Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RSK2, an ERK downstream kinase, is a novel mediator of skeletal muscle cell differentiation through its regulation of NFAT3 activity. We found that the N-terminal (amino acids (aa) 1-68) and C-terminal (aa 416-674) kinase domains of RSK2 directly interacted with nuclear localization signal 1, the Ser/Pro repeat, and the polyproline domains (aa 261-365) of NFAT3. Upon A23187 stimulation, RSK2 induced nuclear localization of NFAT3. RSK2 phosphorylated NFAT3 in vitro (Km=3.559 microM), and activation of NFAT3 by RSK2 enhanced the promoter activity of NFAT3 downstream target genes in vivo. Furthermore, nuclear accumulation of NFAT3 was attenuated markedly in RSK2-/- cells compared with wild-type RSK2+/+ cells. Notably, RSK2 and NFAT3 induced a significant differentiation of C2C12 myoblasts to multinucleated myotubes. Multinucleated myotube differentiation was inhibited by small interfering RNA against RSK2, ERK1/2, or NFAT3. These results demonstrate that RSK2 is an important kinase for NFAT3 in mediating myotube differentiation.
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PMID:RSK2 mediates muscle cell differentiation through regulation of NFAT3. 1721 2

Double-stranded RNA-dependent protein kinase R (PKR) has been implicated in anti-viral (antitumor) and apoptotic responses. PKR is activated by extracellular stresses and phosphorylates the alpha subunit of protein synthesis initiation factor eIF2, thereby inhibiting protein synthesis and impeding virus multiplication. Phosphorylation of eIF2alpha in mammalian cells has been shown to be increased after ultraviolet (UV) stress and to be required for UV-induced repression of protein translation. UVA is an important etiological factor in skin carcinogenesis and we observed that UVA induced phosphorylation of PKR (Thr(451)) and eIF2alpha (Ser(51)) in mouse skin epidermal JB6 Cl41 cells. The induction was suppressed by the MEK1 inhibitor, PD 98059. UVA stimulation of PKR and eIF2alpha phosphorylation was also inhibited by a dominant-negative mutant (DNM) of ERK2- or RSK2-deficient cells (RSK2(-)). An inhibitor of p38, SB 202190 or a DNM of p38alpha kinase (DNM-p38alpha) suppressed UVA-induced phosphorylation of eIF2alpha (Ser(51)) but had no effect on phosphorylation of PKR (Thr(451)). Our data indicated that phosphorylation of PKR at Thr(451) is mediated through ERK2 and RSK2, but not through p38 kinase, and is involved in the regulation of Ser(51) phosphorylation of eIF2alpha in UVA-irradiated JB6 cells. In vitro and in vivo kinase assays indicated that phosphorylation of eIF2alpha at Ser(51) occurred indirectly through ERK2, RSK2 or p38 kinase in the cellular response to UVA. These data may lead to the use of these signaling molecules as targets to develop more effective chemopreventive agents with fewer side effects to control UV-induced skin cancer.
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PMID:Involvement of ERKs, RSK2 and PKR in UVA-induced signal transduction toward phosphorylation of eIF2alpha (Ser(51)). 1740 96

The tyrosine kinase receptor FGFR3 is thought to play a role in hematopoietic malignancies. A new study in this issue of Cancer Cell identifies the serine/threonine kinase RSK2 as a key substrate of FGFR3 in human t(4;14)-positive multiple myeloma (MM) cells. Constitutively active FGFR3 directly phosphorylates RSK2 on Tyr529, which primes RSK2 for activation by the kinases ERK1 and ERK2 (ERK1/2). In turn, RSK2 activity plays an important role in the survival of FGFR3-expressing MM cells.
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PMID:New insights into RSK activation and hematopoietic cancer. 1778 2

The extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway is essential for infection by a variety of viruses. The p90 ribosomal S6 kinases (RSKs) are direct substrates of ERK and functional mediators of ERK MAPK signaling, but their roles in viral infection have never been examined. We demonstrate that ORF45 of Kaposi's sarcoma-associated herpesvirus (KSHV) interacts with RSK1 and RSK2 and strongly stimulates their kinase activities. The activation of RSK by ORF45 is correlated with ERK activation but does not require MEK. We further demonstrate that RSK1/RSK2 is activated during KSHV primary infection and reactivation from latency; a subset of RSK1/RSK2 is present in the viral replication compartment in the nucleus. Depletion of RSK1/RSK2 by small interfering RNA or the specific inhibitor BI-D1870 suppresses KSHV lytic gene expression and progeny virion production, suggesting an essential role of RSK1/RSK2 in KSHV lytic replication.
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PMID:Activation of p90 ribosomal S6 kinase by ORF45 of Kaposi's sarcoma-associated herpesvirus and its role in viral lytic replication. 1805 34

The ERK pathway responds to extracellular stimuli and oncogenes by modulating cellular processes, including transcription, adhesion, survival, and proliferation. ERK has diverse substrates that carry out these functions. The processes that are modulated are determined in part by the substrates that ERK phosphorylates. We demonstrate that PEA-15 (phosphoprotein enriched in astrocytes, 15 kDa) targets ERK to RSK2 and thereby enhances RSK2 activation. PEA-15 independently bound ERK and RSK2 and increased ERK association with RSK2 in a concentration-dependent manner. PEA-15 increased RSK2 activity and CREB-mediated transcription, and this process was regulated by phosphorylation of PEA-15. Finally, phorbol ester stimulation of PEA-15-null lymphocytes resulted in impaired RSK2 activation that was rescued by exogenous PEA-15 expression. Therefore, PEA-15 functions as a scaffold to enhance ERK activation of RSK2, and this activity is regulated by phosphorylation. Thus, PEA-15 can integrate signal transduction to provide a specific physiological outcome from activation of the multipotent ERK MAP kinase pathway.
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PMID:ERK MAP kinase is targeted to RSK2 by the phosphoprotein PEA-15. 1807 17

Growth factors accelerate G0 to S progression in the cell cycle, however, the roles of growth factors in other cell cycle phases are largely unknown. Here, we show that treatment of HeLa cells with hepatocyte growth factor (HGF) at G2 phase induced the G2/M transition delay as evidenced by FACS analysis as well as by mitotic index and time-lapse analyses. Growth factors such as epidermal growth factor (EGF) and fibroblast growth factor (FGF) also induced G2/M transition delay like HGF. HGF treatment at G2 phase causes a delayed activation of cyclin B1-associated kinase and a diminished nuclear translocation of cyclin B1. Either U0126, a MAPK kinase (MEK) inhibitor, or kinase-dead mutant of ribosomal S6 kinase (RSK) abolished the delay. Additionally, knockdown of RSK1, but not RSK2, with siRNA abrogated the delay, indicating that the extracellular-regulated protein kinase (ERK)-RSK1 mediates the HGF-induced delay. We further found that the delay in G2/M transition of cells expressing oncogenic HGF receptor, M1268T, was abolished by RSK1 knockdown. Intriguingly, we observed that HGF induced chromosomal segregation defects, and depletion of RSK1, but not RSK2, aggravated these chromosomal aberrations. Taken together, the ERK-RSK1 activation by growth factors delays G2/M transition and this might be required to maintain genomic integrity during growth factor stimulation.
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PMID:The ERK-RSK1 activation by growth factors at G2 phase delays cell cycle progression and reduces mitotic aberrations. 1845 Apr 23

The p90 ribosomal S6 kinase (RSK) constitute a family of serine/threonine kinases activated downstream of the Ras/mitogen-activated protein kinase (MAPK) pathway. In mammals, four RSK genes have been identified (RSK1, RSK2, RSK3 and RSK4), and RSK orthologues have also been described in D. melanogaster and C. elegans, but not in yeast or plants. The RSK isoforms are composed of two distinct and functional kinase domains that are activated in a sequential manner by a series of phosphorylation events. These enzymes were among the first substrates of extracellular signal-regulated kinase (ERK) to be discovered and have proven to be ubiquitous and multifunctional mediators of ERK signal transduction. While the RSK isoforms promote cell survival though the inactivation of several apoptotic effectors, they also appear to mediate cell growth and proliferation by simultaneously regulating substrates involved in gene transcription and mRNA translation. RSK1-4 are ubiquitously expressed in cell lines and tissues, and at present, little is known about specific and overlapping functions of individual RSK isoforms. The upregulation of RSK1 and RSK2 expression in different types of cancer suggest that they may be involved in oncogenesis and could potentially be targeted in anti-cancer therapies. The recent identification of specific RSK inhibitors will likely help addressing the biological functions of the RSK isoforms and their contributions in pathological conditions.
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PMID:The RSK factors of activating the Ras/MAPK signaling cascade. 1850 9

In a human cancer cell line, we previously found a mutation in codon 322 of the extracellular signal-regulated kinase (ERK2E322K), the protein showed a faster migration when compared to wild-type in SDS-PAGE and constitutive phosphorylation. However, the reason for the faster migration, and the biochemical and biological properties of the mutation is unknown. In this study, we report that the amino acid charge-change mutation in the common docking (CD) domain is important for fast migration. In vitro binding of ERK2E322K to MKP1 and RSK2 was lost, resulting in constitutive activation and possibly contributing to a more efficient colony formation in soft agar. We established transgenic flies by carrying the corresponding CD domain mutation, DERKE335K, which developed smaller and rougher eyes compared with the wild-type. Taken together, these data are consistent with ERK2E322K loss of contact with downstream effectors and its constitutive activation, presenting an oncogenic potential and weak abnormality in differentiation.
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PMID:ERK2 CD domain mutation from a human cancer cell line enhanced anchorage-independent cell growth and abnormality in Drosophila. 1881 40

Viral infections induce signaling pathways in mammalian cells that stimulate innate immune responses and affect cellular processes, such as apoptosis, mitosis, and differentiation. Here, we report that the ribosomal protein S6 kinase alpha 3 (RSK2), which is activated through the "classical" mitogen-activated protein kinase pathway, plays a role in innate immune responses to influenza virus infection. RSK2 functions in the regulation of cell growth and differentiation but was not known to play a role in the cellular antiviral response. We have found that knockdown of RSK2 enhanced viral polymerase activity and growth of influenza viruses. Influenza virus infection stimulates NK-kappaB- and beta interferon-dependent promoters. This stimulation was reduced in RSK2 knockdown cells, suggesting that RSK2 executes its effect through innate immune response pathways. Furthermore, RSK2 knockdown suppressed influenza virus-induced phosphorylation of the double-stranded RNA-activated protein kinase PKR, a known antiviral protein. These findings establish a role for RSK2 in the cellular antiviral response.
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PMID:Mitogen-activated protein kinase-activated kinase RSK2 plays a role in innate immune responses to influenza virus infection. 1912 53

Our previous findings indicated that RSK2 plays a critical role in proliferation and cell transformation induced by tumor promoters, such as epidermal growth factor or 12-O-tetradecanoylphorbol-13-acetate, and that kaempferol, a natural compound found in edible plants, selectively inhibits RSK2 activity. However, the molecular mechanism for RSK2 activation is unclear. Herein, we provide evidence showing that NH(2)-terminal kinase domain (NTD) activation of RSK2 is required for the activation of the extracellular signal-regulated kinase-mediated COOH-terminal kinase domain (CTD). We also found that the NTD plays a key role in substrate phosphorylation and that kaempferol binds with the NTD but not the CTD in both the active and inactive forms. Homology modeling of the RSK2 NH(2)-terminal domain and small-molecule docking, validated by mutagenesis experiments, clearly showed that Val(82) and Lys(100) are critical amino acids for kaempferol binding and RSK2 activity. Furthermore, immunohistofluorescence and Western blot results indicated that the RSK2 protein level is markedly higher in cancer cell lines as well as cancer tissues compared with nonmalignant cell lines or normal tissues. In addition, kaempferol inhibited proliferation of malignant human cancer cell lines, including A431, SK-MEL-5 and SK-MEL-28, and HCT-116. These results indicate that targeting RSK2 with natural compounds, such as kaempferol, might be a good strategy for chemopreventive or chemotherapeutic application.
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PMID:A regulatory mechanism for RSK2 NH(2)-terminal kinase activity. 1943 96


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