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:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Centaurin-alpha1 is known to be a phosphatidylinositol 3,4,5-triphosphate (PIP3)-binding protein that has two pleckstrin homology domains and a putative ADP ribosylation factor GTPase-activating protein domain. However, the physiological function of centaurin-alpha1 is still not understood. Here we have shown that transient expression of centaurin-alpha1 in COS-7 cells results in specific activation of ERK, and the activation is inhibited by co-expression of a dominant negative form of Ras. We have also found that a mutant form of centaurin-alpha1 that is unable to bind PIP3 fails to induce ERK activation and that a phosphatidylinositol 3-kinase inhibitor LY294002 inhibits centaurin-alpha1-dependent ERK activation. Furthermore, transient knockdown of centaurin-alpha1 by small interfering RNAs results in reduced ERK activation after epidermal growth factor stimulation in T-REx 293 cells. These results suggest that centaurin-alpha1 contributes to ERK activation in growth factor signaling, linking the PI3K pathway to the ERK mitogen-activated protein kinase pathway through its ability to interact with PIP3.
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PMID:Centaurin-alpha1 is a phosphatidylinositol 3-kinase-dependent activator of ERK1/2 mitogen-activated protein kinases. 1628 13

We have used HeLa cells without mitochondrial DNA (rho0-cells) and transient rho0-phenocopies, obtained from wild-type cells by short-term treatment with ethidium bromide, to analyze how the absence of a functional mitochondrial respiratory chain slows down proliferation. We ruled out an energetic problem (ATP/ADP content) as well as defective synthesis of pyrimidine, iron-sulfur clusters or heme as important causes for the proliferative defect. Flow cytometric analysis revealed that reactive oxygen species were reduced in rho0-cells and in rho0-phenocopies, and that, quite unusually, all stages of the cell cycle were slowed down. Specific quenching of mitochondrial ROS with the ubiquinone analog MitoQ also resulted in slower growth. Some important cell-cycle regulators were reduced in rho0-cells: cyclin D3, cdk6, p18INK4C, p27KIP1, and p21CIP1/WAF1. In the rho0-phenocopies, the expression pattern did not fully duplicate the complex response observed in rho0-cells, and mainly p21CIP1/WAF1 was downregulated. Activities of the growth regulatory PKB/Akt and MAPK/ERK-signaling pathways did not correlate with proliferation rates of rho0-cells and rho0-phenocopies. Our study demonstrates that loss of a functional mitochondrial electron transport chain inhibits cell-cycle progression, and we postulate that this occurs through the decreased concentration of reactive oxygen species, leading to downregulation of p21CIP1/WAF1.
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PMID:Respiratory chain deficiency slows down cell-cycle progression via reduced ROS generation and is associated with a reduction of p21CIP1/WAF1. 1677 40

The molecular chaperone heat shock protein 90 (HSP90) has emerged as an exciting molecular target for cancer therapy. It operates as part of a multichaperone complex and is essential for the conformation, stability, and function of several key oncogenic client proteins such as mutant p53, ERBB2, B-RAF, C-RAF, and CDK4. The HSP90-based chaperone machine is driven by the hydrolysis of ATP and ADP/ATP nucleotide exchange. Many of the inhibitors of HSP90 interrupt the intrinsic ATPase activity, causing degradation of the client proteins via the ubiquitin-proteasome pathway. The first-in-class HSP90 inhibitor in clinical trials is the geldanamycin analog, 17-allylamino, 17-demethoxygeldanamycin (17-AAG). The results that have emerged from these trials have been encouraging, with stable disease observed in two melanoma patients. Pharmacodynamic endpoints, such as induction of HSP70 and downregulation of C-RAF and CDK4 in peripheral blood mononuclear cells and tumor biopsies from treated patients, provided evidence of HSP90 inhibition at well-tolerated doses. The toxicity of 17-AAG has been mild. Several preclinical studies have shown that 17-AAG may enhance the efficacy of a variety of chemotherapeutic agents. Phase II clinical trials in various cancers have been initiated as well as Phase I trials of combined therapy with 17-AAG. However, there are several limitations with 17-AAG such as solubility, stability, and hepatotoxicity. Thus, it is not surprising that new HSP90 agents are under development against this novel target for cancer therapy and several show promise.
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PMID:Inhibitors of the HSP90 molecular chaperone: current status. 1686 Jun 62

There is evidence that extracellular nucleotides, acting through multiple P2 receptors, may play an important role in the regulation of bone metabolism by activating intracellular signaling cascades. We have studied the modulation of mitogen-activated protein kinase (MAPK) signaling pathways and its relationship to changes in intracellular calcium concentration ([Ca(2+)](i)) induced by ATP in ROS-A 17/2.8 osteoblastic cells. ATP and UTP (10 microM) increased [Ca(2+)](i) by cation release from intracellular stores. We have found that when the cells are subsequently subjected to mechanical stress (medium perturbation), a transient calcium influx occurs. This mechanical stress-activated calcium influx (MSACI) was not observed after ADP stimulation, indicating that P2Y(2) receptor activation is required for MSACI. In addition, ERK 1/2 and p38 MAPK were activated by ATP in a dose- and time-dependent manner. This activation was almost completely blocked using neomycin (2.5mM), an inhibitor of phosphoinositide-phospholipase C (PI-PLC), Ro 318220 (1 microM), a protein kinase C (PKC) inhibitor, and PP1 (50 microM), a potent and selective inhibitor of the Src-family tyrosine kinases. Ca(2+)-free extracellular medium (containing 0.5mM EGTA) and the use of gadolinium (5 microM), which suppressed MSACI, prevented ERK 1/2 and p38 phosphorylation by ATP. Altogether, these results represent the first evidence to date suggesting that P2Y(2) receptor stimulation by ATP in osteoblasts sensitizes mechanical stress activated calcium channels leading to calcium influx and a fast activation of the ERK 1/2 and p38 MAPK pathways. This effect also involves upstream mediators such as PI-PLC, PKC and Src family kinases.
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PMID:Modulation of ERK 1/2 and p38 MAPK signaling pathways by ATP in osteoblasts: involvement of mechanical stress-activated calcium influx, PKC and Src activation. 1689 69

p38 MAP kinase in human platelets is activated by platelet agonists including thrombin, thromboxane A2 (TxA2), ADP, and others. However, both upstream mechanisms of p38 MAP kinase activation, and their downstream sequelae, are presently controversial and essentially unclear. Certain studies report sequential activation of cGMP-dependent protein kinase (PKG) and p38/ERK pathways by platelet agonists, leading to integrin activation and secretion, whereas others establish an essential role of Src/ERK-mediated TxA2 generation for fibrinogen receptor activation in human platelets. Here, we show that ADP secreted from platelet-dense granules, and subsequent activation of P2Y12 receptors, as well as TxA2 release are important upstream mediators of p38 MAP kinase activation by thrombin. However, p38 MAP kinase activation did not significantly contribute to calcium mobilization, P-selectin expression, alphaIIbbeta3 integrin activation, and aggregation of human platelets in response to thrombin. Finally, PKG activation did not stimulate, but rather inhibited, p38 MAP kinase in human platelets.
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PMID:Thrombin stimulation of p38 MAP kinase in human platelets is mediated by ADP and thromboxane A2 and inhibited by cGMP/cGMP-dependent protein kinase. 1699 May 90

A new synthetic isothiocyanate (ITC) derivative, ethyl 4-isothiocyanatobutanoate (E-4IB), appeared to be an effective modulator of cellular proliferation and potent inducer of apoptosis. In cooperation with cisplatin, this compound exerted synergistic effects in human ovarian carcinoma A2780 cells. In the present study we investigated in more detail E4IB-sensitisation for cisplatin-induced apoptosis. Sequential administration of both cytostatic agents led to increased intracellular platinum accumulation, glutathione level depletion and mitochondrial membrane potential dissipation. These events were accompanied with poly (ADP-ribosyl) polymerase cleavage, stimulation of caspase-3 activity, upregulation of p53, FasL and Gadd45alpha, cyclin B1 downregulation and an increase in mitogen-activated protein kinases JNK, ERK and p38 phosphorylation as well as PI3K level alterations. The presented results might have implications for developing new strategies aimed at therapeutic benefit of natural or synthetic ITCs in cooperation with various anticancer drugs.
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PMID:Sensitisation for cisplatin-induced apoptosis by isothiocyanate E-4IB leads to signalling pathways alterations. 1706 Sep 35

Much is known about the distal DNA damage repair response. In particular, many of the enzymes and auxiliary proteins that participate in DNA repair have been characterized. In addition, knowledge of signaling pathways activated in response to DNA damage is increasing. In contrast, comparatively less is known of DNA damage-sensing molecules or of the specific alterations to chromatin structure recognized by such DNA damage sensors. Thus, precisely how chromatin structure is altered in response to DNA damage and how such alterations regulate DNA repair processes remain important unanswered questions. In vertebrates, phosphorylation of the histone variant H2A.X occurs rapidly after double-strand break formation, extends over megabase chromatin domains, and is required for stable accumulation of repair proteins at damage foci. We have shown that reactive oxygen species (ROS)-induced DNA single-strand breaks induce the incorporation of 32P specifically into histone H3. ADP-Ribosylation of histones may stimulate local chromatin relaxation to facilitate the repair process, and, indeed, histone ribosylation preceded DNA damage-induced histone H3 phosphorylation. However, H3 phosphorylation occurred concomitant with overall chromatin condensation, as revealed by decreased sensitivity of chromatin to digestion by micrococcal nuclease and by DAPI staining of nuclei. Inhibitors of the ERK and p38MAPK pathways and inhibition of poly(ADP-ribose) polymerase all reduced ROS-induced H3 phosphorylation, chromatin condensation, and cell death. Precisely how changes in the post-translational modification of histone H3 regulate the survival response remains unclear. Attempts to determine the precise site of histone H3 phosphorylation, putative histone H3 kinases, and histone H3 interacting proteins are underway.
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PMID:Ros-induced histone modifications and their role in cell survival and cell death. 1714

The last decade has seen the molecular chaperone heat shock protein 90 (HSP90) emerge as an exciting target for cancer therapy. This is because HSP90 is involved in maintaining the conformation, stability, activity and cellular localisation of several key oncogenic client proteins. These include, amongst others, ERBB2, C-RAF, CDK4, AKT/PKB, steroid hormone receptors, mutant p53, HIF-1alpha , survivin and telomerase hTERT. Therefore, modulation of this single drug target offers the prospect of simultaneously inhibiting all the multiple signalling pathways and biological processes that have been implicated in the development of the malignant phenotype. The chaperone function of HSP90 requires the formation of a multichaperone complex, which is dependent on the hydrolysis of ATP and ADP/ATP exchange. Most current inhibitors of HSP90 act as nucleotide mimetics, which block the intrinsic ATPase activity of this molecular chaperone. The first-in-class inhibitor to enter and complete phase I clinical trials was the geldanamycin analogue, 17-allylamino-17-demethoxygeldanamycin. The results of these trials have demonstrated that HSP90 is a valid drug target. Evidence of clinical activity has been seen in patients with melanoma, breast and prostate cancer. This article provides a personal perspective of the present efforts to increase our understanding of the molecular and cellular consequences of HSP90 inhibition, with examples from work in our own laboratory. We also review the discovery and development of novel small-molecule inhibitors and discuss alternative approaches to inhibit HSP90 activity, both of which offer exciting prospects for the future.
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PMID:Targeting of multiple signalling pathways by heat shock protein 90 molecular chaperone inhibitors. 1725 53

We have previously shown that ADP-induced thromboxane generation in platelets requires signalling events from the G(q)-coupled P2Y1 receptor (platelet ADP receptor coupled to stimulation of phospholipase C) and the G(i)-coupled P2Y12 receptor (platelet ADP receptor coupled to inhibition of adenylate cyclase) in addition to outside-in signalling. While it is also known that extracellular calcium negatively regulates ADP-induced thromboxane A2 generation, the underlying mechanism remains unclear. In the present study we sought to elucidate the signalling mechanisms and regulation by extracellular calcium of ADP-induced thromboxane A2 generation in platelets. ERK (extracllular-signal-regulated kinase) 2 activation occurred when outside-in signalling was blocked, indicating that it is a downstream event from the P2Y receptors. However, blockade of either P2Y1 or the P2Y12 receptors with corresponding antagonists completely abolished ERK phosphorylation, indicating that both P2Y receptors are required for ADP-induced ERK activation. Inhibitors of Src family kinases or the ERK upstream kinase MEK [MAPK (mitogen-activated protein kinase)/ERK kinase] abrogated ADP-induced ERK phosphorylation and thromboxane A2 generation. Finally ADP- or G(i)+G(z)-induced ERK phosphorylation was blocked in the presence of extracellular calcium. The present studies show that ERK2 is activated downstream of P2Y receptors through a complex mechanism involving Src kinases and this plays an important role in ADP-induced thromboxane A2 generation. We also conclude that extracellular calcium blocks ADP-induced thromboxane A2 generation through the inhibition of ERK activation.
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PMID:Regulation and functional consequences of ADP receptor-mediated ERK2 activation in platelets. 1729 99

We have developed a highly sensitive assay of MEK-mediated ATP hydrolysis by coupling the formation of ADP to NADH oxidation through the enzymes pyruvate kinase and lactate dehydrogenase. Robust ATP hydrolysis is catalyzed by phosphorylated MEK in the absence of the protein substrate ERK. This ERK-uncoupled ATPase activity is dependent on the phosphorylation status of MEK and is abrogated by the selective MEK kinase inhibitor U0126. ADP production is concomitant with Raf-mediated phosphorylation of MEK. Based on this finding, a coupled Raf/MEK assay is developed for measuring the Raf activity. A kinetic treatment derived under steady-state assumptions is presented for the analysis of the reaction progress curve generated by this coupled assay. We have shown that inhibitory potency of selective Raf inhibitors can be determined accurately by this assay.
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PMID:An intrinsic ATPase activity of phospho-MEK-1 uncoupled from downstream ERK phosphorylation. 1749 Jun


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