Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polymorphonuclear neutrophils (PMN) adherent to integrin ligands respond to inflammatory mediators by reorganizing their cytoskeleton and releasing reactive oxygen intermediates. As Src family tyrosine kinases are implicated in these responses, we investigated their possible role in regulating degranulation. Human PMN incubated on fibrinogen released lactoferrin in response to TNF-alpha and this response was inhibited by PP1, a Src family tyrosine kinase inhibitor. This drug had no effect on lactoferrin secretion induced by PMA, an adhesion-independent agonist of PMN degranulation. However, PP1 blocked secretion in PMN plated on plain tissue culture plastic, a surface inducing PMN spreading in the absence of any stimulus. Double knockout hck-/- fgr-/- PMN adherent to collagen or fibrinogen failed to release lactoferrin in response to TNF-alpha but responded to PMA as wild-type PMN. Degranulation induced by spreading over tissue culture plastic was also defective in hck-/- fgr-/- PMN. Defective adhesion-dependent degranulation required the absence of both kinases, because single knockout fgr-/- or hck-/- PMN responded as wild-type cells. Analysis of lactoferrin secretion in hck-/- fgr-/- or PP1-treated, suspended PMN showed that Src kinases are not implicated in degranulation dependent on activation of protein kinase C or increase in intracellular free Ca2+ but may play a role in the response to FMLP of cytochalasin B-treated PMN. These findings identify a role for Src family kinases in a signaling pathway leading to granule-plasma membrane fusion and suggest that Fgr and Hck would be targets for pharmacological control of adhesion-dependent degranulation in the inflammatory site.
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PMID:Adhesion-dependent degranulation of neutrophils requires the Src family kinases Fgr and Hck. 991 42

The C3a receptor (C3aR) is expressed on most human peripheral blood leukocytes with the exception of resting lymphocytes, implying a much higher pathophysiological relevance of the anaphylatoxin C3a as a proinflammatory mediator than previously thought. The response to this complement split product must be tightly regulated in situations with sustained complement activation to avoid deleterious effects caused by overactivated inflammatory cells. Receptor internalization, an important control mechanism described for G protein-coupled receptors, was investigated. Using rabbit polyclonal anti-serum directed against the C3aR second extracellular loop, a flow cytometry-based receptor internalization assay was developed. Within minutes of C3a addition to human granulocytes, C3aR almost completely disappeared from the cell surface. C3aR internalization could also be induced by PMA, an activator of protein kinase C. Similarly, monocytes, the human mast cell line HMC-1, and differentiated monocyte/macrophage-like U937-cells exhibited rapid agonist-dependent receptor internalization. Neither C5a nor FMLP stimulated any cross-internalization of the C3aR. On the contrary, costimulation of granulocytes with C5a, but not FMLP, drastically decreased C3aR internalization. This effect could be blocked by a C5aR-neutralizing mAb. HEK293-cells transfected with the C3aR, with or without Galpha16, a pertussis toxin-resistant G protein alpha subunit required for C3aR signal transduction in these cells, did not exhibit agonist-dependent C3aR internalization. Additionally, preincubation with pertussis toxin had no effect on C3a-induced internalization on PMNs. C3aR internalization is a rapid negative control mechanism and is influenced by the C5aR pathway.
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PMID:Modulation of C3a activity: internalization of the human C3a receptor and its inhibition by C5a. 1035 94

It was shown that vitamin E decreased the stimulating role of oxidative burst activators which influenced on Ca(2+)-dependent mechanisms (A23187, verapamil, FMLP). Jointly addition of this vitamin and blood plasma contained tocopherol-binding proteins influenced on mechanisms associated with protein kinase C. It was shown that Ca ions can also take part in tocopherol's action on blast transformation of lymphocytes.
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PMID:[Role of Ca ions and protein kinase C in the action of vitamin E on respiratory burst of neutrophils and blast transformation of lymphocytes]. 1044 62

Stimulation of neutrophils with LTB(4) or PAF results in the production of a rapidly oscillating actin polymerization/depolymerization response. Treatment of neutrophils with inhibitors of PKC prior to stimulation with ligand resulted in a masking of the F-actin oscillations. Because myosin has been shown to be a substrate for neutrophil PKC, this protein was investigated as a potential downstream mediator of F-actin oscillations. Stimulation of neutrophils with LTB(4) resulted in myosin light chain being serine phosphorylated in a PKC-dependent manner. This phosphorylation was shown to occur in a manner that is kinetically distinct from the myosin phosphorylation induced by FMLP, a potent activator of actin polymerization that alone does not induce F-actin oscillations. Additionally, disruption of intracellular actin-myosin interactions resulted in inhibition of LTB(4)- as well as PAF-induced F-actin oscillations. These data suggest that PKC and downstream phosphorylation of myosin as well as actin-myosin interaction may play roles in mediating the production of neutrophil F-actin oscillations.
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PMID:Regulation of oscillations in filamentous actin content in polymorphonuclear leukocytes stimulated with leukotriene B(4) and platelet-activating factor. 1046

Contaminating leukocytes in the ejaculate are an important source of reactive oxygen species (ROS) in human semen. When present in sufficient numbers, they can have a detrimental influence on sperm function in humans. Unfortunately, there is little published information regarding the importance of leukocytes in stallion semen. The objectives of this study were to determine the production of hydrogen peroxide (H2O2) by activated equine neutrophils and to examine the effect of this ROS production on equine sperm motility in vitro. Motile equine spermatozoa (two ejaculates each from four stallions) and peripheral blood neutrophils were isolated on discontinuous Percoll gradients, washed and resuspended in a modified Tyrode's medium. Spermatozoa (25 x 10(6)/ml) were incubated for 30 min at 38 C with neutrophils (0,0.5 x 10(6),1 x 10(6), 5 x 10(6) and 10 x 10(6)/ml) activated by either the protein kinase C agonist, 12-myristate, 13-acetate phorbol ester (PMA; 100 nM) or the leukocyte chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (FMLP; 0.1 mM). Sperm motility was determined by computer-assisted semen analysis (CASA) at time 0 min (T0) and time 30 min (T30), and H2O2 was measured at T30 with the Amplex Red assay kit. At T30, there was a significant (P < 0.01) increase in H2O2 with the addition of 5 x 10 and 10 x 10(6) neutrophils/ml activated by FMLP (0.76 +/- 0.3 and 0.99 +/- 0.4 microM, respectively, versus 0.0024 +/- 0.002 microM in sperm alone), and this increase was associated with a significant (P < 0.001) decrease in total motility (52 +/- 5.1 and 48 +/- 6.0%, respectively, versus 80 +/- 4.7% in sperm alone). At T30, there was also a significant (P < 0.001) increase in H2O2 with the addition of 5 x 10(6) and 10 x 10(6) neutrophils/ml activated by PMA (1.88 +/- 0.2 and 2.07 +/- 0.3 microM, respectively, versus 0.0009 +/- 0.0006 microM in sperm alone). The results of this study demonstrate that 5 x 10(6) activated neutrophils/ml are sufficient to impair equine sperm motility in vitro.
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PMID:Generation of reactive oxygen species by equine neutrophils and their effect on motility of equine spermatozoa. 1204 97

Activation of group IV cytosolic phospholipase A(2) (gIV-PLA(2)) is the essential first step in the synthesis of inflammatory eicosanoids and in integrin-mediated adhesion of leukocytes. Prior investigations have demonstrated that phosphorylation of gIV-PLA(2) results from activation of at least two isoforms of mitogen-activated protein kinase (MAPK). We investigated the potential role of phosphoinositide 3-kinase (PI3K) in the activation of gIV-PLA(2) and the hydrolysis of membrane phosphatidylcholine in fMLP-stimulated human blood eosinophils. Transduction into eosinophils of Deltap85, a dominant negative form of class IA PI3K adaptor subunit, fused to an HIV-TAT protein transduction domain (TAT-Deltap85) concentration dependently inhibited fMLP-stimulated phosphorylation of protein kinase B, a downstream target of PI3K. FMLP caused increased arachidonic acid (AA) release and secretion of leukotriene C(4) (LTC(4)). TAT-Deltap85 and LY294002, a PI3K inhibitor, blocked the phosphorylation of gIV-PLA(2) at Ser(505) caused by fMLP, thus inhibiting gIV-PLA(2) hydrolysis and production of AA and LTC(4) in eosinophils. FMLP also caused extracellular signal-related kinases 1 and 2 and p38 MAPK phosphorylation in eosinophils; however, neither phosphorylation of extracellular signal-related kinases 1 and 2 nor p38 was inhibited by TAT-Deltap85 or LY294002. Inhibition of 1) p70 S6 kinase by rapamycin, 2) protein kinase B by Akt inhibitor, or 3) protein kinase C by Ro-31-8220, the potential downstream targets of PI3K for activation of gIV-PLA(2), had no effect on AA release or LTC(4) secretion caused by fMLP. We find that PI3K is required for gIV-PLA(2) activation and hydrolytic production of AA in activated eosinophils. Our data suggest that this essential PI3K independently activates gIV-PLA(2) through a pathway that does not involve MAPK.
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PMID:Activation of group IV cytosolic phospholipase A2 in human eosinophils by phosphoinositide 3-kinase through a mitogen-activated protein kinase-independent pathway. 1453 Mar 66

FMLP stimulation of Xenopus oocytes expressing fMLP receptors leads to a concentration-dependent biphasic inward current. To identify the evolution of these currents we have examined the effects of blocking various cell signalling pathways. In addition we have analysed the effects of three intravenous anaesthetics on these fMLP-induced currents. Xenopus oocytes were microinjected with cRNA encoding the fMLP receptor and fMLP-stimulated (100 nM) currents measured, using two-electrode voltage-clamp (-70 mV), before and after injection of heparin (120 ng ml-1), wortmannin (1 microM), U73122 (5 microM) or buffer. Concentration-response curves were established for the action on fMLP-stimulated currents of thiopentone (5-500 microM), methohexitone (0.2-200 microM) and propofol (0.5-500 microM). Heparin significantly enhanced the fast current (p<0.05). Wortmannin had no effect on either current. U73122 inhibited only the slow current (p<0.05). All anaesthetics inhibited both currents, with the maximum inhibition for the fast/slow currents 70%/100%, 60%/60% and 100%/100% for thiopentone (IC50 147/120 microM), methohexitone (IC50 4.7/2.2 microM) and propofol (IC50 33/8 microM), respectively. We suggest (a) the slow current arises via the PLC/PKC pathway because it is reduced by the PLC inhibitor U73122, (b) the PI3K- and PLD-mediated pathways are not involved because wortmannin had no effect and (c) activation of the two conductance channels must be different because U73122 reduced the slow but not the fast current. Since both currents are decreased by all three anaesthetics, their inhibition might be mediated through an action at the agonist/receptor, although, since the slow current is consistently more sensitive than the fast, there may be additionally an action on cell signalling.
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PMID:Anaesthetic sensitivity of fMLP-induced cell signalling in Xenopus oocytes. 1633 14

Human neutrophils are highly specialised for their primary function, i.e. phagocytosis and destruction of microorganisms. Leukocyte recruitment to sites of inflammation and infection is dependent upon the presence of a gradient of locally produced chemotactic factors. The bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) was one of the first of these to be identified and is a highly potent leukocyte chemoattractant. It interacts with its receptor on the neutrophil membrane, activating these cells through a G-protein-coupled pathway. Two functional fMLP receptors have thus far been cloned and characterized, namely FPR (formyl peptide receptor) and FPRL1 (FPR like-1), with high and low affinities for fMLP, respectively. FMLP is known to activate phospholipase C (PLC), PLD, PLA2 and phosphatidylinositol-3-kinase (PI3K), and it also activates tyrosine phosphorylation. The second messengers resulting from the fMLP receptor interaction act on various intracellular kinases, including protein kinase C (PKC) and mitogen-activated protein kinases (MAPKs). The activation of these signal transduction pathways is known to be responsible for various biochemical responses which contribute to physiological defence against bacterial infection and cell disruption. This review will consider the ability of selective analogues (ligands able to discriminate between different biological responses) to activate a single spectrum of signal transduction pathways capable of producing a unique set of cellular responses, hypothesising that a distinctive imprint of signal protein activation may exist. Through more complete understanding of intracellular signaling, new drugs could be developed for the selective inflammatory blockade.
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PMID:Signal transduction pathways triggered by selective formylpeptide analogues in human neutrophils. 1651 93

P-Rex1 (phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 1) is a Rac-specific guanine nucleotide exchange factor activated by Gbetagamma subunits and by PtdIns((3,4,5))P(3). Recent studies indicate that P-Rex1 plays an important role in signaling downstream of neutrophil chemoattractant receptors. Here we report that heterologous expression of P-Rex1, but not Vav1, reconstitutes formyl peptide receptor 1 (FPR1)-mediated NADPH oxidase activation in the transgenic COS(phox) cells expressing gp91(phox), p22(phox), p67(phox) and p47(phox). A successful reconstitution requires the expression of a full-length P-Rex1 with intact DH and PH domains, and is accompanied by P-Rex1 membrane localization as well as Rac1 activation. P-Rex1-dependent superoxide generation in the reconstituted COS(phox) cells was further enhanced by expression of the novel PKC isoform PKCdelta and by overexpression of Akt. Heterologous expression of P-Rex1 in COS(phox) cells potentiated fMet-Leu-Phe-induced Akt phosphorylation, whereas expression of a constitutively active form of Akt enhanced Rac1 activation. In contrast, a dominant negative Akt mutant reduced the fMet-Leu-Phe stimulated superoxide generation as well as Rac1 activation. These results demonstrate that in COS(phox) cells, P-Rex1 is a critical component for FPR1-mediated signaling leading to NADPH oxidase activation, and there is a crosstalk between the P-Rex1-Rac pathway and Akt in superoxide generation.
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PMID:Characterization of P-Rex1 for its role in fMet-Leu-Phe-induced superoxide production in reconstituted COS(phox) cells. 2007 42


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