Regulation of oxytocin secretion by the ovine corpus luteum: effect of activators of protein kinase C

1990 ◽  
Vol 124 (2) ◽  
pp. 225-232 ◽  
Author(s):  
J. J. Hirst ◽  
G. E. Rice ◽  
G. Jenkin ◽  
G. D. Thorburn
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Corpus Luteum ◽  
Phospholipase C ◽  
Tissue Slices ◽  
Kinase C ◽  
Luteal Tissue ◽  
Dose Dependent ◽  
Stimulation Of

ABSTRACT The effect of protein kinase C activation and dibutyryl cyclic AMP on oxytocin secretion by ovine luteal tissue slices was investigated. Several putative regulators of luteal oxytocin secretion were also examined. Oxytocin was secreted by luteal tissue slices at a basal rate of 234·4 ± 32·8 pmol/g per h (n = 24) during 60-min incubations.Activators of protein kinase C: phorbol 12,13-dibutyrate (n = 8), phorbol 12-myristate,13-acetate (n = 4) and 1,2-didecanoylglycerol (n = 5), caused a dose-dependent stimulation of oxytocin secretion in the presence of a calcium ionophore (A23187; 0·2 μmol/l). Phospholipase C (PLC; 50–250 units/l) also caused a dose-dependent stimulation of oxytocin secretion by luteal slices. Phospholipase C-stimulated oxytocin secretion was potentiated by the addition of an inhibitor of diacylglycerol kinase (R59 022; n = 4). These data suggest that the activation of protein kinase C has a role in the stimulation of luteal oxytocin secretion. The results are also consistent with the involvement of protein kinase C in PLC-stimulated oxytocin secretion. The cyclic AMP second messenger system does not appear to be involved in the control of oxytocin secretion by the corpus luteum. Journal of Endocrinology (1990) 124, 225–232

scholarly journals Mastoparan promotes exocytosis and increases intracellular cyclic AMP in human platelets. Evidence for the existence of a Ge-like mechanism of secretion

1992 ◽  
Vol 281 (2) ◽  
pp. 465-472 ◽  
Author(s):  
C P D Wheeler-Jones ◽  
T Saermark ◽  
V V Kakkar ◽  
K S Authi
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
G Protein ◽  
Human Platelets ◽  
Dependent Manner ◽  
Kinase C ◽  
Reversible Electroporation ◽  
Dose Dependent ◽  
Stimulation Of

Recent studies have shown that mastoparan, an amphiphilic peptide derived from wasp venom, accelerates guanine nucleotide exchange and GTPase activity of purified GTP-binding proteins. In the present study we have examined the functional consequences of exposure of intact human platelets to mastoparan. Mastoparan promoted rapid (less than or equal to 1 min) dose-dependent increases in 5-hydroxy[14C]tryptamine and beta-thromboglobulin release from dense-granule and alpha-granule populations respectively. The exocytotic response did not result from a lytic effect of mastoparan and occurred in the complete absence of platelet shape change and aggregation. Liberation of [3H]arachidonate and increases in cytosolic [Ca2+] (detected with fura 2) were not observed in platelets stimulated with mastoparan. Similarly, in platelets preloaded with [3H]inositol during reversible electroporation, mastoparan did not cause the accumulation of [3H]inositol phosphates. Mastoparan-induced secretion was unaffected by preincubation with either the protein kinase C inhibitor staurosporine (10 nM-10 microM) or prostacyclin (PGI2; 100 ng/ml) and was not accompanied by phosphorylation of the 45 kDa protein kinase C substrate or the 20 kDa protein normally associated with platelet activation. The G-protein inhibitor guanosine 5′-[beta-thio]diphosphate (GDP[S]; 1 mM) attenuated the secretion induced by mastoparan in both intact and saponin-permeabilized platelets. Encapsulation of GDP[S] during reversible permeabilization inhibited mastoparan-induced secretion, providing evidence for an intracellular action of GDP[S]. In all these studies thrombin (0.05-0.2 unit/ml) elicited characteristic responses, and thrombin-induced secretion was inhibited by staurosporine, PGI2 and GDP[S]. Mastoparan also increased intra-platelet cyclic AMP in a dose-dependent manner. Mastoparan and PGI2 increased 32P incorporation into a protein of approx. 24 kDa, whereas phosphorylation of a 50 kDa substrate was only seen in PGI2-stimulated platelets. These results indicate that mastoparan promotes secretion by a mechanism which does not involve stimulation of phospholipase C and suggest that the secretory event may result either from a direct fusogenic action of mastoparan and/or from stimulation of the putative exocytosis-linked G-protein, Ge.

Effect of glucocorticoid on prostaglandin F2α-induced prostaglandin E2 synthesis in osteoblast-like cells: inhibition of phosphoinositide hydrolysis by phospholipase C as well as phospholipase A2

1994 ◽  
Vol 131 (5) ◽  
pp. 510-515 ◽  
Author(s):  
Osamu Kozawa ◽  
Haruhiko Tokuda ◽  
Atsushi Suzuki ◽  
Jun Kotoyori ◽  
Yoshiaki Ito ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phospholipase A ◽  
Phosphoinositide Hydrolysis ◽  
Prostaglandin E ◽  
Dependent Manner ◽  
Kinase C ◽  
Dose Dependent

Kozawa O, Tokuda H, Suzuki A, Kotoyori J, Ito Y, Oiso Y. Effect of glucocorticoid on prostaglandin F2α-induced prostaglandin E2 synthesis in osteoblast-like cells: inhibition of phosphoinositide hydrolysis by phospholipase C as well as phospholipase A2. Eur J Endocrinol 1994;131:510–15. ISSN 0804–4643 It is well known that osteoporosis is a common complication of patients with glucocorticoid excess. We showed previously that prostaglandin (PG) F2α stimulates the synthesis of PGE2, a potent bone resorbing agent, and that the activation of protein kinase C amplifies the PGF2α-induced PGE2 synthesis through the potentiation of phospholipase A2 activity in osteoblast-like MC3T3-E1 cells. In the present study, we examined the effect of dexamethasone on PGE2 synthesis induced by PGF2α in MC3T3-E1 cells. The pretreatment with dexamethasone significantly inhibited the PGE2 synthesis in a dose-dependent manner in the range between 0.1 and 10 nmol/l in these cells. This effect of dexamethasone was dependent on the time of pretreatment up to 8 h. Dexamethasone also inhibited PGE2 synthesis induced by melittin, known as a phospholipase A2 activator. Furthermore, dexamethasone significantly inhibited the enhancement of PGF2α- or melittin-induced PGE2 synthesis by 12-O-tetradecanoylphorbol-13-acetate, known as a protein kinase C activator. In addition, dexamethasone significantly inhibited PGF2α-induced formation of inositol phosphates in a dose-dependent manner between 0.1 and 10 nmol/l in MC3T3-E1 cells. These results strongly suggest that glucocorticoid inhibits PGF2α-induced PGE2 synthesis through the inhibition of phosphoinositide hydrolysis by phospholipase C as well as phospholipase A2 in osteoblast-like cells. Osamu Kozawa, Department of Biochemistry, Institute for Developmental Research, Aichi Prefectural Colony, Kasugai, Aichi 480-03, Japan

Leptin Constrains Phospholipase C-Protein Kinase C-Induced Insulin Secretion via a Phosphatidylinositol 3-Kinase-Dependent Pathway

2003 ◽  
Vol 228 (2) ◽  
pp. 175-182 ◽  
Author(s):  
Joo-Won Lee ◽  
Andrew G. Swick ◽  
Dale R. Romsos
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Phosphatidylinositol 3 Kinase ◽  
C Protein ◽  
Kinase C ◽  
Pka Pathway ◽  
Stimulation Of ◽  
Phosphatidylinositol 3

Leptin-deficient Lepob/Lepob mice hypersecrete insulin in response to acetylcholine stimulation of the phospholipase C-protein kinase C (PLC-PKC) pathway, and leptin constrains this hypersecretion. Leptin has been reported to activate phosphatidylinositol 3-kinase (PI 3-K) and subsequently phosphodiesterase (PDE) to impair protein kinase A (PKA)-induced insulin secretion from cultured islets of neonatal rats. We determined if PKA-induced insulin secretion was also hyperresponsive in Islets from Lepob/Lepob mice, and if leptin impaired this pathway in islets from these mice. Additionally, the possible role for PI 3-K and PDE in leptin-induced control of acetylcholine-induced insulin secretion was examined. Stimulation of Insulin secretion with GLP-1, forskolin (an activator of adenylyl cyclase), or IBMX (an inhibitor of PDE) did not cause hypersecretion of insulin from islets of young Lepob/Lepob mice, and leptin did not inhibit GLP-1-induced insulin secretion from islets of these mice. Inhibition of PDE with IBMX also did not block leptin-induced inhibition of acetylcholine-mediated insulin secretion from islets of Lepob/Lepob mice. But, preincubation of islets with wortmannin, an Inhibitor of PI 3-K activity, blocked the ability of leptin to constrain acetylcholine-induced insulin secretion from islets of Lepob/Lepob mice. We conclude that the capacity of the PKA pathway to stimulate insulin secretion is not increased in islets from young Lepob/Lepob mice, and that leptin does not regulate this pathway in islets from mice. Leptin may stimulate PI 3-K to constrain PLC-PKC-induced insulin secretion from Islets of Lepob/Lepob mice.

Mechanisms of PTH-induced rise in cytosolic calcium in adult rat hepatocytes

1994 ◽  
Vol 267 (5) ◽  
pp. G754-G763 ◽  
Author(s):  
M. Klin ◽  
M. Smogorzewski ◽  
H. Khilnani ◽  
M. Michnowska ◽  
S. G. Massry
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
G Protein ◽  
Cytosolic Calcium ◽  
Amino Terminal ◽  
Kinase C ◽  
Dose Dependent ◽  
Kinase A ◽  
Stimulation Of

Available data indicate that the liver is a target organ for parathyroid hormone (PTH) and that this effect is most likely mediated by PTH-induced calcium entry into hepatocytes. The present study examined the effects of both PTH-(1-84) and its amino-terminal fragment [PTH-(1-34)] on cytosolic calcium concentration ([Ca2+]i) of hepatocytes and explored the cellular pathways that mediate this potential action of PTH. Both moieties of PTH produced a dose-dependent rise in [Ca2+]i, but the effect of PTH-(1-84) was greater (P < 0.01) than an equimolar amount of PTH-(1-34). This effect required calcium in the medium and was totally [PTH-(1-34)] or partially [PTH-(1-84)] blocked by PTH antagonist ([Nle8,18,Tyr34]bPTH-(7-34)-NH2] and by verapamil or nifedipine. Sodium or chloride channel blockers did not modify this effect. 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C, dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), and G protein activator also produced a dose-dependent rise in [Ca2+]i. Staurosporine abolished the effect of TPA, and both staurosporine and calphostin C partially inhibited the effect of PTH. Staurosporine and verapamil together produced greater inhibition of PTH action than each alone. Rp-cAMP, a competitive inhibitor of cAMP binding to the R subunit of protein kinase A, and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), a protein kinase A inhibitor, blocked the effect of both DBcAMP and PTH, but the effect of these agents was greater (P < 0.01) on DBcAMP action. G protein inhibitor and pertussis toxin partially blocked the action of PTH. The data indicate that 1) PTH increases [Ca2+]i of hepatocytes; 2) this action of the hormone is receptor mediated; 3) the predominant pathway for this PTH action is the stimulation of a G protein-adenylate cyclase-cAMP system, which then leads to stimulation of a calcium transport system inhibitable by verapamil or nifedipine or activation of L-type calcium channels; 4) activation of protein kinase C is also involved; and 5) the PTH-induced rise in [Ca2+]i is due, in major parts, to movement of extracellular calcium into the cell.

On the signal transducing mechanisms involved in the synergistic interaction between interleukin-1 and bradykinin on prostaglandin biosynthesis in human gingival fibroblasts

1992 ◽  
Vol 12 (4) ◽  
pp. 263-271 ◽  
Author(s):  
Ulf H. Lerner ◽  
Gustaf Brunius ◽  
Thomas Modeer
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Phorbol Esters ◽  
Synergistic Interaction ◽  
Human Gingival Fibroblasts ◽  
Gingival Fibroblasts ◽  
Kinase C ◽  
Stimulation Of

Recombinant human interleukin-1β (IL-1β) and bradykinin (BK) synergistically stimulate prostaglandin E2 (PGE2) formation in human gingival fibroblasts cultured for 24 h. Neither BK or IL-1β per se, nor their combinations, caused any acute stimulation of cellular cyclic AMP accumulation. BK, but not IL-1β, caused a rapid, transient rise of intracellular Ca2+ concentration ([Ca2+]i), as assessed by recordings of fura-2 fluorescence in monolayers of prelabelled gingival fibroblasts. IL-1β did not change the effect of BK on [Ca2+]i. Ionomycin and A 23187, two calcium ionophores, synergistically potentiated the stimulatory effect of IL-1β on PGE2 formation. Three different phorbol esters known to activate protein kinase C also synergistically potentiated the action of IL-1β on PGE2 formation. Exogenously added arachidonic acid significantly enhanced the basal formation of PGE2. In IL-1β treated cells, the enhancement of PGE2 formation seen after addition of arachidonic acid, was synergistically upregulated by IL-1β. These data show that i) the synergistic interaction between IL-1β and BK on PGE2 formation is not due to an effect linked to an upregulation of cyclic AMP or [Ca2+]i; ii) the signal transducing mechanism by which BK interacts with IL-1β, however, may be linked to a BK induced stimulation of [Ca2+]i and/or protein kinase C; iii) the mechanism involved in the action of IL-1β may, at least partly, be due to enhancement of the biosynthesis of prostanoids mediated by an upregulation of cyclooxygenase activity.

scholarly journals G-protein βγ subunits antagonize protein kinase C-dependent phosphorylation and inhibition of phospholipase C-β1

1997 ◽  
Vol 326 (3) ◽  
pp. 701-707 ◽  
Author(s):  
Irene LITOSCH
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
G Protein ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Negative Feedback Regulation ◽  
Kinase C ◽  
Stimulation Of

Protein kinase C (PKC) isoforms phosphorylated phospholipase C-β1 (PLC-β1) in vitro as follows: PKCα ≫ PKCϵ; not PKCζ. PLC-β3 was not phosphorylated by PKCα. G-protein βγ subunits inhibited the PKCα phosphorylation of PLC-β1 in a concentration-dependent manner. Half-maximal inhibition occurred with 500 nM βγ. G-protein βγ subunits also antagonized the PKCα-mediated inhibition of PLC-β1 enzymic activity. PKCα, in turn, inhibited the stimulation of PLC-β1 activity by βγ. There was little effect of PKCα on the stimulation of PLC-β1 by αq/11–guanosine 5′[γ-thio]triphosphate (GTP[S]). These findings demonstrate that G protein βγ subunits antagonize PKCα regulation of PLC-β1. Thus βγ subunits might have a role in modulating the negative feedback regulation of this signalling system by PKC.

Epinephrine-mediated protein kinase C and Rap1b activation requires the co-stimulation of Gz-, Gq-, and Gi-coupled receptors

2011 ◽  
Vol 105 (03) ◽  
pp. 479-486 ◽  
Author(s):  
Ilaria Canobbio ◽  
Silvia Catricalà ◽  
Cesare Balduini ◽  
Paolo Lova ◽  
Gianni Francesco Guidetti ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Adrenergic Receptor ◽  
Dense Granules ◽  
Kinase C ◽  
Adrenergic Antagonist ◽  
Adp Receptors ◽  
Strong Stimulation ◽  
Dose Dependent ◽  
Stimulation Of

SummaryWe have recently shown that ADP-induced activation of protein kinase C (PKC) requires the co-stimulation of both P2Y1 and P2Y12 receptors. In this work, we show that inhibition of ADP-mediated phosphorylation of pleckstrin, the main PKC substrate, caused by antagonists of the P2Y12 receptor can be reversed by stimulation of the α2-adrenergic receptor by epinephrine. However, we also observed that addition of epinephrine alone caused a marked phosphorylation of pleckstrin. This effect occurred in the absence of Gq stimulation, as it was not associated to intracellular Ca2+ release. Epinephrine-induced pleckstrin phosphorylation was time- and dose-dependent, and was inhibited by the α2-adrenergic antagonist yohimbin. Phosphorylation of pleckstrin did not occur when platelet stimulation with epinephrine was performed in the presence of the ADP scavenger apyrase, and was suppressed by antagonists of both P2Y1 and P2Y12 ADP receptors. Importantly, no release of dense granules was measured in epinephrine-treated platelets. Addition of epinephrine to platelets was also able to stimulate Rap1b activation. Similarly to pleckstrin phosphorylation, however, this effect was prevented in the presence of apyrase or upon pharmacologic blockade of either P2Y1 or P2Y12 receptors. These results indicate that sub-threshold amounts of ADP in the medium are essential to allow epinephrine stimulation of α2-adrenergic receptor to elicit platelet responses, and reveal a novel synergism among strong stimulation of Gz and sub-threshold stimulation of both Gq and Gi, able to dissociate PKC activation from intracellular Ca2+ mobilisation.

Adenosine A1 receptor-mediated inhibition of myocardial norepinephrine release involves neither phospholipase C nor protein kinase C but does involve adenylyl cyclase

2006 ◽  
Vol 84 (5) ◽  
pp. 573-577 ◽  
Author(s):  
Frank Schütte ◽  
Christof Burgdorf ◽  
Gert Richardt ◽  
Thomas Kurz
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Adenylyl Cyclase ◽  
Phospholipase C ◽  
Suppressive Effect ◽  
Inhibitory Effect ◽  
Direct Stimulation ◽  
Kinase C ◽  
Gf 109203X ◽  
Stimulation Of

Stimulation of adenosine A1 receptors in the heart exerts cardioprotective effects by inhibiting norepinephrine (NE) release from sympathetic nerve endings. The intraneuronal signal transduction triggered by presynaptic adenosine A1 receptors is still not completely understood. The objective of the present study was to determine whether phospholipase C (PLC), protein kinase C (PKC), and adenylyl cyclase (AC) are involved in the adenosine A1 receptor-mediated inhibition of endogenous (stimulation-induced) NE release in isolated Langendorff-perfused rat hearts as an approach to elucidate their role in the cardiovascular system. Activation of adenosine A1-receptors with 2-chloro-N6-cyclopentyladenosine (CCPA) decreased cardiac NE release by ~40%. Inhibition of PLC with 1-[6-[[(17b)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U 73122) as well as inhibition of PKC with 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl)maleimide (GF 109203X) slightly but significantly decreased NE release; however, the suppressive effect of CCPA on NE release was not modulated by U 73122 or GF 109203X. Blockade of AC with 9-(tetrahydro-2′-furyl)adenine (SQ 22536) reversed the inhibitory effect of CCPA on sympathetic neurotransmitter release irrespective of whether PKC was pharmacologically activated by phorbol 12-myristate 13-acetate or was not activated, indicating a PKC-independent but AC-dependent mechanism. Direct stimulation of AC with forskolin increased NE release by ∼20%; an effect that was antagonized by either CCPA or SQ 22536. These data suggest that the adenosine A1 receptor-mediated inhibition of NE release does not involve PLC or PKC but does involve AC.

Stimulation of transient elevations in cytosolic Ca2+ is related to inhibition of Pi transport in OK cells

1990 ◽  
Vol 259 (3) ◽  
pp. F485-F493 ◽  
Author(s):  
A. Miyauchi ◽  
V. Dobre ◽  
M. Rickmeyer ◽  
J. Cole ◽  
L. Forte ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Cytosolic Calcium ◽  
Wild Type ◽  
Kinase C ◽  
Pi Transport ◽  
Sodium Dependent ◽  
Stimulation Of

Stimulation of changes in cytosolic free calcium by parathyroid hormone was determined in three opossum kidney (OK) cell types, OK wild-type, OKP clone, and OKH clone. All three types of OK cells express parathyroid hormone (PTH)-sensitive adenylate cyclase and adenosine 3',5'-cyclic monophosphate (cAMP) production. However, only the OK wild-type and the OKP clone respond to PTH with inhibition of sodium-dependent Pi transport and transient increase in cytosolic calcium. Characterization of the increases in cytosolic calcium in the wild-type and OKP clones revealed they were due in part to stimulation of Ca2+ release from intracellular stores, probably by inositol 1,4,5-trisphosphate (IP3), which was stimulated by PTH. PTH-stimulated Ca2+ transients were also inhibited by protein kinase C activation. These data are compatible with PTH receptor-mediated phospholipase C activation and its feedback inhibition by protein kinase C. The OKH cells demonstrated a slow increase in cytosolic calcium when stimulated by cyclic nucleotides but no evidence for PTH stimulation of Ca2+ release from intracellular stores. Thus the absence of an inhibitory response of sodium-dependent Pi transport to PTH in the OKH cells is associated with the absence of the rapid transient elevations of cytosolic Ca2+ such as those produced by IP3 production. These data suggest an important cooperative role for cAMP and the phospholipase C-stimulated Ca2(+)-protein kinase C message system in the regulation of Pi transport.

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