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 cortical collecting tubules (CCD) of aldosterone-repleted rabbit kidney, an increase in intracellular sodium concentration (Nai) induces the recruitment and/or activation of latent Na(+)-K(+)-ATPase pumps (Blot-Chabaud et al., J. Biol. Chem. 265: 11676-11681, 1990). The present study was addressed to determine the time course of this Nai-dependent pump recruitment and to examine some of the factors possibly involved in this phenomenon. CCD from adrenalectomized rabbits complemented with aldosterone and dexamethasone were incubated at 4 degrees C either in a K(+)-free saline solution (Na(+)-loaded CCD) or in a sucrose solution (control CCD) and then rewarmed for various time periods to allow pump recruitment to occur. The number of pumps in the membrane was determined by specific [3H]ouabain binding; Nai was measured using 22Na. A rise in Nai induced a threefold increase in the number of basolateral pumps, which was fully achieved within 1-2 min. This pump recruitment was reversible within 15 min after restoration of low Nai. It was unaffected by inhibitors of cytoskeleton and Ca2+ ionophore A 23187. The blocker of the Na(+)-H+ antiporter, amiloride, did not prevent it. The protein kinase C activator, phorbol 12-myristate 13-acetate, did not induce it in the absence of Na+. We conclude that Nai is a major determinant of pump recruitment and/or activation, which occurs over a very short period of time. It may constitute a rapid adaptative response to an increase in the cell Na+ load.
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PMID:Time course of sodium-induced Na(+)-K(+)-ATPase recruitment in rabbit cortical collecting tubule. 132 44

Acidification of the endosomal pathway is important for ligand and receptor sorting, toxin activation, and protein degradation by lysosomal acid hydrolases. Fluorescent probes and imaging methods were developed to measure pH to better than 0.2 U accuracy in individual endocytic vesicles in Swiss 3T3 fibroblasts. Endosomes were pulse labeled with transferrin (Tf), alpha 2-macroglobulin (alpha 2M), or dextran, each conjugated with tetramethylrhodamine and carboxyfluorescein (for pH 5-8) or dichlorocarboxyfluorescein (for pH 4-6); pH in individual labeled vesicles was measured by ratio imaging using a cooled CCD camera and novel image analysis software. Tf-labeled endosomes acidified to pH 6.2 +/- 0.1 with a t1/2 of 4 min at 37 degrees C, and remained small and near the cell periphery. Dextran- and alpha 2M-labeled endosomes acidified to pH 4.7 +/- 0.2, becoming larger and moving toward the nucleus over 30 min; approximately 15% of alpha 2M-labeled endosomes were strongly acidic (pH less than 5.5) at only 1 min after labeling. Replacement of external Cl by NO3 or isethionate strongly and reversibly inhibited acidification. Addition of ouabain (1 mM) at the time of labeling strongly enhanced acidification in the first 5 min; Tf-labeled endosomes acidified to pH 5.3 without a change in morphology. Activation of phospholipase C by vasopressin (50 nM) enhanced acidification of early endosomes; activation of protein kinase C by PMA (100 nM) enhanced acidification strongly, whereas elevation of intracellular Ca by A23187 (1 microM) had no effect on acidification. Activation of protein kinase A by CPT-cAMP (0.5 mM) or forskolin (50 microM) inhibited acidification. Lysosomal pH was not affected by ouabain or the protein kinase activators. These results establish a methodology for quantitative measurement of pH in individual endocytic vesicles, and demonstrate that acidification of endosomes labeled with Tf and alpha 2M (receptor-mediated endocytosis) and dextran (fluid-phase endocytosis) is sensitive to intracellular anion composition, Na/K pump inhibition, and multiple intracellular second messengers.
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PMID:Second messengers regulate endosomal acidification in Swiss 3T3 fibroblasts. 138 79

Although G proteins have been shown to regulate cation channels, regulation of Cl- channels by G proteins has not been demonstrated directly. Accordingly, the objective of this study was to examine whether a G protein regulates Cl- channels in the apical membrane of rabbit kidney CCD cells grown in culture. Previous studies showed that this channel is activated by adenosine and protein kinase C and has a single channel conductance of 305 picosiemens. The PCl-:PNa+ is 9:1 and the PCl-:PHCO3- is 2:1 (Schwiebert, E.M., Light, D.B., Dietl, P., Fejes-Toth, G., Naray-Fejes-Toth, A., and Stanton, B. (1990) Kidney Int. 37,216). In the present study, Cl- channels in the apical membrane of CCD cells were studied by the patch clamp technique. GTP and guanosine 5'-O(3-thiophosphate) (GTP gamma S), a nonhydrolyzable analog of GTP, increased the single channel open probability (Po). In contrast, guanosine 5'-O-(2-thiophosphate), a nonhydrolyzable analog of GDP, and pertussis toxin (PTX) decreased the Po. GTP gamma S, but not GTP, reversed PTX inhibition of the channel. The alpha i-3-subunit of Gi increased the Po in both untreated and PTX-treated membrane patches. Because GTP gamma S activated the Cl- channel in the presence of H8, a protein kinase inhibitor, we conclude that the G protein does not activate the channel by stimulating a protein kinase. Thus, a PTX-sensitive G protein activates a Cl- channel in the apical membrane of renal CCD cells.
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PMID:A GTP-binding protein activates chloride channels in a renal epithelium. 215 54

We have documented new observations with respect to PGE2 action in the rabbit CCD. (1) PGE2 can inhibit both cAMP and vasopressin-induced water flow, depending on the sequence of PGE2 addition with respect to vasopressin or cAMP. (2) PGE2 inhibition of vasopressin or cAMP-stimulated water flow can be reversed with staurosporine. Thus, PGE2 inhibits vasopressin-stimulated water flow by activation of PKC and (3) PGE2 induces release of calcium from intracellular stores. These results strongly suggest the presence of a PGE2 receptor coupled to PIP2 hydrolysis. PGE2 mediated increases in cytosolic calcium are responsible for the inhibitory action of PGE2 on sodium transport. While stimulation of cAMP production by PGE2 may contribute to the inhibition of sodium transport, it is not required since in the presence of 8-CPTcAMP, PGE2 still decreases sodium transport. The effect of PGE2 on sodium transport is pertussis toxin insensitive and is unlikely to be mediated by an inhibitory G protein. Using PGE2 and one of its selective analogues, sulprostone, we have provided evidence for functionally distinct PGE2 receptors. Separate PGE2 receptor subtypes appear to be coupled to separate transport processes. These receptor subtypes may correspond to the EP1, EP2 and EP3 receptors described earlier in smooth muscle. Thus, an EP2 like receptor stimulates cAMP generation and water reabsorption while an EP1 like receptor increases [Ca++]i and inhibits sodium reabsorption. Finally, an EP3 receptor, equivalently activated by sulprostone and PGE2, may couple to Gi and mediate pertussis toxin sensitive inhibition of vasopressin-stimulated water flow.
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PMID:Cellular signalling of PGE2 and its selective receptor analogue sulprostone in rabbit cortical collecting duct. 782 28

The immature kidney is characterized by resistance to arginine vasopressin (AVP). In the immature cortical collecting duct (iCCD), AVP-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) generation is decreased, but the mechanisms involved are not known. We examined cAMP production in isolated CCD from immature and mature rabbits. Cellular cAMP levels were measured by radioimmunoassay under basal conditions and after stimulation with hormone. Basal cAMP production in the iCCD was not different from that in the mature CCD (mCCD). In contrast, AVP- and forskolin-stimulated cAMP generation were severely decreased in the iCCD. Inhibition of endogenous prostaglandin production by indomethacin increased AVP-stimulated cAMP generation in the iCCD to levels that were not different from the mCCD. Inhibition of protein kinase C (PKC) by staurosporine and inhibition of Gi by pertussis toxin elicited a mature cAMP response in the iCCD. These data suggest that the defect in AVP-stimulated cAMP production in the iCCD is mediated by prostaglandins via 1) activation of Gi and 2) direct inhibition of the adenylyl cyclase catalytic subunit. In addition, PKC appears to play a significant role.
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PMID:Prostaglandins mediate the defect in AVP-stimulated cAMP generation in immature collecting duct. 804 63

Hexadecylphosphocholine (HePC), a glycerol-free phospholipid analog, belongs to a new class of drugs that demonstrate selective anticancer activity. The mechanisms underlying the anticancer activity are unclear. To investigate possible signal transduction relationships we examined the influence of HePC on cellular phospholipid metabolism. When HePC was added to cultured human breast fibroblasts (CCD-986-SK cells) that had been radiolabeled with fatty acid, phosphatidylethanol (PEt, the transphosphatidylation product of phospholipase D (PLD)) formation was stimulated as early as 5 min after addition. In cells labeled with [3H]choline, HePC treatment caused release of choline-containing metabolites to the culture medium, concurrent with PEt formation. HePC also elicited formation of diacylglycerol (DG) which, after 30 min increased 3.5-fold over control. As little is known regarding HePC and PLD, attention was directed towards studies on PC metabolism by PLD. PEt formation was shown to be optimal at 20-50 microM HePC, and structure-activity studies showed HePC to be more potent than either lyso-phosphatidylcholine or 1-hexadecyl-2-O-methyl-rac-glycero-3-phosphocholine for PLD activation. PLD activity induced by HePC was totally inhibited by cellular pretreatment with phorbol dibutyrate, and 59% diminished by pretreatment of cells with staurosporine, a protein kinase C (PKC) inhibitor. Our results demonstrate for the first time that HePC activates PLD, and suggest that PKC participates in this response. The relationship of PLD to the anticancer properties of HePC may be clinically relevant to drug actions.
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PMID:The antitumor phospholipid analog, hexadecylphosphocholine, activates cellular phospholipase D. 862 Apr 56

We studied the mechanisms and characteristics of the spontaneously evoked intracellular Ca2+ changes (Ca2+ oscillations) in ileal longitudinal smooth muscle from guinea pig. Two-dimensional images of Ca2+ oscillations were obtained at 33-ms intervals with a Ca2+-sensitive fluorescence probe, fluo-3 using the intensified CCD camera. Nicardipine (10-7 M) significantly decreased the maximum level of fluorescence intensity of the Ca2+ oscillations, inhibited the frequency of the oscillations and tended to decrease the basal level of fluorescence intensity. However, tetrodotoxin (3 x 10-7 M) did not affect these oscillations. Phorbol 12,13-dibutyrate (10-7 M) significantly increased the maximum level of fluorescence intensity and the frequency of Ca2+ oscillations, and it changed them to steady and chronometric Ca2+ oscillations. Cyclopiazonic acid (3 x 10-5 M) also significantly increased the frequency of Ca2+ oscillations. Acetylcholine (10-8 M) increased the basal and maximum level of fluorescence intensity and the frequency of Ca2+ oscillations, and accelerated their onset. The increase of basal level of fluorescence intensity was then decreased by cyclopiazonic acid treatment. These results suggest that the augmentation of Ca2+ oscillations is mainly due to the activation of L-type Ca2+ channels, which is modulated by protein kinase C, and that the emptying of intracellular Ca2+ stores may activate the Ca2+ oscillations mediated through the increase of Ca2+ influx in ileal smooth muscle of guinea pig.
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PMID:Characteristics of Ca2+ oscillations in ileal longitudinal muscle cells of guinea pig. 1087 51

We investigated prostanoid biogenesis by human colonic fibroblasts (CCD-18Co cells and nine primary fibroblast cultures) exposed to a primary (cholic, CA) or a secondary (deoxycholic, DCA) bile acid. Basal PGE2 levels in CCD-18Co cultures and fibroblast strains initiated from normal and adenocarcinomatous colon, respectively, were 1.7 +/- 0.3, 4.0 +/- 2.0, and 15.0 +/- 4.8 ng/mg protein. Peak levels 24 h after exposure to DCA (300 microM) rose, respectively, seven-, six- and sevenfold, but CA elicited no such responses. Increases in PGE2 synthesis were preceded by sequential increases in PGH synthase-2 mRNA and protein expression and were fully prevented by a nonselective (indomethacin) or a selective (celecoxib) nonsteroidal anti-inflammatory drug. DCA, but not CA, caused abrupt, transient increases in fibroblast intracellular Ca2+ concentration ([Ca2+]i) approximately 1 min after exposure. Increased [Ca2+]i was required for DCA-mediated induction of PGE2 synthesis, and protein kinase C was a further essential component of this signaling pathway. Colonic fibroblasts may be a major target for prostanoid biogenesis induced by fecal bile acids and, potentially, other noxious actions of these agents.
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PMID:Ca2+- and PKC-dependent stimulation of PGE2 synthesis by deoxycholic acid in human colonic fibroblasts. 1218 Nov 61

Activation of protein kinase C (PKC) seems to promote vesicle recruitment to the release-ready state prior to Ca2+ -triggered fusion in chromaffin cells. To understand spatio-temporal regulation of vesicle recruitment by PKC, we studied the effects of a phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), on the vesicle movements in living chromaffin cells by imaging with a fluorescence microscope-cooled CCD system. About 60 approximately 80% of the chromaffin vesicles showed a rapid movement, about 20% showed a moderate movement, and the rest showed slow/no movement in resting and post-stimulation. The vesicles with slow/no movement increased to 40% upon a depolarizing stimulation, and TPA increased this population to about 70%. TPA treatment, in addition, increased the number of visible chromaffin vesicles beneath the plasma membrane, suggesting that the potentiation of vesicle recruitment by PKC involves a substantial increase in the subplasmalemmal distribution of vesicles.
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PMID:Spatio-temporal regulation of neurotransmitter release by PKC; studies in adrenal chromaffin cells. 1558 12

Activation of the urotensin II (U-II) receptor, GPR14, leads to an increase in Ca(2+), activation of phospholipase A(2) (PLA(2)) and an increase in arachidonic acid. The signaling pathway for guanylin peptides in the kidney involves an unknown G-protein coupled receptor which activates PLA(2) and increases arachidonic acid as well. To test if guanylin peptides could be, as U-II, agonists for the GPR14 receptor in the kidney, we used HEK293 and CHO cells transfected with hGPR14 (HEK293+hGPR14, CHO+hGPR14, respectively). Effects of guanylin peptides and U-II were studied by slow-whole-cell patch-clamp analysis and microfluorimetric measurements of intracellular Ca(2+). Guanylin peptides and U-II depolarized HEK293+hGPR14 significantly more than wild type cells. These effects were inhibited in the presence of Ba(2+) or PLA(2) inhibition (AACOCF(3)), suggesting that guanylin peptides and U-II increase arachidonic acid and inhibit ROMK channels in these cells. However, only U-II was capable to increase the cellular Ca(2+), suggesting different mechanism of GPR14 activation by guanylin peptides and U-II. This signaling pathway of U-II involves PKC, because U-II effects in HEK293+hGPR14 cells were inhibited by calphostin C. Guanylin peptides activate PLA(2) and inhibit ROMK channels in HEK293 cells transfected with the human GPR14 receptor. Since GPR14 is present in mouse and human CCD it is a candidate for the guanylate cyclase independent receptor for guanylin peptides.
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PMID:Ligands and signaling of the G-protein-coupled receptor GPR14, expressed in human kidney cells. 1759 27


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