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)

Activation of the transcription factor serum response factor (SRF) is dependent on Rho-controlled changes in actin dynamics. We used pathway-specific inhibitors to compare the roles of actin dynamics, extracellular signal-regulated kinase (ERK) signaling, and phosphatidylinositol 3-kinase in signaling either to SRF itself or to four cellular SRF target genes. Serum, lysophosphatidic acid, platelet-derived growth factor, and phorbol 12-myristate 13-acetate (PMA) each activated transcription of a stably integrated SRF reporter gene dependent on functional RhoA GTPase. Inhibition of mitogen-activated protein kinase-ERK kinase (MEK) signalling reduced activation of the SRF reporter by all stimuli by about 50%, except for PMA, which was effectively blocked. Inhibition of phosphatidylinositol 3-kinase slightly reduced reporter activation by serum and lysophosphatidic acid but substantially inhibited activation by platelet-derived growth factor and PMA. Reporter induction by all stimuli was absolutely dependent on actin dynamics. Regulation of the SRF (srf) and vinculin (vcl) genes was similar to that of the SRF reporter gene; activation by all stimuli was Rho-dependent and required actin dynamics but was largely independent of MEK activity. In contrast, activation of fos and egr1 occurred independently of RhoA and actin polymerization but was almost completely dependent on MEK activation. These results show that at least two classes of SRF target genes can be distinguished on the basis of their relative sensitivity to RhoA-actin and MEK-ERK signaling pathways.
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PMID:Differential usage of signal transduction pathways defines two types of serum response factor target gene. 1134 53

Insulin-like growth factor I receptor (IGFR) plays an important role in cell growth and transformation. We dissected the downstream signaling pathways of an oncogenic variant of IGFR, Gag-IGFR, called NM1. Loss of function mutants of NM1, Phe-1136 and dS2, that retain kinase activity but are attenuated in their transforming ability were used to identify signaling pathways that are important for transformation of NIH 3T3 cells. MAPK, phospholipase C gamma, and Stat3 were activated to the same extent by NM1 and its two mutants, suggesting that activation of these pathways, individually or in combination, was not sufficient for NM1-induced cell transformation. The mutant dS2 has decreased IRS-1 phosphorylation levels and IRS-1-associated phosphatidylinositol 3'-kinase activity, suggesting that this impairment may be in part responsible for the defectiveness of dS2. We show that Rho family members, RhoA, Rac1, and Cdc42 are activated by NM1, and this activation, particularly RhoA and Cdc42, is attenuated in both mutants of NM1. Dominant negative mutants of Rho, Rac, and Cdc42 inhibited NM1-induced cell transformation, as measured by focus and colony forming ability. Dominant negative Rho most potently inhibited the focus forming activity, whereas Cdc42 was most effective in inhibiting the colony forming ability of NM1-expressing cells. Conversely, constitutively activated (ca) Rho is more effective than ca Rac or ca Cdc42 in rescuing the focus forming ability of the mutants. By contrast, ca Cdc42 is most effective in rescuing the colony forming ability of both mutants.
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PMID:Differential requirement for Rho family GTPases in an oncogenic insulin-like growth factor-I receptor-induced cell transformation. 1134 42

Leukemia-associated Rho guanine nucleotide exchange factor (LARG) was originally identified as a fusion partner with mixed-lineage leukemia in a patient with acute myeloid leukemia. LARG possesses a tandem Dbl homology and pleckstrin homology domain structure and, consequently, may function as an activator of Rho GTPases. In this study, we demonstrate that LARG is a functional Dbl protein. Expression of LARG in cells caused activation of the serum response factor, a known downstream target of Rho-mediated signaling pathways. Transient overexpression of LARG did not activate the extracellular signal-regulated kinase or c-Jun NH(2)-terminal kinase mitogen-activated protein kinase cascade, suggesting LARG is not an activator of Ras, Rac, or Cdc42. We performed in vitro exchange assays where the isolated Dbl homology (DH) or DH/pleckstrin homology domains of LARG functioned as a strong activator of RhoA, but exhibited no activity toward Rac1 or Cdc42. We found that LARG could complex with RhoA, but not Rac or Cdc42, in vitro, and that expression of LARG caused an increase in the levels of the activated GTP-bound form of RhoA, but not Rac1 or Cdc42, in vivo. Thus, we conclude that LARG is a RhoA-specific guanine nucleotide exchange factor. Finally, like activated RhoA, we determined that LARG cooperated with activated Raf-1 to transform NIH3T3 cells. These data demonstrate that LARG is the first functional Dbl protein mutated in cancer and indicate LARG-mediated activation of RhoA may play a role in the development of human leukemias.
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PMID:Leukemia-associated Rho guanine nucleotide exchange factor, a Dbl family protein found mutated in leukemia, causes transformation by activation of RhoA. 1137 93

We have previously shown that an ecto-NPPase modulates the ATP- and ADP-mediated P2Y(AC)-receptor activation in rat C6 glioma. In the present study, 2MeSADP and Ap(3)A induced no detectable PI turnover and were identified as specific agonists of the P2Y(AC)-receptor with EC(50) values of 250 +/- 37 pM and 1 +/- 0.5 microM, respectively. P2Y(AC)-receptor stimulation increased MAP kinase (ERK1/2) activation that returned to the basal level 4 h after stimulation and was correlated with a gradual desensitization of the P2Y(AC)-purinoceptor. The purinoceptor antagonists DIDS and RB2 blocked MAP kinase activation. An IP(3)-independent Ca(2+)-influx was observed after P2Y(AC)-receptor activation. Inhibition of this influx by Ca(2+)-chelation, did not affect MAP kinase activation. Pertussis toxin, toxin B, selective PKC-inhibitors and a specific MEK-inhibitor inhibited the 2MeSADP- and Ap(3)A-induced MAP kinase activation. In addition, transfection with dominant negative RhoA(Asn19) rendered C6 cells insensitive to P2Y(AC)-receptor-mediated MAP kinase activation whereas dominant negative ras was without effect. Immunoprecipitation experiments indicated a significant increase in the phosphorylation of raf-1 after P2Y(AC)-receptor activation. We may conclude that P2Y(AC)-purinoceptor agonists activate MAP kinase through a G(i)-RhoA-PKC-raf-MEK-dependent, but ras- and Ca(2+)-independent cascade.
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PMID:Agonists of the P2Y(AC)-receptor activate MAP kinase by a ras-independent pathway in rat C6 glioma. 1157 41

Stats (signal transducers and activators of transcription) are latent cytoplasmic transcription factors that on a specific stimulus migrate to the nucleus and exert their transcriptional activity. Here we report a novel signaling pathway whereby RhoA can efficiently modulate Stat3 transcriptional activity by inducing its simultaneous tyrosine and serine phosphorylation. Tyrosine phosphorylation is exerted via a member of the Src family of kinases (SrcFK) and JAK2, whereas the JNK pathway mediates serine phosphorylation. Furthermore, cooperation of both tyrosine as well as serine phosphorylation is necessary for full activation of Stat3. Induction of Stat3 activity depends on the effector domain of RhoA and correlates with induction of both Src Kinase-related and JNK activities. Activation of Stat3 has biological implications. Coexpression of an oncogenic version of RhoA along with the wild-type, nontransforming Stat3 gene, significantly enhances its oncogenic activity on human HEK cells, suggesting that Stat3 is an essential component of RhoA-mediated transformation. In keeping with this, dominant negative Stat3 mutants or inhibition of its tyrosine or serine phosphorylation completely abrogate RhoA oncogenic potential. Taken together, these results indicate that Stat3 is an important player in RhoA-mediated oncogenic transformation, which requires simultaneous phosphorylation at both tyrosine and serine residues by specific signaling events triggered by RhoA effectors.
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PMID:Simultaneous tyrosine and serine phosphorylation of STAT3 transcription factor is involved in Rho A GTPase oncogenic transformation. 1159 9

Rho-like GTPases play a pivotal role in the orchestration of changes in the actin cytoskeleton in response to receptor stimulation, and have been implicated in transcriptional activation, cell growth regulation, and oncogenic transformation. Recently, a role for RhoA in the regulation of cardiac contractility and hypertrophic cardiomyocyte growth has been suggested but the mechanisms underlying RhoA function in the heart remain undefined. We now report that transcription factor GATA-4, a key regulator of cardiac genes, is a nuclear mediator of RhoA signaling and is involved in the control of sarcomere assembly in cardiomyocytes. Both RhoA and GATA-4 are essential for sarcomeric reorganization in response to hypertrophic growth stimuli and overexpression of either protein is sufficient to induce sarcomeric reorganization. Consistent with convergence of RhoA and GATA signaling, RhoA potentiates the transcriptional activity of GATA-4 via a p38 MAPK-dependent pathway that phosphorylates GATA-4 activation domains and GATA binding sites mediate RhoA activation of target cardiac promoters. Moreover, a dominant-negative GATA-4 protein abolishes RhoA-induced sarcomere reorganization. The identification of transcription factor GATA-4 as a RhoA mediator in sarcomere reorganization and cardiac gene regulation provides a link between RhoA effects on transcription and cell remodeling.
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PMID:Tissue-specific GATA factors are transcriptional effectors of the small GTPase RhoA. 1164 Dec 76

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

We have characterized a new member of the mammalian PAK family of serine/threonine kinases, PAK5, which is a novel target of the Rho GTPases Cdc42 and Rac. The kinase domain and GTPase-binding domain (GBD) of PAK5 are most closely related in sequence to those of mammalian PAK4. Outside of these domains, however, PAK5 is completely different in sequence from any known mammalian proteins. PAK5 does share considerable sequence homology with the Drosophila MBT protein (for "mushroom body tiny"), however, which is thought to play a role in development of cells in Drosophila brain. Interestingly, PAK5 is highly expressed in mammalian brain and is not expressed in most other tissues. We have found that PAK5, like Cdc42, promotes the induction of filopodia. In N1E-115 neuroblastoma cells, expression of PAK5 also triggered the induction of neurite-like processes, and a dominant-negative PAK5 mutant inhibited neurite outgrowth. Expression of activated PAK1 caused no noticeable changes in these cells. An activated mutant of PAK5 had an even more dramatic effect than wild-type PAK5, indicating that the morphologic changes induced by PAK5 are directly related to its kinase activity. Although PAK5 activates the JNK pathway, dominant-negative JNK did not inhibit neurite outgrowth. In contrast, the induction of neurites by PAK5 was abolished by expression of activated RhoA. Previous work has shown that Cdc42 and Rac promote neurite outgrowth by a pathway that is antagonistic to Rho. Our results suggest, therefore, that PAK5 operates downstream to Cdc42 and Rac and antagonizes Rho in the pathway, leading to neurite development.
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PMID:PAK5, a new brain-specific kinase, promotes neurite outgrowth in N1E-115 cells. 1175 52

The role of Rho proteins in lysophosphatidic acid (LPA)-mediated induction of cyclo-oxygenase-2 (Cox-2) was investigated in renal mesangial cells. Previous studies had shown that toxin B, an inhibitor of Rho, Rac and Cdc42, suppressed Cox-2 induction. A role for RhoA in pertussis toxin-sensitive LPA signalling was excluded with C3 transferase from Clostridium limosum, used as the fusion toxin C2IN-C3 (where C2IN is part of the C2I toxin of C. botulinum). Incubation of the cells with C2IN-C3 disrupted cytosolic actin stress fibres, but had no effect on Cox-2 induction. Similarly, activation of p42/44 mitogen-activated protein kinase (MAP kinase), an upstream step in Cox-2 induction, was inhibited by toxin B, but not affected by C2IN-C3. Upon treatment with toxin B, focal adhesion kinase and paxillin were dephosphorylated at tyrosine residues and the actin cytoskeleton was completely destroyed. An intact cytoskeleton, however, was not required for p42/44 MAP-kinase activation or Cox-2 induction, as shown by the actin-depolymerizing agent cytochalasin D. Toxin B did not influence functionality of LPA receptors, because G(i)-mediated Ca(2+) release from intracellular stores remained unchanged. Within 1 h, toxin B inactivated and translocated RhoA and Cdc42 to the cellular membranes. Within the same time frame, monoglucosylated Rac1 was degraded. Direct stimulation of Rho proteins by cytotoxic necrotizing factor type 1 (CNF1) induced Cox-2 expression, which was sensitive to inhibition of the MAP-kinase pathway by PD98059, but not to an inhibitor of RhoA kinase. By exclusion of RhoA and non-specific cytoskeletal effects, the results in the present study indicate an important role for Rac and/or Cdc42 in pertussis toxin-sensitive LPA-mediated Cox-2 induction.
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PMID:Role of Rac and Cdc42 in lysophosphatidic acid-mediated cyclo-oxygenase-2 gene expression. 1182 37

We recently designed a dominant negative (DN) farnesyltransferase (FTase)/geranyl-gerahyltransferase I (GGTase I) alpha-subunit that when expressed in vascular smooth muscle cells decreased insulin-stimulated phosphorylation of FTase, FTase activity, amounts of farnesylated p21Ras, DNA synthesis, and cell migration. Currently, we explored the inhibitory effects of DN FTase/GGTase I alpha-subunit in MCF-7 cells on IGF-1- and insulin-stimulated DNA synthesis and cell proliferation. Expression of the DN FTase/GGTase I alpha-subunit completely blocked IGF-1- and insulin-stimulated BrdU incorporation and cell count. DN FTase/GGTase I alpha-subunit inhibited insulin-stimulated phosphorylation of FTase/GGTase I alpha-subunit, FTase and GGTase I activity, and prenylation of p21Ras and RhoA. Expression of DN FTase/GGTase I alpha-subunit diminished IGF-1- and insulin-stimulated phosphorylation of ERK (extracellular signal-regulated kinase), but had no effect on IGF-1- and insulin-stimulated phosphorylation of Akt. Taken together, these data suggest that DN FTase/GGTase I alpha-subunit can assuage the mitogenic effects of IGF-1 and insulin on MCF-7 breast cancer cells.
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PMID:Dominant negative alpha-subunit of FTase inhibits effects of insulin and IGF-I in MCF-7 cells. 1185 11


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