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)

Whole-cell patch clamp experiments were used to investigate the transduction mechanism of adenosine A(2A) receptors in modulating N-methyl-D-aspartate (NMDA)-induced currents in rat striatal brain slices. The A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680) inhibited the NMDA, but not the (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) current in a subset of striatal neurons. Lucifer yellow-filled pipettes in combination with immunostaining of A(2A) receptors were used to identify CGS 21680-sensitive cells as typical medium spiny striatal neurons. Dibutyryl cyclic AMP and the protein kinase A activator Sp-cyclic AMPs, but not the protein kinase A inhibitors Rp-cyclic AMPS or PKI(14 - 24)amide abolished the inhibitory effect of CGS 21680. The phospholipase C inhibitor U-73122, but not the inactive structural analogue U-73343 also interfered with CGS 21680. The activation of protein kinase C by phorbol 12-myristate 13-acetate or the blockade of this enzyme by staurosporine did not alter the effect of CGS 21680. Heparin, an antagonist of inositol 1, 4,5-trisphosphate (InsP(3)) and a more efficient buffering of intracellular Ca(2+) by BAPTA instead of EGTA in the pipette solution, abolished the CGS 21680-induced inhibition. The calmodulin antagonist W-7 and cytochalasin B which enhances actin depolymerization also prevented the effect of CGS 21680; the calmodulin kinase II inhibitors CaM kinase II(281 - 309) and KN-93 but not the inactive structural analogue KN-92 were also effective. The calcineurin inhibitor deltamethrin did not interfere with CGS 21680. It is suggested that the transduction mechanism of A(2A) receptors to inhibit NMDA receptor channels is the phospholipase C/InsP(3)/calmodulin and calmodulin kinase II pathway. The adenylate cyclase/protein kinase A and phospholipase C/protein kinase C pathways do not appear to be involved.
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PMID:Inhibition by adenosine A(2A) receptors of NMDA but not AMPA currents in rat neostriatal neurons. 1080 62

Our previous finding that insulin induces apolipoprotein AI (apoAI) transcription points to the participation of intracellular signaling. This finding prompted us to ask whether two classical G-protein-coupled signaling pathways requiring activated protein kinase A (PKA) or kinase C (PKC) may also regulate apoAI. Therefore, human hepatoma, Hep G2 cells stably transfected with pAI.474-CAT, a reporter construct spanning -474 to -7 of apoAI DNA fused to chloramphenicol acetyltransferase (CAT) were treated with 10 microm forskolin (FSK) or 50 nm phorbol dibutyrate (PDBu) to activate PKA and PKC, respectively. Results showed that the apoAI promoter activity increased 4-5-fold following 24 h of treatment with either FSK or PDBu. Induction by either agent was blocked with actinomycin D but not the protein synthesis inhibitor, cycloheximide. The PKA inhibitor, PKI 14-22 amide, abrogated induction by FSK, 100 microm 8-bromo-cAMP, or 100 ng/ml cholera toxin, but it had no effect on activation via PKC. Similarly, PDBu induction was attenuated by 2 microm of the PKC inhibitor, GF109203X, but it did not affect FSK activity. Next we used deletional constructs to show that the actions of FSK and PDBu required the insulin-responsive core element (IRCE). This motif matched the consensus binding site for the transcription factor, Sp1. The binding of Sp1 to the IRCE was confirmed by gel-retardation and supershift analysis. Site-directed mutagenesis of the IRCE eliminated Sp1 action and induction by FSK or PDBu. Whereas overexpression of Sp1 enhanced basal and FSK or PDBu induced promoter activity, transfection of an antisense oligomer against Sp1 mRNA attenuated both parameters. In summary, activation of PKA or PKC increases apoAI promoter activity. The activity of both signaling pathways is mediated by the IRCE, a motif that binds the transcription factor, Sp1.
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PMID:Activation of apolipoprotein AI gene expression by protein kinase A and kinase C through transcription factor, Sp1. 1082 13

GnRH has been suggested to regulate hCG secretion in the placenta. In the present study, we report isolation of full-length GnRH receptor (GnRHR) complementary DNA from human placental cells, including a choriocarcinoma cell line (JEG-3), immortalized extravillous trophoblasts (IEVT), and first trimester cytotrophoblast cells in primary culture. Sequence analysis of the placental GnRHR complementary DNA revealed a 100% similarity to its pituitary counterpart. Northern blot analysis using polyadenylated RNA isolated from JEG-3 and IEVT cells revealed a 2.5- and 1.2-kb GnRHR transcripts. Using semiquantitative RT-PCR, regulation ofplacental GnRHR gene expression was examined. In contrast to pituitary gonadotrope alphaT3-1 cells, down-regulation of GnRHR messenger RNA (mRNA) levels was not observed in placental cells after 24 h of 0.1-microM GnRH agonist (GnRHa) treatment. Instead, a 43% (P < 0.01) and 30% (P < 0.05) increase in GnRHR mRNA levels was observed in JEG-3 and IEVT cells, respectively. In addition, 10 microM phorbol ester or forskolin treatments resulted in a significant increase in GnRHR expression in both JEG-3 and IEVT cells. The GnRHa-induced increase in GnRHR expression was shown to be a receptor-mediated process, as cotreatment of GnRH antagonist abolished the effect. It has also been demonstrated that these stimulatory effects on GnRHR gene expression were regulated at least in part at the transcriptional level. Pretreatment of JEG-3 cells with a specific protein kinase C inhibitor (GF109203X), adenylate cyclase inhibitor (SQ22536), or protein kinase A inhibitor [PKI-(14-22) amide, myristylated] reversed GnRHa-induced GnRHR gene expression, suggesting that the placental GnRHR couples to the protein kinase C (PKC) and cAMP/ protein kinase A (PKA) pathways. By Northern blot analysis, we observed a 100% (P < 0.001) increase in hCGbeta mRNA levels after 0.1 microM GnRHa treatment in JEG-3 cells. Again, this effect was prevented in the presence of either protein kinase C inhibitor or adenylate cyclase inhibitor, further supporting the role of the PKC and PKA pathways in GnRHR-coupled signaling in placental cells. In summary, these data strongly support the idea that 1) GnRH plays an autocrine/paracrine role in regulating placental function through a receptor-mediated mechanism; and 2) the placental GnRHR couples to both the PKC and PKA pathways.
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PMID:Regulation of human gonadotropin-releasing hormone receptor gene expression in placental cells. 1087 33

We present evidence of a link between low-density lipoprotein (LDL) receptor binding and activation of a platelet G-coupled protein. LDL stimulation induced cytosolic [Ca2+]i mobilization, increase in inositol 1,4,5-triphosphate (IP3) formation and a rapid cytosol-to-membrane translocation of protein kinase C (PKC) enzymatic activity. Pertussis toxin inhibited all the stimulatory effects, whereas cholera toxin had no effect. Using ligand-binding assays, we demonstrated that exposing platelet LDL receptors to high concentrations of LDL (1.5 g/l) caused a rapid down-regulation and desensitization, as shown by the reduction in the Bmax, intracellular [Ca2+]i mobilization and IP3 formation to 65, 73 and 63%, respectively. The inhibitory effects were reversible and dose and time dependent. Furthermore, VLDL (0.2 g/l) and IDL (0.07 g/l) induced similar desensitization effects. However, HDL3 (up to 1.5 g/l), chylomicrons (up to 0.5 g/l) and cyclohexandione-modified LDL (which does not bind to platelets) had no significant effects. Protein kinase C inhibitors (150 nmol/l staurosporine, 100 micromol/l H-7, and 10 nmol/l bisindolylmaleimide) inhibited desensitization to 71%, on average. Sequestration blocking agents (0.30 g/l, concanavalin A) had no significant effect if phosphorylation was operative. However, there was a complete blockade with the concurrent inhibition of both pathways. In contrast, cAMP-dependent protein kinase inhibitors (PKI, 1 micromol/l) or beta2-adrenergic receptor kinase inhibitors (100 nmol/l, heparin), had no effect. Overall results indicate that LDL binds to a pertussis sensitive G-protein coupled receptor and that high levels of lipoproteins down-regulate the number of receptors and desensitize its mediated response by a mechanism that involves PKC-phosphorylation and sequestration of binding sites. This new regulatory mechanism may have implications for the thrombogenicity in hyperlipidemia and for effects of lipid lowering therapy.
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PMID:Low-density lipoprotein (LDL) binds to a G-protein coupled receptor in human platelets. Evidence that the proaggregatory effect induced by LDL is modulated by down-regulation of binding sites and desensitization of its mediated signaling. 1122 31

Neurotrophins are expressed in the adult kidney, but their significance is unclear. We showed previously that nerve growth factor (NGF) inhibits HCO absorption in the rat medullary thick ascending limb (MTAL) via an extracellular signal-regulated kinase (ERK)-dependent pathway. Here we examined whether other neurotrophic factors affect MTAL HCO absorption. Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor had no effect. In contrast, neurotrophin-3 (NT-3, 0.7 nM) inhibited HCO absorption by 40% (half-maximal inhibition at approximately 0.4 nM). Inhibition by NT-3 was additive to inhibition by NGF. Inhibitors of ERK activation that block inhibition by NGF had no effect on inhibition by NT-3. In contrast, 8-bromo-cAMP or forskolin pretreatment blocked inhibition by NT-3 but not NGF. Inhibition by NT-3 was also blocked by the specific protein kinase A (PKA) inhibitor myristoylated PKI(14-22) amide and by vasopressin, which inhibits HCO absorption via cAMP. Inhibitors of phosphatidylinositol 3-kinase or protein kinase C did not affect NT-3-induced inhibition, but inhibition by NT-3 was eliminated by genistein, consistent with involvement of a receptor tyrosine kinase. These results demonstrate that NT-3 inhibits HCO absorption via a cAMP- and PKA-dependent pathway. NT-3 and NGF regulate MTAL ion transport through different signal transduction mechanisms. These studies establish a direct role for NT-3 in regulation of renal tubule transport and identify the MTAL as an important target for neurotrophins, which may be involved in the control of renal acid excretion.
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PMID:Neurotrophin-3 inhibits HCO absorption via a cAMP-dependent pathway in renal thick ascending limb. 1169 38

Rasagiline (N-propargyl-1-(R)-aminoindan) is a selective, irreversible monoamine oxidase B (MAO B) inhibitor which has been developed as an anti-Parkinson drug. In controlled monotherapy and as adjunct to L-dopa it has shown anti-Parkinson activity. In cell culture (PC-12 and neuroblastoma SH-SY5Y cells) it exhibits neuroprotective and anti-apoptotic activity against several neurotoxins (SIN-1, MPTP, 6-hydroxydopamine and N-methyl-(R)-salsolinol) and ischemia. In vivo, it reduces the sequelae of traumatic brain injury in mice and speeds their recovery. The neuroprotective activity of rasagaline does not result from MAO B inhibition, since its S-enantiomer, TVP1022, which has 1000-fold weaker MAO inhibitory activity, exhibits similar neuroprotective properties. Introduction of a carbamate moiety into the rasagiline molecule to confer cholinesterase inhibitory activity for the treatment of Alzheimer's disease, resulted in compounds TV3326 [(N-Propargyl-(3R)Aminoindan-5-YL)-Ethyl Methyl Carbamate] and its S-enantiomer TV3279 [(N-Propargyl-(3S)Aminoindan-5-YL)-Ethyl Methyl Carbamate], which retain the neuroprotective activities of rasagiline and TVP1022. They also antagonize scopolamine-induced impairments in spatial memory. In addition, TV3326 exhibits brain-selective MAO A and B inhibitory activity after chronic administration and has antidepressant-like activity in the forced swim test. This is associated with an increase in brain levels of serotonin. The anti-apoptotic activity of these propargylamine-containing derivatives may be related to their ability to delay the opening of voltage-dependent anion channels (VDAC), which are part of the mitochondrial permeability transition pore. The propargylamine moiety is responsible for the increase in the mitochondrial family of Bcl-2 proteins, prevention in the fall in mitochondrial membrane potential, prevention of the activation of caspase 3, and of translocation of glyceraldehyde-3-phosphate dehydrogenase from the cytoplasm to the nucleus. The latter processes are closely associated with neurotoxin-induced apoptosis. Rasagiline interacts with and prevents the binding of PKI 1195 to the pro-apoptotic peripheral benzodiazepine receptor, which together with Bcl-2, hexokinase, porin, and adenine nucleotide translocator constitutes part of the VDAC. Furthermore, rasagiline, TV3326 and TV3279 are able to influence the processing of amyloid precursor protein by activation of alpha-secretase and increasing the release of soluble alpha APP in rat PC-12 and human neuroblastoma SH-SY5Y cells and in rat and mice cortex and hippocampus. This process has been shown to involve the upregulation of PKC and MAP kinase. It is quite likely that the induction of Bcl-2 and activation of PKC by rasagiline and TV3326 is closely linked to the anti-apoptotic action of these drugs and their ability to process APP by activation of alpha-secretase.
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PMID:Molecular basis of neuroprotective activities of rasagiline and the anti-Alzheimer drug TV3326 [(N-propargyl-(3R)aminoindan-5-YL)-ethyl methyl carbamate]. 1204 33

LH receptor activation leads to the phosphorylation/activation of p42/44 MAPK in preovulatory granulosa cells. As the LH receptor can activate both adenylyl cyclase and phospholipase C, we hypothesized that the LH receptor could elicit phosphorylation of p42/44 MAPK through activation of protein kinase A (PKA) and/or protein kinase C (PKC). Preovulatory granulosa cells in serum-free primary cultures were treated with ovulatory concentrations of human chorionic gonadotropin (hCG), an LH receptor agonist, with or without various inhibitors. The PKA inhibitor H89 as well as the myristoylated PKA inhibitor peptide PKI strongly inhibited hCG-stimulated p42/44 MAPK phosphorylation, whereas the PKC inhibitor GF109203X had no effect on p42/44 MAPK phosphorylation. LH receptor-stimulated phosphorylation of cAMP response element-binding protein (CREB), histone H3, and MAPK kinase (MEK) was also strongly inhibited by H89 and not by GF109203X. The extent of PKC activation was assessed in preovulatory granulosa cells using three criteria: translocation of PKC isoforms to the membrane fraction, phosphorylation of a known PKC substrate, and autophosphorylation of PKC delta on an activation-related site. By all three criteria PKCs were partially activated before hCG stimulation, and hCG treatment failed to elicit further PKC activation, in vitro or in vivo. Taken together, these results indicate that, under primary culture conditions where physiological levels of signaling proteins are present, hCG signals to activate MEK, p42/44 MAPK, CREB, and histone H3 in a predominantly PKA-dependent and PKC-independent manner. Unexpectedly, PKCs were partially activated in the absence of LH receptor activation, and LH receptor activation did not elicit further detectable PKC activation.
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PMID:Acute signaling by the LH receptor is independent of protein kinase C activation. 1213 May 64

Cyclic AMP (cAMP)-responsive element-binding protein (CREB) is a transcription factor important in developing nervous system cells and is activated by a variety of signaling molecules. Aroclor 1254 (A1254), a polychlorinated biphenyl mixture, perturbs Ca(2+) homeostasis and increases CREB phosphorylation in rat neonatal cortical cell cultures in a time- and concentration-dependent manner. The present experiments determined that the cell type responding to A1254 with Ca(2+) increases and phosphorylated CREB (phospho-CREB) was predominantly of neuronal morphology and microtubule-associated protein (MAP2)-positive phenotype. Similarly, glutamate (100 microM) increased phospho-CREB immunoreactivity selectively in MAP2-immunopositive cells. Using Western blotting and immunocytochemical techniques, we identified key signal transduction pathways operative in phosphorylating CREB in cortical cell cultures and examined their participation in 3 ppm A1254-induced CREB activation. Cortical cultures treated with glutamate, forskolin or the phorbol ester phorbol 12-myristate 13-acetate exhibited robust increases in phospho-CREB. Tetrodotoxin (1 microM) completely inhibited CREB phosphorylation by A1254, suggesting that synaptic activity is involved in A1254-induced CREB activation. Buffering [Ca(2+)](i) with bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl) ester in the absence of extracellular Ca(2+) partially inhibited A1254-induced CREB phosphorylation. Inhibition of mitogen-activated protein kinase (10 microM U0126) or protein kinase C (PKC; bisindoylmaleimide, 5 microM) activation did not inhibit A1254-induced CREB phosphorylation. By contrast, inhibition of protein kinase A (PKA) with 100 microM PKA inhibitor peptide, PKI, blocked A1254-induced CREB phosphorylation. Thus, we examined whether A1254 activates PKA by increasing cAMP; 10 microM forskolin, but not A1254, elevated intracellular cAMP levels. These results indicate that in neocortical cells in culture, CREB phosphorylation occurs via Ca(2+)-, PKA-, and PKC-dependent pathways. Furthermore, A1254-induced CREB phosphorylation occurs predominantly in neurons, is dependent on synaptic activity and mediated by Ca(2+)- and PKA-dependent pathways.
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PMID:Identification of calcium-dependent and -independent signaling pathways involved in polychlorinated biphenyl-induced cyclic AMP-responsive element-binding protein phosphorylation in developing cortical neurons. 1242 22

Inward-rectifying potassium (Kir) channels are essential for maintaining the resting membrane potential near the K(+) equilibrium and they are responsible for hyperpolarisation-induced K(+) influx. We characterised the Kir current in primary cultured ovine somatotropes and examined the effect of growth hormone-releasing peptide-2 (GHRP-2) on this current and its related intracellular signalling pathways. The Kir current was, in most cases, isolated using nystatin-perforated patch-clamp techniques. In bath solution containing 5 mM K(+), the Kir current was composed of both transient (fast activated) and delayed (slowly activated) components. An increase in the external K(+) concentration from 5 to 25 mM induced an augmentation of approximately 4-fold in the delayed part of the Kir current and both BaCl(2) and CsCl dose-dependently inhibited this current, confirming the presence of the Kir current in ovine somatotropes. Moreover, this specific effect of high K(+) on the Kir current was only observed in the cells that showed positive staining with anti-growth hormone (GH) antibodies, or in GC cells that belong to a rat somatotrope cell line. Application of GHRP-2 (100 nM) reversibly and significantly reduced the Kir current in bath solutions with 5 or 25 mM K(+) in ovine somatotropes. In addition, we found that the reduction in the Kir current mediated by GHRP-2 was totally abolished by the pretreatments with H89 (1 microM) or Rp-cAMP (100 microM) or by intracellular dialysis of a specific protein kinase A (PKA) inhibitory peptide PKI (10 microM). The specific PKC blocker chelerythrine (1 microM) or inhibitory peptide PKC(19-36) (10 microM) did not show any effects on the GHRP-2-induced decrease in the Kir current. These results suggest that the inhibition of Kir current through PKA-cAMP pathways may play an integral role in GHRP-2-induced depolarisation and GH release in ovine somatotropes.
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PMID:Growth hormone-releasing peptide-2 reduces inward rectifying K+ currents via a PKA-cAMP-mediated signalling pathway in ovine somatotropes. 1245 22

Orexins, orexigenic neuropeptides, are secreted from lateral hypothalamus and orexin receptors are expressed in the pituitary. Since growth hormone (GH) secreted from pituitary is integrally linked to energy homeostasis and metabolism, we studied the effect of orexin-B on voltage-gated Ca(2+) currents and the related signalling mechanisms in primary cultured ovine somatotropes using whole-cell patch-clamp techniques. With a bath solution containing TEA-Cl (40 mM) and Tetrodotoxin (TTX) (1 microM), three subtypes of Ca(2+) currents, namely the long-lasting (L), transient (T), and N currents, were isolated using different holding potentials (-80 and -30 mV) in combination with specific Ca(2+) channel blockers (nifedipine and omega-conotoxin). About 75% of the total current amplitude was contributed by the L current, whereas the N and T currents accounted for the rest. Orexin-B (1-100 nM) dose-dependently and reversibly increased only the L current up to approximately 125% of the control value within 4-5 min. Neither a specific protein kinase A (PKA) blocker (H89, 1 microM) nor an inhibitory peptide (PKI, 10 microM) had any effect on the increase in L current by orexin-B. The orexin-B-induced increase in the L current was abolished by concurrent treatment with calphostin C (Cal-C, 100 nM), protein kinase C (PKC) inhibitory peptide (PKC(19-36), 1 microM), or by pretreatment with phorbol-12,13-dibutyrate (PDBu) (0.5 microM) for 16 h (a downregulator of PKC). Orexin-B also increased in vitro GH secretion in a dose-dependent manner. We conclude that orexin-B increases the L-type Ca(2+) current and GH secretion through orexin receptors and PKC-mediated signalling pathways in ovine somatotropes.
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PMID:Orexin-B augments voltage-gated L-type Ca(2+) current via protein kinase C-mediated signalling pathway in ovine somatotropes. 1267 48


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