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

In response to activation of phagocytic cells and during inflammatory disorders, some proteases and very reactive oxygen species are produced. These proteases and oxidants are involved in many diseases like tissue injury or atherosclerosis. We have shown in vitro that verapamil, a calcium channel blocker, had antielastase and antioxidant properties. This drug inhibited the release of elastase by neutrophils in a dose-dependent manner when these cells were stimulated by phorbol-myristate-acetate (PMA), by N-formyl-methionyl-leucylphenylalanine (fMLP) and by the calcium ionophore A23187 (Ca.I). In addition, verapamil inhibited superoxide anion when human neutrophils were stimulated by PMA, fMLP, dioctanoylglycerol (DiC8), Ca.I or by opsonised zymosan (OZ). Verapamil did not act by scavenging elastase or oxidants as demonstrated in cell-free models which showed no direct antielastase or antioxidant effect involved by verapamil. Superoxide anion and elastase inhibition by verapamil has been considered to the mobilization of cytosolic calcium and inhibition of protein kinase C. The results suggest that verapamil might contribute help the development and progression of atheroma where oxidants and elastase are involved.
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PMID:Verapamil inhibits elastase release and superoxide anion production in human neutrophils. 951 2

Urokinase-type plasminogen activator (uPA) is a key serine protease involved in invasion and metastasis. We had shown that overproduction of uPA in tumor cells is controlled by a phospholipase D-protein kinase C-dependent pathway. Now we studied whether other signaling pathways participate in the regulation of constitutive uPA and metalloproteinase (MMP) overproduction in tumor cells. Staurosporine, a protein kinase inhibitor, stimulated uPA and MMP-9 secretion as measured by radial caseinolysis, zymography and Western blotting. Genistein, a specific tyrosine kinase inhibitor, reduced the constitutive and staurosporine-induced uPA and MMP-9 secretion. Interestingly, the phosphatase inhibitor vanadate stimulated uPA secretion. Verapamil, a calcium channel blocker, inhibited both endogenous and PMA-stimulated secretion of uPA but was unable to inhibit staurosporine-induced secretion. The alcohol n-butanol, a phospholipase D and protein kinase C inhibitor, besides inhibiting constitutive uPA secretion, blocked staurosporine-induced secretion. Our results suggest that constitutive and staurosporine-induced uPA and MMP-9 secretion by LM3 murine mammary tumor cells is controlled by an endogenous tyrosine kinase pathway and probably involves protein phosphatases. In addition, the staurosporine-induced signal regulating urokinase secretion is independent of extracellular calcium but dependent on phospholipase D.
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PMID:Secretion of urokinase and metalloproteinase-9 induced by staurosporine is dependent on a tyrosine kinase pathway in mammary tumor cells. 957 73

The purpose of this study was to test whether the elevated intracellular Ca++ level ([Ca++]i) resulting from store-operated Ca++ entry was associated with vascular smooth muscle contraction. Cyclopiazonic acid (CPA), a selective inhibitor of sarcoplasmic reticulum Ca(++)-ATPase, concentration-dependently (1-10 microM) elevated [Ca++]i in rat aorta, as indicated by an increase in the fura-2 340/380 ratio. Simultaneous measurement of contraction demonstrated that 1 and 10 microM CPA induced insignificant and variable amounts of contraction, respectively. Verapamil (10 microM) had relatively little effect on the 1 and 10 microM CPA-elevated [Ca++]i. In contrast, Ni++ (0.1 mM), in the presence of verapamil, abolished the 1 microM CPA-elevated [Ca++]i. Ni++ (0.1 mM) also partially decreased the 10 microM CPA-elevated [Ca++]i and, furthermore, abolished the associated contraction. A higher Ni++ concentration (1 mM) abolished the 10 microM CPA-elevated [Ca++]i that remained after verapamil and 0.1 mM Ni++. Phorbol dibutyrate (10 nM), a protein kinase C activator, potentiated contractions to 1 and 10 microM CPA in the presence of verapamil. Ni++ (0.1 mM) abolished the enhanced contractions, and decreased the elevated [Ca++]i. These results suggest that 1) elevated [Ca++]i due to store-operated Ca++ entry is dissociated from contraction; 2) the elevated [Ca++]i is restricted to at least two noncontractile compartments that can be differentiated by their relative sensitivities to blockade by low (0.1 mM) and higher (1 mM) Ni++ concentrations, and 3) [Ca++]i elevation within the compartment sensitive to blockade by 0.1 mM Ni++ can be coupled to contraction via protein kinase C activation.
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PMID:Coupling of store-operated Ca++ entry to contraction in rat aorta. 958 Jun 24

The effects of three calcium channel blockers, verapamil, diltiazem and nifedipine, were examined on in vitro proliferation and migration of human retinal pigment epithelial cells. Human retinal pigment epithelial cells were seeded in Dulbecco's modified essential medium with 10% fetal bovine serum and different concentrations of the three calcium channel blockers. After 3 days of treatment, cell proliferation was determined by cell counting and by [3H]-thymidine uptake. Cell viability was determined with trypan blue exclusion. For determination of cell migration, retinal pigment epithelial cells were grown to confluence and then growth-inhibited with mitomycin C. After a 3 mm zone was denuded, the cells were treated with different concentrations of the calcium channel antagonists. After 24 hr, the cells that had migrated over the wound edge were counted. To determine the involvement of protein kinase C in the verapamil effect, its activity was measured in both verapamil-treated and untreated cells. Verapamil dose dependently inhibited serum-induced proliferation of retinal pigment epithelial cells, when measured by cell number (IC50 14.6 microM) or [3H]-thymidine incorporation (IC50 11.3 microM). At concentrations of 15 microM and below, there was no effect on cell viability, as determined by morphology and trypan blue exclusion. Diltiazem inhibited cell proliferation at a concentration of 100 microM; however, 100 microM nifedipine had no effect. Verapamil showed a significant inhibition of serum-induced migration in the range of 10 microM to 0.1 microM. The IC50 of the inhibition of retinal pigment epithelial cell proliferation and migration by verapamil is significantly higher than that seen for effects on calcium channel blockage. Eight micromolar verapamil reversibly inhibited total protein kinase-C activity in retinal pigment epithelial cells suggesting the possibility that the drug may act by inhibiting the protein kinase-C pathway. These data suggest the potential of the calcium channel blocker verapamil as a pharmacological modulator of disorders such as proliferative vitreoretinopathy in which there is increased retinal pigment epithelial cell proliferation and migration.
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PMID:Verapamil inhibits proliferation, migration and protein kinase C activity in human retinal pigment epithelial cells. 970 77

The ability of the CD44 adhesion molecule to interact with its ligand hyaluronic acid (HA) is tightly regulated. CD44-positive mouse LB lymphoma cells are unable to bind HA unless activated by the tumor promoter phorbol 12-myristate 13-acetate (PMA). PMA causes a dose-dependent increase in both CD44 expression level and HA-binding capacity, with the binding of HA observed only above a threshold amount of CD44 molecules. This induction of HA-binding as well as the increase in CD44 expression are prevented by cycloheximide, suggesting a requirement for new additional CD44 molecules on the cell surface and/or cooperating proteins. In the present study, we have investigated which of the signal transduction pathways activated by PMA leads to the increased CD44 expression with subsequent acquisition of HA-binding capacity. By comparing the influence of each inhibitory agent on PMA-activated LB lymphoma cells versus that on a constitutive HA-binder cell line derived from LB cells (designated HA9 cells), we could distinguish between an effect on the PMA-activation phase and a one on the HA-binding phase. Our data show that the PMA-induced HA-binding could not be blocked by agents inhibiting protein kinase C (PKC) (staurosporine, sphingosine, polymyxin B, quercetin) or genestein, an inhibitor of tyrosine protein kinases. However, this PMA response was strongly inhibited by calmodulin antagonists (chlorpromazine, trifluoperazine, W-7) and the calcium blocker verapamil. The calmodulin antagonists inhibited the PMA-induced increase in CD44 expression on LB cells, but had no influence on the ability of the constitutive HA-binder HA9 cell line to interact with HA, indicating an effect on the PMA induction phase rather than on the binding itself. Verapamil also blocked the PMA-induced increase in CD44 expression on LB cells, but in addition it slightly reduced the ability of the HA9 cells to bind HA without affecting their CD44 expression level. In conclusion, our data suggest that CD44 activation by PMA is calcium and calmodulin dependent, rather than mediated by protein kinase C.
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PMID:Calcium- and calmodulin-dependent PMA-activation of the CD44 adhesion molecule. 992 43

1. Volume-activated chloride currents in cultured rat brain endothelial cells were investigated on a functional level using the whole-cell voltage-clamp technique and on a molecular level using the reverse transcriptase-polymerase chain reaction (RT-PCR). 2. Exposure to a hypotonic solution caused the activation of a large, outward rectifying current, which exhibited a slight time-dependent decrease at strong depolarizing potentials. The anion permeability of the induced current was I- (1.7) > Br- (1.2) > Cl- (1.0) > F- (0. 7) > gluconate (0.18). 3. The chloride channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB, 100 microM) rapidly and reversibly inhibited both inward and outward currents. The chloride transport blocker 4,4'-diisothiocyanatostilbene-2, 2'-disulphonic acid (DIDS, 100 microM) also blocked the hypotonicity-induced current in a reversible manner. In this case, the outward current was more effectively suppressed than the inward current. The volume-activated current was also inhibited by the antioestrogen tamoxifen (10 microM). 4. The current was dependent on intracellular ATP and independent of intracellular Ca2+. 5. Activation of protein kinase C by phorbol 12,13-dibutyrate (PDBu, 100 nM) inhibited the increase in current normally observed following hypotonic challenge. 6. Extracellular ATP (10 mM) inhibited the current with a more pronounced effect on the outward than the inward current. 7. Verapamil (100 microM) decreased both the inward and the outward hypotonicity-activated chloride current. 8. RT-PCR analysis was used to determine possible molecular candidates for the volume-sensitive current. Expression of the ClC-2, ClC-3 and ClC-5 chloride channels, as well as pICln, could be shown at the mRNA level. 9. We conclude that rat brain endothelial cells express chloride channels which are activated by osmotic swelling. The biophysical and pharmacological properties of the current show strong similarities to those of ClC-3 channel currents as described in other cell types.
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PMID:Functional and molecular characterization of a volume-sensitive chloride current in rat brain endothelial cells. 1006 24

We investigated the effects of different concentrations of ethanol on contraction of gallbladder isolated from guinea pig. Ethanol at 25 mM significantly inhibited the contraction induced by histamine, but not those by KCl and acetylcholine. A higher concentration (100 mM) of ethanol inhibited both histamine-, acetylcholine- and KCl- induced contractions. The inhibitory effect of the lower concentration (25 mM) of ethanol was not observed in the presence of verapamil, an antagonist of L-type Ca2+ channel or staurosporine, a selective inhibitor of protein kinase C. Verapamil and staurosporine significantly inhibited both histamine- and acetylcholine-induced contractile responses: the inhibitory effect was more potent for the histamine contraction. Our recent study has demonstrated that contraction caused by protein kinase C activation is completely dependent on Ca2+ influx through the L-type Ca2+ channel in gallbladder smooth muscle of guinea pig. Therefore, the difference in 25 mM ethanol effect on histamine- and acetylcholine-induced contractions may be due to different degree of involvement of protein kinase C activation in the agonist-induced contraction. On the other hands, the higher concentration (100 mM) of ethanol inhibits the common pathway of contraction in gallbladder smooth muscle cells.
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PMID:[Mechanism of inhibitory effects of ethanol on gallbladder contraction: differences in cases of histamine- and acetylcholine-induced contraction]. 1020 23

1. The present work was aimed to study the effect of PKC activation and protein-serine/threonine phosphatase (PP1/PP2 A) inhibition on P-glycoprotein (P-gp) mediated transport of L-DOPA in LLC-GA5 Col300 cells, a renal cell line expressing the human P-glycoprotein in the apical membrane. 2. L-DOPA accumulation was a time-and concentration-dependent process with the following kinetic characteristics: kin, 57.3 +/- 1.2 pmol mg protein(-1) min(-1); k(out), 3.3 +/- 0.1 pmol mg(-1) protein min(-1); Amax, 10.6 +/- 0.8; Kn, 198 +/- 64 microM; Vmax, 5.2 +/- 0.7 nmol mg protein(-1). 3. Verapamil (25 microM), a P-glycoprotein inhibitor, markedly increased (approximately 40% increase) the accumulation of a non-saturating concentration of L-DOPA (2.5 microM) at both initial rate of uptake (IRU, 6 min incubation) and at steady-state (SS, 30 min incubation). 4. PKC activation with phorbol 12,13-dibutyrate (PDBu, 1, 3 and 10 nM) produced a concentration-dependent decrease in L-DOPA accumulation at SS, but not at IRU. The inactive phorbol ester, 4alpha-phorbol 12,13-didecanoate (100 nM), produced no change in L-DOPA accumulation. The effect of PDBu was completely reverted by staurosporine (100 nM). The phosphatase inhibitor okadaic acid (100 nM) reduced by 20% the accumulation of L-DOPA at IRU, but not at SS. 5. It is suggested that P-glycoprotein plays a role in regulation of intracellular availability of L-DOPA in renal epithelial cells, and phosphorylation/dephosphorylation of P-glycoprotein may be involved in the regulation of the transporter.
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PMID:P-glycoprotein phosphorylation/dephosphorylation and cellular accumulation of L-DOPA in LLC-GA5 Col300 cells. 1051 74

Several grapefruit juice bioflavonoids, including quercetin, are reported to stimulate P-glycoprotein-mediated drug efflux from cultured tumor cells. To see whether these bioflavonoids alter the permeation of vincristine across the blood-brain barrier, we conducted experiments with cultured mouse brain capillary endothelial cells (MBEC4 cells) in vitro and ddY mice in vivo. The steady-state uptake of [3H]vincristine by MBEC4 cells was decreased by 10 microM quercetin, but increased by 50 microM quercetin. Similarly, the in vivo brain-to-plasma concentration ratio of [3H]vincristine in ddY mice was decreased by coadministration of 0.1 mg/kg quercetin, but increased by 1.0 mg/kg quercetin. Kaempferol had a similar biphasic effect on the in vitro uptake of [3H]vincristine. Other aglycones tested (chrysin, flavon, hesperetin, naringenin) increased [3H]vincristine uptake in the 10-50 microM range, and glycosides (hesperidin, naringin, rutin) were without effect. We then addressed the mechanism of the concentration-dependent biphasic action of quercetin. Verapamil, a P-glycoprotein inhibitor, inhibited the efflux of [3H]vincristine from MBEC4 cells, while 10 microM quercetin significantly stimulated it. The uptake of [3H]vincristine by MBEC4 cells was increased by inhibitors of protein kinase C, but decreased by phorbol 12-myristate-13-acetate (PMA), as well as by 10 microM quercetin. The phosphorylation level of P-glycoprotein was increased in the presence of 5 microM quercetin or 100 nM PMA, but decreased by the protein kinase C inhibitor H7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine, 30 microM). We conclude that low concentrations of quercetin indirectly activate the transport of [3H]vincristine by enhancing the phosphorylation (and hence activity) of P-glycoprotein, whereas high concentrations of quercetin inhibit P-glycoprotein. Our results indicate that patients taking drugs which are P-glycoprotein substrates may need to restrict their intake of bioflavonoid-containing foods and beverages, such as grapefruit juice.
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PMID:Effect of bioflavonoids on vincristine transport across blood-brain barrier. 1081 49

Sphingolipids mediate a number of cellular functions in a variety of cell systems. The role they play in osteoblast signaling is yet unknown. This study investigated the effects of epidermal growth factor (EGF) on the levels of ceramide, sphingosine (SPH), and sphingosine-1-phosphate (S1P) in rat calvariae osteoblastic cells, and whether these metabolites mediated cytosolic calcium ([Ca2+]i) mobilization in these cells. EGF significantly (P<0.05) increased the levels of all three sphingolipids, and the phorbol ester PMA partially inhibited these effects. SPH and S1P markedly increased [Ca2+]i levels, with thapsigargin (depletes [Ca2+]i pools) decreasing the response by 60%. Verapamil (calcium channel blocker) only inhibited ceramide's effects on [Ca2+]i. Furthermore, SPH enhanced the EGF' induced increase in [Ca2+]i. This study demonstrates that ceramide, SPH and S1P mediate [Ca2+]i mobilization in rat calvarial osteoblastic cells, and that EGF induces changes in the levels of these metabolites with PKC playing an important role in the mechanisms regulating these events.
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PMID:Changes in sphingolipid levels induced by epidermal growth factor in osteoblastic cells. Effects of these metabolites on cytosolic calcium levels. 1088 86


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