Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neutrophils and monocytes/macrophages are derived from common progenitors, but exhibit markedly different lifespans. Differentiated neutrophils are short-lived and die rapidly by apoptosis, while monocytic cells are longer-lived. In this report we used the HL-60 cell line as a model system to identify differences in apoptotic pathways which might account for the differing lifespans of granulocytic vs monocytic cells. We observed that induction of granulocytic differentiation by retinoic acid led to robust activation of the executioner protease caspase-3, and early onset of apoptosis. By contrast, caspase-3 was not appreciably activated during phorbol 12-myristate 13-acetate (PMA)-induced monocytic differentiation, and apoptosis was delayed in these cells. Since the activation of caspase-3 is inhibited by members of the inhibitor of apoptosis (IAP) and Bcl-2 protein families, we investigated the expression of anti-apoptotic members of these families. Induction of monocytic differentiation led to marked upregulation of the IAP protein XIAP, as well as the Bcl-2 family member Bcl-X(L). During granulocytic differentiation the levels of XIAP progressively declined, while Bcl-X(L) levels remained unchanged. A different IAP protein, survivin, was downregulated during differentiation along either lineage, as was expression of Bcl-2. The upregulation of Bcl-X(L) during monocytic differentiation coincided with phosphorylation/activation of STAT3, a known activator of bcl-X gene transcription. Moreover, Bcl-X(L) upregulation was dependent on MEK/ERK signaling. Upregulation of XIAP proceeded in a MEK/ERK-independent fashion. Treatment with antisense Bcl-X(L) or XIAP oligonucleotides resulted in significant loss of viability in cells differentiating along the monocytic lineage. Together, these findings indicate that the levels of XIAP and Bcl-X(L) are regulated by distinct pathways during monocytic differentiation, and that upregulation of these proteins contributes to the increased longevity of cells in the monocytic lineage.
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PMID:Differential activation of apoptosis regulatory pathways during monocytic vs granulocytic differentiation: a requirement for Bcl-X(L)and XIAP in the prolonged survival of monocytic cells. 1259 39

Interactions between the protein kinase C (PKC) and Chk1 inhibitor UCN-01 and the heat shock protein 90 (Hsp90) antagonist 17-AAG have been examined in human leukemia cells in relation to effects on signal transduction pathways and apoptosis. Simultaneous exposure (30 hours) of U937 monocytic leukemia cells to minimally toxic concentrations of 17-AAG (eg, 400 nM) and UCN-01 (eg, 75 nM) triggered a pronounced increase in mitochondrial injury (ie, loss of mitochondrial membrane potential [Deltapsim]; cytosolic release of cytochrome c), caspase activation, and apoptosis. Synergistic induction of apoptosis was also observed in other human leukemia cell types (eg, Jurkat, NB4). Coexposure of human leukemia cells to 17-AAG and the PKC inhibitor bisindolylmaleimide (GFX) did not result in enhanced lethality, arguing against the possibility that the PKC inhibitory actions of UCN-01 are responsible for synergistic interactions. The enhanced cytotoxicity of this combination was associated with diminished Akt activation and marked down-regulation of Raf-1, MEK1/2, and mitogen-activated protein kinase (MAPK). Coadministration of 17-AAG and UCN-01 did not modify expression of Hsp90, Hsp27, phospho-JNK, or phospho-p38 MAPK, but was associated with further p34cdc2 dephosphorylation and diminished expression of Bcl-2, Mcl-1, and XIAP. In addition, inducible expression of both a constitutively active MEK1/2 or myristolated Akt construct, which overcame inhibition of ERK and Akt activation, respectively, significantly attenuated 17-AAG/UCN-01-mediated lethality. Together, these findings indicate that the Hsp90 antagonist 17-AAG potentiates UCN-01 cytotoxicity in a variety of human leukemia cell types and suggest that interference with both the Akt and Raf-1/MEK/MAP kinase cytoprotective signaling pathways contribute to this phenomenon.
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PMID:Synergistic antileukemic interactions between 17-AAG and UCN-01 involve interruption of RAF/MEK- and AKT-related pathways. 1273 74

Osteoclasts are multinucleated cells formed by multiple steps of cell differentiation from progenitor cells of hematopoietic origin. Intervention in osteoclast differentiation is considered as an effective therapeutic approach to the treatment for bone diseases involving osteoclasts. In this study, we found that the organic compound (S)-1-lyso-2-stearoylamino-2-deoxy-sn-glycero-3-phosphatidylcholine (SCOH) inhibited osteoclast differentiation. The inhibitory effect of SCOH was observed in mouse bone marrow cell cultures supported either by coculturing with osteoblasts or by adding macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor kappaB ligand (RANKL). M-CSF and RANKL activate the ERK, Akt, and NF-kappaB signal transduction pathways, and SCOH suppressed this activation. SCOH also inhibited the bone resorptive activity of differentiated osteoclasts. It attenuated bone resorption, actin ring formation, and survival of mature osteoclasts. Reduced activation of Akt and NF-kappaB and decreased induction of XIAP were observed in mature osteoclasts treated with SCOH. Thus, this novel phosphatidylcholine derivative may be useful for treating bone-resorption diseases.
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PMID:Inhibition of osteoclast differentiation and bone resorption by a novel lysophosphatidylcholine derivative, SCOH. 1501 39

Normal spontaneous apoptosis in neutrophils is enhanced by "stress" stimuli such as tumor necrosis factor-alpha, Fas ligand, and oxidants, and this effect is inhibited by anti-apoptotic stimuli including granulocyte-macrophage colony-stimulating factor, lipopolysaccharide, and formylmethionine-leucine-phenylalanine. In this report we demonstrate that anti-apoptotic stimuli protect neutrophils from stress-induced apoptosis via activation of the ERK/MAPK pathway. The protection occurs downstream of mitochondrial alterations assessed as a decrease in membrane potential concomitant with enhanced cytochrome c release. ERK activation was shown to inhibit apoptosis by maintaining levels of XIAP, which is normally decreased in the presence of the pro-apoptotic/stress stimuli. This report also demonstrates that potent intra- and extracellular oxidants inhibit the protective effect of ERK. Oxidant-dependent inhibition of ERK was because of activation of p38 MAPK and activation of the protein phosphatases PP1 and PP2A. Our data suggest that ERK suppresses stress-induced apoptosis downstream of mitochondrial alterations by maintaining XIAP levels and that oxidants block this effect through activation of p38 and protein phosphatases.
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PMID:Oxidants inhibit ERK/MAPK and prevent its ability to delay neutrophil apoptosis downstream of mitochondrial changes and at the level of XIAP. 1529 76

Endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of many diseases and in cancer therapy. Although the unfolded protein response is known to alleviate ER stress by reducing the accumulation of misfolded proteins, the exact survival elements and their downstream signaling pathways that directly counteract ER stress-stimulated apoptotic signaling remain elusive. Here, we have shown that endogenous Akt and ERK are rapidly activated and act as downstream effectors of phosphatidylinositol 3-kinase in thapsigargin- or tunicamycin-induced ER stress. Introduction of either dominant-negative Akt or MEK1 or the inhibitors LY294002 and U0126 sensitized cells to ER stress-induced cell death in different cell types. Reverse transcription-PCR analysis of gene expression during ER stress revealed that cIAP-2 and XIAP, members of the IAP family of potent caspase suppressors, were strongly induced. Transcription of cIAP-2 and XIAP was up-regulated by the phosphatidylinositol 3-kinase/Akt pathway as shown by its reversal by dominant-negative Akt or LY294002. Ablation of these IAPs by RNA interference sensitized cells to ER stress-induced death, which was reversed by the caspase inhibitor benzyloxycarbonyl-VAD-fluoromethyl ketone. The protective role of IAPs in ER stress coincided with Smac release from mitochondria to the cytosol. Furthermore, it was shown that mTOR was not required for Akt-mediated survival. These results represent the first demonstration that activation of endogenous Akt/IAPs and MEK/ERK plays a critical role in controlling cell survival by resisting ER stress-induced cell death signaling.
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PMID:Critical role of endogenous Akt/IAPs and MEK1/ERK pathways in counteracting endoplasmic reticulum stress-induced cell death. 1533 11

Anaplastic large-cell lymphoma (ALCL) is a heterogeneous lymphoma category in which a subset of cases carry the t(2;5)(p23;q35) or variant translocations resulting in overexpression of anaplastic lymphoma kinase (ALK). LY293111 (2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]-propoxy]-phenoxy] benzoic acid sodium salt) is a leukotriene B4 receptor antagonist, which was found to be safe and tolerable in Phase I clinical trials. In this study, we investigated the potential therapeutic effects and mechanisms of action of LY293111 in ALCL cell lines. LY293111 inhibited proliferation of both ALK(+) and ALK(-) ALCL cell in a dose-dependent fashion and induced complete G(1)-S cell cycle arrest, which was accompanied by upregulation of p27 and downregulation of cyclin E. Pretreatment with LY293111 for 4 h resulted in profound inhibition of serum-induced phosphorylation of extracellular-regulated kinases-1 and 2 and Akt and a concomitant increase in the phosphorylation of the stress-activated kinase c-jun N-terminal kinases (JNK). Simultaneously, LY293111 induced caspase-dependent apoptosis via activation of the intrinsic pathway, including early loss of mitochondrial inner transmembrane potential and the production of reactive oxygen species (ROS), cleavage of caspases-9, -3, poly ADP-ribose polymerase (PARP) and X-linked inhibitor of apoptosis. The phospho-JNK inhibitor SP600125 partially protected Sup-M2 cells from LY293111-induced apoptosis, PARP cleavage and ROS generation, suggesting a role for JNK in LY293111-induced cell death. These results warrant further studies of LY293111 in ALCL.
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PMID:Leukotriene B4 receptor inhibitor LY293111 induces cell cycle arrest and apoptosis in human anaplastic large-cell lymphoma cells via JNK phosphorylation. 1615 69

Monocytes and macrophages play a key role in the initiation and persistence of inflammatory reactions. The possibility to interfere with the survival of these cells, once recruited and activated at sites of inflammation, is an attractive therapeutic option. Although resting monocytes are susceptible to pharmacologically induced apoptosis, no data are available about the possibility to modulate the survival of activated monocytes. The present work was planned to investigate if dexamethasone is able to promote apoptosis of human monocytes activated by immune complexes. When monocytes were cultured with immune complexes, a dose-dependent inhibition of apoptosis was observed. Dexamethasone stimulated apoptosis of resting and activated monocytes in a dose-dependent manner. Both the immune complex inhibitory activity and dexamethasone stimulatory properties depend on NF-kappaB/XIAP and Ras/MEK/ERK/CD95 pathways. In fact, the exposure of monocytes to immune complexes increased NF-kB activation and XIAP expression, which in turn were inhibited by dexamethasone. On the other hand, immune complex-stimulated monocytes displayed a reduced expression of CD95, which is prevented by dexamethasone, as well as by MEK inhibitor U0126. Furthermore, anti-CD95 ZB4 mAb prevented dexamethasone-induced apoptosis in immune complex stimulated monocytes. Similarly, ZB4 inhibited dexamethasone-mediated augmentation of caspase 3 activity. The present findings suggest that Fc triggering by insoluble immune complexes result in the activation of two intracellular pathways crucial for the survival of monocytes: 1. Ras/MEK/ERK pathway responsible for the down-regulation of CD95 expression; 2. NF-kappaB pathway governing the expression of XIAP. Both the pathways are susceptible to inhibition by monocyte treatment with pharmacologic concentrations of dexamethasone.
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PMID:Dexamethasone -induced apoptosis of human monocytes exposed to immune complexes. Intervention of CD95- and XIAP-dependent pathways. 1616 24

Abnormal activation of tyrosine kinases and of signaling pathways they control plays a critical role in the neoplastic process of human hematopoietic malignancy. The nuclear factor-kappaB (NF-kappaB) pathway is one of the signalings activated by the TEL-Jak2 and TEL-Abl oncoproteins and required for their antiapoptotic activity. To define the signal relay responsible for this activation, we used mouse embryonic fibroblast (MEF) cells and observed that TEL-Jak2- and TEL-Abl-mediated NF-kappaB induction was abolished in cells lacking the IkappaB kinase (IKK)alpha but not in IKKbeta(-/-) cells. Similar observations were performed with oncogenic forms of the FMS-like tyrosine kinase 3 (Flt-3) involved in the pathogenesis of one-third of acute myeloid leukemias. Rescue of TEL-Jak2-mediated NF-kappaB activation was obtained with a kinase-proficient form of IKKalpha in IKKalpha(-/-) MEF. Hematopoietic cells transformed by TEL-Jak2 and TEL-Abl showed sustained IKKalpha activity without promotion of NF-kappaB2/p100 processing, generally associated to IKKalpha functions. Furthermore, IAP1, IAP2 and XIAP, which are central regulators of the NF-kappaB-mediated survival pathway, were highly expressed in cells transformed by these oncoproteins. Our results indicate that these oncogenic tyrosine kinases preferentially use an IKKalpha-dependent mechanism to induce a persistent NF-kappaB activity and allow the production of antiapoptotic effectors that participate to their leukemogenic properties.
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PMID:Activation of the NF-kappaB pathway by the leukemogenic TEL-Jak2 and TEL-Abl fusion proteins leads to the accumulation of antiapoptotic IAP proteins and involves IKKalpha. 1643 62

The BRAFV600E mutation is closely linked to tumorigenesis and malignant phenotype of papillary thyroid cancer. Signaling pathways activated by BRAFV600E are still unclear except a common activation pathway, MAPK cascade. To investigate the possible target of BRAFV600E, we developed two different cell culture models: 1) doxycycline-inducible BRAFV600E-expressing clonal line derived from human thyroid cancer WRO cells originally harboring wild-type BRAF; 2) WRO, KTC-3, and NPA cells infected with an adenovirus vector carrying BRAFV600E. BRAFV600E expression induced ERK phosphorylation and cyclin D1 expression in these cells. The BRAFV600E-overexpressing cells also showed an increase of nuclear factor kappaB (NF-kappaB) DNA-binding activity, resulting in up-regulation of antiapoptotic c-IAP-1, c-IAP-2, and X-linked inhibitor of apoptosis. Furthermore, BRAFV600E expression also induced the expression of matrix metalloproteinase and cell invasion into matrigel through NF-kappaB pathway. Increased invasive ability by BRAFV600E expression was significantly inhibited by a specific NF-kappaB inhibitor, racemic dehydroxymethylepoxyquinomicin. These data indicate that BRAFV600E activates not only MAPK but also NF-kappaB signaling pathway in human thyroid cancer cells, leading to an acquisition of apoptotic resistance and promotion of invasion. Inactivation of NF-kappaB may provide a new therapeutic modality for thyroid cancers with BRAFV600E.
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PMID:BRAFV600E promotes invasiveness of thyroid cancer cells through nuclear factor kappaB activation. 1695 44

Raf-1 serine/threonine protein kinase plays an important role in cell growth, differentiation and cell survival. Recent reports using c-raf-1 gene-knockouts have observed MEK/ERK independent functions of Raf-1 in cell survival and protection from apoptosis. Raf-1 has also been shown to be involved in counteracting specific apoptotic pathways by restraining caspase activation, although the precise mechanism is unknown. XIAP is a potent inhibitor of apoptosis that blocks both the mitochondria and death receptor mediated pathways of apoptosis by directly binding to and inhibiting the initiator and effector caspases. In our efforts to understand the mechanism by which Raf-1 inhibits caspase activation, we discovered a novel interaction between Raf-1 and XIAP. In this study, we describe the physical interaction between Raf-1 and XIAP in vitro and in vivo in mammalian cells. We also demonstrate that Raf-1 phosphorylates XIAP in vitro and in vivo. Additionally, Raf-1 prevents XIAP degradation in response to different apoptotic triggers. Our studies identify XIAP as a new substrate of Raf-1 and provide potentially important insight into mechanisms underlying Raf-1 effects on cell survival.
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PMID:Interaction and stabilization of X-linked inhibitor of apoptosis by Raf-1 protein kinase. 1696 81


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