Extracellular Response Kinase Research Articles

Activation of a Ras–MAPK-Dependent Pathway by Epstein–Barr Virus Latent Membrane Protein 1 Is Essential for Cellular Transformation

The latent membrane protein 1 (LMP1) of Epstein–Barr virus (EBV) is the only EBV protein which possesses the properties of an oncogene. In studies initiated to evaluate the mechanisms involved in EBV-induced malignant transformation, the extracellular response kinase (ERK) 1/2 were found to be activated 2 days after EBV infection of purified resting human B cells. Transfection studies in Rat-1 fibroblasts, an established rodent cell line, showed that LMP1 mediates ERK 1/2 activation. Cotransfection experiments with a dominant negative ras mutant demonstrated that such MAPK activation occurs via a ras-dependent pathway. Finally, cotransfection studies showed that ras activation is required for LMP-1-mediated malignant transformation of Rat-1 cells.

Ras-dependent apoptosis correlates with persistent activation of stress-activated protein kinases and induction of isoform(s) of Bcl-x

Ras proteins are signal transducers for many cellular responses. However, it is not well established whether Ras-signaling also contributes to apoptosis. We have constructed H-RasR12-transformed Rat1 fibroblasts using tetracycline operator/repressor (TetO/TetR)-based conditional vectors. Rat1/TetO-RasR12 (Rat1-Ras) cells produced high levels of H-RasR12 protein and exhibited oncogenic transformation. Treatment of Rat1-Ras cells with 0.1% serum triggered massive apoptosis. Rat1-Ras cells expressed increased basal activities of extracellular response kinase (ERK) and p46/p54 stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK). Interestingly, Ras-dependent apoptosis correlated with further persistent activation of both p46 and p54 SAPK/JNK and concurrent inhibition of ERK. Differential modulation of SAPK/JNK and ERK was not detected in tetracycline-treated cells that did not commit apoptosis. Furthermore, two Bcl-x related proteins of 15 kDa and 18 kDa were highly induced in apoptotic Rat1-Ras cells. Our results establish a direct role for Ras in apoptosis, and suggest a functional relationship between H-Ras, SAPK/JNK, ERK and Bcl-x in regulating apoptosis.

Activation of mitogen-activated protein kinase subfamilies by oxidative stress in the perfused rat heart.

Conference Article| November 01 1997 9 Activation of mitogen-activated protein kinase subfamilies by oxidative stress in the perfused rat heart Peter H. SUGDEN; Peter H. SUGDEN 1Division of Cardiac Medicine, Imperial College School of Medicine at N.H.L.I., Dovehouse Street, London SW3 6LY, United Kingdom Search for other works by this author on: This Site PubMed Google Scholar Stephen J. FULLER; Stephen J. FULLER 1Division of Cardiac Medicine, Imperial College School of Medicine at N.H.L.I., Dovehouse Street, London SW3 6LY, United Kingdom Search for other works by this author on: This Site PubMed Google Scholar Ashour MICHAEL; Ashour MICHAEL 1Division of Cardiac Medicine, Imperial College School of Medicine at N.H.L.I., Dovehouse Street, London SW3 6LY, United Kingdom Search for other works by this author on: This Site PubMed Google Scholar Angela CLERK Angela CLERK 1Division of Cardiac Medicine, Imperial College School of Medicine at N.H.L.I., Dovehouse Street, London SW3 6LY, United Kingdom Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1997) 25 (4): S565. https://doi.org/10.1042/bst025s565 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation Peter H. SUGDEN, Stephen J. FULLER, Ashour MICHAEL, Angela CLERK; 9 Activation of mitogen-activated protein kinase subfamilies by oxidative stress in the perfused rat heart. Biochem Soc Trans 1 November 1997; 25 (4): S565. doi: https://doi.org/10.1042/bst025s565 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search Keywords: ERK, extracellularly-responsive kinase, FPLC, fast protein liquid chromatography, GST, glutathione-S-transferase, MAPK, mitogen-activated protein kinase, MAPKAPK2, MAPK-activated protein kinase 2, SAPK/JNK, stress-activated protein kinase/c-Jun N-terminal kinase This content is only available as a PDF. © 1997 Biochemical Society1997 Article PDF first page preview Close Modal You do not currently have access to this content.

MST/MLK2, a Member of the Mixed Lineage Kinase Family, Directly Phosphorylates and Activates SEK1, an Activator of c-Jun N-terminal Kinase/Stress-activated Protein Kinase

c-Jun N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs) are mitogen-activated protein kinase (MAPK)-related protein kinases that are involved in several cellular events, including growth, differentiation, and apoptosis. Mixed lineage kinases (MLKs) form a family of protein kinases sharing two leucine zipper-like motifs and a kinase domain whose primary structure is similar to both the tyrosine-specific and the serine/threonine-specific kinase classes. We have reported that a member of the MLK family, MUK/DLK/ZPK, can activate JNK/SAPK in vivo, and here we show that another member of the MLK family, MST/MLK2, activates JNK/SAPK. Both MUK/DLK/ZPK and MST/MLK2 cause a slight activation of p38/Mpk2 when overexpressed in COS-1 cells, whereas MST/MLK2, but not MUK/DLK/ZPK, activates extracellular response kinase (ERK) to a certain degree. The activity of SEK1/MKK4/JNKK, a MAPK kinase class protein kinase designated as a direct activator of JNK/SAPK, is also induced by MUK/DLK/ZPK or MST/MLK2 overexpression. Furthermore, recombinant MST/MLK2 produced in bacteria directly phosphorylates and activates SEK1/MKK4/JNKK in vitro, showing that MST/MLK2 acts like a MAPK kinase kinase. Taken together, these results suggest that MLK family members are MAPK kinase kinases preferentially acting on the JNK/SAPK pathway.

Nuclear translocation of mitogen-activated protein kinase kinase (MEK1) in response to mitogenic stimulation.

Mitogen-activated protein kinase kinase (MEK) is a dual-specificity protein kinase that is located primarily in the cellular cytosol, both prior to and upon mitogenic stimulation. The existence of a nuclear export signal in the N-terminal domain of MEK [Fukuda, M., Gotoh, I., Gotoh, Y. & Nishida, E. (1996) J. Biol. Chem. 271, 20024-20028] suggests that there are circumstances under which MEK enters the nucleus and must be exported. Using mutants of MEK, we show that the deletion of the nuclear export signal sequence from constitutively active MEK caused constitutive localization of MEK in the nucleus of COS7 and HEK-293T cells. However, when the same region was deleted from a catalytically inactive MEK, cytoplasmic localization was observed in resting cells, which turned nuclear upon stimulation. Confocal microscopy of COS7 cells expressing the above mutants showed localization of the active MEK in the nuclear envelope and also in the cell periphery. The differences in cellular localization between the wild-type and mutant MEKs are not due to severe changes in specificity because the recombinant, constitutively active MEK that lacked its N-terminal region exhibited the same substrate specificity as the wild-type MEK, both in vitro and in intact cells. Taken together, our results indicate that upon mitogenic stimulation, MEK, like extracellular signal responsive kinase and p90(RSK), is massively translocated to the nucleus. Rapid export from the nucleus, which is mediated by the nuclear export signal, is probably the cause for the cytoplasmic distribution observed with wild-type MEK.

Cloning of a Novel Mitogen-activated Protein Kinase Kinase Kinase, MEKK4, That Selectively Regulates the c-Jun Amino Terminal Kinase Pathway

Mitogen-activated protein kinases (MAPKs) are components of sequential kinase cascades that are activated in response to a variety of extracellular signals. Members of the MAPK family include the extracellular response kinases (ERKs or p42/44(MAPK)), the c-Jun amino-terminal kinases (JNKs), and the p38/Hog 1 protein kinases. MAPKs are phosphorylated and activated by MAPK kinases (MKKs or MEKs), which in turn are phosphorylated and activated by MKK/MEK kinases (Raf and MKKK/MEKKs). We have isolated two cDNAs encoding splice variants of a novel MEK kinase, MEKK4. The MEKK4 mRNA is widely expressed in mouse tissues and encodes for a protein of approximately 180 kDa. The MEKK4 carboxyl-terminal catalytic domain is approximately 55% homologous to the catalytic domains of MEKKs 1, 2, and 3. The amino-terminal region of MEKK4 has little sequence homology to the previously cloned MEKK proteins. MEKK4 specifically activates the JNK pathway but not ERKs or p38, distinguishing it from MEKKs 1, 2 and 3, which are capable of activating the ERK pathway. MEKK4 is localized in a perinuclear, vesicular compartment similar to the Golgi. MEKK4 binds to Cdc42 and Rac; kinase-inactive mutants of MEKK4 block Cdc42/Rac stimulation of the JNK pathway. MEKK4 has a putative pleckstrin homology domain and a proline-rich motif, suggesting specific regulatory functions different from those of the previously characterized MEKKs.

MEKKs, GCKs, MLKs, PAKs, TAKs, and Tpls: upstream regulators of the c-Jun amino-terminal kinases?

Regulation of the mitogen-activated protein kinase (MAPK) family members — which include the extracellular response kinases (ERKs), p38/HOG1, and the c-Jun amino-terminal kinases (JNKs) — plays a central role in mediating the effects of diverse stimuli encompassing cytokines, hormones, growth factors and stresses such as osmotic imbalance, heat shock, inhibition of protein synthesis and irradiation. A rapidly increasing number of kinases that activate the JNK pathways has been described recently, including the MAPK/ERK kinase kinases, p21-activated kinases, germinal center kinase, mixed lineage kinases, tumor progression locus 2, and TGF-β-activated kinase. Thus, regulation of the JNK pathway provides an interesting example of how many different stimuli can converge into regulating pathways critical for the determination of cell fate.

Jun N-terminal Kinase Mediates Activation of Skeletal Muscle Glycogen Synthase by Insulin in Vivo

Mitogen-activated protein kinases (MAPKs) represent a conserved family of Ser/Thr protein kinases with central roles in intracellular signaling. Activation of three prominent members of the MAPK family, i.e. extracellular response kinases (ERK), jun N-terminal kinase (JNK), and p38, was defined in vivo in order to establish their role, if any, in the cardinal response of skeletal muscle to insulin, the activation of glycogen synthesis. Insulin was found to activate ERK, JNK, and p38 in skeletal muscle. The time courses for activation of the three MAPKs by insulin, however, are distinctly different. Activation of JNK occurs most rapidly, within seconds. Activation of p38 by insulin follows that of JNK, within minutes. Activation of ERK occurs last, 4 min after administration of insulin. The temporal relationship between the activation of ERK, JNK, p38 and the downstream elements p90(rsk) and PP-1 in vivo suggest that JNK, but neither ERK nor p38 MAPKs, mediates insulin activation of glycogen synthase in vivo. Activation of JNK by anisomycin in vivo mimics activation of glycogen synthase by insulin. Challenge by anisomycin and insulin, in combination, are not additive, suggesting a common mode of glycogen synthase activation. The p90(rsk) isoform rapidly activated by insulin is identified as RSK3. In addition, RSK3 can be activated by JNK in vitro. Based upon these data a signal linkage map for activation of glycogen synthase in vivo in skeletal muscle can be constructed in which JNK mediates activation of glycogen synthase via RSK3.