Trypsin stimulation of aldosterone and 18-hydroxycorticosterone production by rat adrenal zona glomerulosa tissue is mediated by activation of protein kinase C

1990 ◽  
Vol 5 (1) ◽  
pp. 85-93 ◽  
Author(s):  
G. P. Vinson ◽  
S. M. Laird ◽  
J. P. Hinson ◽  
N. Mallick ◽  
S. Marsigliante ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Polymyxin B ◽  
Zona Glomerulosa ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Tissue Sensitivity ◽  
Protein Components

ABSTRACT When rat adrenal whole capsules, containing the zona glomerulosa, were incubated, addition of the protein kinase C inhibitors TMB-8 (10 μmol/l), W7, H7, polymyxin-B and sphingosine (all 1 μmol/l) was found to inhibit the steroidogenic response to trypsin. Aldosterone and 18-hydroxycorticosterone were strongly, and corticosterone moderately, affected, while the production of 18-hydroxydeoxycorticosterone was neither stimulated by trypsin nor inhibited by the protein kinase C inhibitors. Addition of neomycin, which prevents substrate interaction with phospholipase C, also inhibited the response to trypsin, while addition of phospholipase C itself stimulated aldosterone, 18-hydroxycorticosterone and corticosterone production with the same tissue sensitivity as trypsin. Addition of phospholipase A2 had no effect. Direct assay of protein kinase C activity showed that trypsin stimulation effected the translocation of Ca2+/phospholipid-activated protein kinase C from the cytosolic to the membrane fraction. When glomerulosa tissue was incubated with [32P]ATP, and cytosolic proteins were subjected to isoelectric focusing on polyacrylimide gels, autoradiography showed that incorporation of 32P into several protein components was increased by trypsin stimulation. It was concluded that trypsin exerts its stimulatory effects on steroidogenesis by activating protein kinase C; not, however, by generating the Ca2+/phospholipid-independent fragment, but possibly by enhancing the activity of phospholipase C.

Protein kinase C and progesterone-induced maturation in Xenopus oocytes

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 597-604
Author(s):  
R.L. Varnold ◽  
L.D. Smith
Keyword(s):  
Cell Cycle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Xenopus Oocytes ◽  
Plasma Membranes ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Concomitant Reduction ◽  
Dependent Protein

Though progesterone-induced maturation has been studied extensively in Xenopus oocytes, the mechanism whereby the prophase block arrest is released is not well understood. The current hypothesis suggests that a reduction in cAMP and subsequent inactivation of cAMP-dependent protein kinase is responsible for reentry into the cell cycle. However, several lines of evidence indicate that maturation can be induced without a concomitant reduction in cAMP. We show that the mass of diacylglycerol in whole oocytes and plasma membranes decreases 29% and 10% respectively, within the first 15 sec after the addition of progesterone. Diacylglycerol in plasma membranes further decreased 59% by 5 min. We also show that the protein kinase C inhibitors sphingosine and staurosporine can induce oocyte maturation. In addition, the synthetic diglyceride, DiC8, and microinjected PKC can inhibit or delay progesterone-induced maturation. These results together suggest that a transient decrease in protein kinase C activity may regulate entry into the cell cycle. The mechanism whereby DAG is decreased in response to progesterone is unclear. Initial studies show that progesterone leads to a decrease in IP3 suggesting that progesterone may act by reducing the hydrolysis of PIP2. On the other hand, progesterone caused a decrease in the amount of [3H]arachidonate labelling in DAG during the same time suggesting that progesterone may stimulate lipase activity. The relationship between postulated changes in the PKC pathway and those hypothesized for the PKA pathway are discussed.

Decreased protein kinase C activity is associated with programmed cell death (apoptosis) in freshly isolated rat hepatocytes

1992 ◽  
Vol 12 (3) ◽  
pp. 199-206 ◽  
Author(s):  
Victor Sanchez ◽  
Miguel Lucas ◽  
Aureo Sanz ◽  
Raimundo Goberna
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Time Course ◽  
Rat Hepatocytes ◽  
Polymyxin B ◽  
Isolated Rat Hepatocytes ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Freshly Isolated Rat Hepatocytes ◽  
Isolated Rat

Apoptosis of freshly isolated rat hepatocytes was induced by either the omission of fetal bovine serum in the culture medium or addition of the protein kinase C inhibitors polymyxin B or staurosporin. The time-course of DNA breakdown into oligonucleosome-sized fragments and the activity of protein kinase C was determined. Hepatocytes were found to be sensitive to bleomycin which induced a high degree of DNA breakdown even within 30 min incubation. Both staurosporin and polymyxin B induced DNA degradation in hepatocytes after three hours incubation, an effect that was partially prevented by phorbol myristate acetate (PMA). After eight hours incubation, PMA failed to counteract this action and itself produced the apoptosis of rat hepatocytes. The results suggest the involvement of protein kinase C in hepatocyte survival.

Human interleukin 1β stimulates islet insulin release by a mechanism not dependent on changes in phospholipase C and protein kinase C activities or Ca2+ handling

1989 ◽  
Vol 121 (5) ◽  
pp. 698-704 ◽  
Author(s):  
Nils Welsh ◽  
Thomas Nilsson ◽  
Anders Hallberg ◽  
Per Arkhammar ◽  
Per-Olof Berggren ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Phosphorylation ◽  
Phospholipase C ◽  
Insulin Release ◽  
Interleukin 1Β ◽  
High Concentration ◽  
Adult Rats ◽  
Kinase C ◽  
Protein Kinase C Activity

Abstract. Isolated islets from adult rats or obese hyperglycemic (ob/ob) mice were incubated with human recombinant interleukin 1β in order to study whether the acute effects of the cytokine on islet insulin release are associated with changes in islet phospholipase C activity, Ca2+ handling or protein phosphorylation. The cytokine stimulated insulin release both at low and high glucose concentrations during one hour incubations. In shortterm incubations (<1 min) interleukin 1β did not affect the production of inositoltrisphosphate. Addition of interleukin 1β affected neither the cytoplasmic free Ca2+ concentration at rest nor that observed subsequent to stimulation with a high concentration of glucose. Furthermore, the endogenous protein kinase C activity, as visualized by immunoprecipitation of a 32P-labelled substrate for this enzyme, was not altered by interleukin 1β. Separation of 32P-labelled proteins by means of 2-dimensional gel electrophoresis failed to reveal any specific effects of the cytokine on the total protein phosphorylation activity. These results suggest that the stimulatory effects on insulin release exerted by interleukin 1β are not caused by acute activation of phospholipase C and protein kinase C or by an alteration of islet Ca2+ handling of the B-cells.

scholarly journals Lycopene depresses glutamate release through inhibition of voltage-dependent Ca2+ entry and protein kinase C in rat cerebrocortical nerve terminals

2018 ◽  
Vol 96 (5) ◽  
pp. 479-484 ◽  
Author(s):  
Cheng-Wei Lu ◽  
Chi-Feng Hung ◽  
Wei-Horng Jean ◽  
Tzu-Yu Lin ◽  
Shu-Kuei Huang ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Glutamate Release ◽  
Inhibitory Effect ◽  
Nerve Terminals ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Voltage Dependent ◽  
Intracellular Ca

Lycopene is a natural dietary carotenoid that was reported to exhibit a neuroprotective profile. Considering that excitotoxicity and cell death induced by glutamate are involved in many brain disorders, the effect of lycopene on glutamate release in rat cerebrocortical nerve terminals and the possible mechanism involved in such effect was investigated. We observed here that lycopene inhibited 4-aminopyridine (4-AP)-evoked glutamate release and intrasynaptosomal Ca2+ concentration elevation. The inhibitory effect of lycopene on 4-AP-evoked glutamate release was markedly reduced in the presence of the Cav2.2 (N-type) and Cav2.1 (P/Q-type) channel blocker ω-conotoxin MVIIC, but was insensitive to the intracellular Ca2+-release inhibitors dantrolene and CGP37157. Furthermore, in the presence of the protein kinase C inhibitors GF109203X and Go6976, the action of lycopene on evoked glutamate release was prevented. These results are the first to suggest that lycopene inhibits glutamate release from rat cortical synaptosomes by suppressing presynaptic Ca2+ entry and protein kinase C activity.

scholarly journals The effect of protein kinase C activation on muscarinic-M3- and K+-evoked release of [3H]noradrenaline and increases in intracellular Ca2+ in human neuroblastoma SH-SY5Y cells

1992 ◽  
Vol 282 (3) ◽  
pp. 645-650 ◽  
Author(s):  
N P Murphy ◽  
J G McCormack ◽  
S G Ball ◽  
P F T Vaughan
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Polymyxin B ◽  
Muscarinic Agonist ◽  
Muscarinic Agonists ◽  
Human Neuroblastoma ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
M3 Muscarinic Receptor

Short-term pretreatment (9 min) with the phorbol ester 12-myristate 13-acetate (PMA) alone had no effect on the basal release of [3H]noradrenaline ([3H]NA), but enhanced K+ (100 mM)-, acetylcholine (0.1 mM)-, carbachol (1 mM)-, muscarine (1 mM)- and arecoline (1 mM)-evoked release by 2.3-, 6.4-, 3.0-, 2.0- and 2.0-fold respectively in SH-SY5Y cells. Maximum effects of PMA were observed after a 10 min preincubation at a concentration of 0.1 microM. There was a 4-fold decrease in the EC50 values (concentration required for 50% of maximal stimulation) observed for carbachol- and acetylcholine-evoked release of [3H]NA in the presence of PMA. The inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate did not alter the K(+)- or carbachol-evoked release of [3H]NA. The enhancement of release in the presence of PMA was more potently inhibited by the protein kinase C inhibitors RO 31-7549 [concentration required for 50% inhibition (IC50) = 0.18 microM/bd and RO 31-8220 (IC50 = 0.56 microM) than by either polymyxin-B or H-7. Furthermore, in the absence of PMA, both K(+)- and carbachol-evoked release was inhibited by these antagonists. Atropine, hexahydro-sila-difenidol and pirenzepine antagonized the PMA-enhanced carbachol-evoked release of [3H]NA, with Ki values of 2.75 +/- 0.25 nM, 2.6 +/- 0.64 nM and 294 +/- 17 nM respectively. These values were consistent with the coupling of an M3 muscarinic receptor to the release of [3H]NA in SH-SY5Y cells. Whereas pretreatment with PMA (5 min) enhanced M3-evoked release of [3H]NA, it decreased the muscarinic-agonist-evoked initial peak (greater than 85%) and plateau phase in intracellular Ca2+. These results suggest that noradrenaline release evoked by muscarinic agonists was triggered not only by relatively small changes in Ca2+ but also by activation of protein kinase C.

scholarly journals Sphingosine enhances platelet aggregation through an increase in phospholipase C activity by a protein kinase C-independent mechanism

1992 ◽  
Vol 282 (1) ◽  
pp. 243-247 ◽  
Author(s):  
T Hashizume ◽  
T Sato ◽  
T Fujii
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Platelet Activating Factor ◽  
Membrane Phospholipids ◽  
Stimulus Response ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Low Concentrations ◽  
Positive Modulator

Sphingosine (a potent inhibitor of protein kinase C) at 5-10 microM, which are concentrations lower than those that inhibit this enzyme activity, enhanced the aggregation of rabbit platelets induced by low concentrations of U46619, platelet-activating factor, thrombin and arachidonic acid, whereas H-7 and staurosporine, other protein kinase C inhibitors, failed to do so. Of the sphingosine analogues which also inhibit protein kinase C, psychosine and lyso-GM3 did not show such an enhancing effect. Sphingosine promoted both Ins(1,4,5)P3 formation and an increase in the cytoplasmic free Ca2+ concentration in response to all the agonists used. Furthermore, the hydrolytic action of exogenously added phospholipase C (from Clostridium perfringens) on platelet membrane phospholipids was dose-dependently enhanced by pretreatment of the platelets with sphingosine. These results imply that sphingosine, at relatively low concentrations, brings about hyperaggregability of the platelets by the agonists employed, probably owing to enhancement of the phospholipase C activity. Such an effect appears to be induced by a mechanism independent of protein kinase C inhibition. We suggest that sphingosine might act as a positive modulator for the stimulus-response coupling in the platelets.

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