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)

The small GTP-binding protein ARF has been shown recently to regulate phospholipase D (PLD). In order to investigate the role of ARF proteins in regulated exocytosis, we have used the N-terminal peptide ARF1(2-17) of the ARF1 protein. ARF1 reconstituted PLD activity in cytosol-depleted HL60 cells was inhibited by ARF1(2-17). In the presence of endogenous cytosol, ARF1(2-17) also inhibited GTP-gamma-S-stimulated PLD activity and exocytosis. Mastoparan Politses jadwagae and mastoparan Vespula lewisii which exhibit similar structural properties to ARF1(2-17) also inhibited GTP-gamma-S-stimulated PLD and exocytosis. GTP-gamma-S-stimulated phospholipase C-beta (PLC-beta) was also inhibited by ARF(2-17) and mastoparan. In cytosol-depleted HL60 cells, the ARF(2-17) inhibited the reconstitution of GTP-gamma-S-stimulated PLC-beta activity with exogenously-added PLC-beta 1 and phosphatidylinositol transfer protein. We conclude that the widely-used ARF1(2-17) peptide inhibits both ARF-independent (i.e. PLC-beta) and ARF-dependent pathways (i.e. PLD) and therefore cannot be regarded as a specific inhibitor of ARF function.
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PMID:ARF1(2-17) does not specifically interact with ARF1-dependent pathways. Inhibition by peptide of phospholipases C beta, D and exocytosis in HL60 cells. 804 98

Neutrophils play a major role host defense against invading microbes. Recent studies have emphasized the importance of the phospholipase D (PLD) in the signalling cascade leading to neutrophil activation. Phospholipase D catalyzes the hydrolysis of phospholipids to generate phosphatidic acid with secondarily generation of diradylglycerol; both of these products have been implicated as second messengers. Herein, we discuss the regulation and the biochemistry of the receptor-regulated PLD in human neutrophils. In vivo and in vitro studies suggest an activation mode in which initial receptor-linked activation of phospholipase C generates diacylglycerol and inositol trisphosphate. The resulting calcium flux along with the diacylglycerol activate a conventional isoform of protein kinase C (PKC), probably PKC beta 1. This PKC, in turn phosphorylates a plasma membrane component resulting in PLD activation and a second outpouring of diradylglycerol. The small GTP-binding proteins, RhoA and ARF, also participate in this process, and synergize with a 50 kDa cytosolic regulatory factor.
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PMID:Biochemistry and cell biology of phospholipase D in human neutrophils. 868 27

Major advances have been made recently concerning mechanisms involved in the generation of second messengers derived from agonist-induced phospholipid metabolism. New functions for well-known GTPases have been described, and other well-characterized proteins have been identified as regulators of phospholipases and phosphokinases. ARF and Rho have been recently identified as activators of phospholipase D. Rho regulates not only phospholipase D but also phosphatidylinositol 4-phosphate 5-kinase. Both beta gamma- and alpha-subunits of heterotrimeric G-proteins have been described as regulators of a new isoform of phosphatidylinositol kinase. Phosphatidylinositol transfer protein is now recognized as an essential requirement for both phospholipase C gamma and C beta isozymes to hydrolyze phosphatidylinositol 4,5-bisphosphate in cells. Some of these proteins such as ARF, Rho, and phosphatidylinositol transfer protein have well-defined roles in vesicular traffic and in cytoskeletal reorganization, thus bringing the field of signal transduction closer to the world of vesicular traffic as well as the cytoskeleton.
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PMID:Phospholipid signaling in leukocytes. 937 51

The hydrolysis of membrane phosphatidylcholine by the enzyme phospholipase D is a key initial step in the intracellular release of the signalling molecules phosphatidic acid, diacylglycerol and arachidonic acid. Guanine nucleotide-dependent pathway leading to PLD activation were investigated in enzymatically dispersed rat submandibular acinar cells. Guanosine 5'-O-[gamma-thio]triphosphate (GTP gamma S) caused the time- and concentration-dependent stimulation of PLD in permeabilized cells. This effect was lost in prepermeabilized cells, from which cytosolic components had been allowed to leak, but was restored when endogenous cytosol, or cytosol from platelets, was added back to such cells. PLD was also activated in cytosol-depleted cells by GTP gamma S in combination with purified ARF (ADP-ribosylation factor), a low M(r) guanine nucleotide-binding protein of the ras superfamily. Additional evidence for the involvement of ARF in PLD activation was the inhibition of carbachol- or GTP gamma S-induced stimulation of the enzyme by brefeldin A, a blocker of ARF activation; and the observed translocation of ARF from cytosol to membrane on GTP gamma S treatment in permeabilized cells. The heterotrimeric G-protein stimulator, AlFn, also activated PLD, and this response, too, was inhibited by brefeldin A, suggesting the downstream involvement of ARF in coupling AlFn action to phospholipase D elevation. PLD activation caused by both GTP gamma S and AlFn was only partially reduced after treatment of cells with U73122, a demonstrated inhibitor of phospholipase C in the Gq-coupled phosphoinositide signal-transduction pathway. It is therefore proposed that in rat submandibular mucous acinar cells, a guanine nucleotide-regulated PLD activation pathway exists that involves the sequential actions of a G heterotrimeric protein and ARF. It is further suggested that this pathway is independent of the Gq/PLC/phosphatidylinositol signal transduction system.
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PMID:Activation of phospholipase D by ADP-ribosylation factor in rat submandibular acinar cells. 963 Nov 74

In order to investigate the regulation of presynaptic phospholipase D (PLD) activity by calcium and G proteins, we established a permeabilization procedure for rat cortical synaptosomes using Staphylococcus aureus alpha-toxin (30-100 microg/ml). In permeabilized synaptosomes, PLD activity was significantly stimulated when the concentration of free calcium was increased from 0.1 microM to 1 microM. This activation was inhibited in the presence of KN-62 (1 microM), an inhibitor of calcium/calmodulin-dependent kinase II (CaMKII), but not by the protein kinase C inhibitor, Ro 31-8220 (1-10 microM). Synaptosomal PLD activity was also stimulated in the presence of 1 microM GTPgammaS. When Rho proteins were inhibited by pretreatment of the synaptosomes with Clostridium difficile toxin B (TcdB; 1-10 ng/ml), the effect of GTPgammaS was significantly reduced; in contrast, brefeldin A (10-100 microM), an inhibitor of ARF activation, was ineffective. Calcium stimulation of PLD was inhibited by TcdB, but GTPgammaS-dependent activation was insensitive to KN-62. We conclude that synaptosomal PLD is activated in a pathway which sequentially involves CaMKII and Rho proteins.
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PMID:Regulation of phospholipase D activity in synaptosomes permeabilized with Staphylococcus aureus alpha-toxin. 987 88

The PAC(1), VPAC(1) and VPAC(2) receptors are members of the secretin (Group II) family of G protein-coupled receptors. All members of this family activate adenylate cyclase and several have also been shown to activate phospholipase C. We have recently reported that the rat VPAC(1), VPAC(2) and PAC(1) receptors activate phospholipase D and that distinct pathways are utilised by two intracellular loop 3 splice variants of PAC(1), one of which is ARF-dependent. Phospholipase D activation by the hop1, but not the null (short), form of the PAC(1) receptor is sensitive to brefeldin A, an inhibitor of GTP exchange at ARF. We have expressed the null and hop1 intracellular loop 3 domains of the human PAC(1) receptor in bacteria as GST-fusion proteins and used them as peptide affinity matrices to determine whether a functional interaction exists between these domains and ARF. Using this GST pull-down assay, we have shown binding of the small G protein ARF6 to the hop1 but not the null domain of this receptor.
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PMID:Specific interaction between the hop1 intracellular loop 3 domain of the human PAC(1) receptor and ARF. 1240 33

The membrane phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP(2)), plays a critical role in various, apparently very different cellular processes. As precursor for second messengers generated by phospholipase C isoforms and class I phosphoinositide 3-kinases, PIP(2) is indispensable for cellular signaling by membrane receptors. In addition, PIP(2) directly affects the localization and activity of many cellular proteins via specific interaction with unique phosphoinositide-binding domains and thereby regulates actin cytoskeletal dynamics, vesicle trafficking, ion channel activity, gene expression and cell survival. The activity and subcellular localization of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) isoforms, which catalyze the formation of PIP(2), are actively regulated by membrane receptors, by phosphorylation and by small GTPases of the Rho and ARF families. Spatially and temporally organized regulation of PIP(2) synthesis by PIP5K enables dynamic and versatile PIP(2) signaling and represents an important link in the execution of cellular tasks by Rho and ARF GTPases.
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PMID:Regulation and cellular roles of phosphoinositide 5-kinases. 1546 23

In this study we have shown that N376 to D mutation in the conserved NPxxY motif within the carboxy terminal tail domain (CT) of the 5-HT2A receptor alters the binding preference of GST-fusion protein constructs of the CT domain from ARF1 to an alternative isoform, ARF6. These findings were corroborated by experiments investigating co-immunoprecipitation of the wild type (WT) and N376D mutant of the 5-HT2A receptor with ARF1 or 6 or dominant negative ARF1/6 constructs co-expressed in COS7 cells. In functional assays of 5-HT-induced phospholipase D (PLD) activation responses of the WT receptor were inhibited by a dominant negative mutant of ARF1 but not ARF6, whereas responses of the N376D mutant were strongly inhibited by negative mutant ARF6. No equivalent effect of the ARF mutants was seen on phospholipase C activation. In experiments assaying 5-HT-induced increases in [35S]GTPgammaS binding to ARF 1/6 immunoprecipitates as a measure of ARF activation, increased ARF6 activation was seen only with the mutant receptor. When cellular PLD responses of other NPxxY- or a DPxxY-containing GPCRs were measured in the presence of dominant negative ARF1/6 constructs, the majority, but not all, fitted the pattern exemplified by the 5-HT2A receptor and its N376D mutant. These data suggest that the presence of the N or a D in this highly conserved motif is an important, but not exclusive, determinant of which ARF isoform interacts with the GPCR.
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PMID:Role of the conserved NPxxY motif of the 5-HT2A receptor in determining selective interaction with isoforms of ADP-ribosylation factor (ARF). 1654 42

G protein-coupled receptors (GPCRs) control a variety of fundamental cellular processes by regulating phospholipid signaling pathways. Essential for signaling by a large number of receptors is the hydrolysis of the membrane phosphoinositide PIP(2) by phospholipase C (PLC) into the second messengers IP(3) and DAG. Many receptors also stimulate phospholipase D (PLD), leading to the generation of the versatile lipid, phosphatidic acid. Particular PLC and PLD isoforms take differential positions in receptor signaling and are additionally regulated by small GTPases of the Ras, Rho and ARF families. It is now recognized that the PLC substrate, PIP(2), has signaling capacity by itself and can, by direct interaction, affect the activity and subcellular localization of PLD and several other proteins. As expected, the synthesis of PIP(2) by phosphoinositide 5-kinases is tightly regulated as well. In this review, we present an overview of how these signaling pathways are governed by GPCRs, explain the molecular basis for the spatially and temporally organized, highly dynamic quality of phospholipid signaling, and point to the functional connection of the pathways.
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PMID:Dynamic phospholipid signaling by G protein-coupled receptors. 1705 1

Hydrolysis of phosphatidylcholine by phospholipase D (PLD) leads to the generation of the versatile lipid second messenger, phosphatidic acid (PA), which is involved in fundamental cellular processes, including membrane trafficking, actin cytoskeleton remodeling, cell proliferation and cell survival. PLD activity can be dramatically stimulated by a large number of cell surface receptors and is elaborately regulated by intracellular factors, including protein kinase C isoforms, small GTPases of the ARF, Rho and Ras families and, particularly, by the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP(2)). PIP(2) is well known as substrate for the generation of second messengers by phospholipase C, but is now also understood to recruit and/or activate a variety of actin regulatory proteins, ion channels and other signaling proteins, including PLD, by direct interaction. The synthesis of PIP(2) by phosphoinositide 5-kinase (PIP5K) isoforms is tightly regulated by small GTPases and, interestingly, by PA as well, and the concerted formation of PIP(2) and PA has been shown to mediate receptor-regulated cellular events. This review highlights the regulation of PLD by membrane receptors, and describes how the close encounter of PLD and PIP5K isoforms with small GTPases permits the execution of specific cellular functions.
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PMID:Phospholipase D signaling: orchestration by PIP2 and small GTPases. 1724 4


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