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MAP Kinase Kinase (map + kinase_kinase)
Selected AbstractsActivation of p21-activated kinase 1 is required for lysophosphatidic acid-induced focal adhesion kinase phosphorylation and cell motility in human melanoma A2058 cellsFEBS JOURNAL, Issue 8 2004In Duk Jung Lysophosphatidic acid (LPA), one of the naturally occurring phospholipids, stimulates cell motility through the activation of Rho family members, but the signaling mechanisms remain to be elucidated. In the present study, we investigated the roles of p21-activated kinase 1 (PAK1) on LPA-induced focal adhesion kinase (FAK) phosphorylation and cell motility. Treatment of human melanoma cells A2058 with LPA increased phosphorylation and activation of PAK1, which was blocked by treatment with pertussis toxin and by inhibition of phosphoinositide 3-kinase (PI3K) with an inhibitor LY294002 or by overexpression of catalytically inactive mutant of PI3K,, indicating that LPA-induced PAK1 activation was mediated via a Gi protein and the PI3K, signaling pathway. In addition, we demonstrated that Rac1/Cdc42 signals acted as upstream effector molecules of LPA-induced PAK activation. However, Rho-associated kinase, MAP kinase kinase 1/2 or phospholipase C might not be involved in LPA-induced PAK1 activation or cell motility stimulation. Furthermore, PAK1 was necessary for FAK phosphorylation by LPA, which might cause cell migration, as transfection of the kinase deficient mutant of PAK1 or PAK auto-inhibitory domain significantly abrogated LPA-induced FAK phosphorylation. Taken together, these findings strongly indicated that PAK1 activation was necessary for LPA-induced cell motility and FAK phosphorylation that might be mediated by sequential activation of Gi protein, PI3K, and Rac1/Cdc42. [source] A mouse embryonic stem cell model of Schwann cell differentiation for studies of the role of neurofibromatosis type 1 in Schwann cell development and tumor formationGLIA, Issue 11 2007Therese M. Roth Abstract The neurofibromatosis Type 1 (NF1) gene functions as a tumor suppressor gene. One known function of neurofibromin, the NF1 protein product, is to accelerate the slow intrinsic GTPase activity of Ras to increase the production of inactive rasGDP, with wide-ranging effects on p21ras pathways. Loss of neurofibromin in the autosomal dominant disorder NF1 is associated with tumors of the peripheral nervous system, particularly neurofibromas, benign lesions in which the major affected cell type is the Schwann cell (SC). NF1 is the most common cancer predisposition syndrome affecting the nervous system. We have developed an in vitro system for differentiating mouse embryonic stem cells (mESC) that are NF1 wild type (+/+), heterozygous (+/,), or null (,/,) into SC-like cells to study the role of NF1 in SC development and tumor formation. These mES-generated SC-like cells, regardless of their NF1 status, express SC markers correlated with their stage of maturation, including myelin proteins. They also support and preferentially direct neurite outgrowth from primary neurons. NF1 null and heterozygous SC-like cells proliferate at an accelerated rate compared to NF1 wild type; this growth advantage can be reverted to wild type levels using an inhibitor of MAP kinase kinase (Mek). The mESC of all NF1 types can also be differentiated into neuron-like cells. This novel model system provides an ideal paradigm for studies of the role of NF1 in cell growth and differentiation of the different cell types affected by NF1 in cells with differing levels of neurofibromin that are neither transformed nor malignant. © 2007 Wiley-Liss, Inc. [source] Signalling events involved in interferon-,-inducible macrophage nitric oxide generationIMMUNOLOGY, Issue 4 2003Julie Blanchette Summary Nitric oxide (NO) produced by macrophages (M,) in response to interferon-, (IFN-,) plays a pivotal role in the control of intracellular pathogens. Current knowledge of the specific biochemical cascades involved in this IFN-,-inducible M, function is still limited. In the present study, we evaluated the participation of various second messengers , Janus kinase 2 (JAK2), signal transducer and activator of transcription (STAT) 1,, MAP kinase kinase (MEK1/2), extracellular signal-regulated kinases 1 and 2 (Erk1/Erk2) and nuclear factor kappa B (NF-,B) , in the regulation of NO production by IFN-,-stimulated J774 murine M,. The use of specific signalling inhibitors permitted us to establish that JAK2/STAT1,- and Erk1/Erk2-dependent pathways are the main players in IFN-,-inducible M, NO generation. To determine whether the inhibitory effect was taking place at the pre- and/or post-transcriptional level, we evaluated the effect of each antagonist on inducible nitric oxide synthase (iNOS) gene and protein expression, and on the capacity of IFN-, to induce JAK2, Erk1/Erk2 and STAT1, phosphorylation. All downregulatory effects occurred at the pretranscriptional level, except for NF-,B, which seems to exert its role in NO production through an iNOS-independent event. In addition, electrophoretic mobility shift assay (EMSA) analysis revealed that STAT1, is essential for IFN-,-inducible iNOS expression and NO production, whereas the contribution of NF-,B to this cellular regulation seems to be minimal. Moreover, our data suggest that Erk1/Erk2 are responsible for STAT1, Ser727 residue phosphorylation in IFN-,-stimulated M,, thus contributing to the full activation of STAT1,. Taken together, our results indicate that JAK2, MEK1/2, Erk1/Erk2 and STAT1, are key players in the IFN-,-inducible generation of NO by M,. [source] Regulation of axotomy-induced dopaminergic neuron death and c-Jun phosphorylation by targeted inhibition of cdc42 or mixed lineage kinaseJOURNAL OF NEUROCHEMISTRY, Issue 2 2006Stephen J. Crocker Abstract Mechanical transection of the nigrostriatal dopamine pathway at the medial forebrain bundle (MFB) results in the delayed degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc). We have previously demonstrated that c-Jun activation is an obligate component of neuronal death in this model. Here we identified the small GTPase, cdc42, and mixed lineage kinases (MLKs) as upstream factors regulating neuronal loss and activation of c-Jun following MFB axotomy. Adenovirus-mediated expression of a dominant-negative form of cdc42 in nigral neurons blocked MFB axotomy-induced activation (phosphorylation) of MAP kinase kinase 4 (MKK4) and c-Jun, resulting in attenuation of SNpc neuronal death. Pharmacological inhibition of MLKs, MKK4-activating kinases, significantly reduced the phosphorylation of c-Jun and abrogated dopaminergic neuronal degeneration following MFB axotomy. Taken together, these findings suggest that death of nigral dopaminergic neurons following axotomy can be attenuated by targeting cell signaling events upstream of c-Jun N-terminal mitogen-activated protein kinase/c-Jun. [source] Induction of insulin-like growth factor-I by interleukin-17F in bronchial epithelial cellsCLINICAL & EXPERIMENTAL ALLERGY, Issue 7 2010M. Kawaguchi Summary Cite this as: M. Kawaguchi, J. Fujita, F. Kokubu, G. Ohara, S-K Huang, S. Matsukura, Y. Ishii, M. Adachi, H. Satoh and N. Hizawa, Clinical & Experimental Allergy, 2010 (40) 1036,1043. Background Increased expression of IL-17F has been noted in the airway of asthmatic patients, but its role in asthma has not been fully elucidated. Insulin-like growth factor-I (IGF-I) is known to be involved in airway remodelling and inflammation, while its regulatory mechanisms remain to be defined. Objective To further clarify the biological function of IL-17F, we investigated whether IL-17F is able to regulate the expression of IGF-I in bronchial epithelial cells. Methods Bronchial epithelial cells were stimulated with IL-17F in the presence or absence of T-helper type 2 cytokines. Various kinase inhibitors were added to the culture to identify the key signalling events leading to the expression of IGF-I, in conjunction with the use of short interfering RNAs (siRNAs) targeting mitogen- and stress-activated protein kinase (MSK) 1, p90 ribosomal S6 kinase (p90RSK), and cyclic AMP response element-binding protein (CREB). Results IL-17F significantly induced IGF-I gene and protein expression, and co-stimulation with IL-4 and IL-13 augmented its production. MAP kinase kinase (MEK) inhibitors and the Raf1 kinase inhibitor significantly inhibited IGF-I production, and the combination of PD98059 and Raf1 kinase inhibitor showed further inhibition. Overexpression of Raf1 and Ras dominant-negative mutants inhibited its expression. MSK1 inhibitors significantly blocked IL17F-induced IGF-I expression. Moreover, transfection of the siRNAs targeting MSK1, p90RSK, and CREB blocked its expression. Conclusions In bronchial epithelial cells, IL-17F is able to induce the expression of IGF-I via the Raf1,MEK1/2,ERK1/2,MSK1/p90RSK,CREB pathway in vitro. [source] Expression of the MAPK kinases MKK-4 and MKK-7 in rheumatoid arthritis and their role as key regulators of JNKARTHRITIS & RHEUMATISM, Issue 9 2003Monisha Sundarrajan Objective The mitogen-activated protein (MAP) kinase JNK is a key regulator of interleukin-1 (IL-1),induced collagenase gene expression and joint destruction in arthritis. Two upstream kinases, MKK-4 and MKK-7, have been identified as potential activators of JNK. However, the role of MAP kinase kinases (MAPKKs) and their functional organization within fibroblast-like synoviocytes (FLS) have not been defined. We therefore evaluated the interactions between the various MAP kinase components and determined their subcellular localization. Methods MKKs were identified by immunohistochemistry of rheumatoid arthritis (RA) and osteoarthritis (OA) synovium. Western blotting was used to determine the expression of FLS. Immunoprecipitation experiments using antibodies specific for MKK-4, MKK-7, and JNK were performed. Phosphospecific antibodies and immunohistochemistry were used to evaluate the activation state of synovial MKK-4 and MKK-7. Confocal microscopy was used to determine the subcellular location of the kinases. Results Immunohistochemistry studies demonstrated abundant MKK-4 and MKK-7 in RA and OA synovium, but the levels of phosphorylated kinases were significantly higher in RA synovium. MKK-4 and MKK-7 were constitutively expressed by cultured RA and OA FLS, and IL-1 stimulation resulted in rapid phosphorylation of both kinases. JNK was detected in MKK-4 and MKK-7 immunoprecipitates. Furthermore, MKK-4 coprecipitated with MKK-7 and vice versa, indicating that the 3 kinases form a stable complex in FLS. Confocal microscopy confirmed that JNK, MKK-4, and MKK-7 colocalized in the cytoplasm, with JNK migrating to the nucleus after IL-1 stimulation. The signal complex containing MKK-4, MKK-7, and JNK was functionally active and able to phosphorylate c-Jun after IL-1 stimulation of FLS. Conclusion These studies demonstrate that JNK, MKK-4, and MKK-7 form an active signaling complex in FLS. This novel JNK signalsome is activated in response to IL-1 and migrates to the nucleus. The JNK signalsome represents a new target for therapeutic interventions designed to prevent joint destruction. [source] | |||||||||||||