scholarly journals Platelet protein phosphorylation and protein kinase C activation by phorbol esters with different biological activity and a novel synergistic response with Ca2+ ionophore

1990 ◽  
Vol 188 (2) ◽  
pp. 431-437 ◽  
Author(s):  
Susan F. BROOKS ◽  
Philip C. GORDGE ◽  
Alex TOKER ◽  
A. Tudor EVANS ◽  
Fred J. EVANS ◽  
...  
Keyword(s):  
Biological Activity ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Phosphorylation ◽  
Phorbol Esters ◽  
Platelet Protein ◽  
Kinase C ◽  
Synergistic Response ◽  
Protein Kinase C Activation

Phorbol esters augment spermidine transport without protein kinase C activation

1990 ◽  
Vol 40 (8) ◽  
pp. R1-R4 ◽  
Author(s):  
Naim A. Khan ◽  
V. Quemener ◽  
J.-Ph. Moulinoux
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Kinase C ◽  
Protein Kinase C Activation

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.

scholarly journals Protein kinase C activators selectively inhibit insulin-stimulated system A transport activity in skeletal muscle at a post-receptor level

1990 ◽  
Vol 268 (3) ◽  
pp. 633-639 ◽  
Author(s):  
A Gumà ◽  
M Camps ◽  
M Palacín ◽  
X Testar ◽  
A Zorzano
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Insulin Receptor ◽  
Insulin Action ◽  
Phorbol Esters ◽  
Polymyxin B ◽  
Transport Activity ◽  
System A ◽  
Kinase C ◽  
Protein Kinase C Activation

We have investigated the role of phorbol esters on different biological effects induced by insulin in muscle, such as activation of system A transport activity, glucose utilization and insulin receptor function. System A transport activity was measured by monitoring the uptake of the system A-specific analogue alpha-(methyl)aminoisobutyric acid (MeAIB), by intact rat extensor digitorum longus muscle. The addition of 12-O-tetradecanoylphorbol 13-acetate (TPA, 0.5 microM) for 60 or 180 min did not modify basal MeAIB uptake by muscle, suggesting that insulin signalling required to stimulate MeAIB transport does not involve protein kinase C activation. However, TPA added 30 min before insulin (100 nM) markedly inhibited insulin-stimulated MeAIB uptake. The addition of polymyxin B (0.1 mM) or H-7 (1 mM), protein kinase C inhibitors, alone or in combination with TPA leads to impairment of insulin-stimulated MeAIB uptake. This paradoxical pattern is incompatible with a unique action of Polymyxin B or H-7 on protein kinase C activity. Therefore these agents are not suitable tools with which to investigate whether a certain insulin effect is mediated by protein kinase C. TPA did not cause a generalized inhibition of insulin action. Thus both TPA and insulin increased 3-O-methylglucose uptake by muscle, and their effects were not additive. Furthermore, TPA did not modify insulin-stimulated lactate production by muscle. In keeping with this selective modification of insulin action, treatment of muscles with TPA did not modify insulin receptor binding or kinase activities. In conclusion, phorbol esters do not mimic insulin action on system A transport activity; however, they markedly inhibit insulin-stimulated amino acid transport, with no modification of insulin receptor function in rat skeletal muscle. It is suggested that protein kinase C activation causes a selective post-receptor modification on the biochemical pathway by which insulin activates system A amino acid transport in muscle.

scholarly journals Phorbol ester stimulation of insulin release and secretory-granule protein phosphorylation in a transplantable rat insulinoma

1984 ◽  
Vol 224 (2) ◽  
pp. 483-490 ◽  
Author(s):  
J C Hutton ◽  
M Peshavaria ◽  
K W Brocklehurst
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Phosphorylation ◽  
Insulin Release ◽  
Secretory Granule ◽  
Phorbol Esters ◽  
Coupling Mechanism ◽  
Granule Protein ◽  
Kinase C ◽  
Rat Insulinoma

The effects of tumour-promoting phorbol esters on protein-phosphorylation reactions and secretion in rat insulinoma tissue were investigated with the objective of assessing the possible role of Ca2+- and phospholipid-dependent protein kinases (protein kinase C) in insulin release. 4 beta-Phorbol 12-myristate 13-acetate (TPA) was a potent secretagogue at concentrations above 0.1 microM. TPA-induced release was inhibited by adrenaline or omission of Ca2+ from the extracellular medium and was augmented by theophylline. These findings suggested that TPA activated an exocytotic process. TPA enhanced the Ca2+- and phospholipid-dependent phosphorylation of histone III-S by a soluble protein fraction of the tissue. Endogenous phosphorylation reactions involving soluble and secretory-granule membrane proteins were also stimulated by TPA in tissue homogenates and reconstituted subcellular fractions. Histone phosphorylation and the granule-protein phosphorylation reactions showed similar concentration-dependencies for activation by both Ca2+ and TPA, thus indicating that the same enzyme was involved. It is concluded that the phosphorylation of cytosolic and membrane protein substrates by protein kinase C may be important in the stimulus-secretion coupling mechanism of insulin release.

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