ca2+. Both the Ca2(+)-stimulated and the G protein-mediated PPI-pde activity in permeabilized HL60 cells is maximally inhibited (70-90%) after 60 min pretreatment of intact cells with 10nM PMA. PPI-pde activity can also be observed in membranes prepared from HL60 cells although this activity represents only 10% of the total activity seen in permeabilized cells. In membranes, where PPI-pde activity can also be stimulated by either via the G-protein or directly by Ca2+, PMA pretreatment was also inhibitory regardless of the mode of activation. We suggest that both the membrane-bound PPI-pde activity and that present in the permeabilized cells are targets for protein phosphorylation by protein kinase C leading to inhibition of the catalytic function.
Geny
B
B
INSERM, Unité 204, Centre Hayem, Hospital Saint Louis, Paris France.
Stutchfield
J
J
Cockcroft
S
S
D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D002463:Cell Membrane Permeability; D005459:Fluorides / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013873:Thionucleotides / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D011493:Protein Kinase C; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate; D005459:Fluorides; D002118:Calcium