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)

Growth factors induce c-fos transcription by stimulating phosphorylation of transcription factor TCF/Elk-1, which binds to the serum response element (SRE). Under such conditions Elk-1 could be phosphorylated by the mitogen-activated protein kinases (MAPKs) ERK1 and ERK2. However, c-fos transcription and SRE activity are also induced by stimuli, such as UV irradiation and activation of the protein kinase MEKK1, that cause only an insignificant increase in ERK1/2 activity. However, both of these stimuli strongly activate two other MAPKs, JNK1 and JNK2, and stimulate Elk-1 transcriptional activity and phosphorylation. We find that the JNKs are the predominant Elk-1 activation domain kinases in extracts of UV-irradiated cells and that immunopurified JNK1/2 phosphorylate Elk-1 on the same major sites recognized by ERK1/2, that potentiate its transcriptional activity. Finally, we show that UV irradiation, but not serum or phorbol esters, stimulate translocation of JNK1 to the nucleus. As Elk-1 is most likely phosphorylated while bound to the c-fos promoter, these results suggest that UV irradiation and MEKK1 activation stimulate TCF/Elk-1 activity through JNK activation, while growth factors induce c-fos through ERK activation.
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PMID:Induction of c-fos expression through JNK-mediated TCF/Elk-1 phosphorylation. 884 88

MEK kinase 1 (MEKK1) shares sequence identity with the yeast kinases Ste11 and Byr2, and is capable of phosphorylation and activation of both mitogen-activated protein/extracellular signal-related protein kinase (MAP/ERK) kinase (MEK) and stress-activated protein kinase (SAPK)/ERK kinase (SEK) in vitro. In vivo, however, MEKK1 predominantly activates the SEK/SAPK kinase cascade. Mechanisms of activation of MEKK1 are unclear. We have identified a major site of autophosphorylation (Thr-575) within the 'activation loop' of MEKK1 between the kinase subdomains VII and VIII. Phosphatase treatment of a constitutively active MEKK1 decreased kinase activity by 59%. Dephosphorylated T575 was rapidly re-(auto)phosphorylated by MEKK1. Mutation of T575 to alanine decreased MEKK1 transphosphorylation activity with a SEK substrate to approx. 30% of wild-type. Mutation of a second threonine residue (Thr-587) to alanine eliminated the phosphorylation of MEK or SEK substrate but not autophosphorylation. MEKK1 autophosphorylation is an intramolecular reaction because active MEKK1 cannot transphosphorylate a kinase-inactive MEKK1. Inactive MEKK1 was not phosphorylated on Thr-575 within cells, suggesting that the phosphorylation of Thr-575 in vivo results from autophosphorylation rather than phosphorylation by an upstream kinase. Autoactivation of MEKK1 via autophosphorylation of Thr-575 might be an immediate response to initial kinase activation through non-phosphorylation mechanisms.
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PMID:Regulation of the activity of MEK kinase 1 (MEKK1) by autophosphorylation within the kinase activation domain. 907 60

The protooncogene G alpha(i-2) plays a pivotal role in signaling pathways that control renal cell growth and differentiation. Mitogen-activated protein kinases (MAPKs) are potential downstream effectors for G alpha(i-2) in these pathways. In predifferentiated LLC-PK1 renal cells, the temporal maximal expression of G alpha(i-2) coincided with maximal activation of MAPK(p42/p44). By contrast, pertussis toxin treatment of these cells inhibited cell growth and reduced MAPK(p42/p44) activity by 30%. These findings reflected upstream activation of MAPK kinase (MEK1), as transient transfection of cells with a plasmid encoding a constitutively active form of MEK1 increased MAPK(p42/p44) activity and cell growth, whereas treatment with PD-098059, an inhibitor of MEK1 activity, reduced MAPK(p42/p44) activity and cell growth. Expression of a guanosinetriphosphatase (GTPase)-deficient G alpha(i-2) in these cells increased MAPK(p42/p44) activity and correspondingly reduced cell doubling time from 24 to 10 h without altering the activity of Raf-1 or c-Jun/stress-activated protein kinases (SAPKs). By contrast, expression of a GTPase-deficient G alpha(i-3) in these cells reduced both their cell doubling time by 30% and MAPK(p42/p44) activity by 60%. As the known MEKK isoforms (MEKK1, -2, and -3) can also activate SAPKs, these findings suggest the GTP-charged G alpha(i-2) subunit transduces growth signals in renal cells via activation of MAPK(p42/p44) and that such activation may be linked to pathways containing novel MEKK isoforms that preferentially activate MEKs.
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PMID:G alpha(i-2) mediates renal LLC-PK1 growth by a Raf-independent activation of p42/p44 MAP kinase. 912 7

Post-natal growth of cardiac muscle cells occurs by hypertrophy rather than division and is associated with changes in gene expression and muscle fiber morphology. We show here that the protein kinase MEKK1 can induce reporter gene expression from the atrial natriuretic factor (ANF) promoter, a genetic marker that is activated during in vivo hypertrophy. MEKK1 induced both stress-activated protein kinase (SAPK) and extracellular signal-regulated protein kinase (ERK) activity; however, while the SAPK cascade stimulated ANF expression, activation of the ERK cascade inhibited expression. C3 transferase, a specific inhibitor of the small GTPase Rho, also inhibited both MEKK- and phenylephrine-induced ANF expression, indicating an additional requirement for Rho-dependent signals. Microinjection or transfection of C3 transferase into the same cells did not disrupt actin muscle fiber morphology, indicating that Rho-dependent pathways do not regulate actin morphology in cardiac muscle cells. While active MEKK1 was a potent activator of hypertrophic gene expression, this kinase did not induce actin organization and prevented phenylephrine-induced organization. These data suggest that multiple signals control hypertrophic phenotypes. Positive and negative signals mediated by parallel MAP kinase cascades interact with Rho-dependent pathways to regulate hypertrophic gene expression while other signals induce muscle fiber morphology in cardiac muscle cells.
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PMID:MAP kinase- and Rho-dependent signals interact to regulate gene expression but not actin morphology in cardiac muscle cells. 915 15

Mast cells synthesize and secrete specific cytokines and chemokines which play an important role in allergic inflammation. Aggregation of the high-affinity Fc receptor (FcepsilonRI) for immunoglobulin E (IgE) in MC/9 mouse mast cells stimulates the synthesis and secretion of tumor necrosis factor alpha (TNF-alpha). FcepsilonRI aggregation activates several sequential protein kinase pathways, leading to increased activity of extracellular signal-regulated kinases (ERKs), c-Jun amino-terminal kinases (JNKs), and the p38 mitogen-activated protein (MAP) kinase. Inhibition of ERKs with the compound PD 098059 had little effect on FcepsilonRI-stimulated TNF-alpha production. Aggregation of FcepsilonRI stimulated MEK kinase 1 (MEKK1) activity, which activates JNK kinase (JNKK), the kinase that phosphorylates and activates JNKs. Expression of activated MEKK1 (DeltaMEKK1) in MC/9 cells strongly stimulated JNK activity but only weakly stimulated p38 activity, and it induced a large activation of TNF-alpha promoter-regulated luciferase gene expression. Inhibitory mutant JNK2 expressed in MC/9 cells significantly blunted FcepsilonRI stimulation of TNF-alpha promoter-driven luciferase expression. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase, diminished FcepsilonRI-mediated TNF-alpha synthesis, significantly blunted JNK activation and TNF-alpha promoter-driven luciferase expression, and only weakly inhibited p38 kinase activation. Inhibition of NFkappaB activation resulting from DeltaMEKK1 expression or FcepsilonRI stimulation did not affect TNF-alpha promoter-driven luciferase expression. Our findings define a MEKK-regulated JNK pathway activated by FcepsilonRI that regulates TNF-alpha production in mast cells.
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PMID:Mast cell tumor necrosis factor alpha production is regulated by MEK kinases. 917 22

The c-Jun N-terminal kinase (JNK), or stress-activated protein kinase plays a crucial role in cellular responses stimulated by environmental stress and proinflammatory cytokines. However, the mechanisms that lead to the activation of the JNK pathway have not been elucidated. We have isolated a cDNA encoding a novel protein kinase that has significant sequence similarities to human germinal center kinase (GCK) and human hematopoietic progenitor kinase 1. The novel GCK-like kinase (GLK) has a nucleotide sequence that encodes an ORF of 885 amino acids with 11 kinase subdomains. Endogenous GLK could be activated by UV radiation and proinflammatory cytokine tumor necrosis factor alpha. When transiently expressed in 293 cells, GLK specifically activated the JNK, but not the p42/44(MAPK)/extracellular signal-regulated kinase or p38 kinase signaling pathways. Interestingly, deletion of amino acids 353-835 in the putative C-terminal regulatory region, or mutation of Lys-35 in the putative ATP-binding domain, markedly reduced the ability of GLK to activate JNK. This result indicates that both kinase activity and the C-terminal region of GLK are required for maximal activation of JNK. Furthermore, GLK-induced JNK activation could be inhibited by a dominant-negative mutant of mitogen-activated protein kinase kinase kinase 1 (MEKK1) or mitogen-activated protein kinase kinase 4/SAPK/ERK kinase 1 (SEK1), suggesting that GLK may function upstream of MEKK1 in the JNK signaling pathway.
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PMID:Activation of the c-Jun N-terminal kinase pathway by a novel protein kinase related to human germinal center kinase. 927 85

c-Jun NH2-terminal protein kinase (JNK), a distant member of the mitogen-activated protein (MAP) kinase family, regulates gene expression in response to various extracellular stimuli. JNK is activated by JNK-activating kinase 1 (JNKK1), a dual specificity protein kinase that phosphorylates JNK on threonine 183 and tyrosine 185 residues. Here we show that JNKK2, a novel member of the MAP kinase kinase family, was phosphorylated and activated by MEKK1, a MAP kinase kinase kinase in the JNK signaling cascade. JNKK2 activity was also stimulated by constitutively active forms of Rac and Cdc42Hs, members of the Rho small GTP-binding protein family. Unlike JNKK1 that activates both JNK and p38 MAP kinases, JNKK2 stimulated only JNK. Transient transfection assays demonstrated that JNKK2 potentiated the stimulation of c-Jun transcriptional activity by MEKK1. The existence of multiple JNK-activating kinases may contribute to the specificity of the JNK signaling cascade.
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PMID:Identification of c-Jun NH2-terminal protein kinase (JNK)-activating kinase 2 as an activator of JNK but not p38. 931 68

Mitogen-activated protein (MAP) kinases mediate responses to a wide array of cellular stimuli. These cascades consist of a MAP kinase or extracellular signal-regulated kinase (ERK), activated by a MAP/ERK kinase (MEK), in turn activated by a MEK kinase (MEKK). MEKK1 has been shown to be a strong activator of the c-Jun N-terminal kinase/stress-actived protein kinase (JNK/SAPK) pathway. We report here that JNK/SAPK binds directly to the N-terminal, noncatalytic domain of MEKK1 in vitro and in transfected cells. Immobilized MEKK1-derived peptides extract JNK/SAPK selectively from cell lysates. MEKK1 coimmunoprecipitates with multiple JNK/SAPK isoforms in transfected cells. Expression of the N terminus of MEKK1 lacking the kinase domain increases activation of endogenous JNK/SAPK by MEKK1. The data are consistent with a model in which MEKK1-JNK/SAPK binding facilitates the receipt of signals from upstream inputs and localizes JNK/SAPK to intracellular targets of the pathway.
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PMID:MEKK1 binds directly to the c-Jun N-terminal kinases/stress-activated protein kinases. 940

A key step by which tumor necrosis factor (TNF) signals the activation of nuclear factor-kappaB (NF-kappaB) and the stress-activated protein kinase (SAPK, also called c-Jun N-terminal kinase or JNK) is the recruitment to the TNF receptor of TNF receptor-associated factor 2 (TRAF2). However, the subsequent steps in TRAF2-induced SAPK and NF-kappaB activation remain unresolved. Here we report the identification of a TNF-responsive serine/threonine protein kinase termed GCK related (GCKR) that likely signals via mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase kinase 1 (MEKK1) to activate the SAPK pathway. TNF, TRAF2, and ultraviolet (UV) light, which in part uses the TNF receptor signaling pathway, all increased GCKR activity. A TRAF2 mutant, which inhibits both TRAF2-induced NF-kappaB and SAPK activation, blocked TNF-induced GCKR activation. Finally, interference with GCKR expression impeded TRAF2- and TNF-induced SAPK activation but not that of NF-kappaB. This suggests a divergence in the TNF signaling pathway that leads to SAPK and NF-kappaB activation, which is located downstream of TRAF2 but upstream of GCKR.
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PMID:Activation of stress-activated protein kinase/c-Jun N-terminal kinase, but not NF-kappaB, by the tumor necrosis factor (TNF) receptor 1 through a TNF receptor-associated factor 2- and germinal center kinase related-dependent pathway. 940 7

Mitogen-activated protein kinase (MAPK) kinases (MKKs) are dual-specificity protein kinases that phosphorylate and activate MAPK. We have isolated a cDNA encoding a novel protein kinase that has significant homology to MKKs. The novel kinase MKK7 has a nucleotide sequence that encodes an open reading frame of 347 amino acids with 11 kinase subdomains. MKK7 is ubiquitously expressed in all adult and embryonic organs but displays high expression in epithelial tissues at later stages of fetal development. When transiently expressed in 293 cells, MKK7 specifically activated stress-activated protein kinases (SAPKs)/c-Jun N-terminal protein kinases (JNKs) but not extracellular-regulated kinase or p38 kinase. A kinase-negative mutant of MKK7 inhibits interleukin-1beta, lipopolysaccharide, and MEKK1-induced SAPK/JNK activation. Thus, MKK7 is a new member of the MAPK kinase family that functions upstream of SAPK/JNK in the SAPK/JNK signaling pathway.
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PMID:Activation of stress-activated protein kinases/c-Jun N-terminal protein kinases (SAPKs/JNKs) by a novel mitogen-activated protein kinase kinase. 940 46


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