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)

The small Ras-related GTPase, TC10, has been classified on the basis of sequence homology to be a member of the Rho family. This family, which includes the Rho, Rac and CDC42 subfamilies, has been shown to regulate a variety of apparently diverse cellular processes such as actin cytoskeletal organization, mitogen-activated protein kinase (MAPK) cascades, cell cycle progression and transformation. In order to begin a study of TC10 biological function, we expressed wild type and various mutant forms of this protein in mammalian cells and investigated both the intracellular localization of the expressed proteins and their abilities to stimulate known Rho family-associated processes. Wild type TC10 was located predominantly in the cell membrane (apparently in the same regions as actin filaments), GTPase defective (75L) and GTP-binding defective (31N) mutants were located predominantly in cytoplasmic perinuclear regions, and a deletion mutant lacking the carboxyl terminal residues required for post-translational prenylation was located predominantly in the nucleus. The GTPase defective (constitutively active) TC10 mutant: (1) stimulated the formation of long filopodia; (2) activated c-Jun amino terminal kinase (JNK); (3) activated serum response factor (SRF)-dependent transcription; (4) activated NF-kappaB-dependent transcription; and (5) synergized with an activated Raf-kinase (Raf-CAAX) to transform NIH3T3 cells. In addition, wild type TC10 function is required for full H-Ras transforming potential. We demonstrate that an intact effector domain and carboxyl terminal prenylation signal are required for proper TC10 function and that TC10 signals to at least two separable downstream target pathways. In addition, TC10 interacted with the actin-binding and filament-forming protein, profilin, in both a two-hybrid cDNA library screen, and an in vitro binding assay. Taken together, these data support a classification of TC10 as a member of the Rho family, and in particular, suggest that TC10 functions to regulate cellular signaling to the actin cytoskeleton and processes associated with cell growth.
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PMID:Cellular functions of TC10, a Rho family GTPase: regulation of morphology, signal transduction and cell growth. 1044 46

A putative Akt kinase phosphorylation site ((64)ydRIRplSYp(73)) was found in Rac1/CDC42 and Rho family proteins (RhoA, RhoB, RhoC, and RhoG). Phosphorylation of Rac1 by Akt kinase was assayed with recombinant Rac1 protein and the fluorescein-labeled Rac1 peptide. It was shown that the Rac1 peptide and the recombinant protein were phosphorylated by the activated recombinant Akt kinase and the lysate of SK-MEL28 cells, a human melanoma cell line. The phosphorylation of Rac1 inhibited its GTP-binding activity without any significant change in GTPase activity. Both the GTP-binding and GTPase activities of Rac1 S71A protein (with the serine residue to be phosphorylated replaced with alanine) were abolished regardless of the treatment of Akt kinase. Akt kinase activity and Rac1 peptide phosphorylation were down-regulated by the treatment of SK-MEL28 cells with wortmannin or LY294002 (a phosphoinositide 3-kinase inhibitor), but JNK/SAPK kinase activity was up-regulated. Thus, the results suggest that Akt kinase of the phosphoinositide 3-kinase signal transduction pathway phosphorylates serine 71 of Rac1 as one of its authentic substrates and modulates the Rac1 signal transduction pathway through phosphorylation.
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PMID:Akt protein kinase inhibits Rac1-GTP binding through phosphorylation at serine 71 of Rac1. 1061 34

G-protein-coupled receptors (GPCRs) are a large group of integral membrane receptors that transmit signals from a diverse array of external stimuli, including neurotransmitters, hormones, phospholipids, photons, odorants and taste ligands. In response to ligand binding, the GPCRs initiate diverse downstream signaling pathways through four groups of G proteins and other interacting proteins. Key components in GPCR-induced intracellular signaling are four groups of mitogen-activated protein kinase (MAPK) cascades: extracellular signal-related kinase (ERK), Jun N-terminal kinase (JNK), p38MAPK and big MAPK (BMK). The hallmark of MAPK signaling is the stimulation-dependent nuclear translocation of the involved kinases, which regulate gene expression and the cytoplasmic acute response to mitogenic, stress-related, apoptotic and survival stimuli. A special type of GPCR is the gonadotropin-releasing hormone (GnRH) receptor, which uses primarily the Gq protein for its downstream signaling. GnRH activates all four MAPK cascades by a PKC-dependent mechanism. Common signaling molecules, including the tyrosine kinase c-SRC and the small GTPases CDC42, RAC and RAS, are implicated in various aspects of the GnRH-MAPK pathways. Thus, the activation of MAPK cascades by GnRH opens a new vista in the understanding of the transcriptional regulation of genes encoding gonadotropins. However, additional studies on cell lines and whole animals are required to understand GnRH signaling in the context of other hormones during the reproductive cycle of mouse and human.
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PMID:Activation of MAPK cascades by G-protein-coupled receptors: the case of gonadotropin-releasing hormone receptor. 1070 49

CDC42 encodes a highly conserved GTPase of the Rho family that is best known for its role in regulating cell polarity and actin organization. In addition, various studies of both yeast and mammalian cells have suggested that Cdc42p, through its interaction with p21-activated kinases (PAKs), plays a role in signaling pathways that regulate target gene transcription. However, recent studies of the yeast pheromone response pathway suggested that prior results with temperature-sensitive cdc42 mutants were misleading and that Cdc42p and the Cdc42p-PAK interaction are not involved in signaling. To clarify this issue, we have identified and characterized novel viable pheromone-resistant cdc42 alleles that retain the ability to perform polarity-related functions. Mutation of the Cdc42p residue Val36 or Tyr40 caused defects in pheromone signaling and in the localization of the Ste20p PAK in vivo and affected binding to the Ste20p Cdc42p-Rac interactive binding (CRIB) domain in vitro. Epistasis analysis suggested that they affect the signaling step at which Ste20p acts, and overproduction of Ste20p rescued the defect. These results suggest that Cdc42p is in fact required for pheromone response and that interaction with the PAK Ste20p is critical for that role. Furthermore, the ste20DeltaCRIB allele, previously used to disrupt the Cdc42p-Ste20p interaction, behaved as an activated allele, largely bypassing the signaling defect of the cdc42 mutants. Additional observations lead us to suggest that Cdc42p collaborates with the SH3-domain protein Bem1p to facilitate signal transduction, possibly by providing a cell surface scaffold that aids in the local concentration of signaling kinases, thus promoting activation of a mitogen-activated protein kinase cascade by Ste20p.
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PMID:Role of Cdc42p in pheromone-stimulated signal transduction in Saccharomyces cerevisiae. 1100 52

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) promotes its function primarily by activating two receptor tyrosine kinases, Flt-1 (VEGFR-1) and KDR (VEGFR-2). Recently, it has been shown that KDR is responsible for VPF/VEGF-stimulated endothelial cell (EC) proliferation and migration, whereas Flt-1 activation down-modulates KDR-mediated EC proliferation. Although KDR-mediated EC proliferation and migration have been extensively studied, much less is known about Flt-1-mediated antiproliferation. Here, we demonstrate that Flt-1-mediated antiproliferative activity can be blocked completely by the dominant negative mutant of CDC42 (CDC42-17N) and partially by a Rac1 dominant negative mutant (Rac1-17N) but is not affected by a RhoA dominant negative mutant (RhoA-19N). Both CDC42-17N and Rac1-17N increase the intracellular Ca(2+) mobilization in response to VPF/VEGF but have no effect on KDR and MAPK phosphorylation. Using the chimeric-receptor EGLT in which the extracellular domain of epidermal growth factor receptor was fused to the transmembrane and intracellular domains of Flt-1, we also demonstrate that CDC42 and Rac1 are activated by EGLT. Previously, we showed that phosphatidylinositol 3-kinase is required for Flt-1-mediated antiproliferative activity, but phospholipase C is not required. As expected, CDC42 and Rac1 activation mediated by EGLT can be completely inhibited by PI3K inhibitors, wortmannin and LY294002, and the p85 dominant negative mutant but not by either the phospholipase C inhibitor, or an intracellular Ca(2+) chilator BAPTA/AM. Surprisingly, pertussis toxin and overexpression of the free Gbetagamma-specific sequestering minigene hbetaARK1(495) also inhibit EGLT-mediated CDC42 and Rac1 activation completely. Moreover, pertussis toxin treatment also increases the intracellular Ca(2+) mobilization and inhibits the antiproliferation activity, thus suggesting that pertussis toxin-sensitive G proteins and the Gbetagamma subunits are involved in the signaling pathway of Flt-1 that down-regulates EC proliferation. Taken together, these results further expand our understanding of Flt-1-mediated antiproliferative activity in VPF/VEGF-stimulated endothelium.
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PMID:Flt-1-mediated down-regulation of endothelial cell proliferation through pertussis toxin-sensitive G proteins, beta gamma subunits, small GTPase CDC42, and partly by Rac-1. 1172 72

The hypothalamic gonadotropin-releasing hormone (GnRH) is a key regulator of the reproductive system, triggering the synthesis and release of LH and FSH in the pituitary. GnRH transmits its signal via two specific serpentine receptors that belong to the large group of G-protein coupled receptors (GPCRs). Here we review the intracellular signaling pathways mediated by the GnRH receptor (GnRHR). In pituitary-derived alpha T3-1 cells, a widely used model for GnRH action, GnRHR signaling includes activation of mitogen-activated protein kinase (MAPK) cascades, which provide an important link for the transmission of signals from the cell surface to the nucleus and play a role in the regulation of gonadotropin transcription. Activation of ERK--one of the MAPK cascades--by GnRH in these cells depends mainly on the phosphorylation of Raf1 by PKC, supported by a pathway involving c-Src, dynamin, and Ras. On the other hand, the activation of JNK, another MAPK cascade, involves PKC, c-Src, CDC42/Rac1, and probably MEKK1. The GnRHR is also expressed in non-pituitary cells and was found to be involved in the inhibition of cell proliferation in certain cells. Therefore, GnRHR represents a potential target for GnRH-analogs used for cancer treatment. Interestingly, the signaling mechanism of the GnRHR in other cell types significantly differs from that in pituitary cells. Studies conducted in GnRHR-expressing COS7 cells have shown that GnRHR transmits its signals mainly via Gi, EGF receptor, c-Src, and is not dependent on PKC. Understanding the signaling mechanisms elicited by GnRHR can shed light on the mechanism of action of GnRH in pituitary and extra-pituitary tissues.
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PMID:Intracellular signaling pathways mediated by the gonadotropin-releasing hormone (GnRH) receptor. 1175 Jul 25

The role of ERK and Jun N-terminal kinase (JNK) in basal- and GnRH-stimulated LHbeta-promoter activity was examined in the gonadotroph cell line LbetaT-2. GnRH agonist (GnRH-A) stimulates the MAPK cascades ERK, JNK, and p38MAPK, with a peak at 7 min for ERK and at 60 min for JNK and p38MAPK. The rat glycoprotein hormone LHbeta-subunit promoter, linked to the chloramphenicol acetyl transferase (CAT) reporter gene, was used to follow its activation. Addition of GnRH-A (10 nM) to LbetaT-2 cells resulted in a 6-fold increase in LHbeta-CAT activity at 8 h, which was markedly reduced by a GnRH antagonist. The PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA), but not the Ca(2+) ionophore ionomycin, stimulated LHbeta-CAT activity. Addition of GnRH-A and TPA together did not produce an additive response. Down-regulation of PKC, but not removal of Ca(2+), abolished the GnRH-A and the TPA response. Cotransfection of the LHbeta-promoter and the constitutively active form of Raf-1 stimulated basal and GnRH-A-induced LHbeta-CAT activity. The dominant negative forms of the ERK cascade members Ras, Raf-1, and MAPK/ERK kinase (MEK) markedly reduced basal and GnRH-A-induced LHbeta-CAT activity, Similar results were obtained with the MEK inhibitor PD 098059. Cotransfection of the LHbeta-promoter and the constitutively active CDC42 stimulated basal and GnRH-A-induced LHbeta-CAT activity. The dominant negative forms of the JNK cascade members Rac, CDC42, and SEK markedly diminished basal and GnRH-A-induced LHbeta-CAT activity. Interestingly, the constitutively active form of c-Src stimulated the basal and the GnRH-A response, whereas the dominant negative form of c-Src, or the c-Src inhibitor PP1 diminished basal and the GnRH-A response. We conclude that ERK and JNK are involved in basal and GnRH-A stimulation of LHbeta-CAT activity. c-Src participates also in LHbeta-promoter activation by a mechanism which might be linked to ERK and JNK activation.
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PMID:Activation of MAPK cascades by GnRH: ERK and Jun N-terminal kinase are involved in basal and GnRH-stimulated activity of the glycoprotein hormone LHbeta-subunit promoter. 1186 27

WNT signals are transduced to the JNK pathway, the Ca2+-releasing pathway, or the beta-catenin - TCF pathway through seven-transmembrane-type WNT receptors encoded by Frizzled genes (FZD1-FZD10). WRCH1/ARHV and CDC42 are potentially implicated in the WNT-JNK pathway. Here, WRCH2/ARHV cDNAs were isolated by using bioinformatics and cDNA-PCR. WRCH2 gene, consisting of at least 3 exons, encoded a 236-amino-acid protein with proline-rich domain and GTPase domain. WRCH2 was homologous to WRCH1 (55.4% total-amino-acid identity) and CDC42 (43.5% total-amino-acid identity). WRCH2 gene was located on human chromosome 15q15, which is one of fragile sites in the human genome. A single nucleotide substitution (632 Gright curved arrow A) was identified between WRCH2 cDNA and human genome draft sequences, which resulted in Arg177Lys amino-acid substitution. WRCH2 mRNA was relatively highly expressed in pancreas, placenta, and fetal brain. WRCH2 mRNA was over-expressed in TMK1 (gastric cancer), Hs700T (pancreatic cancer), HeLa S3 (cervical cancer), and A549 (lung cancer). WRCH2 mRNA was moderately expressed in MKN74, MKN45, MKN28, KATO-III (gastric cancer), HL-60 (pro-myelocytic leukemia), Raji (Burkitt's lymphoma), and SW480 (colorectal cancer). WRCH2 mRNA was up-regulated in 3 out of 8 cases of primary gastric cancer. Because Wrch1 can activate PAK1 and JNK1, and induce filopodium formation and stress fiber dissolution, over-expression of WRCH2 mRNA in human cancer cells might also lead to more malignant phenotype.
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PMID:Molecular cloning and characterization of WRCH2 on human chromosome 15q15. 1195 92

The p21-activated kinase (PAK) family of protein kinases has recently attracted considerable attention as an effector of Rho family of small G proteins and as an upstream regulator of MAPK signalling pathways during cellular events such as re-arrangement of the cytoskeleton and apoptosis. We have cloned a novel human PAK family kinase that has been designated as PAK5. PAK5 contains a CDC42/Rac1 interactive binding (CRIB) motif at the N-terminus and a Ste20-like kinase domain at the C-terminus. PAK5 is structurally most related to PAK4 and PAK6 to make up the PAK-II subfamily. We have shown that PAK5 preferentially binds to CDC42 in the presence of GTP and that CRIB motif is essential for this interaction. PAK5 is a functional protein kinase but unlike PAK-I family kinases (PAK1, 2, and 3), the kinase activity of PAK5 does not seem to require the binding of CDC42. Overexpression of PAK5 activates the JNK kinase pathway but not p38 or ERK pathways. PAK5 transcript is predominantly expressed in brain as revealed by Northern blot and in situ hybridization. The expression pattern of PAK5 is distinct from that of PAK4 and PAK6, suggesting a functional division among PAK-II subfamily kinases based on differential tissue distribution.
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PMID:Cloning and characterization of PAK5, a novel member of mammalian p21-activated kinase-II subfamily that is predominantly expressed in brain. 1203 33

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) functions by activating two receptor tyrosine kinases, Flt-1 (VEGFR-1) and KDR (VEGFR-2), both of which are selectively expressed on the primary vascular endothelium. KDR is responsible for VPF/VEGF-stimulated endothelial cell (EC) proliferation and migration, whereas Flt-1 down-modulates KDR-mediated EC proliferation. Flt-1 mediates down-regulation of EC proliferation through pertussis toxin-sensitive G proteins, betagamma subunits, small GTPase CDC42, and partly by Rac-1. However, the molecular mechanism by which KDR mediates EC migration is not clear yet. Here we show for the first time that activation of RhoA and Rac1 is fully and partially required for KDR-mediated human umbilical vein endothelial cell (HUVEC) migration, respectively, and that CDC42, however, is not involved. Furthermore, overexpression of the RhoA dominant negative mutant RhoA-19N does not affect VPF/VEGF-stimulated KDR phosphorylation, intracellular Ca(2+) mobilization, and mitogen-activated protein kinase phosphorylation. Utilizing the receptor chimeras (EGDR and EGLT) in which the extracellular domain of the epidermal growth factor receptor (EGFR) was fused to the transmembrane domain and the intracellular domains of KDR and Flt-1, respectively, we demonstrate that RhoA activation is mediated by EGDR, not by EGLT, and that EGDR mediates activation of Rac1, not CDC42. Furthermore, the EGDR-mediated RhoA and Rac1 activation is regulated by G proteins Gq/11, Gbetagamma, and phospholipase C independent of phosphatidylinositol 3-kinase and intracellular Ca(2+) mobilization. Interestingly, the RhoA activation can be partially inhibited by overexpression of Rac1-17N, but overexpression of RhoA-19N has no effect on Rac1 activation. Finally, Gq/11 and Gbetagamma subunits are also required for VPF/VEGF-stimulated HUVEC migration. Taken together, our results indicate that KDR stimulates endothelial cell migration through a heterotrimeric G protein Gq/11 and Gbetagamma-mediated RhoA pathway.
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PMID:KDR stimulates endothelial cell migration through heterotrimeric G protein Gq/11-mediated activation of a small GTPase RhoA. 1224 99


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