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

Atrial natriuretic factor (ANF) is stored in atrial myocytes as a prohormone (ANF-(1-126] and is cosecretionally processed to the circulating ANF-related peptides, ANF-(1-98) and ANF-(99-126). Recently, we have shown that the cosecretional processing of ANF can be replicated in primary cultures of neonatal rat atrial myocytes maintained under serum-free conditions and that glucocorticoids are responsible for supporting this processing activity. Activators of protein kinase C (phorbol esters and alpha-adrenergic agonists) and of protein kinase A (cAMP analogs, forskolin, and beta-adrenergic agonists) were tested for their abilities to alter the rate of ANF secretion from the primary cultures. ANF secretion was stimulated approximately 4-fold after a 1-h incubation of the cultures with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA); maximal release occurred at about 100 nM TPA. Reversed-phase high performance liquid chromatography analysis of secreted material indicated that the cells efficiently cosecretionally processed ANF under both basal and TPA-stimulated conditions. However, incubating the cultures for more than 1 h with TPA resulted in a blunted secretory response to further TPA challenge and a 40-50% decrease in the quantity of ANF in the cells. The alpha-adrenergic receptor agonist phenylephrine was also capable of stimulating ANF secretion by about 4-fold at a half-maximal dose of about 1 microM. Phenylephrine-stimulated ANF secretion was inhibited by the alpha 1-adrenergic antagonist prazosin with half-maximal inhibition occurring at approximately 1 nM. Forskolin, 8-bromoadenosine 3':5'-cyclic monophosphate, and N6-2(1)-O-dibutyryladenosine 3':5'-cyclic monophosphate inhibited basal, TPA- and phenylephrine-stimulated ANF secretion. The beta-adrenergic agonist isoproterenol partially inhibited phenylephrine-stimulated ANF secretion with the maximal effect occurring at 1 nM. These results indicate that ANF secretion from the neonatal rat atrial cultures is enhanced by activators of protein kinase C, and decreased by activators of protein kinase A, and that these secretory effects may be mediated through the actions of alpha- and beta-adrenergic receptors, respectively.
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PMID:Regulation of atrial natriuretic factor-(99-126) secretion from neonatal rat primary atrial cultures by activators of protein kinases A and C. 254 6

We quantified the TSH-induced morphological change in FRTL-5 thyroid cells according to a morphological index corresponding to the mean cell area measured from microscopic photographs. Within 15 min, TSH induced, at 10 pM and higher concentrations, a decrease in morphological index together with a rise in cAMP levels in a TSH dose-dependent manner. Forskolin, 3-isobutyl-1-methylxanthine, and RO 20-1724, the latter two being phosphodiesterase inhibitors, mimicked these TSH effects, indicating that the rise in cAMP levels is responsible for the TSH effect. Extracellular ATP and its derivatives, known as purinergic receptor agonists, decreased cAMP levels and caused a complete reversal of the TSH morphological effect. Prior exposure of the cells to islet-activating protein (pertussis toxin), the depletion of extracellular Ca2+, or the addition of low doses of protein kinase-C inhibitors completely abolished the inhibitory action of ATP on the TSH effect, whereas phorbol 12-myristate 13-acetate, which activates protein kinase-C, mimicked the ATP action to some extent. Thus, although the TSH-induced change in cell morphology seems to be dependent on cAMP levels, the inhibition of TSH action by ATP seems to be mediated by at least two signal transduction pathways involving islet-activating protein substrate G-proteins: one inhibiting adenylate cyclase and the other involving Ca2+ and protein kinase-C.
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PMID:Extracellular adenosine triphosphate completely reverses the thyrotropin-induced morphological change in FRTL-5 cells. 254 96

To determine the rat PRL (rPRL) promoter sequences that mediate pituitary-specific and cAMP-induced gene expression in vivo, various lengths of the rPRL promoter were ligated to the luciferase reporter gene and introduced into pituitary and non-pituitary cell lines. A 30-fold increase in rPRL promoter activity was observed in GH4 rat pituitary tumor cells compared to nonpituitary Rat2 fibroblast and HeLa cervical carcinoma cells. About 45% of this cell-specific promoter activity was competed by a plasmid containing the -67 to -45 rPRL promoter region, which is the most proximal binding site for a lactotroph-specific factor. Compared to a -425 rPRL construct, transfection with rPRL 5'-end points of -212, -178, and -127 contained 23%, 45%, and 1%, respectively, of luciferase activity. Forskolin stimulation resulted in a 10-fold induction of all the rPRL promoter fragments tested. Of note, a -127 deletion which was devoid of any basal promoter activity was also induced 10-fold by forskolin. The forskolin effect was abolished when GH4 rat pituitary cells were cotransfected with a plasmid encoding a protein kinase A inhibitor, indicating protein kinase A is involved in the activation mechanism. These data document that both positive and negative effectors influence basal rPRL promoter activity. Furthermore, the minimum sequences required for pituitary-specific rPRL promoter activity are altered by intracellular cAMP levels. Taken together, the data indicate that hormone-activated and cell-specific factors may interact to establish a particular setpoint for rPRL gene expression.
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PMID:Analysis of rat prolactin promoter sequences that mediate pituitary-specific and 3',5'-cyclic adenosine monophosphate-regulated gene expression in vivo. 254 56

1. Retinas from channel catfish were dissociated and the cells maintained in culture. Horizontal cells that normally receive input from cone photoreceptors were identified. The conductance of the electrical junction formed between a pair of 'cone' horizontal cells was measured by controlling the membrane voltage of each cell with a voltage clamp maintained through either a micropipette or a patch pipette. The two techniques yielded similar results. 2. Transjunctional current was measured while transjunctional voltage was stepped to values between +/- 60 mV. The current (measured 5 ms after a step) was proportional to voltage over the range tested. For steps to voltages greater than +/- 45 mV, the current exhibited a slight time-dependent decline. 3. Dopamine decreased junctional conductance in a dose-dependent fashion. A 50% reduction was obtained with 10 nM-dopamine. The D1 agonist fenoldopam (100 nM) also decreased junctional conductance. The uncoupling produced by either agent was rapid and reversible. 4. The introduction of 100 microM-cyclic AMP into one cell of a pair decreased junctional conductance by, on average, 40%. Forskolin (1-10 microM), an activator of adenylate cyclase, decreased junctional conductance 50-90%. 5. The introduction of 80 microM-cyclic GMP into one cell of a pair decreased junctional conductance by, on average, 40%. Nitroprusside (1-10 microM), an activator of guanylate cyclase, reduced junctional conductance 40-65%. 6. The introduction of a peptide inhibitor specific for the cyclic AMP-dependent protein kinase reversed a decrease in junctional conductance produced by superfusion with either dopamine (1 microM), fenoldopam (100 nM) or forskolin (5-10 microM). 7. Intracellular Ca2+ concentration was measured with the fluorescent indicator Fura-2. The intracellular Ca2+ concentration was increased by activation of a Ca2+ current. Junctional conductance remained constant as the internal Ca2+ concentration changed from 100 to 700 nM. 8. Intracellular pH was measured with the fluorescent indicator bis-carboxyethylcarboxyfluorescein. The application of acetate (2.5 mM) reduced intracellular pH by 0.2-0.3 units and decreased junctional conductance by approximately 50%. A subsequent application of fenoldopam did not alter intracellular pH, but decreased junctional conductance by more than 50%. 9. The sensitivity of the junctional conductance between isolated horizontal cells to dopamine is consistent with dopamine having a direct effect on coupling in intact retina. Dopamine regulates the activity of a cyclic AMP-dependent protein kinase which in turn modulates junctional conductance. Changes in intracellular pH and Ca2+ concentration are not involved in mediating the effect of dopamine on coupling. Cyclic GMP and intracellular pH may participate in regulatory pathways independent of that used by cyclic AMP.
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PMID:Modulation of an electrical synapse between solitary pairs of catfish horizontal cells by dopamine and second messengers. 255 70

To study the maturation of fetal pancreatic B-cells, cell suspensions of pancreas from 21.5-day-old fetuses were cultured in RPMI medium containing 10 mM glucose. Forskolin (1 microM), used to stimulate adenylate cyclase, moderately delayed the neoformation of islets, slightly accelerated the proliferation of endocrine cells, and considerably increased insulin release by the cultures. The latter increase was not completely compensated for by the stimulation of insulin biosynthesis, so that the islet insulin content was decreased. The phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 25 nM), used to stimulate protein kinase-C, had little effect on the evolution of the cultures, but increased insulin release. This increase was almost compensated for by the stimulation of insulin biosynthesis. After 9-10 days of culture, insulin release in response to 15 mM glucose or 10 mM leucine was studied with perifused islets. In control islets, glucose produced a sustained increase in insulin release, which, however, was 6-fold smaller than that produced by leucine. Addition of forskolin or TPA to the perifusion medium markedly amplified the response to glucose without causing a biphasic pattern of release. In islets cultured with forskolin, the insulin response to glucose or leucine was decreased, largely owing to the lower insulin stores. In islets cultured with TPA, the insulin response to glucose or leucine was also decreased, but these differences cannot be explained simply by changes in insulin content. Neither treatment affected the kinetics of release. In conclusion, acute stimulation of adenylate cyclase or protein kinase-C markedly increased insulin release from fetal islets without causing an adult-like biphasic pattern of secretion. Chronic stimulation did not accelerate maturation of B-cells.
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PMID:Effects of stimulation of adenylate cyclase and protein kinase-C on cultured fetal rat B-cells. 267 88

An understanding of the regulation of CRF secretion in rats is currently incomplete, in part due to the lack of sensitive in vitro models available for studying this neuropeptide. In particular, the effects of catecholamines on CRF secretion, and the receptor subtypes mediating these actions have long been the subject of much debate. A cultured cell model has been adapted for studying secretory responses of hypothalamic cells of 1-week-old rats. Between 7-16 days in monolayer culture the cells secreted detectable levels of immunoreactive CRF, and this release was paralleled by the appearance of punctate bead-like regions of immunoreactivity along fine cellular processes. CRF secretion was increased up to 4-fold by norepinephrine (EC50, approximately 0.5 microM). The increase in CRF secretion produced by norepinephrine was blocked by the beta-receptor antagonist propranolol, but not by the alpha-antagonist prazosin. Moreover, the beta-receptor agonist isoproterenol significantly elevated CRF secretion, whereas the alpha-agonist phenylephrine was without effect, except at high concentrations. Addition of phenylephrine, however, potentiated the effect of isoproterenol, but this response was still significantly less than that produced by norepinephrine. Forskolin (EC50, approximately 0.7 microM) and the active phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (EC50, approximately 40 nM) also increased CRF secretion by 3- to 4-fold. Inactive phorbol derivatives had no effect on CRF release from these cultures. The results indicate that cultured neonatal rat hypothalamic cells are a powerful model for the study of CRF release in vitro, and that norepinephrine acts directly at the isolated cell level to stimulate secretion of this peptide, primarily by activating beta-adrenoceptors. The results also suggest that at least two functional second messenger systems (adenylate cyclase and protein kinase-C) are involved in CRF secretion and are already functional in the neonatal hypothalamus.
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PMID:Secretion of corticotropin-releasing factor from cultured rat hypothalamic cells: effects of catecholamines. 278 68

The nicotinic acetylcholine receptor (AcChoR) from rat myotubes prelabeled in culture with [32P]orthophosphate was isolated by acetylcholine affinity chromatography followed by immunoaffinity chromatography. Under basal conditions, the nicotinic AcChoR was shown to be phosphorylated in situ on the beta and delta subunits. Regulation of AcChoR phosphorylation by cAMP-dependent protein kinase was explored by the addition of forskolin or cAMP analogues to prelabeled cell cultures. Forskolin, an activator of adenylate cyclase, stimulated the phosphorylation of the delta subunit 20-fold over basal phosphorylation and induced phosphorylation of the alpha subunit. The effect of forskolin was dose dependent with a half-maximal response at 8 microM in the presence of 35 microM Ro 20-1724, a phosphodiesterase inhibitor. Stimulation of delta subunit phosphorylation was almost maximal within 5 min, whereas stimulation of alpha subunit phosphorylation was not maximal until 45 min after forskolin treatment. Stimulation of AcChoR phosphorylation by 8-benzylthioadenosine 3',5'-cyclic monophosphate was identical to that obtained by forskolin. Two-dimensional thermolytic phosphopeptide maps of the delta subunit revealed a single major phosphopeptide. These results correlate closely with the observed effects of forskolin on AcChoR desensitization in muscle and suggest that cAMP-dependent phosphorylation of the delta subunit increases the rate of AcChoR desensitization in rat myotubes.
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PMID:Regulation of nicotinic acetylcholine receptor phosphorylation in rat myotubes by forskolin and cAMP. 281 83

The mechanisms whereby activation of the cyclic AMP-dependent protein kinase A or the Ca2+-phospholipid-dependent protein kinase C amplifies insulin release were studied with mouse islets. Forskolin and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) were used to stimulate adenylate cyclase and protein kinase C respectively. The sulphonylurea tolbutamide was used to initiate insulin release in the presence of 3 mM-glucose. Tolbutamide alone inhibited 86Rb+ efflux, depolarized beta-cell membrane, triggered electrical activity, accelerated 45Ca2+ influx and efflux and stimulated insulin release. Forskolin alone only slightly inhibited 86Rb+ efflux, but markedly increased the effects of tolbutamide on electrical activity, 45Ca2+ influx and efflux, and insulin release. In the absence of Ca2+, only the inhibition of 86Rb+ efflux persisted. TPA (100 nM) alone slightly accelerated 45Ca2+ efflux and insulin release without affecting 45Ca2+ influx or beta-cell membrane potential. It increased the effects of tolbutamide on 45Ca2+ efflux and insulin release without changing 86Rb+ efflux, 45Ca2+ influx or electrical activity. Omission of extracellular Ca2+ suppressed all effects due to the combination of TPA and tolbutamide, but not those of TPA alone. Though ineffective alone, 10 nM-TPA amplified the releasing action of tolbutamide without affecting its ionic and electrical effects. In conclusion, the two amplification systems of insulin release involve at least partially distinct mechanisms. The cyclic AMP but not the protein kinase C system initiating signal (Ca2+ influx) triggered by the primary secretagogue.
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PMID:Distinct mechanisms for two amplification systems of insulin release. 282 37

Evidence is presented indicating that a cAMP-dependent mechanism activates tryptophan hydroxylase (TrpH), the rate-limiting enzyme for serotonin (5-HT) biosynthesis. Forskolin, a selective activator of adenylate cyclase, stimulated 5-HT formation in synaptoneurosome preparations of rat striatum, substantia nigra, hypothalamus, and amygdala. Further studies of striatum revealed that the forskolin-induced activation of serotonin synthesis is readily reversible. Also, it may be self-limited by a mechanism of desensitization, since after an initial exposure to forskolin followed by removal, a re-exposure of synaptoneurosomes to forskolin was no longer stimulatory. In contrast to these results for 5-HT synthesis, forskolin-induced stimulation of dopamine synthesis persisted following removal of forskolin; hence the response was not rapidly reversible or desensitized. In soluble extracts of striatum, 8-thiomethyl-cyclic AMP enhanced TrpH activity, supporting a direct role of cyclic AMP and cyclic AMP-dependent protein kinase in regulating TrpH. In agreement with previous reports, 8-thiomethyl cyclic AMP also stimulated tyrosine hydroxylase activity in soluble striatal extracts. We conclude that cyclic AMP is an important regulator of TrpH, in addition to its known effects on tyrosine hydroxylase.
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PMID:Regulation of tryptophan hydroxylase activity by a cyclic AMP-dependent mechanism in rat striatum. 282 48

Forskolin and isoproterenol, agonists of adenylate cyclase activity, and dibutyryl cyclic AMP, stimulated an S6 kinase activity in astroglial cells. This activity was insensitive to the thermostable inhibitor of cyclic AMP-dependent protein kinase and had the same behaviour on a DEAE-Sephacel column as the mitogen stimulated S6 kinase. These observations support the idea that the cyclic AMP cascade, as well as various growth factors, can activate S6 kinase.
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PMID:Activation of an S6 kinase from rat astroglial cells by cAMP. 283 Jan 39


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