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)

In this report, we elucidate the role of Na(+)-K+ pump in the regulation of polyamine spermidine (Spd) transport in murine leukemia (L 1210) cells in culture. Ouabain, known to bind extracellularly to the alpha-subunit of the Na(+)-K+ pump, inhibits the pump activity. The L 1210 cells were found to possess ouabain binding sites at 7.5 fmol/10(6) cells. Ouabain significantly inhibited the Spd uptake in a dose-dependent manner. The maximum inhibition of Spd uptake by ouabain was observed beyond 200 microM. Spd transport was inversely correlated with the [3H]ouabain binding to L 1210 cells: an increase in the saturation of ouabain binding to L 1210 cells resulted in a decrease of the Spd uptake process. Treatment of L 1210 cells with protein kinase C activator phorbol esters increased the Spd transport and, also, ouabain-sensitive 86Rb+ uptake, a measure of the activity of the Na(+)-K+ pump. H-7, a protein kinase C inhibitor, significantly inhibited the ouabain-sensitive 86Rb+ uptake by L 1210 cells. Phorbol esters stimulated the level, but not the rate, of 22Na+ influx. Addition of H-7 to L 1210 cells inhibited the 22Na+ influx process. A concomitant phorbol ester-induced increase in 22Na+ influx, [14C]Spd uptake, together with the functioning of Na(+)-K+ pump, indicates the role of the "Na+ cycle" in the regulation of the polyamine transport process.
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PMID:Phorbol esters augment polyamine transport by influencing Na(+)-K+ pump in murine leukemia cells. 131 10

The mechanisms by which 86Rb+ (used as a tracer for K+) enters human nonpigmented ciliary epithelial cells were investigated. Ouabain-inhibitable bumetanide-insensitive 86Rb+ transport accounted for approximately 70-80% of total, whereas bumetanide-inhibitable ouabain-insensitive uptake accounted for 15-25% of total. K+ channel blockers such as BaCl2 reduced uptake by approximately 5%. Bumetanide inhibited 86Rb+ uptake with an IC50 of 0.5 microM, while furosemide inhibited with an IC50 of about 20 microM. Bumetanide-inhibitable 86Rb+ uptake was reduced in Na(+)-free or Cl(-)-free media, suggesting that Na+ and Cl- were required for optimal uptake via this mechanism. These characteristics are consistent with a Na+, K+, Cl- cotransporter in NPE cells. Treatment of NPE cells for 15 min with phorbol 12-myristate, 13-acetate (PMA), an activator of protein kinase C, caused a 50-70% decrease in 86Rb+ uptake via the Na+, K+, Cl- cotransporter. Other 86Rb+ uptake mechanisms were not affected. 86Rb+ uptake via the Na+, K+, Cl- cotransporter could be inhibited by other phorbol esters and by dioctanoylglycerol, an analog of diacylglycerol, but not by 4 alpha phorbol didecanoate, an ineffective activator of protein kinase C. Staurosporine, a protein kinase C inhibitor, blocked phorbol ester inhibition of 86Rb+ uptake. These data suggest that a Na+, K+, Cl- cotransporter in NPE cells is inhibited by activation of protein kinase C.
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PMID:Potassium transport in nonpigmented epithelial cells of ocular ciliary body: inhibition of a Na+, K+, Cl- cotransporter by protein kinase C. 152 31

A myo-inositol-related defect in nerve Na(+)-K(+)-ATPase in experimental diabetes has been invoked in the pathogenesis of diabetic neuropathy, but the mechanism linking altered myo-inositol metabolism and Na(+)-K(+)-ATPase regulation in diabetic nerve is uncertain. Decreased Na(+)-K(+)-ATPase in diabetic rat nerve is normalized by aldose reductase inhibitors or dietary myo-inositol, which preserve normal nerve myo-inositol content in vivo. Decreased Na(+)-K(+)-ATPase in diabetic rabbit nerve is acutely reversed by exposure to protein kinase C agonists in vitro. This study explored the relationship between the myo-inositol-sensitive and protein kinase C-agonist-sensitive Na(+)-K(+)-ATPase defects in diabetic rat nerve. Ouabain-sensitive ATPase activity was measured in an enriched membrane fraction isolated from nondiabetic, streptozocin-induced diabetic, and myo-inositol-supplemented streptozocin-induced diabetic rats before and after the membranes were exposed to protein kinase C agonists in vitro. The decreased ouabain-sensitive ATPase activity in plasma membranes from untreated diabetic rats was increased after exposure to two structurally unrelated protein kinase C agonists; the normal ouabain-sensitive ATPase in plasma membranes from myo-inositol-supplemented diabetic rats was unaffected by protein kinase C agonists. The nonadditivity and implied equivalence of the Na(+)-K(+)-ATPase defect corrected by myo-inositol in vivo and by protein kinase C agonists in vitro are consistent with the postulated existence of a deficient myo-inositol-dependent phospholipid-derived protein kinase C agonist (presumably diacylglycerol) in diabetic nerve that regulates nerve Na(+)-K(+)-ATPase either directly or via a protein kinase C mechanism.
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PMID:Normalization of Na(+)-K(+)-ATPase activity in isolated membrane fraction from sciatic nerves of streptozocin-induced diabetic rats by dietary myo-inositol supplementation in vivo or protein kinase C agonists in vitro. 185 Jul 4

Fast (-7 degrees C/min) cooling of guinea-pig isolated trachea produced a rapidly developing, transient contraction followed by relaxation. Cooling-induced contraction was dependent on temperature (30, 20 or 10 degrees C) and responses in trachea obtained from actively sensitized guinea pigs were significantly greater (20 and 10 degrees C) than those observed in normal trachea. Cooling to 20 degrees C was selected for subsequent experiments. Pretreatment with sufficient concentrations of atropine, clemastine, cromoglycate, indomethacin, or nordihydroguaiaretic acid did not depress contraction to cooling in either normal or sensitized trachea. This indicates a direct effect of cooling. The contraction produced by cooling was resistant to verapamil (1 mumol/l) or dantrolene (0.3 mmol/l). Calmodulin antagonists (trifluoperazine, W-7 and calmidazolium; all of them at 10-100 mumol/l) inhibited contraction in sensitized and normal trachea. Activators of protein kinase C (phorbol 12,13-diacetate, 1 mumol/l) enhanced while inhibitors (H-7, 20 mumol/l; staurosporine, 10 mumol/l) depressed cooling-induced contraction in both normal and sensitized tissues. Incubation (20 min) in a Ca(2+)-free solution inhibited cooling-induced contraction in normal but not in sensitized trachea. Exposure to a low Na+ (25 mmol/l) or a K(+)-free medium abolished contraction to cooling in normal and sensitized trachea. Ouabain (0.1-10 mumol/l) and vanadate (0.01-5 mmol/l) inhibited cooling-induced contraction to a greater extent in normal than in sensitized trachea. Polymyxin B (0.5 mmol/l) selectively depressed responses to cooling in sensitized trachea. In a separate series of experiments, it was shown that sensitized trachea was hyperresponsive to ouabain and vanadate. Previous cooling to 20 degrees C abolished responses to ouabain but only attenuated those to vanadate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cooling-induced contraction of trachea isolated from normal and sensitized guinea-pigs. 185 23

The effect of the Na/K-ATPase inhibitor ouabain on phosphoinositide (Ptdlns) hydrolysis was studied in rat brain cortical slices. Ouabain induced a dose-dependent accumulation of inositol phosphates (InsPs) which was much higher in neonatal rats (1570 +/- 40% of basal) than in adult animals (287 +/- 18% of basal). For this reason, all experiments were conducted with 7 day-old rats. Strophantidin caused a similar stimulation of Ptdlns hydrolysis, although it was less potent than ouabain. The order of potency for ouabain-stimulated InsPs accumulation in brain areas was hippocampus greater than cortex greater than brainstem greater than cerebellum. The effect of ouabain was not blocked by antagonists for the muscarinic, alpha1 -adrenergic and glutamate receptors. Also ineffective were the K+ channel blockers 4-aminopyridine and tetraethylammonium, the sodium channel blocker tetrodotoxin, and the calcium channel blocker verapamil, whereas the Na/Ca exchanger blocker amiloride partially antagonized the effect of ouabain. The accumulation of InsPs induced by ouabain was additive to that of carbachol and norepinephrine, as well as to that induced by high K+ and veratrine, but not to that of glutamate. Removal of Na+ ions from the incubation buffer completely prevented the accumulation of InsPs induced by ouabain. The effect of ouabain was also dependent upon extracellular calcium and was under negative feedback control of protein kinase C. Despite the higher effect of ouabain on Ptdlns hydrolysis of immature rats, the density of [3H]ouabain binding sites, as well as the activity of Na/K-ATPase were higher in adult animals. Furthermore, a poor correlation was found between ouabain-stimulated Ptdlns hydrolysis and [3H]ouabain binding in brain regions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of ouabain-induced phosphoinositide hydrolysis in brain slices of the neonatal rat. 196 25

The present study was undertaken to examine the cellular interaction between a Na+/K(+)-ATPase inhibitor, ouabain, and arginine vasopressin (AVP) in rat vascular smooth muscle cells (VSMC) in culture. Preincubation with 10(-5) M ouabain for 60 min increased basal cytosolic free Ca2+ [( Ca2+]i) concentration and intracellular 45Ca2+ uptake. Ouabain, however, did not affect basal 45Ca2+ efflux or AVP-stimulated 45Ca2+ efflux. As assessed by cell shape change, preincubation with 10(-5) M ouabain for 60 min also enhanced the sustained cellular contractile effect of a submaximal (10(-8) M AVP, 21.5% vs. 30.5%, P less than 0.01) but not maximal dose of 10(-6) M AVP. Preincubation with 10(-5) M ouabain for 60 min did not change AVP-induced V1-specific surface receptor binding or AVP-induced inositol phosphate production but did however potentiate the mobilization of [Ca2+]i induced by a submaximal (10(-8) M AVP, 301 vs. 385 nM, P less than 0.01) but not a maximal dose of AVP. These effects of ouabain on the mobilization of [Ca2+]i were abolished by incubation in Ca2(+)-free buffer or 5 X 10(-5) M verapamil. Ouabain (10(-5) M) also enhanced the sustained cellular contractile effect of a direct protein kinase C activator, phorbol 12-myristate 13-acetate. The present results therefore indicate that the inhibition of Na+/K(+)-ATPase may enhance the vascular action of AVP, and perhaps other vasoconstrictors, by increasing the AVP-induced mobilization of [Ca2+]i and by potentiating the activity of protein kinase C stimulated by AVP through enhancing basal and AVP-stimulated cellular Ca2+ uptake.
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PMID:Effect of inhibition of Na+/K(+)-adenosine triphosphatase on vascular action of vasopressin. 217 Apr 49

Full-grown prophase-arrested oocytes of Xenopus laevis were treated with 50 nM phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, or with 50 nM 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD) that does not activate protein kinase C. The effect on membrane currents and capacitance, inulin uptake and ouabain binding, and on membrane morphology were analyzed. (i) During application of PMA, current generated by the Na+/K+ pump decreases; in addition, Cl- and K+ channels become inhibited. This general decrease in membrane conductance reaches steady state after about 60 min. 4 alpha PDD was ineffective. (ii) Ouabain binding experiments demonstrate that PMA (K1/2 = 7 nM), but not 4 alpha PPD, induces a reduction of the number of pump molecules in the surface membrane. Permeabilization of oocytes by digitonin plus 0.02% SDS renders all binding sites present prior to PMA treatment again accessible for ouabain. The KD value for ouabain binding is not influenced. 4 alpha PDD was ineffective. (iii) Exposure of oocytes to PMA reduces membrane capacitance and stimulates uptake of inulin suggesting an increase in endocytosis. Electron micrographs show that PMA reduces the number and length of microvilli, leading finally to a smooth membrane surface with a reduced surface area. From these results we conclude that stimulation of protein kinase C leads to downregulation of the sodium pump. A major portion of this inhibition is brought about by reduction in area of surface membrane with a concomitant internalization of pump molecules. In addition to this mode of downregulation, a direct effect of stimulation of protein kinase C on the pump molecule cannot be excluded.
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PMID:Activation of protein kinase C by phorbol ester induces downregulation of the Na+/K(+)-ATPase in oocytes of Xenopus laevis. 217 38

1. The present experiments were designed to determine the effect of melittin on renin secretion. Melittin is a polypeptide component of bee venom which stimulates phospholipase A2 activity, thereby increasing arachidonic acid release and prostaglandin (PG) synthesis, and which inhibits protein kinase C activity. Either of these actions might be expected to stimulate renin secretion, since renin secretion is stimulated by arachidonic acid and by several PGs, and since renin secretion is inhibited by several activators of protein kinase C. 2. In rat renin cortical slices incubated at 37 degrees C in a buffered and oxygenated physiological saline solution, 0.1-10 microM-melittin produced a concentration-dependent stimulation of both prostaglandin E2 (PGE2) synthesis and renin secretion. However, melittin-stimulated renin secretion is independent of melittin-stimulated phospholipase A2 activity, arachidonic acid release, and PG synthesis, since 20 microM-quinacrine (a phospholipase A2 antagonist) and 50 microM-meclofenamate (a cyclooxygenase antagonist) antagonized basal and melittin-stimulated PGE2 synthesis but had no effects on basal or melittin-stimulated renin secretion. 3. Furthermore, melittin-stimulated renin secretion is not produced by inhibition of protein kinase C, since an activator of protein kinase C (12-O-tetradecanoylphorbol 13-acetate, TPA), enhanced rather than antagonized melittin-stimulated renin secretion. Ouabain partially antagonized, but did not completely block, melittin-stimulated renin secretion. 4. Thus, melittin-stimulated phospholipase A2 activity probably accounts for stimulated PGE2 production, but not for stimulated renin secretion. The mechanism of melittin-stimulated renin secretion is unclear; an effect on protein kinase C does not appear to be involved, and in contrast to the stimulatory effects of a variety of other substances, melittin-stimulated renin secretion is only partially antagonized by ouabain.
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PMID:Effect of melittin on renin and prostaglandin E2 release from rat renal cortical slices. 223 11

Norepinephrine and carbamoylcholine stimulate accumulation of [3H]inositol phosphates from [3H]inositol-labeled guinea pig cerebral cortical synaptoneurosomes through interaction with alpha 1-adrenergic and muscarinic receptors, respectively. In addition to such agonist, a variety of natural products that affect voltage-dependent sodium channels can markedly stimulate accumulation of [3H]inositol phosphates. These include alkaloids that activate sodium channels, such as batrachotoxin, veratridine, and aconitine; peptide toxins that alter activation or slow inactivation of sodium channels, such as various scorpion toxins from Leiurus, Centruroides, and Tityus species; and agents that cause repetitive firing of sodium channel-dependent action potentials, such as pyrethroids and pumiliotoxin B. Ouabain, and agent that will increase accumulation of internal sodium by inhibition of Na+, K+-ATPase, also stimulates formation of [3H]inositol phosphates, as does monensin, a sodium ionophore. Tetrodotoxin and saxitoxin, specific blockers of voltage-dependent sodium channels, prevent or reduce the stimulatory effects of sodium channel agents and ouabain on phosphatidylinositol turnover, while having lesser or no effect, respectively, on receptor-mediated or monensin-mediated stimulation. Removal of extracellular sodium ions markedly reduces stimulatory effects of sodium channel agents, while removal of extracellular calcium ions with EGTA blocks both receptor-mediated and sodium channel agent-mediated phosphatidylinositol turnover. The results provide evidence for a hitherto unsuspected messenger role for sodium ions in excitable tissue, whereby neuronal activity and the resultant influx of sodium will cause activation of phospholipase systems involved in hydrolysis of phosphatidylinositols, thereby generating two second messengers, the inositol phosphates, which mobilize calcium from internal stores, and the diacylglycerols, which activate protein kinase C.
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PMID:Regulation of phosphatidylinositol turnover in brain synaptoneurosomes: stimulatory effects of agents that enhance influx of sodium ions. 242 64

Elevated cellular sorbitol levels resulting from conversion of increased glucose by aldose reductase might deplete cellular myoinositol content, which could then lower inositol phosphates (InsPs) and diacylglycerol levels, key regulators of protein kinase C (PKC). Secondary to altered PKC activity, other cellular enzymes such as (Na,K)-ATPase could be affected. To test this hypothesis we examined the association between PKC activity, (Na,K)-ATPase activity, and sorbitol, myoinositol, and InsP levels in cultured bovine retinal capillary endothelial cells, a cell type prominently involved in diabetic retinopathy. Elevating glucose concentration in culture media from 100 to 400 mg/dl led to a 100% increase in sorbitol levels, which could be inhibited completely by sorbinil, an aldose reductase inhibitor. In contrast, no changes were observed in myoinositol or InsP levels. Subfractionated PKC activities showed a 100% increase in the membranous pool with a parallel decrease in the cytosolic fraction. Adding sorbinil did not affect PKC activity, whereas the PKC agonist, phorbol myristate acetate (PMA), stimulated translocation of PKC. Ouabain-inhibitable (Na,K)-ATPase activity was decreased 70% by elevated glucose levels. This decrease could be prevented by adding either PMA or sorbinil. Thus, in retinal capillary endothelial cells elevated glucose concentration can affect PKC and (Na,K)-ATPase activities, probably via different mechanisms.
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PMID:Differential regulation of protein kinase C and (Na,K)-adenosine triphosphatase activities by elevated glucose levels in retinal capillary endothelial cells. 839 Feb 75


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