Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lactate dehydrogenase C4 (LDH-C4) is a tissue-specific enzyme in the mammalian testis and the only lactate dehydrogenase isozyme of sperm. Inhibitors of LDH activity were used to determine whether this enzyme plays a role in sperm capacitation, the acrosome reaction and/or fertilization. Oxamate or its derivative was used to inhibit sperm LDH activity in a medium promoting capacitation. Complete inhibition of LDH activity blocked capacitation. This effect could be reversed partially by the addition of dbcAMP or pentoxifylline to the culture medium. Western blotting showed that oxamate and N-isopropyl oxamate inhibited the tyrosine phosphorylation of proteins during the sperm capacitation process. Presumably, glycolysis is the primary energy pathway for sperm metabolism. The oxidation of reduced NAD with the conversion of pyruvate to lactate by LDH provides ATP necessary for protein kinase A (PKA) activity. Our data indicate that LDH-C4 plays an important metabolic role in sperm capacitation.
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PMID:Inhibition of lactate dehydrogenase C4 (LDH-C4) blocks capacitation of mouse sperm in vitro. 1505 59

Our previous work shows that delta-opioid receptor (DOR) protects cortical neurons from hypoxic insults. Since an enhanced anaerobic capacity is important for neurons to adapt to the reduction of oxidative phosphorylation, we asked whether DOR plays a role in neuronal regulation of anaerobic capacity, thus protecting neurons from O(2) deprivation. Indeed, there is evidence suggesting that DOR may regulate protein kinase A (PKA) and C (PKC), which are involved in regulation of lactate dehydrogenase (LDH). However, little is known regarding the role of DOR and protein kinases in the regulation of glycolytic and related enzymes. As a first step, the present studies were performed in primary cultures of rat cortical neurons to clarify two issues: (1) Are protein kinases involved in the regulation of LDH activity in hypoxia? and (2) Does DOR affect LDH activity in hypoxic neurons? The results showed that PKC activation yielded substantial increases in normoxic LDH activity and significantly augmented LDH activity in hypoxic neurons, while PKC inhibition decreased LDH activity in both normoxic and hypoxic neurons. PKA activation significantly increased LDH activity in normoxic neurons and further elevated LDH activity in hypoxic neurons. However, PKA inhibition did not decrease in LDH activity in either normoxic or hypoxic neurons. Although DOR inhibition slightly reduced LDH activity in normoxia, DOR activation or inactivation did not alter LDH activity in hypoxic neurons. These data suggest that in cortical neurons, (i) PKC up-regulates LDH activity and plays an important role in its up-regulation during hypoxia; (ii) PKA is less likely involved in the regulation of LDH activity during hypoxia although its stimulation may slightly increase LDH activity and (iii) DOR does not contribute to LDH activity up-regulation during hypoxia.
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PMID:Effect of protein kinases on lactate dehydrogenase activity in cortical neurons during hypoxia. 1512 May 97

The skeletal muscle specific Ca(2)+/calmodulin-dependent protein kinase (CaMKIIbeta(M)) is localized to the sarcoplasmic reticulum (SR) by an anchoring protein, alphaKAP, but its function remains to be defined. Protein interactions of CaMKIIbeta(M) indicated that it exists in complex with enzymes involved in glycolysis at the SR membrane. The kinase was found to complex with glycogen phosphorylase, glycogen debranching enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and creatine kinase in the SR membrane. CaMKIIbeta(M) was also found to assemble with aldolase A, GAPDH, enolase, lactate dehydrogenase, creatine kinase, pyruvate kinase, and phosphorylase b kinase from the cytosolic fraction. The interacting proteins were substrates of CaMKIIbeta(M), and their phosphorylation was enhanced in a Ca(2+)- and calmodulin (CaM)-dependent manner. The CaMKIIbeta(M) could directly phosphorylate GAPDH and markedly increase ( approximately 3.4-fold) its activity in a Ca(2+)/CaM-dependent manner. These data suggest that the muscle CaMKIIbeta(M) isoform may serve to assemble the glycogen-mobilizing and glycolytic enzymes at the SR membrane and specifically modulate the activity of GAPDH in response to calcium signaling. Thus, the activation of CaMKIIbeta(M) in response to calcium signaling would serve to modulate GAPDH and thereby ATP and NADH levels at the SR membrane, which in turn will regulate calcium transport processes.
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PMID:The muscle-specific calmodulin-dependent protein kinase assembles with the glycolytic enzyme complex at the sarcoplasmic reticulum and modulates the activity of glyceraldehyde-3-phosphate dehydrogenase in a Ca2+/calmodulin-dependent manner. 1519 64

Polybrominated diphenyl ethers (PBDEs) are an important class of flame retardants. Because of their presence in maternal milk and their structural similarity to polychlorinated biphenyls (PCBs), concern has been raised on their possible developmental neurotoxicity. Aim of the present study was to investigate the in vitro effects of PBDE-99 (2,2', 4,4', 5-pentabromodiphenyl ether) on astroglial cells (human 132-1N1 astrocytoma cells) and comparing it with those of the PCB mixture Aroclor 1254. Both PBDE-99 and Aroclor 1254 caused a concentration-dependent inhibition of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) reduction, however, only the latter increased lactate dehydrogenase (LDH) release or cell death, assessed by the trypan blue assay. PBDE-99 caused translocation of the three protein kinase C (PKC) isozymes (alpha, epsilon, zeta) present in 132-1N1 astrocytoma cells, while Aroclor 1254 affected only PKCalpha and epsilon translocation. However, pre-incubation with the PKC inhibitor GF109203X or PKC down-regulation by the phorbol ester PMA, had minimal or no effect on PBDE-99 or Aroclor 1254-induced cytotoxicity. Similarly, the calcium chelator BAPTA-AM, the tyrosine kinase inhibitor genistein, and the MEK (mitogen activated protein kinase kinase) inhibitor PD98059 had no effect on PBDE-99 and Aroclor 1254 cytoxicity. On the other hand, the phosphatidylinositol 3 kinase (PI-3K) inhibitor LY290042 enhanced PBDE-99 toxicity, but did not affect Aroclor 1254. Because of the involvement of PI-3K in apoptotic cell death, the ability of PBDE-99 and Aroclor 1254 to induce apoptosis in astrocytoma cells was investigated. PBDE-99, but not Aroclor 1254, caused apoptotic cell death in astrocytoma cells, assessed by the TUNEL method and by Hoechst 33258 staining, via a p53 dependent mechanism. These results suggest that PBDE-99 and Aroclor 1254 exert differential cytotoxic effects on human astroglial cells.
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PMID:Differential in vitro neurotoxicity of the flame retardant PBDE-99 and of the PCB Aroclor 1254 in human astrocytoma cells. 1547 74

Ghrelin, a 28-amino acid peptide originally isolated from rat stomach, is an endogenous ligand of the growth hormone secretagogue receptor (GHS-R). Evidence has been provided that ghrelin and GHS-Rs are highly expressed in the cardiovascular system, including endothelial cells (ECs), of which they regulate the growth in vitro. It, therefore, seemed worthwhile to investigate the effect of ghrelin on in vitro angiogenesis, using cultures of rat ECs derived from brain microvessels (neuromicrovascular ECs, NECs). ECs, when cultured on a supportive matrix, form a network of tubule-like structures, and such process is enhanced by the classic angiogenic factors, including fibroblast growth factor-2 (FGF-2). After seeding on Matrigel-coated wells, NECs formed within 18 h a meshwork of capillary-like structures; vinblastine (2 x 10(-12) M) disrupted the meshwork, while FGF-2 (50 ng/ml) increased its density. Ghrelin (10(-8) M) exerted a vinblastine-like effect and counteracted the stimulatory action of FGF-2. Computerized image-analysis confirmed these observations. FGF-2 enhanced the proliferation rate and lowered the apoptotic rate of NECs cultured on plastic wells, and ghrelin exerted opposite effects and completely reversed the proliferogenic and antiapoptotic actions of FGF-2. In contrast to vinblastine, ghrelin did not increase lactate dehydrogenase release from cultured NECs, thereby ruling out the possibility that its effects may ensue from an aspecific cytotoxic action. FGF-2 enhanced tyrosine kinase (TK) and mitogen activated protein kinase (MAPK) p42/p44 activities of NECs. Ghrelin significantly decreased TK and MAPK p42/p44 activities and effectively counteracted the effect of FGF-2. Taken together, the present findings indicate that ghrelin exerts a marked in vitro antiangiogenic action, and that the mechanism underlying this effect involves the inhibition of TK/MAPK-dependent cascades.
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PMID:Ghrelin inhibits in vitro angiogenic activity of rat brain microvascular endothelial cells. 1549 55

Hydrophobic bile salts induce either necrosis or apoptosis depending on the severity of the injury caused by them. Since bile salt-induced apoptosis is influenced by Ca2+- and protein kinase-signaling pathways, and both necrosis and apoptosis share common initiating mechanisms, we analyzed whether these signaling cascades also influence bile salt-induced necrosis in isolated rat hepatocytes. Taurochenodeoxycholate (TCDC, 0.25-1.50 mM, 2 h) reduced, in a dose-dependent manner, the percentage of viable hepatocytes, and increased the release of the cytosolic enzyme, lactate dehydrogenase (LDH) and alanine aminotransferase (ALAT), and that of the plasma membrane enzyme, alkaline phosphatase (AP). The PKC inhibitors, H7 (100 microM) and chelerythrine (2.5 microM), both prevented significantly TCDC-induced necrosis. On the contrary, the PKA activator, dibutyryl-cAMP, exacerbated TCDC-induced cell damage in a dose-dependent manner; this effect was more likely due to cAMP-mediated PKA activation, as the PKA inhibitor, KT5720 (1 microM), counteracted this effect. Instead, the intracellular Ca2+ chelator, BAPTA/AM (20 microM), was without effect. TCDC (1 mM) increased lipid peroxidation from 0.7 +/- 0.2 to 7.5 +/- 0.9 nmol of malondialdehyde per mg of protein, p < 0.001; the addition of the free radical scavenger, diphenyl-p-phenylendiamine, completely blocked this increase and prevented significantly TCDC-induced necrosis. PKC inhibition induced only a slight attenuation of TCDC-induced lipid peroxidation. Possible mechanisms accounting for the modulatory effect of signal transduction pathways on TCDC-induced necrosis, including signaling influence on TCDC transport events and TCDC-induced oxidative stress, are discussed.
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PMID:Signaling modulation of bile salt-induced necrosis in isolated rat hepatocytes. 1549 97

Longitudinal bone growth results from coordination of proliferation and hypertrophy of chondrocytes, calcification of the matrix, vascular invasion, and completion of endochondral bone formation in the growth plate. Although proliferative and hypertrophic chondrocytes are well characterized histomorphologically, the understanding of factors governing this transition is not fully explained. Our hypothesis was that significant differential gene expression exists between proliferative and hypertrophic chondrocytes that may provide clues to the regulation of this transition at the transcriptional level. Normal Sprague-Dawley rat growth plate chondrocytes from the proliferative zone (PZ) and hypertrophic zone (HZ) were isolated by laser capture microdissection and then subjected to microarray analysis. Confirmation of the differential expression of selected genes was done by in situ hybridization and quantitative reverse transcription (RT) polymerase chain reaction (PCR). A total of 40 transcripts showed at least twofold greater expression in the PZ compared to HZ at both 6 and 7 weeks of age, while 52 transcripts showed twofold greater expression in the HZ compared to PZ at these time points. Many of the differentially expressed genes in each zone had very high levels of expression and thus were classified as "enriched transcripts" for that zone. The PZ-enriched transcripts included fibromodulin, proline arginine-rich end leucine-rich repeat protein, lactate dehydrogenase, and enolase 1 alpha. In contrast, HZ-enriched transcripts included collagen I, protein kinase (lysine deficient 4), proteasome (prosome, macropain) activator subunit 4, prostaglandin I2 synthase, and integrin-binding sialoprotein, matrix metalloproteinase 13 (MMP13), and collagen X. Other genes were highly expressed in cells from both zones, including collagen II, aggrecan, cartilage oligomeric protein, cartilage link protein, laminin receptor, and eukaryotic translocation elongation factor. Functional classification of the PZ-enriched transcripts showed an increased percentage of genes expressed in nuclear cell cycle and transcription functions. In contrast, the HZ-enriched transcripts were more involved in extracellular structure and membrane receptor and transporter functions. Pathway analysis indicated that transforming growth factor beta and parathyroid hormone-related protein (PTHrP) pathways were important in both zones, and bone morphogenic protein pathway played a role in the HZ. It is likely that these differentially expressed genes are involved in regulation of the transition from proliferation to differentiation functions in the growth plate.
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PMID:Microarray analysis of proliferative and hypertrophic growth plate zones identifies differentiation markers and signal pathways. 1558 9

CB1 cannabinoid receptors (CB1Rs) are involved in protecting the brain from ischemia and related disorders. However, the underlying protective mechanisms are incompletely understood. We investigated the effect of CB1R activation on oxidative injury, which has been implicated in neuronal death after cerebral ischemia and neurodegenerative disorders, in mouse cortical neuron cultures. The CB1R agonist Win 55212-2 [R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl)methanone mesylate] reduced neuronal death, measured by lactate dehydrogenase release, in cultures treated with 50 microM FeCl2, and its protective effect was attenuated by the CB1R antagonist SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-cichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride]. The endocannabinoid anandamide reproduced the effect of Win 55212-2, as did the antioxidant 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). Neuronal injury was more severe after in vitro or in vivo administration of FeCl2 to CB1R-knockout compared with wild-type mice. Win 55212-2 reduced the formation of reactive oxidative species in cortical neuron cultures treated with FeCl2, consistent with an antioxidant action. Pertussis toxin reduced CB1R-mediated protection, which points to a protective mechanism that involves signaling through G(i/o) proteins. Since CB1R-activated G protein signaling inhibits protein kinase A but activates phosphatidylinositol 3-kinase (PI3K), we tested the involvement of these pathways in CB1R-mediated neuroprotection. Dibutyryl-cyclic adenosine monophosphate (dbcAMP) blocked protection by Win 55212-2, whereas the PI3K inhibitor wortmannin did not, and the effect of dbcAMP was inhibited by the protein kinase A inhibitor H89 [N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide] (> or =10 nM). CB1R-induced, SR141716A-, pertussis toxin-, and dbcAMP-sensitive protection was also observed for two other oxidative insults, exposure to H2O2 or buthionine sulfoximine. Therefore, receptor-stimulated inhibition of protein kinase A seems to be required for the neuroprotective effect of CB1R activation against oxidative neuronal injury.
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PMID:Involvement of protein kinase A in cannabinoid receptor-mediated protection from oxidative neuronal injury. 1562 18

Ochratoxin A (OTA) is a mycotoxin involved in the development of chronic nephropathies and a known carcinogen. As we have shown previously, OTA activates mitogen-activated protein kinases [extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-jun amino-terminal kinase (JNK), and extracellular-regulated protein kinase 38 (p38)] in proximal tubular cells (opossum kidney and normal rat kidney epithelial). ERK1/2, JNK, or p38 are thought to mediate opposite action on apoptosis, fibrosis, and inflammation. As we have already shown, OTA activates the latter processes. Here, we investigated the effect of OTA in the absence or presence of the ERK1/2 inhibitor U0126 [1,4-diamino-2,3-dicyano-1,4bis(2-aminophenylthio)-butadiene] to test whether OTA then will exert increased toxicity. In the presence of ERK1/2 inhibition, OTA decreased cell number and protein to a significantly larger extent compared with OTA alone. The same was true for epithelial tightness, apoptosis (caspase-3 activity), and necrosis (lactate dehydrogenase release). Furthermore, simultaneous inhibition of ERK1/2 amplified the effect of OTA on markers of inflammation (nuclear factor of the kappa-enhancer in B cells activity), fibrosis (collagen secretion), and epithelial mesenchymal transition (alpha smooth muscle actin). OTA induces phenomena typical for chronic interstitial nephropathy and activates ERK1/2, JNK, and p38 in proximal tubular cells. Inhibition of ERK1/2 aggravates the effects of OTA or even induces toxicity at normally nontoxic concentrations. This is highly likely due to activation of JNK and p38. Our data indicate a new mechanistic explanation for the toxic actions induced by OTA, and they are notable with respect to a possible coexposition of the kidney to OTA and naturally occurring ERK1/2 inhibitors. Finally, our data give rise to an attractive hypothesis on the coincidence of increased OTA exposition and urinary tract tumors in humans.
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PMID:Proximal tubular toxicity of ochratoxin A is amplified by simultaneous inhibition of the extracellular signal-regulated kinases 1/2. 1562 19

Extracellular ATP (ATPe) binds to P2X7 receptors (P2X7R) expressed on the surface of cells of hematopoietic lineage, including murine thymocytes. Activation of P2X7R by ATPe results in the opening of cation-specific channels, and prolonged ATPe exposure leads to the formation of non-selective pores enabling transmembrane passage of solutes up to 900 Da. In the presence of ATPe, P2X7R-mediated thymocyte death is due primarily to necrosis/lysis and not apoptosis, as measured by the release of lactate dehydrogenase indicative of a loss of plasma membrane integrity. The present study is focused on the identification of P2X7R signaling mediators in ATP-induced thymocyte necrosis/lysis. Thus, extracellular signal-regulated protein kinase 1/2 (Erk1/2) phosphorylation was found to be required for cell lysis, and both events were independent of ATP-induced calcium influx. P2X7R-dependent thymocyte death involved the chronological activation of Src family tyrosine kinase(s), phosphatidylinositol 3-kinase, the mitogen-activated protein (MAP) kinase(Erk1/2) module, and the proteasome. Although independent of this signaling cascade, non-selective pore formation may modulate ATP-mediated thymocyte death. These results therefore suggest a role for both activation of MAP kinase(Erk1/2) and non-selective pore opening in P2X7R-induced thymocyte death.
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PMID:A role for mitogen-activated protein kinase(Erk1/2) activation and non-selective pore formation in P2X7 receptor-mediated thymocyte death. 1593 34


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