Protein kinase C activation by 12-O-tetradecanoylphorbol 13-acetate modulates messenger ribonucleic acid levels for two of the regulatory subunits of 3',5'-cyclic adenosine monophosphate-dependent protein kinases (RII beta and RI alpha) via multiple and distinct mechanisms.

Endocrinology ◽  
1992 ◽  
Vol 130 (3) ◽  
pp. 1271-1280
Author(s):  
K A Taskén ◽  
H K Knutsen ◽  
L Eikvar ◽  
K Taskén ◽  
W Eskild ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Kinases ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Regulatory Subunits ◽  
Messenger Ribonucleic Acid ◽  
Kinase C ◽  
Dependent Protein ◽  
Protein Kinase C Activation

Activation of Endogenous Protein Kinase C by Halothane in Synaptosomes

1996 ◽  
Vol 84 (3) ◽  
pp. 652-662 ◽  
Author(s):  
Hugh C. Hemmings ◽  
Anna I. B. Adamo
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Kinases ◽  
Synaptic Membranes ◽  
Dependent Protein Kinase ◽  
Kinase C ◽  
Endogenous Protein ◽  
Dependent Protein ◽  
Protein Kinase C Activation ◽  
Synapsin 1

Background Protein kinase C is a signal transducing enzyme that is an important regulator of multiple physiologic processes and a potential molecular target for general anesthetic actions. However, the results of previous studies of the effects of general anesthetics on protein kinase C activation in vitro have been inconsistent. Methods The effects of halothane on endogenous brain protein kinase C activation were analyzed in isolated rat cerebrocortical nerve terminals (synaptosomes) and in synaptic membranes. Protein kinase C activation was monitored by the phosphorylation of MARCKS, a specific endogenous substrate. Results Halothane stimulated basal Ca2+ dependent phosphorylation of MARCKS (Mr = 83,000) in lysed synaptic membranes (2.1-fold; P< 0.01) and in intact synaptosomes (1.4-fold; P< 0.01). The EC50 for stimulation of MARCKS phosphorylation by halothene in synaptic membranes was 1.8 vol%. A selective peptide protein kinase C inhibitor, but not a protein phosphatase inhibitor (okadaic acid) or a peptide inhibitor of Ca2+/calmodulin-dependent protein kinase II, another Ca2+/-dependent signal transducing enzyme, blocked halothane-stimulated MARCKS phosphorylation in synaptic membranes. Halothane did not affect the phosphorylation of synapsin 1, a synaptic vesicle-associated protein substrate for Ca2+/calmodulin-dependent protein kinase II and AMP-dependent protein kinase, in synaptic membranes or intact synaptosomes subjected to KC1-evoked depolarization. However, halothane stimulated synapsin 1 phosphorylation evoked by ionomycin (a Ca2+ ionophore that permeabilizes membranes to Ca2+) in intact synaptosomes. Conclusions Halothane acutely stimulated basal protein kinase C activity in synaptosomes when assayed with endogenous nerve terminal substrates, lipids, and protein kinase C. This effect appeared to be selective for protein kinases C, because two other structurally similar second messenger-regulated protein kinases were not affected. Direct determinations of anesthetic effects on endogenous protein kinase C activation, translocation, and/or down-regulation are necessary to determine the ultimate effect of anesthetics on the protein kinase C signaling pathway in intact cells.

scholarly journals Prostacyclin inhibits platelet aggregation induced by phorbol ester or Ca2+ ionophore at steps distal to activation of protein kinase C and Ca2+-dependent protein kinases

1989 ◽  
Vol 258 (1) ◽  
pp. 57-65 ◽  
Author(s):  
W Siess ◽  
E G Lapetina
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Protein Kinases ◽  
Shape Change ◽  
Ionophore A23187 ◽  
Maximal Effect ◽  
Kinase C ◽  
Dependent Protein ◽  
High Concentrations

Suspensions of aspirin-treated, 32P-prelabelled, washed platelets containing ADP scavengers in the buffer were activated with either phorbol 12,13-dibutyrate (PdBu) or the Ca2+ ionophore A23187. High concentrations of PdBu (greater than or equal to 50 nM) induced platelet aggregation and the protein kinase C (PKC)-dependent phosphorylation of proteins with molecular masses of 20 (myosin light chain), 38 and 47 kDa. No increase in cytosolic Ca2+ was observed. Preincubation of platelets with prostacyclin (PGI2) stimulated the phosphorylation of a 50 kDa protein [EC50 (concn. giving half-maximal effect) 0.6 ng of PGI2/ml] and completely abolished platelet aggregation [ID50 (concn. giving 50% inhibition) 0.5 ng of PGI2/ml] induced by PdBu, but had no effect on phosphorylation of the 20, 38 and 47 kDa proteins elicited by PdBu. The Ca2+ ionophore A23187 induced shape change, aggregation, mobilization of Ca2+, rapid phosphorylation of the 20 and 47 kDa proteins and the formation of phosphatidic acid. Preincubation of platelets with PGI2 (500 ng/ml) inhibited platelet aggregation, but not shape change, Ca2+ mobilization or the phosphorylation of the 20 and 47 kDa proteins induced by Ca2+ ionophore A23187. The results indicate that PGI2, through activation of cyclic AMP-dependent kinases, inhibits platelet aggregation at steps distal to protein phosphorylation evoked by protein kinase C and Ca2+-dependent protein kinases.

Phorbol esters stimulate somatostatin release from cultured cells

1986 ◽  
Vol 250 (5) ◽  
pp. G686-G690 ◽  
Author(s):  
K. Sugano ◽  
J. Park ◽  
A. Soll ◽  
T. Yamada
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Cultured Cells ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Ionophore A23187 ◽  
Muscarinic Agonists ◽  
Kinase C ◽  
Somatostatin Cells

Recent studies suggest that 12-O-tetradecanoylphorbol 13-acetate (TPA), one of a family of phorbol esters that are known tumor promoters, can activate intracellular Ca2+, phospholipid-dependent protein kinase (protein kinase C) directly. To examine the possible involvement of protein kinase C-mediated mechanisms in regulating gastric somatostatin release, we studied the effects of TPA on isolated enriched canine gastric somatostatin cells in short-term culture. TPA markedly stimulated somatostatin release such that nearly 10% of total cellular content of somatostatin was released into media within 2 h of incubation. Among the phorbol compounds tested, TPA was the most potent, with half-maximum effective dose (ED50) obtained at a dose of 5 X 10(-9) M. Phorbol 12,13-dibutyrate (PDBu) also stimulated somatostatin release but with only 5% of the potency of TPA, whereas phorbol compounds with no biological activity in other systems failed to stimulate somatostatin release. In the absence of extracellular Ca2+, the effects of TPA were significantly attenuated. In contrast, stimulation of somatostatin release by forskolin (10(-4) M) was not affected by Ca2+ deprivation but was potentiated by TPA. No such potentiation was observed when TPA was combined with the Ca2+ ionophore A23187. Carbamylcholine (10(-5) M), which inhibits the stimulatory actions of beta-adrenergic agonists or dibutyryl cyclic adenosine monophosphate on somatostatin cells, also inhibited TPA-induced somatostatin release. These data suggest the presence of dual stimulatory mechanisms for gut somatostatin release, both of which are susceptible to inhibition by muscarinic agonists.

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