Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01185 (vasopressin)
 23,126 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between phospholipase D and C activation was studied in intact rat hepatocytes and rat liver plasma membranes. In intact hepatocytes, in the presence of ethanol, vasopressin, phorbol ester, and calcium independently stimulated phosphatidylethanol (PETH) formation, a specific marker of phospholipase D activity. Leupeptin (10-1500 microM) inhibited PETH formation induced by vasopressin, but was ineffective in response to phorbol ester or calcium. Leupeptin also inhibited the formation of inositol phosphates in intact cells in response to vasopressin. In liver plasma membranes, GTP[S] induced the production of phosphatidic acid and, in the presence of ethanol, PETH. Plasma membrane-associated phospholipase D did not require calcium and was insensitive to protein kinase C inhibitors. Leupeptin inhibited PETH formation in response to GTP[S]. The inhibition by leupeptin could be overcome by increasing the concentration of GTP[S]. In plasma membranes, the inhibitory effects of leupeptin on phospholipase D occurred at doses that far exceed those required to maximally inhibit proteolysis. These data highlight a central role for phospholipase C in the activation of phospholipase D, and a minor role for a direct G-protein activation. The findings also demonstrate a novel use of leupeptin as an inhibitor of phospholipases D and C, perhaps at the level of a G protein.
 ...
PMID:Leupeptin inhibits phospholipases D and C activation in rat hepatocytes. 806 Oct 57

Activation of mitogen-activated protein kinases (MAPKs) was examined in the A7r5 rat vascular smooth muscle cell line. Treatment of A7r5 cells with vasopressin, phorbol ester (PMA), or serum resulted in activation of two MAPKs, Erk-1 and Erk-2. Phosphatidylinositol-specific phospholipase C was activated in response to vasopressin but not to PMA. Vasopressin and PMA both caused maximal activation of PLD within 5 minutes. Application of bacterial phospholipase D (PLD) to A7r5 cells increased phosphatidic acid to levels similar to those seen with vasopressin or PMA. Acute exposure of the cells to vasopressin, PMA, or PLD increased phosphorylation of many of the same cytosolic and membrane proteins. However, bacterial PLD did not promote significant activation of Erk-1 and Erk-2. Phosphatidic acid and lysophosphatidic acid (LPA) likewise did not stimulate MAPK activity in A7r5 cells. Serum and vasopressin stimulated DNA synthesis when present for more than 30 min, while PLD, PMA, phosphatidic acid, and LPA were not mitogenic. These data suggest that activations of MAPKs and PLD are concurrent but independent responses to vasopressin in A7r5 cells. Acute activation of these enzymes is not sufficient to simulate DNA synthesis.
 ...
PMID:Activations of mitogen-activated protein kinases and phospholipase D in A7r5 vascular smooth muscle cells. 808 51

Activation of phospholipase D (PLD) by receptor-coupled stimuli (vasopressin, ATP), phorbol esters, and Ca2+ ionophores was studied in isolated rat hepatocytes, double labeled with [3H]arachidonate and [14C]stearate. Phosphatidylethanol (Peth) was formed when cells were stimulated in the presence of ethanol. The effect of combinations of agonists was not additive, indicating that the same PLD isozyme(s) were activated. With all agonists, the 3H- and 14C-specific radioactivity in Peth was higher than in any of the main phospholipid classes. The 3H/14C ratios of Peth and phosphatidylcholine (PC) were identical and differed from other phospholipid classes, indicating that the predominant PLD substrate was a PC pool labeled preferentially with radioactive fatty acids. Ethanol (50-300 mM) decreased the initial rate of phosphatidic acid (PA) formation, but did not affect total PLD activity. Agonist-induced changes in steady state accumulation of PA or 1,2-diacylglycerol were also unaffected. A slow degradation of Peth (apparent t1/2 > 60 min) occurred after ethanol removal from cells prestimulated with vasopressin. The rate of degradation was unaffected by agonists that stimulate PLD. Thus, Peth formation is a suitable cumulative indicator for PLD activation in intact hepatocytes. Peth accumulation declined over a period of 5-20 min, depending on the agonist. The decline was not due to increased Peth degradation, or limitations in substrate supply to PLD, or enzyme inhibition by accumulated Peth. Instead, a homologous desensitization of PLD occurs with all agonists. This desensitization may involve the action of selective protein kinase C isozymes.
 ...
PMID:Activation and desensitization of phospholipase D in intact rat hepatocytes. 828 37

Ca(2+)-dependent and protein kinase C-dependent mechanisms of phospholipase D (PLD) activation were studied in rat hepatocytes by measuring phosphatidylethanol (Peth) formation in the presence of ethanol. Stimulation of Peth formation by 12-O-tetradecanoyl-phorbol 13-acetate (TPA), vasopressin, or A23187 was inhibited by multiple protein kinase C inhibitors or by protein kinase C down-regulation, indicating that this enzyme is involved in the action of all these agents. A controlled elevation of the cytosolic Ca2+ concentration ([Ca2+]cyt) over the range of 0.1-2.0 microM activated Peth formation in the absence of other agonists. Staurosporin potentiated Ca(2+)-induced Peth formation by shifting the [Ca2+]cyt dose-response curve to the left. Other protein kinase C inhibitors (calphostin C, bisindolylmaleimide) inhibited Ca(2+)-mediated Peth formation, but this inhibition was reduced in staurosporin-treated cells. Okadaic acid potentiated PLD activation by TPA, but suppressed PLD activation by elevated [Ca2+]cyt. Desensitization of TPA-induced PLD activity did not affect PLD activation by Ca2+. These data indicate that [Ca2+]cyt and protein kinase C control distinct pathways of PLD activation, but the Ca(2+)-mediated pathway is suppressed by a staurosporin-sensitive protein kinase. Both mechanisms contribute to vasopressin-induced Peth formation in intact hepatocytes. Activation of protein kinase A enhanced vasopressin-induced Peth formation, but not TPA-stimulated or Ca(2+)-stimulated stimulated Peth formation. Protein kinase A acted by enhancing hormonal Ca2+ mobilization, rather than by directly activating PLD, and thereby shifted the balance of Ca(2+)-dependent and protein kinase C-dependent activation mechanisms of PLD in intact cells.
 ...
PMID:The role of cytosolic Ca2+, protein kinase C, and protein kinase A in hormonal stimulation of phospholipase D in rat hepatocytes. 828 38

The hydrolysis of inositol phospholipids induced by vasopressin in hepatocytes during 60 min was quantified chemically. There was a large release of myo-inositol which was abolished by Li+, indicating that it was derived from inositol phosphates and not from phospholipase D action on PtdIns. There was also a large release of inositol phosphates which was increased approx. 2-fold by Li+ at 30 min, but then remained constant, suggesting that inositol phospholipid breakdown declined substantially beyond this time. In cells prelabelled with myo-[3H]inositol and treated with Li+, [3H]PtdIns(4,5)P2 decreased maximally (50%) at 15 s and then recovered to a level at 5 min that was maintained at 25% below control for 40 min. [3H]PtdIns4P and [3H]PtdIns showed slower decreases to approx. 30% below control at 15 min, but with no further changes. Labelled Ins(1,4,5)P3 and Ins(1,3,4)P3 showed 2-4-fold increases within 30 s and then declined to values that were maintained at a constant level above the control, except for [3H]Ins(1,3,4)P3, which showed a second increase. [3H]Ins(1,4)P2 showed a very large increase over 10 min, whereas [3H]Ins4P and [3H]Ins1P showed little change before 6 and 15 min respectively. The total [3H]inositol phosphates showed little further increase after 20 min. These data are consistent with a rapid, but not sustained, hydrolysis of PtdIns-(4,5)P2, but not of PtdIns, by phospholipase C, but do not exclude PtdIns4P as a substrate. Phosphatidate was rapidly increased by vasopressin, whereas diacylglycerol was increased after a 1-2 min lag. Both were maintained at levels 2-3-fold above control for 60 min. The vasopressin-induced increase in inositol phosphates plus myo-inositol (approx. 120 nmol/100 mg) was greater than the increase in diacylglycerol plus phosphatidate (approx. 60 nmol/100 mg) between 10 and 40 min. This indicates that there was substantial further metabolism of these lipids. Addition of 75 mM ethanol resulted in rapid production of phosphatidylethanol in response to vasopressin and a 35% reduction in phosphatidate, but no decrease in diacylglycerol. In summary, the results indicate that inositol phospholipid hydrolysis by phospholipase C can account for most of the diacylglycerol and phosphatidate that accumulate during 60 min of vasopressin action, but that these phospholipids are probably not the major source of the phosphatidate that is formed during the first 2 min by phospholipase D, or of the diacylglycerol and phosphatidate that are formed beyond 30 min.
 ...
PMID:Quantification of inositol phospholipid breakdown in isolated rat hepatocytes. 838 49

Rats were infused with endotoxin (50 micrograms/100 g body wt) for 3 h, and the parenchymal cells of the liver were maintained in primary culture for 1-3 h. The effects of vasopressin, norepinephrine, and glucagon on the activation of phosphatidylinositol (PI)-phospholipase C, phosphatidylcholine (PC)-phospholipase D, and glycogen phosphorylase a were investigated. Activation of PI-phospholipase C was markedly reduced, particularly with norepinephrine. This confirms that one of the early metabolic impairments seen in acute endotoxin treatment is inhibition of PI-phospholipase C activity. However, the ability of vasopressin, norepinephrine, and glucagon to stimulate glycogen phosphorylase a and PC-phospholipase D was not affected by this endotoxin treatment. We conclude that activation of phosphorylase a by vasopressin and norepinephrine is not entirely dependent on the activation of PI-phospholipase C and inositol trisphosphate formation.
 ...
PMID:LPS inhibits PI-phospholipase C but not PC-phospholipase D or phosphorylase activation by vasopressin and norepinephrine. 838 92

In the present study we report that bradykinin stimulated phospholipase D activity in rat Leydig cells. Bradykinin added for 8 min stimulated choline formation in a dose-dependent manner and, in the presence of ethanol, bradykinin (100 nmol/l) stimulated transphosphatidylation by phospholipase D resulting in the formation of phosphatidylethanol. This stimulation was abolished after down-regulation of protein kinase C by long-term pretreatment for 22 h with phorbol 12-myristate 13-acetate (PMA). The stimulation of phospholipase D by the simultaneous addition for 8 min of maximum concentrations of PMA and vasopressin (AVP), PMA and bradykinin, or AVP and bradykinin produced no additive phosphatidylethanol or choline response, suggesting that AVP, bradykinin and PMA stimulated phospholipase D-catalysed phosphatidylcholine hydrolysis by a similar protein kinase C-dependent mechanism. Furthermore, LH (10 ng/ml), insulin (500 nmol/l), GH (100 ng/ml), interleukin-1 beta (5 U/ml) and platelet-activating factor (200 nmol/l) were found not to activate phospholipase D, whereas the Ca2+ ionophore A23187 (10 mumol/l) stimulated phosphatidylethanol formation, suggesting that Ca2+ might be a regulator of phospholipase D in Leydig cells.
 ...
PMID:Bradykinin and vasopressin activate phospholipase D in rat Leydig cells by a protein kinase C-dependent mechanism. 842 67

Regulation of phospholipase D (PLD) activity was investigated in cultured monolayers of bovine pulmonary artery endothelial cells (BPAECs). Agonists such as bradykinin, histamine, vasopressin, alpha-thrombin, and adenosine triphosphate (ATP) stimulated up to 15-fold accumulation of phosphatidylethanol (PEt) in the presence of ethanol through PLD-catalyzed phosphatidyltransferase activity. To examine mechanisms of PLD regulation, we investigated the role of protein kinase C (PKC) and Ca2+ fluxes in agonist-induced PLD activation. The PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA, 100 nmol/L) produced up to a 25-fold increase in PEt formation in a time- and dose-dependent manner. PEt production was also stimulated by other cell-permeant PKC activators such as 1,2 dioctanoylglycerol and 1-oleyl-2-acetylglycerol, whereas inactive phorbol derivatives 4-alpha-phorbol-12,13-didecanoate and 4-beta-phorbol showed no effect. The effect of TPA on PEt accumulation was inhibited by the PKC inhibitors staurosporine (5 mumol/L, 95% inhibition) and sphingosine (10 mumol/L, 50% inhibition). TPA-induced PEt accumulation was almost completely abolished (> 95% inhibition) by PKC down-regulation accomplished by long-term treatment with 100 nmol/L TPA. In contrast, bradykinin- or ATP-induced phosphorus 32-labeled PA and [32P]-labeled PEt formation was only partially blocked (70% inhibition) by either staurosporine (10 mumol/L) or PKC down-regulation, suggesting that part of agonist-stimulated PLD activity may occur in the absence of PKC activation. An increase in Cai2+ appears to be involved in agonist-induced PLD activation as bradykinin-, ATP-, or Ca2+ ionophore-induced [32P]. PEt production was attenuated by either depletion of extra-cellular Ca2+ with EGTA or chelation of intracellular Ca2+ by BAPTA. TPA-mediated PEt accumulation was not affected by EGTA treatment, whereas BAPTA reduced TPA-mediated PEt formation by 50%. These results suggest that direct PKC activation is a potent stimulus for PLD activity and that the major pathway for agonist-induced PLD activation involves PKC activation and is dependent on an increase in intracellular Ca2+. Further, these studies suggest that agonist-induced PLD activation may also involve a PKC-independent mechanism.
 ...
PMID:Agonist-induced activation of phospholipase D in bovine pulmonary artery endothelial cells: regulation by protein kinase C and calcium. 843 44

The aim of the present study was to compare the transphosphatidylation activity of phospholipase D (PLD) under different substrate labeling conditions, in order to investigate whether PLD in rat Leydig cells exhibited any substrate preferences for the alkyl- or acyl-form of phosphatidylcholine (PtdCho). The [3H]phosphatidylethanol formation in response to 4 beta-phorbol 12-myristate 13-acetate (PMA), sphingosine, or Ca(++)-ionophore A23187, was lower when Leydig cells were labeled with 1-O-[3H]alkyl lysoPtdCho compared with the responses when [3H]myristic acid was employed. In contrast, the results for the receptor agonists (vasopressin, bradykinin, and lysophosphatidic acid), using the two labels, showed more consistency. Thus, the PLD-activity induced by PMA, sphingosine, or A23187 has a more selective substrate range (i.e. mainly acyl-linked PtdCho) than the PLD-activity stimulated via a receptor. Our data suggests the existence of PLD isozymes that differ with respect to substrate specificity and activation mechanisms.
 ...
PMID:Differential phospholipid-labeling suggests two subtypes of phospholipase D in rat Leydig cells. 855 94

The hydrolysis of phospholipids in vasopressin-stimulated baby hamster kidney (BHK)-21 and H9c2 myoblastic cells was investigated. Phosphatidylcholine and phosphatidylethanolamine in these cells were pulse labelled with [3H]glycerol, [3H]myristate, [3H]choline or [3H]ethanolamine, and chased with the non-labelled precursor until linear turnover rates were obtained. When cells labelled with [3H]glycerol or [3H]myristate were stimulated by vasopressin, no significant decrease in the labelling of phosphatidylcholine was detected, but the labelling of phosphatidic acid was elevated. However, the labellings of phosphatidylethanolamine and its hydrolytic product were not affected by vasopressin stimulation. When the cells were pulse labelled with [3H]-choline, vasopressin stimulation caused a decrease in the labelled phosphatidylcholine with a corresponding increase in the labelled choline. The apparent discrepancy between the two types of labelling might be explained by the recycling of labelled phosphatidic acid back into phosphatidylcholine, thus masking the reduction in the labelled phospholipid during vasopressin stimulation. Alternatively, the labelled choline produced by vasopressin stimulation was released into the medium, thus reducing the recycling of label precursor back into the phospholipid and making the decrease in the labelling of phosphatidylcholine readily detectable. Further studies revealed that vasopressin treatment caused an enhancement of phospholipase D activity in these cells. The presence of substrate-specific phospholipase D isoforms in mammalian tissues led us to postulate that the differential stimulation of phospholipid hydrolysis by vasopressin was caused by the enhancement of a phosphatidylcholine-specific phospholipase D in both BHK-21 and the H9c2 cells.
 ...
PMID:Enhancement of phospholipid hydrolysis in vasopressin-stimulated BHK-21 and H9c2 cells. 858 16


<< Previous 1 2 3 4 Next >>