PMA and staurosporine affect expression of the PCK gene in LLC-PK1-F+ cells.
The addition of phorbol 12-myristate 13-acetate (PMA) to renal LLC-PK1-F+ cells caused a rapid decrease in the level of phosphoenolpyruvate carboxykinase (PCK) mRNA and reversed the stimulatory effects of exposure to acidic medium (pH 6.9, 10 mM HCO-3) or cAMP. In contrast, prolonged treatment with PMA increased the levels of PCK mRNA. The two effects correlated with the membrane translocation and downregulation of the alpha-isozyme of protein kinase C and were blocked by pretreatment with specific inhibitors of protein kinase C. The rapid decrease in PCK mRNA caused by PMA occurred with a half-life (t1/2 = 1 h) that is significantly faster than that measured during recovery from acid medium or following inhibition of transcription (t1/2 = 4 h). The effect of PMA was reversed by staurosporine, which apparently acts by inhibiting a signaling pathway other than protein kinase C. Staurosporine had no effect on the half-life of the PCK mRNA, but it stimulated the activity of a chloramphenicol acetyltransferase gene that was driven by the initial 490 base pairs of the PCK promoter and transiently transfected into LLC-PK1-F+ cells. This effect was additive to that of cAMP, and neither stimulation was reversed by PMA. The stimulatory effect of staurosporine was mapped to the cAMP response element (CRE-1) and P3(II) element of the PCK promoter. The data indicate that, in LLC-PK1-F+ cells, activation of protein kinase C decreases the stability of the PCK mRNA, whereas transcription of the PCK gene may be suppressed by a kinase that is inhibited by staurosporine.
Liu
W
W
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
Feifel
E
E
Holcomb
T
T
Liu
X
X
Spitaler
N
N
Gstraunthaler
G
G
Curthoys
N P
NP
D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D000242:Cyclic AMP / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells; D015870:Gene Expression / Q000187:drug effects*; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D018374:LLC-PK1 Cells; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000037:antagonists & inhibitors / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology*; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D000242:Cyclic AMP; D015500:Chloramphenicol O-Acetyltransferase; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate