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)

An Arg-specific mono(ADP-ribosyl)transferase activity on the surface of human polymorphonuclear neutrophil leucocytes (PMNs) was confirmed by the use of diethylamino-(benzylidineamino)guanidine (DEA-BAG) as an ADP-ribose acceptor. Two separate HPLC systems were used to separate ADP-ribosyl-DEA-BAG from reaction mixtures, and its presence was confirmed by electrospray mass spectrometry. ADP-ribosyl-DEA-BAG was produced in the presence of PMNs, but not in their absence. Incubation of DEA-BAG with ADP-ribose (0.1-10 mM) did not yield ADP-ribosyl-DEA-BAG, which indicates that ADP-ribosyl-DEA-BAG formed in the presence of PMNs was not simply a product of a reaction between DEA-BAG and free ADP-ribose, due possibly to the hydrolysis of NAD+ by an NAD+ glycohydrolase. The assay of mono(ADP-ribosyl)transferase with agmatine as a substrate was modified for intact PMNs, and the activity was found to be approx. 50-fold lower than that in rabbit cardiac membranes. The Km of the enzyme for NAD+ was 100.1 30.4 microM and the Vmax 1.4 0.2 pmol of ADP-ribosylagmatine/h per 10(6) cells. The enzyme is likely to be linked to the cell surface via a glycosylphosphatidylinositol anchor, since incubation of intact PMNs with phosphoinositol-specific phospholipase C (PI-PLC) led to a 98% decrease in mono(ADP-ribosyl)transferase activity in the cells. Cell surface proteins were labelled after exposure of intact PMNs to [32P]NAD+. Their molecular masses were 79, 67, 46, 36 and 26 kDa. The time course for labelling was non-linear under these conditions over a period of 4 h. The labelled products were identified as mono(ADP-ribosyl)ated proteins by hydrolysis with snake venom phosphodiesterase to yield 5'-AMP.
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PMID:Arginine-specific mono(ADP-ribosyl)transferase activity on the surface of human polymorphonuclear neutrophil leucocytes. 861 41

1. Mono(ADP-ribosyl)transferase activity has been identified on the external surface of human polymorphonuclear neutrophil leucocytes (PMNs). The enzyme is released from the plasma membrane by phosphoinositide-specific phospholipase C, suggesting a glycosylphosphatidylinositol (GPI) linkage of the enzyme to the plasma membrane. Partial sequence of cDNA encoding the enzyme suggests that it is identical to the GPI-linked mono(ADP-ribosyl)-transferase identified previously on human skeletal muscle. 2. A panel of inhibitors of mono(ADP-ribosyl)transferase (including vitamins K1 and K3, novobiocin and nicotinamide) showed a rank order of inhibitory potency similar to that described for other mono(ADP-ribosyl)transferases. Furthermore, the mono(ADP-ribosyl)ation of agmatine was inhibited also by diethylamino (benzylidineamino)guanidine (DEA-BAG), another substrate of the enzyme related structurally to arginine. 3. There was a close linear correlation between the IC50 values for inhibition of mono(ADP-ribosyl)ation of agmatine by DEA-BAG or the enzyme inhibitors and their IC50 values for inhibition of receptor-dependent polymerization of cytoskeletal actin and chemotaxis. 4. These results suggest a role for mono(ADP-ribosyl)transferase in the transduction pathway involved in receptor-dependent re-alignment of the cytoskeleton during neutrophil chemotaxis.
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PMID:A possible role for mono (ADP-ribosyl) transferase in the signalling pathway mediating neutrophil chemotaxis. 880 50

1. Chemotaxis of human neutrophils is mediated by numerous agents [e.g. N-formyl-methionyl-leucyl-phenylalanine (FMLP) and platelet activating factor (PAF)] whose receptors are coupled to phospholipase C. However, the subsequent transduction pathway mediating cell movement remains obscure. We now propose involvement of mono(ADP-ribosyl)transferase activity in receptor-dependent chemotaxis. 2. Human neutrophils were isolated from whole blood and measurements were made of FMLP or PAF-dependent actin polymerization and chemotaxis. The activity of cell surface Arg-specific mono(ADP-ribosyl)transferase was also measured. Each of these activities was inhibited by vitamin K3 and similar IC50 values obtained (4.67 +/- 1.46 microM, 2.0 +/- 0.1 microM and 4.7 +/- 0.1 microM respectively). 3. There were similar close correlations between inhibition of (a) enzyme activity and (b) actin polymerization or chemotaxis by other known inhibitors of mono(ADP-ribosyl)transferase, namely vitamin K1, novobiocin, nicotinamide and the efficient pseudosubstrate, diethylamino(benzylidineamino)guanidine (DEA-BAG). 4. Intracellular Ca2+ was measured by laser scanning confocal microscopy with two fluorescent dyes (Fluo-3 and Fura-Red). Exposure of human neutrophils to FMLP or PAF was followed by transient increases in intracellular Ca2+ concentration, but the inhibitors of mono(ADP-ribosyl)transferase listed above had no effect on the magnitude of the response. 5. A panel of selective inhibitors of protein kinase C, tyrosine kinase, protein kinases A and G or phosphatases 1 and 2A showed no consistent inhibition of FMLP-dependent polymerization of actin. 6. We conclude that eukaryotic Arg-specific mono(ADP-ribosyl)transferase activity may be implicated in the transduction pathway mediating chemotaxis of human neutrophils, with involvement in the assembly of actin-containing cytoskeletal microfilaments.
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PMID:Reduction by inhibitors of mono(ADP-ribosyl)transferase of chemotaxis in human neutrophil leucocytes by inhibition of the assembly of filamentous actin. 881 33

We have previously shown that the stimulatory effect of TRH on alpha-MSH secretion from the frog pars intermedia is associated with Ca2+ influx through voltage-dependent Ca2+ channels, activation of a phospholipase C and mobilization of intracellular Ca2+ stores. The aim of the present study was to investigate the contribution of protein kinase C (PKC), adenylyl cyclase (AC), Ca2+/calmodulin-dependent protein kinase II (CAM KII), phospholipase A2, and protein tyrosine kinase (PTK) in TRH-induced alpha-MSH release. Incubation of frog neurointermediate lobes (NILs) with phorbol 12-myristate-13-acetate (24 h), which causes desensitization of PKC, or with the PKC inhibitor NPC-15437, reduced by approximately 50% of the effect of TRH on alpha-MSH release. In most melanotrope cells, TRH induces a sustained and biphasic increase in cytosolic Ca2+ concentration ([Ca2+]i). Preincubation with phorbol 12-myristate-13-acetate or NPC-15437 suppressed the plateau phase of the Ca2+ response. Incubation of NILs with TRH (10(-6) M; 20 min) had no effect on cAMP production. In addition, the AC inhibitor SQ 22,536 did not affect the secretory response of NILs to TRH. These data indicate that the phospholipase C/PKC pathway, but not the AC/protein kinase A pathway, is involved in TRH-induced alpha-MSH release. The calmodulin inhibitor W-7 and the CAM KII inhibitor KN-93 did not significantly reduce the response to TRH. Similarly, the phospholipase A2 inhibitors quinacrine and 7-7'-DEA did not impair the effect of TRH on alpha-MSH secretion. The PTK inhibitors ST638 and Tyr-A23 had no effect on TRH-induced [Ca2+]i increase but inhibited in a dose-dependent manner TRH-evoked alpha-MSH release (ED50 = 1.22x10(-5) M and ED50 = 1.47x10(-5) M, respectively). Taken together, these data indicate that, in frog melanotrope cells, PKC and PTK are involved in TRH-induced alpha-MSH secretion. Activation of PKC is responsible for the sustained phase of the increase in [Ca2+]i, whereas activation of PTK does not affect Ca2+ mobilization.
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PMID:Involvement of protein kinase C and protein tyrosine kinase in thyrotropin-releasing hormone-induced stimulation of alpha-melanocyte-stimulating hormone secretion in frog melanotrope cells. 1038 23

This study examined the mechanism by which cGMP contributes to the vasodilator response to nitric oxide (NO) in rat middle cerebral arteries (MCA). Administration of a NO donor, diethylaminodiazen-1-ium-1,2-dioate (DEA-NONOate), or 8-bromo-cGMP (8-BrcGMP) increased the diameter of serotonin-preconstricted MCA by 79 +/- 3%. The response to DEA-NONOate, but not 8-BrcGMP, was attenuated by iberiotoxin (10(-7) M) or a 80 mM high-K(+) media, suggesting that activation of K(+) channels contributes to the vasodilator response to NO but not 8-BrcGMP. The effects of NO and cGMP on the vasoconstrictor response to Ca(2+) were also studied in MCA that were permeabilized with alpha-toxin and ionomycin. Elevations in bath Ca(2+) from 10(-8) to 10(-5) M decreased the diameter of permeabilized MCA by 76 +/- 5%. DEA-NONOate (10(-6) M) and 8-BrcGMP (10(-4) M) blunted this response by 60%. Inhibition of guanylyl cyclase with 1H-[1,2,4]oxadiazole[4,3-a] quinoxalin-1-one (10(-5) M) blocked the inhibitory effect of the NO donor, but not 8-BrcGMP, on Ca(2+)-induced vasoconstriction. 8-BrcGMP (10(-4) M) had no effect on intracellular Ca(2+) concentration ([Ca(2+)](i)) in control, serotonin-stimulated, or alpha-toxin- and ionomycin-permeabilized vascular smooth muscle cells isolated from the MCA. These results indicate that the vasodilator response to NO in rat MCA is mediated by activation of Ca(2+)-activated K(+) channels via a cGMP-independent pathway and that cGMP also contributes to the vasodilator response to NO by decreasing the contractile response to elevations in [Ca(2+)](i).
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PMID:Mechanism of cGMP contribution to the vasodilator response to NO in rat middle cerebral arteries. 1195 37