Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In neurons and transformed cell lines, opioid receptors are coupled to various signaling mechanisms involved in Ca2+ mobilization, including inhibition or activation of Ca2+ channels and phospholipase C-beta (PLC-beta), the enzyme responsible for generation of the Ca2+ mobilizing messenger inositol-1,4,5-trisphosphate [Ins(1,4,5)P3]. In the current study, we used selective PLC-beta and G protein antibodies to identify the PLC-beta isozyme activated by opioid receptors in intestinal smooth muscle and the G proteins to which the PLC-beta isozyme and adenylyl cyclase are coupled. [D-Pen2,D-Pen5]Enkephalin, a delta receptor agonist, stimulated Ins(1,4,5)P3 formation, Ca2+ release, and contraction; inhibited forskolin-stimulated cAMP formation in dispersed muscle cells; and stimulated phosphoinositide hydrolysis in plasma membranes; all of the effects were blocked by pertussis toxin. [D-Pen2,D-Pen5]Enkephalin-stimulated Ins(1,4,5)P3 formation, Ca2+ release, and contraction in permeabilized muscle cells and phosphoinositide hydrolysis in plasma membranes were selectively blocked by G beta antibody and PLC-beta 3 antibody; contractions stimulated by [D-Ala2,N-MePhe4,Gly-ol5]enkephalin, a mu receptor agonist, and U-69,593, a kappa receptor agonist, were also blocked by G beta and PLC-beta 3 antibodies. Inhibition of forskolin-stimulated cAMP formation by delta, mu, and kappa receptor agonists was partially blocked by G alpha i2 and G alpha o antibodies and additively blocked by a combination of the antibodies. The delta, mu, and kappa receptor agonists stimulated the binding of guanosine-5'-O-(3-thio)triphosphate to the alpha subunits of Gi2 and G(o) but not to the alpha subunits of other G proteins. We conclude that opioid mu, delta, and kappa receptors are selectively coupled to Gi2 and G(o) in intestinal smooth muscle. The beta gamma subunits of both G proteins activate PLC-beta 3, thereby stimulating Ins(1,4,5)P3-dependent Ca2+ release and smooth muscle contraction, whereas the alpha subunits inhibit adenylyl cyclase activity.
 ...
PMID:Opioid mu, delta, and kappa receptor-induced activation of phospholipase C-beta 3 and inhibition of adenylyl cyclase is mediated by Gi2 and G(o) in smooth muscle. 886 32

Xenopus oocytes exhibit both pertussis toxin-sensitive and -insensitive inositol lipid signaling responses to G protein-coupled receptor activation. The G protein subunits Galphai, Galphao, Galphaq, Galphas, and Gbetagamma all have been proposed to function as activators of phospholipase C in oocytes. Ma et al. (Ma, H.-W., Blitzer, R. D., Healy, E. C., Premont, R. T., Landau, E. M., and Iyengar, R. J. Biol. Chem. 268, 19915-19918) cloned a Xenopus phospholipase C (PLC-betaX) that exhibits homology to the PLC-beta class of isoenzymes. Although this enzyme was proposed to function as a signaling protein in the pertussis toxin-sensitive inositol lipid signaling pathway of oocytes, its regulation by G protein subunits has not been directly assessed. As such we have utilized baculovirus-promoted overexpression of PLC-betaX in Sf9 insect cells and have purified a recombinant 150-kDa isoenzyme. PLC-betaX catalyzes hydrolysis of phosphatidylinositol(4,5)bisphosphate and phosphatidylinositol(4)monophosphate, and reaction velocity is dependent on Ca2+. Recombinant PLC-betaX was activated by both Galphaq and Gbetagamma. PLC-betaX exhibited a higher apparent affinity for Galphaq than Gbetagamma, and Galphaq was more efficacious than Gbetagamma at lower concentrations of PLC-betaX. Relative to other PLC-beta isoenzymes, PLC-betaX was less sensitive to stimulation by Galphaq than PLC-beta1 but similar to PLC-beta2 and PLC-betaT. PLC-betaX was more sensitive to stimulation by Gbetagamma than PLC-beta1 but less sensitive than PLC-beta2 and PLC-betaT. In contrast PLC-betaX was not activated by the pertussis toxin substrate G proteins Galphai1, Galphai2, Galphai3, or Galphao. These results are consistent with the idea that PLC-betaX is regulated by alpha-subunits of the Gq family and by Gbetagamma and do not support the idea that alpha-subunits of pertussis toxin-sensitive G proteins are directly involved in regulation of this protein.
 ...
PMID:Purification and G protein subunit regulation of a phospholipase C-beta from Xenopus laevis oocytes. 894 Jan 9

The negative correlation between coronary heart disease and plasma levels of HDL has been attributed to the ability of HDL to take up cellular cholesterol. The HDL3-induced removal of cellular cholesterol was reported to be impaired in fibroblasts from patients with familial HDL deficiency (Tangier disease, TD). In addition, we have recently shown that HDL3 stimulates the hydrolysis of phosphatidylcholine (PC) in cholesterol-loaded fibroblasts. To investigate whether this cell signaling pathway is involved in cholesterol efflux mechanisms, we compared the HDL3-induced PC hydrolysis in normal fibroblasts and in fibroblasts from a TD kindred, in whom the HDL3- and apolipoprotein A-I (apo A-I)-induced mobilization of cellular cholesterol was found to be reduced by 50%. The HDL3-induced formation of phosphatidic acid (PA) via PC-specific phospholipase D (PC-PLD) was markedly reduced by 60-80% in these cells, whereas the formation of diacylglycerol (DG) via PC-specific phospholipase C (PC-PLC) was two- to threefold enhanced. Defective regulation of PC-PLC and PC-PLD was similarly observed in response to apo A-I and endothelin, but not in response to the receptor-independent stimulation of PC hydrolysis by PMA. A Tangier-like PA and DG formation pattern could be induced in normal cells after preincubation with pertussis toxin, suggesting the involvement of a G-protein. The impaired mobilization of radiolabeled cellular cholesterol in TD cells could completely be overcome by increasing the PA levels in the presence of the PA phosphohydrolase inhibitor propranolol. Conversely, the inhibition of PA formation in the presence of 0.3% butanol as well as the inhibition of DG formation in the presence of the PC-PLC inhibitor D 609 reduced the mobilization of cellular cholesterol both in normal and in TD cells. Our data indicate that the coordinate formation of PA and DG via PC-PLD and PC-PLC is essential for efficient cholesterol efflux. The molecular defect in this TD kindred appears to affect an upstream effector of protein kinase C responsible for the G-protein-dependent regulation of PC-specific phospholipases.
 ...
PMID:Defective regulation of phosphatidylcholine-specific phospholipases C and D in a kindred with Tangier disease. Evidence for the involvement of phosphatidylcholine breakdown in HDL-mediated cholesterol efflux mechanisms. 894 49

The profile of biochemical responses following stimulation of human platelets with 1-alkyl-2-lyso-sn-glycero-3-phosphate (ALPA), a derivative of platelet-activating factor (PAF), was investigated. In the presence of extracellular Ca2+, ALPA evoked a dose-dependent increase and sustained elevation of the intracellular free Ca2+ concentration and stimulated the formation of phosphatidic acid. Platelets released free [3H]arachidonic and [3H]oleic acid at maximal rates between 5 and 15 s following ALPA stimulation. However, in platelets labeled with myo-[3H]inositol, ALPA induced [3H]phosphoinositide breakdown and formation of [3H]inositol phosphates with slower kinetics. Intracellular Ca2+ mobilization and the release of free fatty acids and inositol phosphates were not inhibited by pretreatment of platelets with pertussis toxin (PTX) or the PAF receptor antagonist WEB 2086. Following platelet stimulation with ALPA, tyrosine phosphorylation of proteins with apparent molecular masses of 65-95, 110-130, and 145-170 kDa was increased in a time-dependent manner, while phosphorylation of 40- to 45-kDa proteins was decreased. One of the platelet proteins phosphorylated on tyrosine residues in response to ALPA was found to be PLC-gamma1. Exogenous [3H]ALPA was metabolized primarily to [1-3H]alkyl-2,3-diacylglycerol. The metabolic conversion of [3H]ALPA involved a dephosphorylation reaction, and the formation of the dephosphorylated product, [1-3H]alkyl-monoglycerol, was detected within 5 s. These data demonstrate that an ether-linked lysophosphatidic acid can activate human platelets by a PTX-insensitive mechanism which does not involve the PAF receptor. Upon stimulation of platelets, ALPA induces the activation of phospholipases A2 and C, and tyrosine phosphorylation of several cellular proteins including PLC-gamma1. These signal transduction responses in platelets are accompanied by rapid metabolism of ALPA.
 ...
PMID:Signaling responses to alkyllysophosphatidic acid: the activation of phospholipases A2 and C and protein tyrosine phosphorylation in human platelets. 895 Oct 35

The objective of this study was to investigate the mechanism of action of PGF2 alpha in cultured human myometrial cells. We measured the effects of PGF2 alpha and fluprostenol, a selective PGF2 alpha receptor (FP receptor) agonist, on phospholipase C(PLC) activation, on changes in the intracellular free calcium concentration ([Ca2+]i), and on protein tyrosine phosphorylation. PGF2 alpha and fluprostenol activated PLC (determined by measuring the formation of inositol phosphates) and increased [Ca2+]i in a concentration-dependent manner. The apparent affinity of the FP receptor for fluprostenol was higher than that for PGF2 alpha when measuring PLC activation, but the receptor displayed similar affinities for both agonists when measuring increases in [Ca2+]i. These effects were not altered by treating the cells with pertussis toxin (PT), suggesting that the FP receptor is linked to PLC activation by a G protein of the Gq family. By contrast, the effect of oxytocin on PLC activation involved both PT-resistant and PT-sensitive pathways. Human myometrial cells responded to pervanadate and epidermal growth factor with increased PLC activity and increased tyrosine phosphorylation, demonstrating a functional PLC-gamma tyrosine kinase pathway. However, neither fluprostenol nor oxytocin stimulated tyrosine phosphorylation, but the effects of both agonists were inhibited after protein kinase C stimulation. These data suggest that fluprostenol and oxytocin activate PLC-beta rather than PLC-gamma isoforms. The effect of fluprostenol is Ca2+ dependent, but is unlikely to involve a direct effect of Ca2+ on PLC activity.
 ...
PMID:Fluprostenol activates phospholipase C and Ca2+ mobilization in human myometrial cells. 896 35

5-HT activates the peristaltic reflex and is the neurotransmitter of a subset of myenteric interneurons. Hyperpolarizing afterpotential (AH)/type 2 neurons respond to 5-HT with a long-lived depolarization that is caused by the inhibition of a Ca(2+)-activated K+ conductance (gKCa). This effect is mediated by a G-protein-coupled receptor, 5-HT1P. 5-HT1P agonists specifically activate G alpha o, the immunoreactivity of which was found to be highly abundant and membrane-associated in almost all enteric neurons. Responses of hyperpolarizing AH/type 2 neurons to 5-HT were inhibited by intracellular injection of GDP beta S or anti-G alpha o Fab fragments but were potentiated and prolonged by intracellular GTP gamma S. Responses to 5-HT were antagonized by pertussis toxin, downregulation of protein kinase C (PKC) and inhibitors of phosphatidylcholine phospholipase C (PC-PLC), PKC (including pseudosubstrate peptides, chelerythrine, and the alpha/beta isoform-specific inhibitor Go 6976), protein kinase A (PKA), and adenylate cyclase. Responses to 5-HT were mimicked by activators of PKC, and 5-HT induced a concentration-dependent increase in the membrane-associated PKC activity in isolated myenteric ganglia. Immunocytochemical studies suggested that the most abundant isoforms of PKC in enteric neurons are alpha and delta. These data suggest that signal transduction of the 5-HT1P-mediated slow response to 5-HT involves activation of PC-PLC by G alpha o to liberate diacylglycerol, which stimulates PKC (most likely alpha). PKC probably activates adenylate cyclase, which through cAMP, activates PKA. Activation of both PKA and PKC lead to closure of gKCa.
 ...
PMID:Mediation by protein kinases C and A of Go-linked slow responses of enteric neurons to 5-HT. 899 56

Occupancy of oxytocin receptor (OTR) binding sites in pregnant rat myometrial membranes with iodinated oxytocin antagonist (OTA), followed by detergent solubilization and size selection, showed that radioactivity eluted in two distinct peaks: one corresponding in size to the isolated receptor (approximately 60 kDa) and the other ranging from 240 to 320 kDa. The unliganded 240- to 320-kDa fraction contained OTRs coupled to G proteins, as the addition of oxytocin (OT) increased guanosine 35S-labeled 5'-O-(3-thiotriphosphate) binding up to twofold in a dose-dependent manner. The effects of OT were blocked by coincubation with OTA. G protein alpha-subunits associated with OTRs in the 240- to 320-kDa peak were identified by immunoadsorption. Significant amounts of both G alpha q/11 and G alpha i3 were associated with the OTR; a lesser amount of G alpha s was complexed. Using the same approach but with antibodies to effector enzymes, we observed that phospholipase C beta 1 (PLC beta 1) and PLA2 were also associated with the OTR. The results corroborate the well-established interaction of OTR with Gq and further show that Gi coupling might be an important component of OTR signal transduction. To further investigate the interaction of Gi with the OTR, we showed that OT stimulation of guanosine 5'-triphosphatase activity in intact myometrial membranes was inhibited by pertussis toxin. Pertussis toxin-stimulated ADP ribosylation of G alpha i in myometrial membranes was also decreased by OT treatment. These findings with pertussis toxin strongly indicate that OTR is coupled to Gi in rat myometrial membranes. The 60-kDa OTR peak (noncoupled receptor) was demonstrable in the myometrium only before the end of gestation and after parturition and accounted for about one-half the 125I-OTA binding activity. At term, there was about a fivefold increase in binding and almost a complete shift to the 240- to 320-kDa-size complex. Thus the established increased sensitivity of the myometrium to OT at term could be the result of both upregulation of OTRs and an increase in the fraction of receptors coupled to signal transduction components, one of which is Gi.
 ...
PMID:Coupling of oxytocin receptor to G proteins in rat myometrium during labor: Gi receptor interaction. 917 88

The [(3)H]inositol incorporation into the membrane fraction of A-431 human epidermoid carcinoma cells was markedly increased by stimulation of the cells with either epidermal growth factor (EGF), ATP, bradykinin, or a calcium ionophore A23187 in the presence of 1 mM extracellular calcium ions; most incorporated [(3)H]inositol was found to have accumulated as phosphatidylinositol (PI). The EGF- and ATP-stimulated PI synthesis was inhibited by two protein kinase C inhibitors, staurosporine and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), and an intracellular calcium chelator, 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA/AM), but not by the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7). Pretreatment of cells with pertussis toxin (IAP, islet-activating protein) inhibited the PI synthesis, [Ca(2+)]i elevation, and inositol trisphosphate (IP(3)) production by ATP, suggesting that the phospholipase C(PLC) system coupled with IAP-sensitive G protein is involved in the ATP-stimulated PI synthesis. On the other hand, the ATP stimulation increased the release of [(3)H]choline and [(32)P)phosphatidic acid (PA) from radiolabeled cells, and such release was not inhibited by IAP. In the presence of n-butyl alcohol, which prevents the production of PA by generation of phosphatidylbutanol, the ATP-stimulated PI synthesis was reduced. Because n-butyl alcohol did not inhibit IP(3) production and [Ca(2+)]i elevation, this fact suggests that the lAP-insensitive PLD system is involved in the ATP-stimulated PI synthesis. In A-431 cells, the stimulation of P(2)-purinergic receptors appears to activate the IAP-sensitive PLC system and IAP-insensitive PLD system, both of which are essential for the stimulation of PI synthesis. The present results imply the general prospect that ligand stimulation, which mobilizes second messengers and consumes their precursors, simultaneously provokes the pathway to synthesize and salvage the second messenger precursors as well.
 ...
PMID:ATP- and EGF-stimulated phosphatidulinositol synthesis by two different pathways, phospholipase D and diacylglycerol kinase, in A-431 epidermoid carcinoma cells. 921 28

We have previously reported that gastrin induces a rapid and transient tyrosine phosphorylation of phospholipase C gamma 1 (PLC gamma 1) in association with inositol 1,4,5-trisphosphate (IP3) formation in rat colonic epithelial cells (34). In this study, we demonstrate that gastrin regulates IP3 formation mainly through PLC gamma 1 isozyme. Immunoblotting analysis revealed the expression of PLC beta 3 and -gamma 1, but not PLC beta 1, -beta 2, or -beta 4 in the rat colonic epitheliums. To explore what PLC isozyme(s) modulates gastrin effect on IP3, immunoneutralizing antibody to PLC beta 1, -beta 3, or -gamma 1 was introduced into the colonic cells using a lipid carrier. The gastrin-stimulated increase in IP3 concentration was specifically prevented by anti-PLC gamma 1 but not by anti-PLC beta 1 or -beta 3 antibody. Immunoprecipitation assays have also revealed that gastrin promoted an increase in tyrosine phosphorylation and co-precipitation of a 60 kDa src kinase with PLC gamma 1. Administration of antibody specific to pp60c-src into the colonic cells prevented the gastrin-stimulated increases in IP3. Tyrosine phosphorylation of PLC gamma 1 may be a major mechanism through which gastrin regulates IP3 level in the colonic cells. Pretreatment of cells with the tyrosine kinase inhibitor genistein abrogated gastrin's effect on IP3, while extended pretreatment with pertussis toxin, a G-protein inhibitor, did not affect the ability of gastrin to stimulate IP3 formation. Colonic cells expressed the G alpha i subunits1-3; however, immunoblotting analysis did not reveal any difference in G alpha i proteins' expression between control and gastrin treated cells. The results provide direct evidence that gastrin regulates IP3 level by a signaling mechanism that involves PLC gamma 1 and pp60c-src kinase.
 ...
PMID:Gastrin induces IP3 formation through phospholipase C gamma 1 and pp60c-src kinase. 943 36

P2 receptor subtypes and their signaling mechanisms were characterized in dispersed smooth muscle cells. UTP and ATP stimulated inositol 1,4,5-triphosphate formation, Ca2+ release, and contraction that were abolished by U-73122 and guanosine 5'-O-(3-thio)diphosphate, and partly inhibited (50-60%) by pertussis toxin (PTX). ATP analogs (adenosine 5'-(alpha, beta-methylene)triphosphate, adenosine 5'-(beta, gamma-methylene)triphosphate, and 2-methylthio-ATP) stimulated Ca2+ influx and contraction that were abolished by nifedipine and in Ca2+-free medium. Micromolar concentrations of ATP stimulated both Ca2+ influx and Ca2+ release. ATP and UTP activated Gq/11 and Gi3 in gastric and aortic smooth muscle and heart membranes, Gq/11 and Gi1 and/or Gi2 in liver membranes, and Go and Gi1-3 in brain membranes. Phosphoinositide hydrolysis stimulated by ATP and UTP was mediated concurrently by Galphaq/11-dependent activation of phospholipase (PL) C-beta1 and Gbetagammai3-dependent activation of PLC-beta3. Phosphoinositide hydrolysis was partially inhibited by PTX or by antibodies to Galphaq/11, Gbeta, PLC-beta1, or PLC-beta3, and completely inhibited by the following combinations (PLC-beta1 and PLC-beta3 antibodies; Galphaq/11 and Gbeta antibodies; PLC-beta1 and Gbeta antibodies; PTX with either PLC-beta1 or Galphaq/11 antibody). The pattern of responses implied that P2Y2 receptors in visceral, and probably vascular, smooth muscle are coupled to PLC-beta1 via Galphaq/11 and to PLC-beta3 via Gbetagammai3. These receptors co-exist with ligand-gated P2X1 receptors activated by ATP analogs and high levels of ATP.
 ...
PMID:Coexpression of ligand-gated P2X and G protein-coupled P2Y receptors in smooth muscle. Preferential activation of P2Y receptors coupled to phospholipase C (PLC)-beta1 via Galphaq/11 and to PLC-beta3 via Gbetagammai3. 946 31


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>