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: UNIPROT:P05412 (c-Jun)
11,453 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium concentration within the endoplasmic reticulum (ER) plays an essential role in cell physiology. We have investigated the effects of basiliolides, a novel class of C19 dilactones isolated from Thapsia garganica, on Ca(2+) mobilization in T cells. Basiliolide A1 induced a rapid mobilization of intracellular Ca(2+) in the leukemia T-cell line Jurkat. First, a rapid calcium peak was observed and inhibited by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester. This initial calcium mobilization was followed by a sustained elevation, mediated by the entry of extracellular calcium through store-operated calcium release-activated Ca(2+) (CRAC) channels and sensitive to inhibition by EGTA, and by the CRAC channel inhibitor N-{4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl}-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP-2). Basiliolide A1 mobilized Ca(2+) from ER stores, but in contrast to thapsigargin, it did not induce apoptosis. Basiliolide A1 induced nuclear factor of activated T cells 1 dephosphorylation and activation that was inhibited by BTP-2 and cyclosporine A. In addition, we found that basiliolide A1 alone did not mediate IkappaBalpha degradation or RelA phosphorylation (ser536), but it synergized with phorbol 12-myristate 13-acetate to induce a complete degradation of the nuclear factor-kappaB inhibitory protein and to activate the c-Jun NH(2)-terminal kinase. Moreover, basiliolide A1 regulated both interleukin-2 and tumor necrosis factor-alpha gene expression at the transcriptional level. In basiliolide B, oxidation of one of the two geminal methyls to a carboxymethyl group retained most of the activity of basiliolide A1. In contrast, basiliolide C, where the 15-carbon is oxidized to an acetoxymethine, was much less active. These findings qualify these compounds as new probes to investigate intracellular calcium homeostasis.
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PMID:Basiliolides, a class of tetracyclic C19 dilactones from Thapsia garganica, release Ca(2+) from the endoplasmic reticulum and regulate the activity of the transcription factors nuclear factor of activated T cells, nuclear factor-kappaB, and activator protein 1 in T lymphocytes. 1684 Jun 45

Selective serotonin reuptake inhibitors (SSRIs), a group of antidepressants, are generally used for treatment of various mood and anxiety disorders. There has been much research showing the anti-tumor and cytotoxic activities of some antidepressants; but the detailed mechanisms were unclear. In cultured human osteosarcoma cells (MG63), paroxetine reduced cell viability in a concentration- and time-dependent manner. Paroxetine caused apoptosis as assessed by propidium iodide-stained cells and increased caspase-3 activation. Although immunoblotting data revealed that paroxetine could activate the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), only SB203580 (a p38 MAPK inhibitor) partially prevented cells from apoptosis. Paroxetine also induced [Ca(2+)](i) increases which involved the mobilization of intracellular Ca(2+) stored in the endoplasmic reticulum and Ca(2+) influx from extracellular medium. However, pretreatment with BAPTA/AM, a Ca(2+) chelator, to prevent paroxetine-induced [Ca(2+)](i) increases did not protect cells from death. The results suggest that in MG63 cells, paroxetine caused Ca(2+)-independent apoptosis via inducing p38 MAPK-associated caspase-3 activation.
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PMID:Paroxetine-induced apoptosis in human osteosarcoma cells: activation of p38 MAP kinase and caspase-3 pathways without involvement of [Ca2+]i elevation. 1717 98

Ansamycin antibiotics that target heat shock protein 90 function are being developed as anticancer agents but are also known to be dose limiting in patients due to hepatotoxicity. Herein, to better understand how the normal tissue toxicity of geldanamycins could be ameliorated to improve the therapeutic index of these agents, we examined the interactions of 17-allylamino-17-demethoxygeldanamycin (17AAG) and the secondary bile acid deoxycholic acid (DCA) in hepatocytes and fibroblasts. DCA and 17AAG interacted in a greater than additive fashion to cause hepatocyte cell death within 2 to 6 h of coadministration. As single agents DCA, but not 17AAG, enhanced the activity of extracellular signal-regulated kinase 1/2, AKT, c-Jun NH(2)-terminal kinase 1/2 (JNK1/2), and p38 mitogen-activated protein kinase (MAPK). Combined exposure of cells to DCA and 17AAG further enhanced JNK1/2 and p38 MAPK activity. Inhibition of JNK1/2 or p38 MAPK, but not activator protein-1, suppressed the lethality of 17AAG and of 17AAG and DCA. Constitutive activation of AKT, but not MAPK/extracellular signal-regulated kinase kinase 1/2, suppressed 17AAG- and DCA-induced cell killing and reduced activation of JNK1/2. DCA and 17AAG exposure promoted association of BAX with mitochondria, and functional inhibition of BAX or caspase-9, but not of BID and caspase-8, suppressed 17AAG and DCA lethality. DCA and 17AAG interacted in a greater than additive fashion to promote and prolong the generation of reactive oxygen species (ROS). ROS-quenching agents, inhibition of mitochondrial function, expression of dominant-negative thioredoxin reductase, or expression of dominant-negative apoptosis signaling kinase 1 suppressed JNK1/2 and p38 MAPK activation and reduced cell killing after 17AAG and DCA exposure. The potentiation of DCA-induced ROS production by 17AAG was abolished by Ca(2+) chelation and ROS generation, and cell killing following 17AAG and DCA treatment was abolished in cells lacking expression of PKR-like endoplasmic reticulum kinase. Thus, DCA and 17AAG interact to stimulate Ca(2+)-dependent and PKR-like endoplasmic reticulum kinase-dependent ROS production; high levels of ROS promote intense activation of the p38 MAPK and JNK1/2 pathways that signal to activate the intrinsic apoptosis pathway.
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PMID:17-Allylamino-17-demethoxygeldanamycin enhances the lethality of deoxycholic acid in primary rodent hepatocytes and established cell lines. 1730 59

MAPKs and inhibitory-kappaB kinase (IKK) were suggested to link various conditions thought to develop in adipose tissue in obesity (oxidative, endoplasmic reticulum stress, inflammation) with insulin resistance. Yet whether in obesity these kinases are affected in a fat-depot-differential manner is unknown. We assessed the expression and phosphorylation of these kinases in paired omental and abdominal-sc fat biopsies from 48 severely obese women (body mass index > 32 kg/m(2)). Protein and mRNAs of p38MAPK, ERK, c-Jun kinase-1, and IKKbeta were increased 1.5-2.5-fold in omental vs. sc fat. The phosphorylated (activated) forms of these kinases were also increased to similar magnitudes as the total expression. However, phosphorylation of insulin receptor substrate-1 on Ser312 (equivalent of murine Ser307) was not increased in omental, compared with sc, fat. Consistently, fat tissue fragments stimulated with insulin demonstrated that tyrosine phosphorylation and signal transduction to Akt/protein kinase B in omental fat was not inferior to that observable in sc fat. Comparison with lean women (body mass index 23.2 +/- 2.9 kg/m(2)) revealed similar ERK2 and IKKbeta expression and phosphorylation in both fat depots. However, as compared with lean controls, obese women exhibited 480 and 270% higher amount of the phosphorylated forms of p38MAPK and c-Jun kinase, respectively, in omental, but not sc, fat, and this expression level correlated with clinical parameters of glycemia and insulin sensitivity. Increased expression of stress-activated kinases and IKK and their phosphorylated forms in omental fat occurs in obesity, potentially contributing to differential roles of omental and sc fat in the pathophysiology of obesity.
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PMID:Mitogen-activated protein kinases, inhibitory-kappaB kinase, and insulin signaling in human omental versus subcutaneous adipose tissue in obesity. 1731 77

Lipid accumulation in non-adipose tissues leads to cell dysfunction and apoptosis, a phenomenon known as lipotoxicity. Recent evidence suggests that lipotoxicity in hepatocytes involves endoplasmic reticulum (ER) stress and c-Jun NH(2)-terminal kinase-mediated apoptosis. The present study examined (1) the dose-response and time course characteristics of fatty acid-mediated ER stress and apoptosis in H4IIE liver cells; (2) whether saturated fatty acid-induced apoptosis involved the ER-associated caspase-12; and (3) whether trans-10, cis-12-conjugated linoleic acid, an inhibitor of stearoyl-CoA desaturase, influenced fatty acid-mediated ER stress and apoptosis. Saturated fatty acids induced ER stress in a dose-dependent manner with a time course that was delayed relative to chemical-induction of ER stress. Saturated fatty acids increased caspase-9 and caspase-3 activity, however increased caspase-12 activity was not observed. Inhibition of stearoyl-CoA desaturase, using conjugated linoleic acid (trans-10, cis-12), augmented saturated fatty acid-induced ER stress and apoptosis. These data suggest that saturated fatty acids induce ER stress and apoptosis at physiologic concentrations and with a relatively rapid time course. It would appear that saturated fatty acid-mediated apoptosis occurs independently of caspase-12 activation. Since conjugated linoleic acid inhibited stearoyl-CoA desaturase activity, it is hypothesized that saturation, per se, plays a role in lipotoxicity in liver cells.
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PMID:Saturated fatty acid-mediated endoplasmic reticulum stress and apoptosis are augmented by trans-10, cis-12-conjugated linoleic acid in liver cells. 1742 27

Protein kinase Cdelta (PKCdelta) regulates cell apoptosis and survival in diverse cellular systems. PKCdelta translocates to different subcellular sites in response to apoptotic stimuli; however, the role of its subcellular localization in its proapoptotic and antiapoptotic functions is just beginning to be understood. Here, we used a PKCdelta constitutively active mutant targeted to the cytosol, nucleus, mitochondria, and endoplasmic reticulum (ER) and examined whether the subcellular localization of PKCdelta affects its apoptotic and survival functions. PKCdelta-Cyto, PKCdelta-Mito, and PKCdelta-Nuc induced cell apoptosis, whereas no apoptosis was observed with the PKCdelta-ER. PKCdelta-Cyto and PKCdelta-Mito underwent cleavage, whereas no cleavage was observed in the PKCdelta-Nuc and PKCdelta-ER. Similarly, caspase-3 activity was increased in cells overexpressing PKCdelta-Cyto and PKCdelta-Mito. In contrast to the apoptotic effects of the PKCdelta-Cyto, PKCdelta-Mito, and PKCdelta-Nuc, the PKCdelta-ER protected the cells from tumor necrosis factor-related apoptosis-inducing ligand-induced and etoposide-induced apoptosis. Moreover, overexpression of a PKCdelta kinase-dead mutant targeted to the ER abrogated the protective effect of the endogenous PKCdelta and increased tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. The localization of PKCdelta differentially affected the activation of downstream signaling pathways. PKCdelta-Cyto increased the phosphorylation of p38 and decreased the phosphorylation of AKT and the expression of X-linked inhibitor of apoptosis protein, whereas PKCdelta-Nuc increased c-Jun NH(2)-terminal kinase phosphorylation. Moreover, p38 phosphorylation and the decrease in X-linked inhibitor of apoptosis protein expression played a role in the apoptotic effect of PKCdelta-Cyto, whereas c-Jun NH(2)-terminal kinase activation mediated the apoptotic effect of PKCdelta-Nuc. Our results indicate that the subcellular localization of PKCdelta plays important roles in its proapoptotic and antiapoptotic functions and in the activation of downstream signaling pathways.
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PMID:The localization of protein kinase Cdelta in different subcellular sites affects its proapoptotic and antiapoptotic functions and the activation of distinct downstream signaling pathways. 1757 21

Two major protein degradation systems exist in cells, the ubiquitin proteasome system and the autophagy machinery. Here, we investigated the functional relationship of the two systems and the underlying mechanisms. Proteasome inhibition activated autophagy, suggesting that the two are functionally coupled. Autophagy played a compensatory role as suppression of autophagy promoted the accumulation of polyubiquitinated protein aggregates. Autophagy was likely activated in response to endoplasmic reticulum stress caused by misfolded proteins during proteasome inhibition. Suppression of a major unfolded protein response pathway mediated by IRE1 by either gene deletion or RNA interference dramatically suppressed the activation of autophagy by proteasome inhibitors. Interestingly, c-Jun NH(2)-terminal kinase (JNK) but not XBP-1, both of which are the known downstream targets of IRE1, seemed to participate in autophagy induction by proteasome inhibitors. Finally, proteasome inhibitor-induced autophagy was important for controlling endoplasmic reticulum stress and reducing cell death in cancer cells. Our studies thus provide a mechanistic view and elucidate the functional significance of the link between the two protein degradation systems.
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PMID:Linking of autophagy to ubiquitin-proteasome system is important for the regulation of endoplasmic reticulum stress and cell viability. 1762 Mar 65

Geranylgeranylacetone (GGA), an antiulcer agent, has the ability to induce 70-kDa heat shock protein (HSP70) in various cell types and to protect cells from apoptogenic insults. However, little is known about effects of GGA on other HSP families of molecules. We found that, at concentrations >/=100 microM, GGA caused selective expression of 78-kDa glucose-regulated protein (GRP78), an HSP70 family member inducible by endoplasmic reticulum (ER) stress, without affecting the level of HSP70 in various cell types. Induction of ER stress by GGA was also evidenced by expression of another endogenous marker, CCAAT/enhancer-binding protein-homologous protein (CHOP); decreased activity of ER stress-responsive alkaline phosphatase; and unfolded protein response (UPR), including activation of the activating transcription factor 6 (ATF6) pathway and the inositol-requiring ER-to-nucleus signal kinase 1-X-box-binding protein 1 (IRE1-XBP1) pathway. Incubation of mesangial cells with GGA caused significant apoptosis, which was attenuated by transfection with inhibitors of caspase-12 (i.e., a dominant-negative mutant of caspase-12 and MAGE-3). Dominant-negative suppression of IRE1 or XBP1 significantly attenuated apoptosis without affecting the levels of CHOP and GRP78. Inhibition of c-Jun NH(2)-terminal kinase, the molecule downstream of IRE1, by 1,9-pyrazoloanthrone (SP600125) did not improve cell survival. Blockade of ATF6 by 4-(2-aminoethyl) benzenesulfonyl fluoride enhanced apoptosis by GGA, and it was correlated with attenuated induction of both GRP78 and CHOP. Overexpression of GRP78 or dominant-negative inhibition of CHOP significantly attenuated GGA-induced apoptosis. These results suggested that GGA triggers both proapoptotic (IRE1-XBP1, ATF6-CHOP) and antiapoptotic (ATF6-GRP78) UPR and thereby coordinates cellular fate even without induction of HSP70.
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PMID:Geranylgeranylacetone, an inducer of the 70-kDa heat shock protein (HSP70), elicits unfolded protein response and coordinates cellular fate independently of HSP70. 1770 88

The endoplasmic reticulum (ER) has been posited as a potential anticancer target. The synthetic antitumor alkyl-lysophospholipid analogue edelfosine accumulates in the ER of solid tumor cells. This ER accumulation of the drug leads to the inhibition of phosphatidylcholine and protein synthesis, G(2)-M arrest, depletion of ER-stored Ca(2+), Bax up-regulation and activation, transcriptional factor growth arrest and DNA damage-inducible gene 153 up-regulation, caspase-4 and caspase-8 activation, and eventually to apoptosis. Edelfosine prompted ER stress apoptotic signaling, but not the survival unfolded protein response. Edelfosine also induced persistent c-Jun NH(2)-terminal kinase (JNK) activation. Gene transfer-mediated overexpression of apoptosis signal-regulating kinase 1, which plays a crucial role in ER stress, enhanced edelfosine-induced JNK activation and apoptosis. Inhibition of JNK, caspase-4, or caspase-8 activation diminished edelfosine-induced apoptosis. Edelfosine treatment led to the generation of the p20 caspase-8 cleavage fragment of BAP31, directing proapoptotic signals between the ER and the mitochondria. bax(-/-)bak(-/-) double-knockout cells fail to undergo edelfosine-induced ER-stored Ca(2+) release and apoptosis. Wild-type and bax(-/-)bak(-/-) cells showed similar patterns of phosphatidylcholine and protein synthesis inhibition, despite their differences in drug sensitivity. Thus, edelfosine-induced apoptosis is dependent on Bax/Bak-mediated ER-stored Ca(2+) release, but phosphatidylcholine and protein synthesis inhibition is not critical. Transfection-enforced expression of Bcl-X(L), which localizes specifically in mitochondria, prevented apoptosis without inhibiting ER-stored Ca(2+) release. These data reveal that edelfosine induces an ER stress response in solid tumor cells, providing novel insights into the edelfosine-mediated antitumor activity. Our data also indicate that mitochondria are indispensable for this edelfosine-induced cell death initiated by ER stress.
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PMID:Endoplasmic reticulum stress in the proapoptotic action of edelfosine in solid tumor cells. 1797 80

Methylenetetrahydrofolate reductase (MTHFR), an enzyme in folate and homocysteine metabolism, influences many cellular processes including methionine and nucleotide synthesis, methylation reactions, and maintenance of homocysteine at nontoxic levels. Mild deficiency of MTHFR is common in many populations and modifies risk for several complex traits including vascular disease, birth defects, and cancer. We recently demonstrated that MTHFR can be up-regulated by NF-kappaB, an important mediator of cell survival that is activated by endoplasmic reticulum (ER) stress. This observation, coupled with the reports that homocysteine can induce ER stress, prompted us to examine the possible regulation of MTHFR by ER stress. We found that several well characterized stress inducers (tunicamycin, thapsigargin, and A23187) as well as homocysteine could increase Mthfr mRNA and protein in Neuro-2a cells. The induction of MTHFR was also observed after overexpression of inositol-requiring enzyme-1 (IRE1) and was inhibited by a dominant-negative mutant of IRE1. Because IRE1 triggers c-Jun signaling, we examined the possible involvement of c-Jun in up-regulation of MTHFR. Transfection of c-Jun and two activators of c-Jun (LiCl and sodium valproate) increased MTHFR expression, whereas a reported inhibitor of c-Jun (SP600125) and a dominant-negative derivative of c-Jun N-terminal kinase-1 reduced MTHFR activation. We conclude that ER stress increases MTHFR expression and that IRE1 and c-Jun mediate this activation. These findings provide a novel mechanism by which the ER can regulate homeostasis and allude to an important role for MTHFR in cell survival.
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PMID:Endoplasmic reticulum stress increases the expression of methylenetetrahydrofolate reductase through the IRE1 transducer. 1806 14


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