scholarly journals The phosphorylation of protein kinase C as a potential measure of activation

1989 ◽  
Vol 261 (1) ◽  
pp. 131-136 ◽  
Author(s):  
F E Mitchell ◽  
R M Marais ◽  
P J Parker
Keyword(s):  
Protein Kinase C ◽  
Growth Factor ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Phosphorylation State ◽  
Kinase C ◽  
Epidermal Growth ◽  
Potential Measure ◽  
Protein Kinase C Activation

As a means of determining the role of protein kinase C in the signal transduction from novel growth factors and hormones, we investigated the effects of well-characterized agents on the phosphorylation state of protein kinase C itself. These studies show that agents that stimulate protein kinase C either directly (phorbol esters) or indirectly through phosphatidylinositol breakdown (platelet-derived growth factor) induce an increase in the phosphorylation state of the kinase. By contrast, epidermal growth factor, which does not stimulate protein kinase C in fibroblasts, does not increase the phosphorylation state of protein kinase C, but leads to a decrease. The data suggest that the phosphorylation state of protein kinase C is dynamically controlled and can be used to provide evidence of protein kinase C activation.

Serum and growth factor induction of Na(+)-K(+)-ATPase subunit mRNAs in Clone 9 cells: role of protein kinase C

1991 ◽  
Vol 261 (4) ◽  
pp. C699-C707 ◽  
Author(s):  
A. Bhutada ◽  
F. Ismail-Beigi
Keyword(s):  
Protein Kinase C ◽  
Growth Factor ◽  
Protein Kinase ◽  
Calf Serum ◽  
Atpase Subunit ◽  
Subunit Mrna ◽  
Kinase C ◽  
Epidermal Growth ◽  
Dissociation Constant Kd

In a previous study, we found that addition of serum to confluent Clone 9 cells, a nontransformed rat liver cell line, increased the abundance of mRNA alpha 1 and mRNA beta 1 at 3 h by 2- and 2.7-fold, respectively [Bhutada et al. Am. J. Physiol. 258 (Cell Physiol. 27): C1044-C1050, 1990]. We now report that exposure of these cells to 160 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) for 6 h increases mRNA alpha 1 and mRNA beta 1 by 1.7 +/- 0.2- and 2.1 +/- 0.3-fold, respectively. Incubation in the presence of 160 nM TPA for 24 h reduced high-affinity phorbol dibutyrate-binding sites [dissociation constant (Kd) = 5 nM; maximum binding (Bmax) = 1.2 pmol/mg protein] to undetectable levels. In such cells, exposure to 10% serum for 6 h still resulted in two- and fourfold increment in mRNA alpha 1 and mRNA beta 1 abundances, respectively, while further addition of TPA to these protein kinase C (PKC)-depleted cells resulted in no change in the subunit mRNA abundances. The increments in mRNA alpha 1 content in response to 10% serum and 160 nM TPA at 6 h were additive, whereas the increments in mRNA beta 1 were not. The following agents increased mRNA alpha 1 and mRNA beta 1 abundance in both control and PKC-depleted cells: epidermal growth factor, platelet-derived growth factor, basic fibroblast growth factor, insulin, dexamethasone, and hypothyroid calf serum. In contrast, N6,2'-O-dibutyryl-adenosine 3',5'-cyclic monophosphate and aldosterone had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

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