Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ca2+ plays an essential role in pituitary adenylate cyclase-activating polypeptide (PACAP)-stimulated growth hormone (GH) secretion from porcine somatotropes. Here, Indo-1 microfluorimetry was used to investigate the dynamics of free cytosolic Ca2+ concentration ([Ca2+]i) in single porcine somatotropes in response to PACAP38 and PACAP27. We also evaluated the relative contributions of extra- and intracellular Ca2+ sources and of cAMP-dependent protein kinase (PKA) and phospholipase C (PLC). A high proportion of somatotropes responded to PACAP38 (79.4%) and PACAP27 (68.4%) with [Ca2+]i rises that could be followed by a refractory plateau (type 1 response), or by a decrease in [Ca2+]i during which somatotropes were responsive to a subsequent PACAP pulse (type II response). Although Ca2+ profiles in response to both peptides were similar, PACAP38-induced [Ca2+]i rises were higher. Somatotrope response to PACAP38 or PACAP27 was markedly reduced by removing extracellular Ca2+, blocking Ca2+ entry through L-type voltage sensitive Ca2+ channels (VSCC), or inhibiting PKA. Conversely, Ca2+ depletion from intracellular stores or PLC inactivation did not affect the response to PACAP27 but considerably reduced maximal [Ca2+]i induced by PACAP38. We conclude that both peptides stimulate extracellular Ca2+ influx through L-type VSCC by a PKA-dependent mechanism. However, PACAP38 also triggers a PLC-mediated Ca2+ mobilization from intracellular stores, thereby indicating that the two molecular forms of PACAP activate common and distinct second messenger pathways within porcine somatotropes.
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PMID:Pituitary adenylate cyclase-activating polypeptides 38 and 27 increase cytosolic free Ca2+ concentration in porcine somatotropes through common and distinct mechanisms. 992 28

The colon cancer cell line HT29 is a useful model to study intestinal chloride secretion. These cells have both cAMP-activated and calcium-activated chloride channels. Changes in elemental content of the cells after stimulation with agonists were determined by X-ray microanalysis in the scanning or scanning transmission electron microscope. Exposure of HT29 cells to pituitary adenylate cyclase activating polypeptide-27 (PACAP) caused a transient decrease in the cellular Cl and K concentrations, indicating (net) efflux of chloride. The effect of PACAP is inhibited by somatostatin, which is known to inhibit cAMP-activated as well as calcium-activated chloride secretion and by U-73122, an inhibitor of phospholipase C. Alloxan, an inhibitor of adenylate cyclase, did not significantly affect the PACAP-induced loss of chloride. The calcium-chelating agent EGTA inhibited the PACAP-induced loss of chloride, indicating the need for extracellular calcium ions. Also vasointestinal polypeptide (VIP) caused a decrease of the cellular chloride concentration in HT29 cells. VIP-induced loss of chloride could be inhibited by pre-treating the cells with somatostatin or UK14,304, an alpha-2 adrenergic agonist that has been shown previously to inhibit purinergically activated chloride efflux. Our results indicate that there is cross-talk between the cAMP- and the calcium-activated pathways for chloride secretion in HT29 cells.
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PMID:Effects of pituitary adenylate cyclase activating polypeptide-27 (PACAP) and vasoactive intestinal polypeptide (VIP) on chloride in HT29 cells studied by X-ray microanalysis. 1007 2

Neuropeptide receptors couple via G-proteins to two principal signaling pathways that elevate cAMP through adenylate cyclase (AC) or mobilize intracellular Ca(2+) through phospholipase C (PLC)-stimulated inositol phosphate (IP) turnover and production of inositol 1,4,5-trisphosphate (IP(3)). We showed previously that high-affinity receptors for pituitary adenylate cyclase-activating polypeptide (PACAP) are present on chick ciliary ganglion neurons and that receptor occupation increases cAMP production, resulting in enhanced acetylcholine sensitivity. After we suppressed AC activity and cAMP production with 2'-5' dideoxyadenosine, however, PACAP no longer increased acetylcholine sensitivity but instead reduced it, suggesting that an AC-independent signal pathway activated by PACAP inhibits some nicotinic acetylcholine receptors (AChRs). We now use fast-perfusion, imaging, and biochemical methods to identify the AChRs modulated by PACAP and to characterize the signal pathway responsible for their inhibition. Without previous AC block, both the rapidly desensitizing, alpha-bungarotoxin (alphaBgt)-sensitive alpha7-AChRs and the slowly desensitizing, alphaBgt-insensitive alpha3*-AChRs on the neurons were potentiated by PACAP. After AC blockade, however, PACAP inhibited alpha7-AChRs but left alpha3*-AChRs unaffected. The selective inhibition of alpha7-AChRs appeared to use a PLC signaling pathway because it was not seen after lowering PLC activity or buffering intracellular Ca(2+) and was mimicked by dialyzing neurons with an IP(3) receptor agonist. PACAP also induced IP turnover and increased [Ca(2+)](i) assessed directly with Fluo-3AM imaging. Given our previous findings that PACAP receptors couple to AC, the present results demonstrate a remarkable ability of a single neuropeptide to activate two signaling pathways and in so doing selectively regulate two classes of downstream ion channel targets.
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PMID:Pituitary adenylate cyclase-activating polypeptide activates a phospholipase C-dependent signal pathway in chick ciliary ganglion neurons that selectively inhibits alpha7-containing nicotinic receptors. 1041 62

Pituitary adenylate cyclase-activating polypeptides (PACAP) have potent regulatory and neurotrophic activities on superior cervical ganglion (SCG) sympathetic neurons with pharmacological profiles consistent for the PACAP-selective PAC(1) receptor. Multiple PAC(1) receptor isoforms are suggested to determine differential peptide potency and receptor coupling to multiple intracellular signaling pathways. The current studies examined rat SCG PAC(1) receptor splice variant expression and coupling to intracellular signaling pathways mediating PACAP-stimulated peptide release. PAC(1) receptor mRNA was localized in over 90% of SCG neurons, which correlated with the cells expressing receptor protein. The neurons expressed the PAC(1)(short)HOP1 receptor but not VIP/PACAP-nonselective VPAC(1) receptors; low VPAC(2) receptor mRNA levels were restricted to ganglionic nonneuronal cells. PACAP27 and PACAP38 potently and efficaciously stimulated both cAMP and inositol phosphate production; inhibition of phospholipase C augmented PACAP-stimulated cAMP production, but inhibition of adenylyl cyclase did not alter stimulated inositol phosphate production. Phospholipase C inhibition blunted neuron peptide release, suggesting that the phosphatidylinositol pathway was a prominent component of the secretory response. These studies demonstrate preferential sympathetic neuron expression of PACAP-selective receptor variants contributing to regulation of autonomic function.
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PMID:Pituitary adenylate cyclase-activating polypeptides directly stimulate sympathetic neuron neuropeptide Y release through PAC(1) receptor isoform activation of specific intracellular signaling pathways. 1048 12

Prostaglandin E2 (PGE2) causes Ca2+ release from intracellular Ca2+ stores and stimulates phosphoinositide metabolism in bovine adrenal medullary cells. These results have been interpreted as PGE2 induces Ca2+ release from inositol trisphosphate (IP3)-sensitive stores. However, we have recently shown that pituitary adenylate cyclase-activating polypeptide (PACAP), bradykinin, and angiotensin II release Ca2+ from caffeine/ryanodine-sensitive stores, although they cause a concomitant increase of intracellular IP3. In light of these results, the mechanism of PGE2-induced Ca2+ release was investigated in the present study. PGE2 dose-dependently caused a transient but consistent Ca2+ release from internal Ca2+ stores. The PGE2-induced Ca2+ release was unaffected by cinnarizine, a blocker of IP3-induced Ca2+ release. By contrast, it was potently inhibited by prior application of caffeine and ryanodine. Although IP3 production in response to PGE2 was abolished by the phospholipase C inhibitor U-73122, Ca2+ release in response to PGE2 was unaffected by U-73122. The PGE2-induced Ca2+ release was unaffected by Rp-adenosine 3',5'-cyclic monophosphothioate, an inhibitor of protein kinase A, and forskolin, a cyclic AMP (cAMP)-elevating agent, did not cause Ca2+ release. The EP1 agonist 17-phenyl-trinorPGE2 and the EP1/EP3 agonist sulprostone mimicked the Ca(2+)-releasing effects of PGE2, whereas the EP2 agonist butaprost or the EP2/EP3 agonist misoprostol caused little or no Ca2+ release. The EP1 antagonist SC-51322 significantly suppressed the Ca2+ release response induced by PGE2, whereas the EP4 antagonist AH-23828B had little effect. These results suggest that PGE2, acting on EP1-like receptors, induces Ca2+ release from ryanodine/caffeine-sensitive stores through a mechanism independent of IP3 and cAMP and that PGE2 may share the same mechanism with PACAP and the other peptide ligands in causing Ca2+ release in bovine adrenal medullary cells.
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PMID:Prostaglandin E2 induces Ca2+ release from ryanodine/caffeine-sensitive stores in bovine adrenal medullary cells via EP1-like receptors. 1053 77

Pituitary adenylate cyclase activating peptide (PACAP) is a novel neuropeptide with regulatory and trophic functions that is related to vasoactive intestinal peptide (VIP). Here we investigate the expression of specific PACAP receptors (PAC1) and common VIP/PACAP receptors (VPAC1 and VPAC2) in the human hyperplastic prostate by immunological methods. The PAC1 receptor corresponded to a 60-KDa protein whereas the already known VPAC1 and VPAC2 receptors possessed molecular masses of 58 and 68 KDa, respectively. The heterogeneity of VIP/PACAP receptors in this tissue was confirmed by radioligand binding studies using [125I]PACAP-27 by means of stoichiometric and pharmacological experiments. At least two classes of PACAP binding sites showing different affinities could be resolved, with Kd values of 0.81 and 51.4 nM, respectively. The order of potency in displacing [125I]PACAP-27 binding was PACAP-27 approximately equal to PACAP-38 > VIP. PACAP-27 and VIP stimulated similarly adenylate cyclase activity, presumably through common VIP/PACAP receptors. The PAC1 receptor was not coupled to activation of either adenylate cyclase, nitric oxide synthase, or phospholipase C. It appears to be a novel subtype of PAC1 receptor because PACAP-27 (but not PACAP-38 or VIP) led to increased phosphoinositide synthesis, an interesting feature because phosphoinositides are involved via receptor mechanisms in the regulation of cell proliferation.
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PMID:Identification and functional properties of the pituitary adenylate cyclase activating peptide (PAC1) receptor in human benign hyperplastic prostate. 1061 84

Pituitary adenylate cyclase-activating polypeptide (PACAP) gene expression was analyzed in PC12 cells. PC12 cells transfected with a PACAP promoter-luciferase reporter construct were utilized to investigate the effects of PACAP, either alone or in combination with nerve growth factor (NGF), on PACAP transcriptional response. PACAP induced transcription from the PACAP promoter through PACAP type I receptor (PAC1 receptor). PACAP gene transcription was also induced by NGF. Simultaneous treatment with PACAP and NGF resulted in a synergistic transcriptional response that was more than three times the predicted response, based on a simple additive effect of both agents. This synergism in transcriptional response paralleled the PACAP mRNA levels, as determined by RT-PCR and northern blotting. The level of PACAP mRNA peaked 3 h after stimulation and gradually returned to basal levels by 48 h. PC12 cells are known to express predominantly the hop isoform of the PAC1 receptor, which positively couples to both adenylate cyclase and phospholipase C. To determine the role of the cyclic AMP and protein kinase C pathways in PACAP gene expression, the effects of forskolin and phorbol 12-myristate 13-acetate (PMA) were then examined. PMA did not alter PACAP mRNA levels but enhanced forskolin-induced PACAP mRNA expression. Down-regulation of protein kinase C blocked the ability of PACAP to stimulate PACAP mRNA expression. The mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) kinase 1/2 (MEK1/2) inhibitor PD98059 also blocked the PACAP mRNA expression induced by either PACAP or NGF but not that induced by a combination of PACAP and NGF. These results suggest that PACAP stimulates the PACAP gene expression in PC12 cells at least in part through activation of adenylate cyclase and protein kinase C signaling pathways and that the ERK1/2 cascade is involved in PACAP and NGF-induced PACAP gene expression, although redundant signaling pathways may also be involved. The present finding showing that PACAP in combination with NGF causes a synergistic increase in PACAP gene expression in PC12 cells supports the idea that PACAP acts as an autocrine regulatory factor.
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PMID:Synergistic induction of pituitary adenylate cyclase-activating polypeptide (PACAP) gene expression by nerve growth factor and PACAP in PC12 cells. 1064

Pituitary adenylate cyclase activating polypeptide (PACAP) was isolated from ovine hypothalamus and known to stimulate the production of cAMP in anterior pituitary cells. In the recent report, the expression of PACAP was detected in preovulatory follicles, and treatment with PACAP stimulated the production of progesterone and prostaglandin E(2) through the action of AC and PLC pathways in the ovary. PACAP binds to three type receptors. Type I A receptor is coupled to adenylate cyclase (AC) and phospholipase C (PLC) pathways, while type I B and type II receptors are only coupled to AC. Thus, the present study aimed to evaluate the temporal expression of PACAP and its type I A receptor mRNAs in the rat ovary after treatment with pregnant mare's serum gonadotropin and human chorionic gonadotropin (hCG). Northern blot analysis showed that PACAP transcripts were transiently expressed from 3-9 hr after hCG treatment, reaching a maximum at 6 hr. During these time points, PACAP mRNAs were specifically and strongly expressed in granulosa cells and cumulus cells of large preovulatory follicles and interstitial glandular cells. Type I A receptor mRNAs were also transiently expressed in granulosa cells of large preovulatory follicles from 3-9 hr after hCG treatment. PACAP and its type I A receptor mRNAs were expressed in the same preovulatory follicles. These results demonstrate that PACAP acts as an autoregulator or pararegulator through type I A receptor in granulosa cells and cumulus cells of large preovulatory follicles. Thus, we suggest that PACAP may have a critical role in granulosa cells of preovulatory follicles for the preparation of ovulation.
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PMID:Expression of pituitary adenylate cyclase activating polypeptide (PACAP) and PACAP type I A receptor mRNAs in granulosa cells of preovulatory follicles of the rat ovary. 1069 44

Pituitary adenylyl cyclase-activating peptide (PACAP) stimulates calcium transients and catecholamine secretion in adrenal chromaffin and PC12 cells. The PACAP type 1 receptor in these cells couples to both adenylyl cyclase and phospolipase C pathways, but although phospolipase C has been implicated in the response to PACAP, the role of adenylyl cyclase is unclear. In this study, we show that PACAP38 stimulates Ca(2+) influx in PC12 cells by activating a cation current that depends upon the dual activation of both the PLC and adenylyl cyclase signaling pathways but does not involve protein kinase C. In activating the current, PACAP38 has to overcome an inhibitory effect of Ras. Thus, in cells expressing a dominant negative form of Ras (PC12asn17-W7), PACAP38 induced larger, more rapidly activating currents. This effect of Ras could be overidden by intracellular guanosine-5'-O-3-(thio)triphosphate (GTPgammaS), suggesting that it was mediated by inhibition of downstream G proteins. Ras may also inhibit the current through a G protein-independent mechanism, because cAMP analogues activated the current in PC12asn17-W7 cells, provided GTPgammaS was present, but not in PC12 cells expressing wild type Ras. We conclude that coupling of PACAP to both adenylyl cyclase and phospholipase C is required to activate Ca(2+) influx in PC12 cells and that tonic inhibition by Ras delays and limits the response.
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PMID:Pituitary adenylyl cyclase-activating peptide activates multiple intracellular signaling pathways to regulate ion channels in PC12 cells. 1074 46

The pituitary adenylate cyclase-activating polypeptide (PACAP) type 1 (PAC1) receptor is a G protein-coupled receptor and class II receptor member. The receptor domains critical for signaling are unknown. To explore the role of the C terminus, truncations of 63 residues (Tr406), 53 residues (Tr416), 49 residues (Tr420), 44 residues (Tr424), and 37 residues (Tr433) were constructed and expressed in NIH/3T3 cells, and immunofluorescence, radioligand binding, adenylyl cyclase (AC) and phospholipase C (PLC) assays were performed. (125)I-PACAP-27 binding (K(d) = 0.6-1.5 nm) for the Tr406 and Tr433 were similar to wild type Hop and Null splice variants (K(d) = approximately 1.1 nm). Although internalization of ligand for both the Tr406 and Tr433 mutants was reduced to 50-60% at 60 min compared with 76-87% for WT, loss of G protein coupling did not account for differences in internalization. Despite similar binding properties Tr406 and Tr416 mutants showed no AC or PLC response. Addition of 14 amino acids distal to HopTr406 resulted in normal AC and PLC responses. Site-directed mutagenesis indicated that Arg(416) and Ser(417) are essential for G protein activation. The proximal C terminus mediates signal transduction, and the distal is involved with internalization. Two residues within the C terminus, Arg(416) and Ser(417) conserved among class II receptors are the likely sites for G protein coupling.
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PMID:Identification of an essential amino acid motif within the C terminus of the pituitary adenylate cyclase-activating polypeptide type I receptor that is critical for signal transduction but not for receptor internalization. 1090 67


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