Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mouse spleen-derived mast cell line (PT-18) was employed to examine the mechanisms of adenosine 3':5'-monophosphate (cAMP)-mediated inhibition of antigen-induced lipid mediator biosynthesis. Specifically, we tested the hypothesis that increasing cAMP in mast cells inhibits lipid mediator biosynthesis by a mechanism independent of effects on histamine release (degranulation) or changes in cytosolic calcium concentration. Forskolin inhibited antigen-induced prostaglandin D2 (PGD2), leukotriene C4 (LTC4), and leukotriene B4 (LTB4) production by 30-50%. In contrast, forskolin had no inhibitory effect on antigen-induced increases in cytosolic calcium concentration, as monitored by the calcium indicator fura-2, or histamine release from the cells. The combination of the phosphodiesterase inhibitor isobutylmethylxanthine with forskolin inhibited the antigen-induced production of PGD2 and LTC4 by 90-100% and histamine release by about 60%. These responses were accompanied by a virtual abolition of the antigen-induced increase in cytosolic calcium. To test further the hypothesis that increasing cAMP can lead to inhibition of lipid mediator biosynthesis in the absence of effects on cytosolic calcium, we employed the calcium ionophores A23187 and ionomycin. Forskolin alone or in combination with isobutylmethylxanthine had no effect on ionophore-induced increases in cytosolic calcium but effectively inhibited leukotriene biosynthesis. In addition, increasing cyclic AMP led to an inhibition of ionophore-induced production of platelet-activating factor and liberation of arachidonic acid. These data suggest that a relatively modest increase in cAMP-dependent protein kinase activity in mast cells leads to inhibition of the lipase-catalyzed cleavage of arachidonic acid from membrane phospholipids in the absence of measurable effects on either histamine release or changes in cytosolic calcium concentration. This effect results in a selective inhibition of the biosynthesis of lipid mediators including LTC4, LTB4, PGD2, and platelet-activating factor.
 ...
PMID:Inhibition by adenosine 3':5'-monophosphate of eicosanoid and platelet-activating factor biosynthesis in the mouse PT-18 mast cell. 169 Nov 75

1. Bull-frog sympathetic neurones in primary culture were voltage clamped in the whole-cell configuration. The pipette solution contained ATP (5 mM). 2. A hyperpolarization-activated sodium-potassium current (H-current: IH) was separated from other membrane currents in a nominally calcium-free solution containing cobalt (2 mM), magnesium (4 mM), barium (2 mM), tetraethylammonium (20 mM), tetrodotoxin (3 microM), apamin (30 nM) and 4-aminopyridine (1 mM). IH was selectively blocked by caesium (10-300 microM). 3. The steady-state activation of IH occurred between -60 and -130 mV. The H-conductance was 4.1-6.6 nS at the half-activation voltage of -90 mV. With the concentrations of potassium and sodium ions in the superfusate at 20 and 70 mM, respectively, the reversal potential of IH was about -20 mV. IH was activated with a time constant of 2.8 s at -90 mV and 22 degrees C. The Q10 between 16 and 26 degrees C was 4.3. 4. A non-hydrolysable ATP analogue in the pipette solution did not support IH activation. Intracellular 'loading' of GTP-gamma-S (30-500 microM) led to a progressive activation of IH. 5. Forskolin (10 microM) increased the maximum conductance of IH by 70%. This was associated with a depolarizing shift in the half-activation voltage (5-10 mV) and in the voltage dependence of the activation/deactivation time constant of IH. 6. Essentially the same results as with forskolin were obtained by intracellular 'loading' with cyclic AMP (3-10 microM) or bath application of 8-bromo cyclic AMP (0.1-1 mM), dibutyryl cyclic AMP (1 mM) and 3-isobutyl-1-methylxanthine (0.1-1 mM). 7. The protein kinase inhibitor H-8 (1-10 microM) decreased the peak amplitude of IH. Phorbol 12-myristate 13-acetate (10 microM), a protein kinase C activator, was without effect. 8. It is concluded that a voltage-dependent cation current can be regulated by the basal activity of adenylate cyclase, presumably through protein kinase A, in vertebrate sympathetic neurones.
 ...
PMID:Cyclic AMP regulates an inward rectifying sodium-potassium current in dissociated bull-frog sympathetic neurones. 169 Dec 92

Forskolin-pretreatment of A431 cells reduced both intrinsic and epidermal growth factor (EGF)-induced EGF receptor phosphorylation, however, phosphorylation of phospholipase C-gamma (PLC-gamma) was stimulated under the same conditions. No significant difference was detected in the amount of phosphotyrosine of PLC-gamma between two cultures with or without forskolin treatment followed by EGF. On the other hand, phosphorylation of a 47 kDa protein (P47) which cross-reacted with an anti-PLC-gamma monoclonal antibody, was stimulated by both forskolin and EGF. Phosphorylation was exclusively on serine residues in this case. These results indicate that both PLC-gamma and P47 are phosphorylated by a cAMP-dependent protein kinase and the EGF-stimulated serine kinase, and suggest that serine phosphorylation of PLC-gamma has no effect on ligand-dependent coupling with the EGF receptor.
 ...
PMID:Examination of the role of serine phosphorylation in phospholipase C-gamma and its related P47 in cAMP-mediated depression of epidermal growth factor signal transduction. 169 48

The effects of forskolin, a potent activator of adenylate cyclase, were examined on the frog neuromuscular junction. The depolarization elicited by ionophoretically applied acetylcholine was markedly reduced in amplitude and its time course was speeded up after treatment with 20-100 microM forskolin. The amplitude of extracellularly recorded miniature endplate potentials was decreased by the same factor as that of ionophoretically evoked responses and their decay time constant became shorter. All these changes, but not the shortening of spontaneous responses, were produced by 3-isobutyl-1-methylxantine and by N6-2'-O-dibutyryl cyclic AMP, both known to elevate intracellular cAMP. Forskolin-induced actions can be thus ascribed to the activation of cAMP-dependent protein kinase and to a direct effect on acetylcholine receptor channel.
 ...
PMID:The effect of forskolin on the response of acetylcholine receptors in frog sartorius endplate. 169 69

Long-term regulation of mammalian steroid hormone synthesis occurs principally by transcriptional regulation of the gene for the rate-limiting cholesterol side-chain cleavage enzyme P450scc. Adrenal steroidogenesis is regulated primarily by two hormones: adrenocorticotropin, which works via cyclic AMP (cAMP) and protein kinase A, and angiotensin II, which works via Ca2+ and protein kinase C. Forskolin and 8-bromo-cAMP stimulated, while prolonged treatment with a phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA]) and a calcium ionophore (A23187) additively suppressed accumulation of endogenous P450scc mRNA in transformed murine adrenal Y1 cells. In Y1 cells transfected with 2,327 base pairs of the human P450scc promoter fused to the bacterial gene for chloramphenicol acetyltransferase (CAT), forskolin increased CAT activity 900% while combined TPA plus A23187 reduced CAT activity to 15% of the control level. Forskolin induced the P450scc promoter as rapidly as a promoter containing two cAMP-responsive elements fused to a simian virus 40 promoter, a system known to respond directly to cAMP. Basal expression was increased by sequences between -89 and -152 and was increased further by sequences between -605 and -2327. This upstream region also conferred inducibility by cAMP. TPA plus A23187 transiently increased CAT activity before repressing it, reflecting the complex actions of angiotensin II in vivo. Repression by prolonged treatment with TPA plus A23187 was mediated by multiple elements between -89 and -343. Induction of CAT activity by forskolin was not diminished by treatment with TPA plus A23187, nor were the regions of the promoter responsible for regulation by the two pathways coisolated. Thus, the human gene for P450scc is repressed by TPA plus A23187 by mechanisms and sequences independent of those that mediate induction by cAMP.
 ...
PMID:Human P450scc gene transcription is induced by cyclic AMP and repressed by 12-O-tetradecanoylphorbol-13-acetate and A23187 through independent cis elements. 170 Feb 77

We have determined the effect of forskolin, an adenyl cyclase agonist, and 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, on the accumulation and cytotoxicity of cisplatin (DDP) in 2008 human ovarian carcinoma cells. In DDP-sensitive 2008 cells, forskolin and IBMX caused 2.1-fold and 2.3-fold increases, respectively, in the short-term accumulation of DDP relative to untreated cells. The inactive analogue, 1,9-dideoxyforskolin, decreased DDP accumulation. Forskolin and IBMX also increased accumulation in A2780 cells. Neither forskolin nor IBMX had any effect on DDP accumulation in DDP-resistant 2008 cells. The effects were detectable as early as 1 min and persisted at 60 min. The concentrations for half-maximal stimulation of DDP accumulation were approximately 0.2 microM for forskolin and 0.2 mM for IBMX. Forskolin caused marked increases in cAMP levels in both sensitive and resistant 2008 cells within 1 min, although there were differences in the subsequent time-courses of the response. Both 2008 cell types had identical cAMP-dependent protein kinase (PKA) activity. These results suggest that there is a target downstream of PKA that is an important participant in DDP accumulation, and that this target is defective or missing in DDP-resistant cells. Following a 1-hr exposure to drugs, forskolin and IBMX at concentrations that were by themselves completely non-toxic increased the slopes of the clonogenic survival vs. DDP concentration curves in 2008 cells 1.9-fold and 3.3-fold, respectively. In DDP-resistant 2008 cells, however, forskolin and IBMX increased the slopes only 1.2 and 2.6-fold, respectively. These effects of forskolin and IBMX on DDP cytotoxicity did not directly correlate with the effects on the 1-hr DDP accumulation which suggested that, in addition to modulating DDP accumulation, these agents increase the cytotoxicity of the intracellular platinum. The results indicate that modulation of cAMP levels can have important effects on DDP accumulation and cytotoxicity in 2008 cells and that these effects are significantly diminished in DDP-resistant cells.
 ...
PMID:Modulation of cis-diamminedichloroplatinum(II) accumulation and sensitivity by forskolin and 3-isobutyl-1-methylxanthine in sensitive and resistant human ovarian carcinoma cells. 171 75

Past studies revealed that NGF and fibroblast growth factor (FGF) prevent the death of PC 12 pheochromocytoma cells that otherwise occurs in serum-free medium. Additional agents were tested here for their abilities to promote long-term survival of naive and NGF-pretreated (primed) PC 12 cells in serum-free conditions. Forskolin and permeant cAMP analogs effectively prevented serum-free cell death, as did micromolar levels of insulin and 10-100-nM levels of insulin-like growth factors I and II. In contrast to NGF and FGF, none of these agents caused neuronal differentiation of naive cells or neurite regeneration by primed cells. Each of the agents also prevented rapid cell death in a balanced salt solution, thus apparently ruling out a mechanism dependent on regulation of nutrient uptake. Epidermal growth factor and elevated K+ appeared to slow the rate of cell death, but did not promote long-term survival; phorbol ester, dexamethasone, or vanadate did not prevent cell death. Each of the survival-promoting agents was effective even when macromolecular synthesis was blocked. Because the synthesis inhibitors themselves did not significantly prevent cell death, such findings indicate that survival was promoted by mechanisms that do not require synthesis of RNA or protein. In addition, various lines of experimental evidence (using the kinase inhibitor K-252a or PC 12 cell variants deficient either in protein kinase A activity or in responsiveness to NGF) further suggested that the effective agents maintain survival by independent initial pathways. Regulation of protein kinase activity appears to be a common feature of each pathway and may therefore play a key convergent role in mediating prevention of cell death.
 ...
PMID:Multiple agents rescue PC12 cells from serum-free cell death by translation- and transcription-independent mechanisms. 171 94

Dopamine exerts multiple effects on retinal horizontal cells. Dopamine, via cyclic AMP and protein kinase A, reduces the light responsiveness of horizontal cells and the electrical coupling between the cells. The gating kinetics of both gap-junctional and glutamate channels are altered as a result of phosphorylation by protein kinase A. Dopamine also causes a reversible retraction of neurites of horizontal cells maintained in culture. Diacylglycerol analogues as well as phorbol esters mimic this effect of dopamine, but not cyclic AMP analogues or Forskolin. The results suggest that dopamine causes neurite retraction by the activation of protein kinase C via diacylglycerol.
 ...
PMID:Retinal neuromodulation: the role of dopamine. 171 2

Recent evidence has suggested that cAMP plays a role as a second messenger in the decrease in nociceptive threshold (or hyperalgesia) produced by agents acting on primary afferent terminals. In support of this hypothesis we report that intradermal injection of a direct activator of adenyl cyclase, forskolin, produces a dose-dependent hyperalgesia in the rat. The duration of this hyperalgesia was prolonged by the phosphodiesterase inhibitors, isobutylmethylxanthine and rolipram. Forskolin hyperalgesia was antagonized by the Rp isomer of cyclic adenosine-3'5'-monophosphothioate, an analog of cAMP that prevents the phosphorylation of the cAMP protein kinase. The Rp isomer of cyclic adenosine-3'5'-monophosphothioate also inhibited the hyperalgesia induced by a membrane-permeable analogue of cAMP, 8-bromocyclic adenosine monophosphate, as well as the hyperalgesia induced by agents that are presumed to act directly on primary afferent nociceptors: prostaglandin E2, prostaglandin I2, (8R,15S)-dihydroxyicosa(5E-9,11,13Z)tetraenoic acid; and the adenosine A2-agonist 2-phenylaminoadenosine. Although the cAMP second messenger system contributes to primary afferent hyperalgesia, we found no evidence for a contribution of protein kinase C. Thus, hyperalgesia induced by prostaglandin E2, prostacyclin (prostaglandin I2), (8R,15S)-dihydroxyicosa(5E-9,11,13Z)tetraenoic acid, the adenosine A2-agonist 2-phenylaminoadenosine, 8-bromocyclic adenosine monophosphate and the direct activator of adenyl cyclase, forskolin, were not significantly attenuated by the selective inhibition of protein kinase C by the 19-31 fragment of protein kinase C. Two other inhibitors of protein kinase C, sphingosine and staurosporine, also failed to attenuate prostaglandin E2-induced hyperalgesia.
 ...
PMID:Further confirmation of the role of adenyl cyclase and of cAMP-dependent protein kinase in primary afferent hyperalgesia. 172 88

Metalloproteinases, such as collagenase or gelatinase, and their associated inhibitors appear to control connective tissue remodeling during follicular rupture. We examined the regulation of metalloproteinase inhibitor activity by various treatments in cultured rat granulosa cells. Granulosa cells were harvested from immature PMSG-primed rats and cultured with LH, the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), cAMP, or forskolin. Inhibitor activity was measured in the medium. Increasing concentrations of either LH (0.1-1000 ng/ml) or TPA (2.5-100 nM) resulted in a dose-dependent increase in metalloproteinase inhibitor activity (2.9- and 2.4-fold increases above control, respectively). There was also a time-dependent induction of inhibitor activity in cells incubated in the presence of LH (100 ng/ml) for 6, 12, 18, or 24 h. Forskolin (0.1 mM) or cAMP (1 mM) treatment increased inhibitor activity 2.8- and 1.6-fold above that in control cultures. LH and TPA treatment in combination resulted in an additive increase in inhibitor activity compared to LH or TPA treatment alone. This finding suggested that the granulosa cell inhibitor activity might be induced through separate intracellular pathways. The inhibitor present in conditioned medium was isolated by chromatographic separation on a Sepharose 6B mol wt exclusion column. The inhibitor present was approximately 28,000 mol wt, which is consistent with the size of tissue inhibitor of metalloproteinase (TIMP). In addition to the granulosa cell experiments, changes in ovarian mRNA levels for TIMP were determined. There was a preovulatory increase in TIMP mRNA from whole rat ovaries, with the highest levels detected 12 h after hCG administration. The present study establishes that metalloproteinase inhibitor activity from rat granulosa cells is induced through separate pathways: a LH-cAMP-dependent protein kinase-A pathway and a cAMP-independent protein kinase-C pathway. Furthermore, a TIMP-like protein is observed in granulosa cell-conditioned medium, while TIMP mRNA is present in rat ovaries and increases before ovulation, suggesting that the granulosa cell metalloproteinase inhibitor is TIMP. We propose that TIMP acts in part to control the site and extent of follicular connective tissue remodeling associated with ovulation.
 ...
PMID:Hormonal regulation of matrix metalloproteinase inhibitors in rat granulosa cells and ovaries. 184 3


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>