Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of diacylglycerol (DG) as a source of arachidonic acid during gonadotropin-releasing hormone (GnRH) stimulation of gonadotropin secretion was analyzed in primary cultures of rat anterior pituitary cells. An inhibitor of DG lipase (RHC 80267, RHC) caused dose-dependent blockade of GnRH-stimulated luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. The DG lipase inhibitor did not alter gonadotropin responses to arachidonic acid, and addition of arachidonic acid reversed its inhibition of GnRH-stimulated LH and FSH release. In [3H]arachidonic acid-prelabeled cells, incubation with RHC increased the accumulation of [3H]DG. These results suggest that DG lipase participates in GnRH action and that arachidonic acid mobilization from DG is involved in the mechanism of gonadotropin release. Gonadotropin responses to tetradecanoyl phorbol acetate and dioctanoyl glycerol were not altered by RHC, and the addition of these activators of protein kinase C (Ca2+- and phospholipid-dependent enzyme) did not prevent the inhibition of GnRH-induced gonadotropin release by RHC. Activation of phospholipase A2 by melittin increased LH and FSH secretion, whereas blockade of this enzyme by quinacrine reduced GnRH-stimulated hormone release. However, RHC did not diminish the gonadotropin response to melittin. The inhibitory actions of RHC and quinacrine were additive and were reversed by concomitant treatment with arachidonic acid. Ionomycin also increased LH and FSH release, and the gonadotropin responses to the ionophore were unaltered by RHC but were reduced by quinacrine. Incubation of cells in Ca2+-depleted (+/- [ethylenebis(oxyethylenenitrilo)]tetraacetic acid) medium reduced but did not abolish the LH and FSH releasing activity of GnRH. Treatment with RHC also reduced the gonadotropin responses to GnRH under Ca2+-depleted conditions. These observations indicate that RHC inhibition of GnRH action is not due to nonspecific actions on Ca2+ entry, protein kinase C activation and actions, nor phospholipase A2 enzyme activity. The results of this study provide further evidence for an extracellular Ca2+-independent mechanism of GnRH action, and suggest that GnRH causes mobilization of arachidonic acid by two distinct lipases, namely, phospholipase A2 and DG lipase, during stimulation of gonadotropin secretion.
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PMID:Dependence of secretory responses to gonadotropin-releasing hormone on diacylglycerol metabolism. Studies with a diacylglycerol lipase inhibitor, RHC 80267. 314 14

This study compares the selective effect of androgens on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release induced either by LH-releasing hormone (LH-RH) or by protein kinase C activation in rat anterior pituitary cells in culture. In control cells, phorbol-12-myristate-13-acetate (PMA) stimulated the release of radioimmunoassayable LH and FSH in a dose-dependent manner at an ED50 value of 5.95 +/- 1.45 nM. The maximal release of gonadotropins induced during a 3-hour incubation with PMA was 40-60% of that induced by LH-RH. Preincubation of the cells for 2-4 days with 10 nM 5 alpha-dihydrotestosterone (DHT) decreased by approximately 60% the subsequent release of LH induced by 100 nM LH-RH or by 500 nM PMA during a subsequent 3-hour incubation. The inhibitory effect of DHT was completely suppressed by coincubation with the antiandrogen hydroxyflutamide. DHT exerted a similar inhibitory effect on LH release induced by another stimulator of protein kinase C activity, namely 1-oleoyl-2-acetylglycerol. The potent inhibitory action of DHT on LH-RH- or PMA-induced LH release was exerted at an ED50 value of approximately 10 pM. Contrary to the effect on LH, the FSH response to LH-RH or to PMA was increased by preincubation with 2 nM DHT, the stimulatory effect of the androgen being completely antagonized by hydroxyflutamide.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Androgens exert selective effects on protein kinase C induced LH and FSH release in rat anterior pituitary cells in culture. 314 69

The in vitro ability of ovine (o) follicle-stimulating hormone (FSH), (o)luteinizing hormone (LH), (o)prolactin (PRL), and recombinant human FSH (rhFSH) to stimulate progesterone (P4) synthesis by rat corpora lutea on Day 4 of pregnancy was investigated. Dispersed luteal cells (large + small cells) were incubated in the presence of the gonadotropins (1-100 ng) alone or in various combinations (10 ng each) for 4 or 24 hr. Given alone, all the ovine preparations stimulated P4 in a dose-dependent manner with even 1 ng of each hormone significantly enhancing P4 production. Significantly, rhFSH--which is devoid of LH contamination--at 10 and 100 ng also stimulated P4 production, thus clearly establishing for the first time that FSH is a luteotropic hormone in the rat. The combination of oFSH + LH + PRL (10 ng each) significantly stimulated P4 synthesis to a greater extent than the combination of any two hormones or individual hormones at both 4 hr or an additional 24 hr of incubation (P < 0.05). This verified in vitro a previously established in vivo luteotropic complex. One hundred nanamolars of phorbol 12-myristate 13-acetate (PMA) did not affect basal P4 secretion but inhibited cAMP, oFSH, and oLH stimulation of P4. Thus, the luteotropic effects of FSH, LH, and activators of protein kinase A are antagonized by the protein kinase C pathway.
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PMID:In vitro effects of interactions of follicle-stimulating hormone, luteinizing hormone, and prolactin on progesterone synthesis by rat luteal cells during pregnancy. 763 45

The regulation of the follistatin mRNA by hormones and endocrine manipulations was examined in granulosa cell cultures. The follistatin mRNA accumulation was stimulated in a dose-dependent manner by follicle-stimulating hormone (FSH) with a maximal response twice as great as in control cultures at a dose of 100 ng/ml FSH. The time course of the FSH effect on follistatin mRNA had a biphasic effect in which FSH increased follistatin mRNA within 2 h, and subsequently reduced it to below the control level. 8-Br-8 brom-adenosine 3,5-cyclic monophosphate (cAMP) (2 mM) and phorbol 12-myristate 13-acetate (PMA) (10 nm) induced a time-dependent increase in follistatin mRNA levels, with the maximal response at 6 h and 2 h, respectively. Co-treatment of the granulosa cells with cAMP and PMA demonstrated that 0.2 mM of 8-Br-cAMP suppressed the follistatin mRNA of the control and the samples with a small amount of PMA in the granulosa cells. Follistatin expression is therefore regulated by protein kinase A and protein kinase C pathways in rat granulosa cells. A more dramatic stimulation of follistatin mRNA was observed when this culture was treated with activin, and follistatin also blocked the effect of activin on the follistatin mRNA.
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PMID:Regulation of follistatin messenger ribonucleic acid in cultured rat granulosa cells. 766 79

The present study examines the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on agonist-regulated 3',5'-cyclic adenosine monophosphate (cAMP) formation and cAMP-mediated effects in cultured Sertoli cells from immature rats. Concentration-dependent stimulation of cAMP levels by follicle-stimulating hormone (FSH) was inhibited dramatically by the coaddition of 100 nmol/l TPA, which exerted a similar inhibition of glucagon- and isoproterenol-stimulated cAMP production. These results show that protein kinase C (PKC) activation by TPA attenuates Gs-protein-mediated agonist activation of cAMP production. (-)-N6(R)-Phenylisopropyladenosine (L-PIA), an A1-adenosine receptor agonist, inhibited cAMP stimulation by FSH in a concentration-dependent manner. When L-PIA was added in increasing concentrations simultaneously with 100 nmol/l TPA, the L-PIA still inhibited FSH-stimulated cAMP production in a concentration-dependent manner. In the presence of TPA, the half-inhibitory concentration (IC50) for L-PIA inhibition of cAMP formation was reduced by more than one order of magnitude, indicating that PKC activation by TPA increases the sensitivity of Sertoli cells to Gi-protein-mediated agonist inhibition of cAMP production. The inhibitory effects of TPA on FSH-stimulated cAMP production were still observed when cAMP phosphodiesterase activity was inhibited by 1 mmol/l methylisobutylxanthine or when the activity of G alpha i-protein was eliminated by pretreatment with 100 micrograms/l pertussis toxin. Taken together, the results indicate that PKC activation inhibits agonist-dependent stimulation of cAMP production by phosphorylation of components common to all the activating agonists used, and not via stimulation of G(i)-protein activity or degradation of cAMP by cAMP phosphodiesterase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protein kinase C activation and positive and negative agonist regulation of 3',5'-cyclic adenosine monophosphate levels in cultured rat Sertoli cells. 768 9

A range of selective tyrosine kinase inhibitors, piceatannol, methyl-2,5-dihydroxycinnamate (MDC), genistein, psi-tectorigenin and lavendustin A, all reduced luteinizing hormone-releasing hormone (LHRH)-induced luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release from pro-oestrous rat hemipituitaries incubated in vitro. In general, both 'initial' release and the augmented release resulting from LHRH self-priming, were reduced in parallel in a concentration-dependent fashion. The effects of piceatannol were independent of the steroidal status of the pituitary tissue. Both piceatannol and MDC greatly reduced LH release by ionomycin and a protein kinase C (PKC) activator, phorbol 12,13-dibutyrate (PDBu), suggesting that the tyrosine kinase(s)-dependent step is in the later stages of the stimulus-secretion pathway activated by the LHRH receptor. These data were supported by immunoblots for phosphotyrosine showing that in the gonadotrope-derived alpha T3-1 cell line, treatment with LHRH caused piceatannol-sensitive increases in specific tyrosine phosphorylation of several proteins (major bands at 65-75 and 120-130 kDa). Treatment of cells with PDBu mimicked the tyrosine phosphorylations evoked by LHRH whereas the PKC inhibitor, GF109203X, partially reduced both LHRH- and PDBu-induced tyrosine phosphorylations. Direct effects of MDC and piceatannol on PKC were assessed in an in vitro PKC assay; piceatannol, but not MDC, inhibited PKC activity but at considerably higher concentrations than required for inhibition of LHRH-induced gonadotropin secretion. These data support a role for tyrosine kinase activation in LHRH-induced secretion.
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PMID:Effect of tyrosine kinase inhibitors on luteinizing hormone-releasing hormone (LHRH)-induced gonadotropin release from the anterior pituitary. 778 17

Inhibins and activins are dimeric peptide hormones that regulate the circulating levels of follicle-stimulating hormone (FSH). In turn, FSH stimulates inhibin gene expression in the ovarian follicle; studies to date suggest that this effect is mediated by cAMP and that a cAMP-responsive element, identified in the 5'-flanking region of the alpha-inhibin gene, at least partially effects this response. To explore further the transcriptional regulation of the inhibin/activin genes, we have isolated and sequenced the 5'-flanking regions of the bovine alpha-, beta A- and beta B-inhibin/activin subunit genes and have analysed these regions by primer-extension analysis and DNase I footprinting with the transcription factor AP-2. Analyses indicated that all three gene promoter regions have a number of AP-2-binding sites that are resistant to competition by poly(dI-dC), suggesting that cAMP may control the inhibin/activin ratio by operating through alternative signal-transduction pathways or that inhibin/activin gene expression may be controlled by signals operating through the protein kinase C pathway. A comparison of the DNA sequences protected by AP-2 against DNase I digestion revealed a consensus AP-2-binding site of 5'-GSCCCDSS-3', where S represents a base pairing involving three (C or G) hydrogen bonds and D represents any base other than C. The nucleotide sequences of the bovine beta-subunit structural genes also are reported.
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PMID:Genomic cloning and sequence analyses of the bovine alpha-, beta A- and beta B-inhibin/activin genes. Identification of transcription factor AP-2-binding sites in the 5'-flanking regions by DNase I footprinting. 781 65

Tissue-type plasminogen activator (tPA) secretion is a specific response of Sertoli cells to follicle-stimulating hormone (FSH), which is lower after preincubation of the cells with low FSH concentrations because of FSH receptor/Gs protein uncoupling. In this report, we present evidence that this desensitization induced by the lowest FSH concentrations is suppressed by specific peptidic inhibitors of endogenous PKA and PKC in permeabilized Sertoli cells. In contrast, desensitization promoted by slightly higher FSH concentrations is not mediated through PKA or PKC activation but is dependent on protein neosynthesis.
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PMID:Protein kinases and protein synthesis are involved in desensitization of the plasminogen activator response of rat Sertoli cells by follicle-stimulating hormone. 792 33

This study was conducted to investigate whether endothelin-1 (ET-1) has direct effects on the functions of porcine granulosa cells harvested from small or medium follicles. Positive ET-1-like immunoreactivity (ET-1-LI) was observed in the cultured porcine granulosa cells, and Northern blot analysis demonstrated the expression of mRNA for prepro-ET-1 in these cells. The binding study showed the presence of a nonselective, single class of binding sites which predominantly included the subtype ETB. Increased ET-1-LI was detected in human follicular fluid obtained from the patients with stimulated ovarian cycles. ET-1 stimulated basal and follicle-stimulating hormone (FSH)-stimulated secretion of progesterone during short-term incubation (2 h), while it inhibited FSH- and human-chorionic-gonadotropin-stimulated accumulation of progesterone during long-term incubation (48 h) of immature or moderately mature granulosa cells. ET-1 significantly increased DNA synthesis in the cells. These biological actions were induced by ET-1, probably via a cAMP-protein kinase A pathway and intracellular calcium mobilization-protein kinase C pathway. The results suggest that ET-1 exerts autocrine/paracrine effects on porcine granulosa cell functions.
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PMID:Endothelin-1 as a local ovarian regulator in porcine granulosa cells. 808 93

In this study the localization and regulation of steady-state follistatin messenger ribonucleic acid (mRNA) levels in testicular cell cultures were examined with a solution-hybridization assay using a specific 32P-labelled cytosolic RNA antisense probe for follistatin and a 35S-labelled cytosolic RNA antisense probe for cyclophilin as internal standard. Testes from immature rats were dispersed with collagenase and fractionated in Sertoli and Leydig cell-enriched cultures. Follistatin mRNA was mainly localized to the Sertoli cell-enriched fraction and the expression of follistatin mRNA could be stimulated in vitro with fetal calf serum, epidermal growth factor or phorbol-12-myristate-13-acetate (an activator of protein kinase C), whereas follicle-stimulating hormone and forskolin (an activator of protein kinase A) had no effect. Neither prostaglandin E2, the synthetic glucocorticoid RU 28362 or all-trans-retinoic acid, which all regulate follistatin mRNA levels in non-testicular cell types, nor extracellular adenosine triphosphate (a purinergic receptor agonist) or testosterone had any obvious influence on follistatin mRNA levels in Sertoli cell-enriched cultures. From this study it is concluded that Sertoli cells are likely to be the source of follistatin expression in the rat testis, that follistatin mRNA levels in Sertoli cell-enriched cultures are subjected to regulation by epidermal growth factor and the protein kinase C-dependent pathway but are not regulated by extracellular adenosine triphosphate, follicle-stimulating hormone, all-trans-retinoic acid, prostaglandin E2, forskolin, testosterone or the glucocorticoid RU 28362 and that the regulation of follistatin mRNA is sex- and tissue-specific.
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PMID:Expression of follistatin messenger ribonucleic acid in Sertoli cell-enriched cultures: regulation by epidermal growth factor and protein kinase C-dependent pathway but not by follicle-stimulating hormone and protein kinase A-dependent pathway. 810 86


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