Gene/Protein Disease Symptom Drug Enzyme Compound
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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 GTPases Cdc42, Rac and RhoA have important regulatory roles in mediating cytoskeletal rearrangements, MAP kinase cascades and induction of G1 cell cycle progression. The activity of the GTPases is regulated by guanine nucleotide exchange factors (GEFs) which accelerate their GDP/GTP exchange rate, and thereby activate them. All the GEFs for the Rho-GTPases family share two conserved domains: the DH domain (for Dbl-homology domain) responsible for the enzymatic activity, and the PH domain, probably responsible for the proper localization of the molecule. Trio is a multifunctional protein that is comprised of two functional Rho-GEFs domains and a serine/threonine kinase domain. We have shown in vitro and in vivo that the first GEF domain (GEFD1) activates Rac1, while the second GEF domain (GEFD2) acts on RhoA. Moreover, the co-expression of both domains induces simultaneously the activation of both GTPases. To our knowledge, this is the first example of a member of the Rho-GEF family, that contains two functional exchange factor domains, with restricted and different specificity. We are currently investigating how these GEF domains are activated, by addressing the role of the PH domains in GTPases activation by Trio. We have shown that: 1) the PH1 of Trio is necessary for Rac activation by the GEFD1; 2) the PH1 of Trio targets the molecule to the cytoskeleton; 3) the GEFD1 domain of Trio binds, in a two-hybrid screen, the actin binding protein filamin. These data suggest that the PH1 targets Trio to the cytoskeleton close to Rac and its effectors, probably via interaction with the actin-binding protein filamin, consistent with a role of Trio in actin cytoskeleton remodeling.
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PMID:[Role of the multifunctional Trio protein in the control of the Rac1 and RhoA gtpase signaling pathways]. 975 78

Adherent cells assemble fibronectin into a fibrillar matrix on their apical surface. The fibril formation is initiated by fibronectin binding to the integrins alpha5 beta1 and alphav beta3, and is completed by a process that includes fibronectin self-assembly. We found that a 76- amino acid fragment of fibronectin (III1-C) that forms one of the self-assembly sites caused disassembly of preformed fibronectin matrix without affecting cell adhesion. Treating attached fibroblasts or endothelial cells with III1-C inhibited cell migration and proliferation. Rho-dependent stress fiber formation and Rho-dependent focal contact protein phosphorylation were also inhibited, whereas Cdc42 was activated, leading to actin polymerization into filopodia. ACK (activated Cdc42-binding kinase) and p38 MAPK (mitogen-activated protein kinase), two downstream effectors of Cdc42, were activated, whereas PAK (p21-activated kinase) and JNK/SAPK (c-Jun NH2-terminal kinase/ stress-activated protein kinase) were inhibited. III1-C treatment also modulated activation of JNK and ERK (extracellular signal-regulated kinases) in response to growth factors, and reduced the activity of the cyclin E-cdk2 complex. These results indicate that the absence of fibronectin matrix causes activation of Cdc42, and that fibronectin matrix is required for Rho activation and cell cycle progression.
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PMID:Fibronectin matrix regulates activation of RHO and CDC42 GTPases and cell cycle progression. 976 37

Adenovirus (Ad) endocytosis via alphav integrins requires activation of the lipid kinase phosphatidylinositol-3-OH kinase (PI3K). Previous studies have linked PI3K activity to both the Ras and Rho signaling cascades, each of which has the capacity to alter the host cell actin cytoskeleton. Ad interaction with cells also stimulates reorganization of cortical actin filaments and the formation of membrane ruffles (lamellipodia). We demonstrate here that members of the Rho family of small GTP binding proteins, Rac and CDC42, act downstream of PI3K to promote Ad endocytosis. Ad internalization was significantly reduced in cells treated with Clostridium difficile toxin B and in cells expressing a dominant-negative Rac or CDC42 but not a H-Ras protein. Viral endocytosis was also inhibited by cytochalasin D as well as by expression of effector domain mutants of Rac or CDC42 that impair cytoskeletal function but not JNK/MAP kinase pathway activation. Thus, Ad endocytosis requires assembly of the actin cytoskeleton, an event initiated by activation of PI3K and, subsequently, Rac and CDC42.
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PMID:Adenovirus endocytosis requires actin cytoskeleton reorganization mediated by Rho family GTPases. 976 25

Endothelium of the cerebral blood vessels, which constitutes the blood-brain barrier, controls leukocyte adhesion and trafficking to the brain. Investigating signaling pathways triggered by the engagement of adhesion molecules expressed on brain endothelial cells, we report here that ICAM-1 cross-linking induces tyrosine phosphorylation of three cytoskeleton-associated proteins: focal adhesion kinase, paxillin, and p130Cas (Cas), which are found to associate as complexes. Tyrosine-phosphorylated Cas associates with the adaptor protein Crk and the GTP exchange factor C3G. In the same conditions the small G protein Rho was activated, as shown by the increase in its GTP loading. In addition, tyrosine phosphorylation of focal adhesion kinase, paxillin, and Cas as well as triggering of the Crk signaling pathway are blocked by pretreatment of the cells with the exoenzyme C3, a specific Rho inhibitor. C3-sensitive activation of the c-Jun N-terminal kinase in response to ICAM-1 cross-linking is also observed, whereas no significant activation of Ras or of the extracellular signal-regulated kinase was detected. In conclusion, these results suggest that through coupling to Rho activation and phosphorylation of cytoskeletal proteins and transcription factors, ICAM-1 cross-linking participates in the cell shape changes and gene regulation that may accompany lymphocyte migration through the blood-brain barrier.
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PMID:ICAM-1 signaling pathways associated with Rho activation in microvascular brain endothelial cells. 982 May 57

The ras-related protein Rho p21 regulates various actin-dependent functions, including smooth muscle contraction. However, the precise mechanism of action of Rho p21 is still not clear. We report here that Rho A is a key regulator of agonist-induced contractile effects in rabbit colonic smooth muscle. Endothelin-1 and C2 ceramide were used. Both seem to activate phosphoinositide 3-kinase (PI 3-kinase) through G protein and pp60(src), respectively. Immunoprecipitation and immunoblotting revealed one form of 21-kDa Rho A that translocated from the cytosol to the membrane in response to stimulation by either endothelin (10(-7) M) or ceramide (10(-7) M) ( approximately 30% increase at 30 s that was sustained at 4 min). The translocation of Rho A to the membrane was confirmed by immunostaining. The translocation of Rho A was inhibited by Clostridium botulinum C3 exoenzyme, which ADP ribosylated Rho A, but was not inhibited by the pp60(src) inhibitor herbimycin A or by the protein kinase C (PKC) inhibitor calphostin C, suggesting that Rho A may be upstream of pp60(src) and PKC or may belong to a different pathway than these proteins. Both ceramide- and endothelin-induced PI 3-kinase activation was inhibited by C3 exoenzyme pretreatment. However, the C3 exoenzyme inhibited endothelin- but not ceramide-induced mitogen-activated protein kinase phosphorylation, indicating that Rho regulates ceramide- and endothelin-induced contraction through different pathways. Furthermore, the dominant negative form of Rho (N19Rho) inhibited the actin binding protein, 27-kDa heat shock protein (HSP27), reorganization in response to ceramide and endothelin observed under confocal microscopy.
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PMID:Rho A regulates sustained smooth muscle contraction through cytoskeletal reorganization of HSP27. 984 84

In the present study, we determined the agonist specificity and the signalling mechanisms of a putative sphingosine 1-phosphate (S1P) receptor, AGR16. In CHO cells transiently transfected with an AGR16 expression vector, but not in cells transfected with an empty vector, the addition of a low concentration of S1P (1 nM) caused an increase in the intracellular free Ca2+ concentration ([Ca2+]i) by mobilization of Ca2+ from both intra- and extra-cellular pools. To determine the spectrum of agonists for AGR16, we employed K562 cells, which in the naive state do not respond at all to either S1P or structurally related lipids with an increase in [Ca2+]i. In K562 cells stably expressing AGR16, S1P and sphingosylphosphorylcholine (SPC) dose-dependently increased [Ca2+]i with half-maximal values of 3 nM and 100 nM respectively. In CHO cells stably expressing AGR16 (CHO-AGR16), but not in parental CHO cells, we observed specific binding of [32P]S1P, which was displaced by unlabelled S1P and SPC. In CHO-AGR16 cells, but not in parental CHO cells, S1P stimulated the production of inositol phosphates and Ca2+ mobilization which was only 30% inhibited by pertussis toxin (PTX), different from the case of the recently identified S1P receptor EDG1. Also in CHO-AGR16 cells, but not in CHO cells, S1P at higher concentrations activated mitogen-activated protein kinase (MAPK) in a PTX-sensitive and Ras-dependent manner. S1P also induced the activation of two stress-activated MAPKs, c-Jun N-terminal kinase and p38, in a manner that was totally insensitive to PTX. In CHO-AGR16 cells, S1P induced stress-fibre formation, with an increase in myosin light chain phosphorylation, in a PTX-insensitive and Rho-dependent manner. S1P also induced an increase in the cellular cAMP content in CHO-AGR16 cells, which contrasts sharply with the case of EDG1. These results establish that the S1P receptor AGR16 is coupled via both PTX-sensitive and -insensitive G-proteins to multiple effector pathways.
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PMID:The novel sphingosine 1-phosphate receptor AGR16 is coupled via pertussis toxin-sensitive and -insensitive G-proteins to multiple signalling pathways. 985 26

Cross-linking the high affinity IgE receptor Fc epsilonRI of basophils and mast cells activates receptor-associated protein-tyrosine kinases and stimulates a signaling cascade leading to secretion, ruffling, spreading, and cytokine production. Previous evidence that the pan-prenylation inhibitor lovastatin blocks Ag-stimulated Ca2+ influx, secretion, and membrane/cytoskeletal responses implicated isoprenylated proteins in the Fc epsilonRI-coupled signaling cascade but could not distinguish between contributions of C15 (farnesylated) and C20 (geranylgeranylated) species. Here we establish concentrations of lovastatin and the farnesyl-specific inhibitor BZA-5B that inhibit the farnesylation and Ag-induced activation of Ras species in RBL-2H3 cells (H-Ras, K-RasA, and K-RasB). These inhibitors have little effect on tyrosine kinase activation, which initiates Fc epsilonRI signaling. Although Ras is disabled, only lovastatin substantially blocks Raf-1 activation, and neither inhibitor affects mitogen-activated protein kinase kinase/extracellular signal regulated kinase kinase (MEK) or ERK1/ERK2 activation. Thus, the pathway to Fc epsilonRI-mediated MEK/ERK and ERK activation can apparently bypass Ras and Raf-1. Predictably, only lovastatin inhibits Ag-induced ruffling, spreading, and secretion, previously linked to geranylgeranylated Rho and Rab family members. Additionally, only lovastatin inhibits phospholipase Cgamma-mediated inositol (1,4,5) trisphosphate production, sustained Ca2+ influx, and Ca2+-dependent IL-4 production, suggesting novel roles for geranylgeranylated (lovastatin-sensitive, BZA-5B-insensitive) proteins in Fc epsilonRI signal propagation. Remarkably, BZA-5B concentrations too low to inactivate Ras reduce the lag time to Ag-induced Ca2+ stores release and enhance secretion. These results link a non-Ras farnesylated protein(s) to the negative regulation of Ca2+ release from intracellular stores and secretion. We identified no clear role for Ras in Fc epsilonRI-coupled signaling but suggest its involvement in mast cell growth regulation based on the inhibition of cell proliferation by both BZA-5B and lovastatin.
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PMID:MEK and ERK activation in ras-disabled RBL-2H3 mast cells and novel roles for geranylgeranylated and farnesylated proteins in Fc epsilonRI-mediated signaling. 986 3

The Rho subfamily of Ras-related small GTPases participates in a variety of cellular events including organization of the actin cytoskeleton and signalling by c-Jun N-terminal kinase and p38 kinase cascades. These functions of the Rho subfamily are likely to be required in many developmental events. We have been studying the participation of the RHO subfamily in dorsal closure of the Drosophila embryo, a process involving morphogenesis of the epidermis. We have previously shown that Drac1, a Rho subfamily protein, is required for the presence of an actomyosin contractile apparatus believed to be driving the cell shape changes essential to dorsal closure. Expression of a dominant negative Drac1 transgene causes a loss of this contractile apparatus from the leading edge of the advancing epidermis and dorsal closure fails. We now show that two other Rho subfamily proteins, Dcdc42 and RhoA, as well as Ras1 are also required for dorsal closure. Dcdc42 appears to have conflicting roles during dorsal closure: establishment and/or maintenance of the leading edge cytoskeleton versus its down regulation. Down regulation of the leading edge cytoskeleton may be controlled by the serine/threonine kinase DPAK, a potential Drac1/Dcdc42 effector. RhoA is required for the integrity of the leading edge cytoskeleton specifically in cells flanking the segment borders. We have begun to characterize the interactions of the various small GTPases in regulating dorsal closure and find no evidence for the hierarchy of Rho subfamily activity described in some mammalian cell types. Rather, our results suggest that while all &Rgr; subfamily p21s tested are required for dorsal closure, they act largely in parallel.
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PMID:Participation of small GTPases in dorsal closure of the Drosophila embryo: distinct roles for Rho subfamily proteins in epithelial morphogenesis. 988 81

Endothelin-1 (ET-1) mitogenic activity in astrocytes is mediated by the activation of the extracellular signal-regulated kinase (ERK) pathway together with the Rho-dependent activation of the focal adhesion kinase (FAK) pathway. To clarify the mechanisms responsible for the coordinate activation of both pathways in the ET-1 signal propagation, the involvement of caveolae microdomains, suggested to play a role in signal transduction, was evaluated. In this study, it is reported that caveolae of primary astrocytes are enriched in endothelin receptor (ETB-R). Furthermore, signaling molecules such as the adaptor proteins Shc and Grb2, and the small G protein Rho, also reside within these microdomains. Selective disassembly of caveolae by filipin III impairs the ET-1-induced tyrosine phosphorylation of proteins including ERK and FAK. In agreement with these observations, astrocytes pretreated with filipin III also failed to form stress fibers and focal adhesions and did not undergo the associated morphological changes in response to ET-1. This study reveals that structural integrity of caveolae is necessary for the adhesion-dependent mitogenic signals induced by ET-1 in astrocytes, through compartmentation of ETB-R with the upstream signaling molecules of the ERK and FAK pathways.
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PMID:Requirement of caveolae microdomains in extracellular signal-regulated kinase and focal adhesion kinase activation induced by endothelin-1 in primary astrocytes. 988 62

We previously observed that the trophic actions of gastrin (G17) on the AR42J rat acinar cell line are mediated by mitogen-activated protein kinase (MAPK)-induced c-fos gene transcription via protein kinase C (PKC)-dependent and -independent pathways. In this study, we further investigated the signaling pathways that target c-fos in response to G17. G17 led to a sixfold induction in luciferase activity in cells transfected with plasmids containing the -356+109 sequence of the murine c-fos promoter, which includes the Sis-inducible element (SIE), serum response element (SRE), and the Ca2+/cAMP response element (CRE) regulatory elements. Addition of either the selective PKC inhibitor GF-109203X or the MAPK/extracellular signal-regulated kinase inhibitor PD-98059 resulted in an 80% reduction in luciferase activity. G17 induced the transcriptional activity of both Elk-1 and Sap-1a, transcription factors that bind to the E26 transformation specific (Ets) DNA sequence of the SRE, and this effect was inhibited by both GF-109203X and PD-98059. Point mutations in the Ets sequence led to a 4-fold induction of c-fos transcription stimulated by G17 and to a 1.3-fold induction in response to epidermal growth factor (EGF). In contrast, mutations in the CA rich G (CArG) sequence of the SRE prevented transcriptional activation by both G17 and EGF. G17 induction of the Ets mutant construct was unaffected by either GF-109203X or PD-98059. Because activation of the SRE involves the small GTP-binding protein Rho A, we examined the role of Rho A in G17 induction of c-fos transcription. Inactivation of Rho A by either the specific inhibitor C3 or by expression of a dominant negative Rho A gene inhibited G17 induction of both the wild-type and the Ets mutant constructs by 60%. C3 also inhibited G17-stimulated AR42J cell proliferation. Thus G17 targets the c-fos promoter CArG sequence via Rho A-dependent pathways, and Rho A appears to play an important role in the regulation of the trophic action of G17.
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PMID:Gastrin induces c-fos gene transcription via multiple signaling pathways. 995 Aug 15


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