Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Folliculo-stellate cells of the anterior pituitary are thought to modulate pituitary hormone secretion through a paracrine mechanism. Angiotensin II and pituitary adenylate cyclase-activating polypeptide (PACAP) have previously been shown to increase the intracellular Ca2+ concentration ([Ca2+]i) of these cells. In the present study, we examined the effects of various peptides such as bradykinin, angiotensin II, endothelin-1, PACAP, galanin and neurotensin by Ca2+-imaging of folliculo-stellate cells in primary culture. Bradykinin and angiotensin II increased [Ca2+]i in folliculo-stellate cells. Both responses were completely suppressed by thapsigargin and were significantly suppressed by the phospholipase C inhibitor, U-73122. Ryanodine did not significantly modify the responses. A B2 antagonist and angiotensin II receptor antagonist inhibited the response induced by bradykinin and angiotensin II, respectively. Endothelin-1 and PACAP increased [Ca2+]i in fewer than 50% of folliculo-stellate cells but galanin and neurotensin did not influence [Ca2+]i in any of the folliculo-stellate cells tested. These results indicate that bradykinin and angiotensin II increase [Ca2+]i in folliculo-stellate cells by activating phospholipase C through B2 receptor and AT1 receptor, respectively, and that endothelin-1 and PACAP also increase [Ca2+]i in some folliculo-stellate cells.
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PMID:Bradykinin and angiotensin II-induced [Ca2+]i rise in cultured rat pituitary folliculo-stellate cells. 1173 52

Angiotensin II (Ang II) plays an important role in the central control of blood pressure and baroreflexes. These effects are initiated by stimulation of Ang II type 1 (AT(1)) receptors on neurons within the hypothalamus and brain stem, and involve increasing the activity of noradrenergic, substance P, and glutamatergic pathways. The goal of this study is to investigate the intracellular signaling molecules, which are involved in mediating the Ang II-induced increases in neuronal activity. Using neurons in primary culture from newborn rat hypothalamus and brain stem, we have previously determined that Ang II elicits an AT(1) receptor-mediated inhibition of delayed rectifier K(+) current, a stimulation of Ca(2+) current, and a consequent increase in firing rate. In the present study we have demonstrated that this chronotropic action of Ang II in neuronal cultures involves activation of Ca(2+)-dependent signaling molecules. The Ang II-induced increase in firing rate was abolished by inhibition of phospholipase C with U73122 (10 micromol/L), and was attenuated by the protein kinase C inhibitor calphostin C (10 micromol/L) or by the calcium/calmodulin-dependent kinase II (CaMKII) inhibitor KN-93 (10 micromol/L). A combination of calphostin C and KN-93 completely inhibited this Ang II action. These results indicate that the AT(1) receptor-mediated increase in neuronal firing rate involves activation of both PKC and CaMKII, and suggest that these enzymes are potential targets for manipulating the central actions of Ang II.
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PMID:Chronotropic action of angiotensin II in neurons via protein kinase C and CaMKII. 1188 8

Cardiac microvascular endothelial cells (EC) play an important role in the physiological regulation of coronary blood flow, but their function has not been rigorously examined, because suitable in vitro models have not been available. Cardiac macrovascular and microvascular EC were isolated and cultured from 14-16-week-old Sprague-Dawley rats to examine the pharmacological responses of carbachol-induced nitric oxide (NO) production using a Griess method. Carbachol-induced NO production was only detected in cardiac macrovascular EC, which suggests that endothelial production of NO differs between macrovascular and microvascular EC. Next, cardiac microvascular EC was treated with either vehicle, angiotensin-converting enzyme (ACE) inhibitor (captopril, 10 micromol/L) or angiotensin II type 1 (AT1) receptor antagonist (CV11974, 10 micromol/L) for 4 days. Carbachol-induced NO production was improved by captopril (136+/-45nmol, p<0.01 vs vehicle) and CV11974 (146+/-30nmol, p<0.01 vs vehicle). Angiotensin II concentration in the culture medium and protein expressions of endothelial nitric oxide synthase and AT1 receptor in the EC were similar among the 3 groups. Interestingly, the level of muscarinic subtype 3 (M3) receptor was significantly increased in the EC treated with captopril (214%, p<0.01) and CV11974 (296%, p<0.01). When cardiac microvascular EC were treated with neomycin (non-selective phospholipase C inhibitor), carbachol-induced NO production was also improved (146+/-35nmol, p<0.01, neomycin I mmol/L) together with increased expression of M3 receptor (p<0.01). These data suggest that the upregulation of the M3 receptor by captopril or CV11974 occurs via a phospholipase C-dependent pathway. Cardiac microvascular EC also produced NO constitutively, as did the macrovascular EC, but carbachol-induced NO production was decreased. The present data suggest that the upregulation of the M3 receptor by the ACE inhibitor and AT1 receptor antagonist is a new beneficial effect of these drugs on microvascular endothelial function.
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PMID:Comparison of nitric oxide production in response to carbachol between macrovascular and microvascular cardiac endothelial cells. 1203 Mar 50

Angiotensin II (AngII) contributes to the maintenance of extracellular fluid volume by regulating sodium transport in the nephron. In nonepithelial cells, activation of phospholipase C (PLC) by AT-1 receptors stimulates the generation of 1,4,5-trisphosphate (IP(3)) and the release of intracellular calcium. Calcineurin, a serine-threonine phosphatase, is activated by calcium and calmodulin, and both PLC and calcineurin have been linked to sodium transport in the proximal tubule. An examination of whether AngII activates calcineurin in a model of proximal tubule epithelia (LLC-PK1 cells) was performed; AngII increased calcineurin activity within 30 s. An examination of whether AngII activates PLC in proximal tubule epithelia was also performed after first showing that all three families of PLC isoforms are present in LLC-PK1 cells. Application of AngII increased IP(3) generation by 60% within 15 s, which coincided with AngII-induced tyrosine phosphorylation of the PLC-gamma1 isoform also observed at 15 s. AngII-induced tyrosine phosphorylation was blocked by the AT-1 receptor antagonist, Losartan. Subsequently, an inhibitor of tyrosine phosphorylation blocked the AngII-induced activation of calcineurin, as did coincubation with an inhibitor of PLC activity and with an antagonist of the AT-1 receptor. It is therefore concluded that AngII stimulates calcineurin phosphatase activity in proximal tubule epithelial cells through a mechanism involving AT-1 receptor-mediated tyrosine phosphorylation of the PLC isoform.
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PMID:Angiotensin II stimulates calcineurin activity in proximal tubule epithelia through AT-1 receptor-mediated tyrosine phosphorylation of the PLC-gamma1 isoform. 1208 70

Angiotensin II (AngII) plays a critical role in control of cardiovascular and renal homeostasis. In addition to its physiological action as a vasoconstrictor, growing evidence supports the notion that AngII contributes to cardiovascular diseases such as hypertension, atherosclerosis, and heart failure. The physiological and pathological actions of AngII in adults are mediated largely via the AngII type 1 receptor (AT1R), a heterotrimeric G-protein-coupled receptor (GPCR). Besides coupling with heterotrimeric G proteins to activate phospholipase C-beta (PLC-beta), AT1R also activates receptor tyrosine kinases (PDGF-R, EGF-R and IGF-R) and non-receptor tyrosine kinases (Src, Fyn, Yes, proline-rich tyrosine kinase 2 (Pyk2), focal adhesion kinase (FAK) and JAK2). These tyrosine kinases play critical roles in AngII-stimulated cell signal events.
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PMID:Angiotensin II signaling pathways mediated by tyrosine kinases. 1267 64

Cardiac fibroblasts regulate formation of extracellular matrix in the heart, playing key roles in cardiac remodeling and hypertrophy. In this study, we sought to characterize cross-talk between Gq and Gs signaling pathways and its impact on modulating collagen synthesis by cardiac fibroblasts. Angiotensin II (ANG II) activates cell proliferation and collagen synthesis but also potentiates cyclic AMP (cAMP) production stimulated by beta-adrenergic receptors (beta-AR). The potentiation of beta-AR-stimulated cAMP production by ANG II is reduced by phospholipase C inhibition and enhanced by overexpression of Gq. Ionomycin and thapsigargin increased intracellular Ca2+ levels and potentiated isoproterenol- and forskolin-stimulated cAMP production, whereas chelation of Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid/AM inhibited such potentiation. Inhibitors of tyrosine kinases, protein kinase C, or Gbetagamma did not alter this cross-talk. Immunoblot analyses showed prominent expression of adenylyl cyclase 3 (AC3), a Ca2+-activated isoform, along with AC2, AC4, AC5, AC6, and AC7. Of those isoforms, only AC3 and AC5/6 proteins were detected in caveolin-rich fractions. Overexpression of AC6 increased betaAR-stimulated cAMP accumulation but did not alter the size of the ANG II potentiation, suggesting that the cross-talk is AC isoform-specific. Isoproterenol-mediated inhibition of serum-stimulated collagen synthesis increased from 31 to 48% in the presence of ANG II, indicating that betaAR-regulated collagen synthesis increased in the presence of ANG II. These data indicate that ANG II potentiates cAMP formation via Ca2+-dependent activation of AC activity, which in turn attenuates collagen synthesis and demonstrates one functional consequence of cross-talk between Gq and Gs signaling pathways in cardiac fibroblasts.
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PMID:Angiotensin II enhances adenylyl cyclase signaling via Ca2+/calmodulin. Gq-Gs cross-talk regulates collagen production in cardiac fibroblasts. 1271

Angiotensin II (Ang II) modulates, via Ang II type 1 (AT(1)) receptors, the activity of brain catecholaminergic neurons. Here we utilized catecholaminergic CATH.a cells to define the effects of Ang II on delayed rectifier K(+) current (I(Kv)), one of the factors that determines changes in neuronal activation. Receptor binding analyses demonstrated the presence of AT(1) receptors in CATH.a cells. Whole cell voltage clamp experiments in these cells revealed that Ang II (100nM) produced a significant inhibition of I(Kv), that was abolished by the AT(1) receptor blocker, losartan (1 microM), or by inhibition of phospholipase C (PLC) with U73122 (10 microM). Furthermore, this action of Ang II was completely abolished by co-inhibition of protein kinase C (PKC) and calcium/calmodulin protein kinase II (CaMKII). These results demonstrate that Ang II produces an inhibition of I(Kv) in CATH.a cells, via an intracellular pathway that includes PLC, PKC, and CaMKII.
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PMID:Modulation of delayed rectifier potassium current by angiotensin II in CATH.a cells. 1455 Feb 59

Angiotensin II (Ang II) increases the cytosolic Ca2+ concentration in different cell types. In this study, we investigate the effect of Ang II on the Ca2+ ATPase of purified basolateral membranes of kidney proximal tubules. This enzyme pumps Ca2+ out of the cytosol in a reaction coupled to ATP hydrolysis, and it is responsible for the fine-tuned regulation of cytosolic Ca2+ activity. Ca2+-ATPase activity is inhibited by picomolar concentrations of Ang II, with maximal inhibition being attained at approximately 50% of the control values. The presence of raising concentrations (10(-11) to 10(-7) M) of losartan (an AT1-receptor antagonist) or PD123319 (an AT2-receptor antagonist) gradually reverts inhibition by Ang II. Both the phospholipase C (PLC) inhibitor U-73122 (10(-6) M) and the inhibitor of protein kinase C (PKC) staurosporine (10(-7) M) prevent inhibition of the Ca2+ pump by Ang II. Incubation of the previously isolated membranes with a PKC activator-the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (10(-8) M)-mimics the inhibition found with Ang II, and the effects of the compounds are not additive. Taken as a whole, these results indicate the Ang II inhibits Ca2+-ATPase by activation of a PKC system present in primed state in these membranes after binding of the hormone to losartan- and PD123319-sensitive receptors coupled to a PLC. Therefore, inhibition of the basolateral membrane Ca2+-ATPase by kinase-mediated phosphorylation appears to be one of the pathways by which Ang II promotes an increase in the cytosolic Ca2+ concentration of proximal tubule cells.
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PMID:Protein kinase C-mediated inhibition of renal Ca2+ ATPase by physiological concentrations of angiotensin II is reversed by AT1- and AT2-receptor antagonists. 1568 Apr 81

Angiotensin II (Ang II) has been reported to indirectly influence atrial electrical activity and to play a critical role in atrial arrhythmias in hypertensive patients. However, it is unclear whether Ang II has direct effects on the electrophysiological activity of the atrium affected by hypertension. We examined the effects of Ang II on the action potentials of atrial myocytes enzymatically isolated from spontaneous hypertensive rats (SHRs). The action potentials were recorded by the perforated patch-clamp technique and the atrial expression of the receptors AT1a and AT2 was measured by radioimmunoassay. Ang II significantly shortened the action potential durations (APDs) of SHRs without changes in the resting membrane potentials (RMPs). Pretreatment with selective AT1a blockers abolished the Ang II-induced reduction of atrial APDs of SHRs; however, a selective AT2 blocker did not, which was consistent with the results of the receptor assay. Pretreatment with phosphatidylinositol 3 (PI3)-kinase inhibitor, phospholipase C inhibitor, or protein kinase C (PKC) inhibitor abolished the Ang II-induced shortening of atrial APDs, but pertussis toxin and protein kinase A (PKA) inhibitor did not. To study the effects of chronic AT1a inhibition on Ang II-induced shortening of atrial APD, SHRs were treated with AT1a blocker for 4 weeks. AT1a blocker abolished the Ang II-induced reduction of atrial APDs of SHRs and also significantly lowered their blood pressure. In conclusion, Ang II shortened atrial APDs of SHRs via AT1a coupled with the Gq-mediated inositol triphosphate (IP3)-PKC pathway. Our findings indicated that Ang II caused atrial arrhythmias in hypertensive patients by shortening the effective refractory period of the atrium.
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PMID:Effects of angiotensin II on the action potential durations of atrial myocytes in hypertensive rats. 1602 45

We are probing the regulation of phosphatidylcholine (PC) synthesis by angiotensin II. In the accompanying paper, we showed that manipulation of the lipid second messengers, arachidonic acid or hydroxyeicosatetraenoic acid, produced downstream of the angiotensin AT1a receptor did not affect the PC synthesis rates in a manner consistent with direct activation of the rate limiting enzyme in the pathway, CTP:phosphocholine cytidylyltransferase (CCT). However, suppression of diacylglycerol (DAG) production with an inhibitor of phospholipase C-beta reduced angiotensin-dependent PC synthesis as well as ERK1/2 phosphorylation. Here, we show that the stimulation of PC synthesis and activation of CCT by angiotensin requires a signaling pathway that involves protein kinase C and ERK1/2. The inhibitors bis-indolylmaleimide I and PD98059 blocked ERK1/2 phosphorylation and completely eliminated angiotensin stimulation of the CCT-catalyzed reaction and PC synthesis. Exogenous addition of DAG using a lipid vesicle delivery system exactly mimicked the kinetics of angiotensin-promoted PC synthesis, suggesting that this mode of DAG delivery can effectively substitute for the DAG generated downstream of the activated AT1a receptor. Moreover, exogenous DAG activated ERK1/2, and the activation of PC synthesis by DAG was blocked by inhibition of protein kinase C and MEK. These data suggest that angiotensin-dependent DAG and the exogenously supplied DAG stimulate PC synthesis, not solely by direct action on CCT, but via a signaling pathway involving protein kinase C and ERK1/2. Angiotensin did not alter the net phosphorylation state of CCT as probed by immunoprecipitation of 32P-labeled CCT. Angiotensin stimulation of ERK1/2 likely mediates effects on CCT via a process other than CCT dephosphorylation.
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PMID:Angiotensin stimulates phosphatidylcholine synthesis via a pathway involving diacylglycerol, protein kinase C, ERK1/2, and CTP:phosphocholine cytidylyltransferase. 1658 Feb 50


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