Biomedical subjects

R J Davis

Publications and source records attributed to R J Davis.

At least 145 records · Page 8Linked to original sources

PubMed1996

Activation of p38 mitogen-activated protein kinase by c-Abl-dependent and -independent mechanisms.

The p38 mitogen-activated protein (MAP) kinase defines a subgroup of the mammalian MAP kinases that are induced in response to lipopolysaccharide, hyperosmolarity, and interleukin 1. p38 MAP kinase appears to play a role in regulating inflammatory responses, including cytokine secretion and apoptosis. Here we show that diverse classes of DNA-damaging agents such as cisplatinum, 1-beta-D-arabinofuranosylcytosine, UV light, ionizing radiation, and methyl methanesulfonate activate p38 MAP kinase. We also demonstrate that cells deficient in c-Abl fail to activate p38 MAP kinase after treatment with cisplatinum and 1-beta-D-arabinofuranosylcytosine but not after exposure to UV and methyl methanesulfonate. Reconstitution of c-Abl in the Abl-/- cells restores that response. Similar results were obtained for induction of the Jun-NH2-kinase/stress-activated protein kinase. These findings indicate that p38 MAP and Jun-NH2-kinase/stress-activated protein kinases are differentially regulated in response to different classes of DNA-damaging agents.

3T3 Cells↗

PubMed1996

Differential activation of mitogen-activated protein kinases by nitric oxide-related species.

Many studies have identified nitric oxide (NO) and related chemical species (NOx) as having critical roles in neurotransmission, vasoregulation, and cellular signaling. Previous work in this laboratory has focused on elucidating the mechanism of NOx signaling in cells. We have demonstrated that NOx-induced activation of the guanine nucleotide-binding protein p21(ras) leads to nuclear translocation of the transcription factor NFkappaB. Here, we investigated whether intermediary signaling elements, namely the mitogen-activated protein (MAP) kinases, are involved in mediating NOx signaling. We found that NOx activates the extracellular signal-regulated kinase (ERK), p38, and c-Jun NH2-terminal kinase (JNK) subgroups of MAP kinases in human Jurkat T cells. JNK was found to be 100-fold more sensitive to NOx stimulation than p38 and ERK. In addition, the activation of JNK and p38 by NOx was more rapid than ERK activation. Depletion of intracellular glutathione augmented the NOx-induced increase in kinase activity. Furthermore, endogenous NO, generated from NO synthase, activated ERK, and NOx-induced MAP kinase activation was effectively blocked by the farnesyl transferase inhibitor alpha-hydroxyfarnesylphosphonic acid. These data support the hypothesis that critical signaling kinases, such as ERK, p38, and JNK, are activated by NO-related species and thus participate in NO signal transduction. These findings establish a role for multiple MAP kinase signaling pathways in the cellular response to NOx.

Alkyl and Aryl Transferases↗

PubMed1996

Binding of zinc finger protein ZPR1 to the epidermal growth factor receptor.

ZPR1 is a zinc finger protein that binds to the cytoplasmic tyrosine kinase domain of the epidermal growth factor receptor (EGFR). Deletion analysis demonstrated that this binding interaction is mediated by the zinc fingers of ZPR1 and subdomains X and XI of the EGFR tyrosine kinase. Treatment of mammalian cells with EGF caused decreased binding of ZPR1 to the EGFR and the accumulation of ZPR1 in the nucleus. The effect of EGF to regulate ZPR1 binding is dependent on tyrosine phosphorylation of the EGFR. ZPR1 therefore represents a prototype for a class of molecule that binds to the EGFR and is released from the receptor after activation.

Amino Acid Sequence↗

PubMed1996

Selective interaction of JNK protein kinase isoforms with transcription factors.

The JNK protein kinase is a member of the MAP kinase group that is activated in response to dual phosphorylation on threonine and tyrosine. Ten JNK isoforms were identified in human brain by molecular cloning. These protein kinases correspond to alternatively spliced isoforms derived from the JNK1, JNK2 and JNK3 genes. The protein kinase activity of these JNK isoforms was measured using the transcription factors ATF2, Elk-1 and members of the Jun family as substrates. Treatment of cells with interleukin-1 (IL-1) caused activation of the JNK isoforms. This activation was blocked by expression of the MAP kinase phosphatase MKP-1. Comparison of the binding activity of the JNK isoforms demonstrated that the JNK proteins differ in their interaction with ATF2, Elk-1 and Jun transcription factors. Individual members of the JNK group may therefore selectively target specific transcription factors in vivo.

Activating Transcription Factor 2↗

PubMed1996

The seven-transmembrane-spanning receptors for endothelin and thrombin cause proliferation of airway smooth muscle cells and activation of the extracellular regulated kinase and c-Jun NH2-terminal kinase groups of mitogen-activated protein kinases.

In airway smooth muscle cells ligand binding to the seven-transmembrane endothelin and thrombin receptors stimulates cell growth. Rapid activation of the extracellular regulated kinase 2 and c-Jun NH2-terminal kinase groups of mitogen-activated protein kinases was also observed. The results demonstrate a novel mechanism of seven-transmembrane receptor signaling involving activation of the Jun kinase pathway. Receptor coupling to Jun kinase activation may involve heterotrimeric G proteins since the kinase was enzymatically activated in cells treated with aluminum fluoride. The activity of Raf-1, measured by immune complex kinase assay, revealed that platelet-derived growth factor and phorbol 12-myristate 13-acetate both stimulated Raf-1 activity, while thrombin and endothelin did not appreciably stimulate Raf-1. The data suggest that endothelin and thrombin stimulate Raf-1-independent mechanisms of mitogen-activated protein kinase activation. Endothelin- or thrombin-induced activation of mitogen-activated protein kinases was significantly inhibited by activation of cyclic AMP-dependent protein kinase by forskolin. Proliferation of airway smooth muscle cells, measured by incorporation of [3H]thymidine into DNA, was also greatly attenuated by forskolin.

Animals↗

PubMed1996

Transcription factor AP-1 regulation by mitogen-activated protein kinase signal transduction pathways.

Mitogen-activated protein (MAP) kinases are proline-directed serine/threonine kinases that are activated by dual phosphorylation on threonine and tyrosine residues in response to a wide array of extracellular stimuli. Three distinct groups of MAP kinases have been identified in mammalian cells [extracellular-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38]. These MAP kinases are mediators of signal transduction from the cell surface to the nucleus. One nuclear target of these MAP kinase signaling pathways is the transcription factor AP-1. MAP kinases regulate AP-1 transcriptional activity by multiple mechanisms. Here we review recent progress towards understanding AP-1 regulation by the ERK, JNK, and p38 MAP kinase signal transduction pathways.

Animals↗

PubMed1996

Central implants of dilute estradiol enhance the satiety effect of CCK-8.

The following studies evaluated whether direct placement of estradiol into different brain areas could increase the satiating potency of CCK in female rats. In Experiment 1, estradiol implants in the PVN, but not in the VMN or third ventricle, significantly enhanced the satiety actions of CCK (5.0 micrograms/kg). In Experiment 2, a lower dose of CCK (0.5 micrograms/kg) suppressed food intake in females with estradiol implants in the PVN but not in animals with implants in the VMN or preoptic area. In both experiments, estradiol implants in the PVN significantly lowered food intake and body weight during the 2-day period of hormone treatment. Implants in other areas had no significant effects on feeding or body weight. These data support the hypothesis that the satiety effect of CCK is enhanced by estradiol and suggest that the PVN is involved in the interaction between CCK and estradiol.

Animals↗

PubMed1996

In vivo amplification of the PAX3-FKHR and PAX7-FKHR fusion genes in alveolar rhabdomyosarcoma.

In the pediatric cancer alveolar rhabdomyosarcoma, characteristic t(2;13)(q35;q14) or variant t(1;13)(p36;q14) chromosomal translocations generate PAX3-FKHR or PAX7-FKHR fusion genes. Using fluorescence in situ hybridization, reverse transcriptase-polymerase chain reaction and quantitative Southern blot analyses, we demonstrate that these fusion genes are amplified in 20% of fusion-positive tumors. In particular, we found in vivo amplification of these fusions in one of 22 PAX3-FKHR-positive cases and five of seven PAX7-FKHR-positive cases. These findings indicate that translocation and amplification can occur sequentially in a cancer to alter both the structure and copy number of a gene and thereby activate oncogenic activity by complementary mechanisms.

Base Sequence↗

PubMed1996

MKK3- and MKK6-regulated gene expression is mediated by the p38 mitogen-activated protein kinase signal transduction pathway.

The p38 mitogen-activated protein (MAP) kinase signal transduction pathway is activated by proinflammatory cytokines and environmental stress. The detection of p38 MAP kinase in the nucleus of activated cells suggests that p38 MAP kinase can mediate signaling to the nucleus. To test this hypothesis, we constructed expression vectors for activated MKK3 and MKK6, two MAP kinase kinases that phosphorylate and activate p38 MAP kinase. Expression of activated MKK3 and MKK6 in cultured cells caused a selective increase in p38 MAP kinase activity. Cotransfection experiments demonstrated that p38 MAP kinase activation causes increased reporter gene expression mediated by the transcription factors ATF2 and Elk-1. These data demonstrate that the nucleus is one target of the p38 MAP kinase signal transduction pathway.

Amino Acid Sequence↗

PubMed1996

Determinants of DNA-binding specificity of ETS-domain transcription factors.

Several mechanisms are employed by members of transcription factor families to achieve sequence-specific DNA recognition. In this study, we have investigated how members of the ETS-domain transcription factor family achieve such specificity. We have used the ternary complex factor (TCF) subfamily as an example. ERK2 mitogen-activated protein kinase stimulates serum response factor-dependent and autonomous DNA binding by the TCFs Elk-1 and SAP-la. Phosphorylated Elk-1 and SAP-la exhibit specificities of DNA binding similar to those of their isolated ETS domains. The ETS domains of Elk-1 and SAP-la and SAP-2 exhibit related but distinct DNA-binding specificities. A single residue, D-69 (Elk-1) or V-68 (SAP-1), has been identified as the critical determinant for the differential binding specificities of Elk-1 and SAP-1a, and an additional residue, D-38 (Elk-1) or Q-37 (SAP-1), further modulates their DNA binding. Creation of mutations D38Q and D69V is sufficient to confer SAP-la DNA-binding specificity upon Elk-1 and thereby allow it to bind to a greater spectrum of sites. Molecular modelling indicates that these two residues (D-38 and D-69) are located away from the DNA-binding interface of Elk-1. Our data suggest a mechanism in which these residues modulate DNA binding by influencing the interaction of other residues with DNA.

Amino Acid Sequence↗

PubMed1995

The epidermal growth factor receptor is covalently linked to ubiquitin.

Incubation of cultured human fibroblasts with epidermal growth factor (EGF) causes a proliferative response that is mediated by the binding of the growth factor to specific cell surface receptors. One event that occurs rapidly following EGF binding is the covalent modification of the EGF receptor (EGF-R) by phosphorylation on Ser, Thr, and Tyr residues. Here we report the identification of ubiquitination as a second form of EGF-stimulated covalent modification of the receptor. The LGF receptor was not ubiquitinated in serum-starved cells. However, treatment with EGF caused a rapid increase in EGF-R ubiquitination. In contrast, no EGF-stimulated ubiquitination was found in experiments using cells that express a mutant tyrosine kinase-negative EGF-R. Similarly, ubiquitination of the EGF-R was not observed at 4 degrees C or if the cells are depleted of intracellular K+. Together, these data establish ubiquitination as a form of EGF-stimulated covalent modification of the EGF-R.

Animals↗

PubMed1995

Cdc42 and PAK-mediated signaling leads to Jun kinase and p38 mitogen-activated protein kinase activation.

The PAK family of protein kinases has been suggested as a potential target of the Cdc42 and Rac GTPases based on studies in vitro. We show that PAK-3 is activated by Cdc42 in vivo. Both, activated (GTPase-defective) Cdc42 and a constitutively active PAK-3 mutant stimulated the activity of Jun kinase 1 (JNK1) in transfected cells. Activated Cdc42 also stimulated the activity of the related p38 mitogen-activated protein kinase but was a less effective activator of ERK2. The effect of Cdc42 on JNK activity was similar to that of the potent inflammatory cytokine interleukin-1 (IL-1). The observation that a dominant-negative Cdc42 mutant inhibited IL-1 activation of JNK1 indicates a role for Cdc42 in IL-1 signaling. These results suggest that Cdc42 and PAK may mediate the effects of cytokines on transcriptional regulation.

Adenosine Triphosphate↗

PubMed1995

Opposing effects of ERK and JNK-p38 MAP kinases on apoptosis.

Apoptosis plays an important role during neuronal development, and defects in apoptosis may underlie various neurodegenerative disorders. To characterize molecular mechanisms that regulate neuronal apoptosis, the contributions to cell death of mitogen-activated protein (MAP) kinase family members, including ERK (extracellular signal-regulated kinase), JNK (c-JUN NH2-terminal protein kinase), and p38, were examined after withdrawal of nerve growth factor (NGF) from rat PC-12 pheochromocytoma cells. NGF withdrawal led to sustained activation of the JNK and p38 enzymes and inhibition of ERKs. The effects of dominant-interfering or constitutively activated forms of various components of the JNK-p38 and ERK signaling pathways demonstrated that activation of JNK and p38 and concurrent inhibition of ERK are critical for induction of apoptosis in these cells. Therefore, the dynamic balance between growth factor-activated ERK and stress-activated JNK-p38 pathways may be important in determining whether a cell survives or undergoes apoptosis.

Alkaloids↗

PubMed1995

Integration of MAP kinase signal transduction pathways at the serum response element.

The ternary complex factor (TCF) subfamily of ETS-domain transcription factors bind with serum response factor (SRF) to the serum response element (SRE) and mediate increased gene expression. The TCF protein Elk-1 is phosphorylated by the JNK and ERK groups of mitogen-activated protein (MAP) kinases causing increased DNA binding, ternary complex formation, and transcriptional activation. Activated SRE-dependent gene expression is induced by JNK in cells treated with interleukin-1 and by ERK after treatment with phorbol ester. The Elk-1 transcription factor therefore integrates MAP kinase signaling pathways in vivo to coordinate biological responses to different extracellular stimuli.

Animals↗

PubMed1995

Pro-inflammatory cytokines and environmental stress cause p38 mitogen-activated protein kinase activation by dual phosphorylation on tyrosine and threonine.

Protein kinases activated by dual phosphorylation on Tyr and Thr (MAP kinases) can be grouped into two major classes: ERK and JNK. The ERK group regulates multiple targets in response to growth factors via a Ras-dependent mechanism. In contrast, JNK activates the transcription factor c-Jun in response to pro-inflammatory cytokines and exposure of cells to several forms of environmental stress. Recently, a novel mammalian protein kinase (p38) that shares sequence similarity with mitogen-activated protein (MAP) kinases was identified. Here, we demonstrate that p38, like JNK, is activated by treatment of cells with pro-inflammatory cytokines and environmental stress. The mechanism of p38 activation is mediated by dual phosphorylation on Thr-180 and Tyr-182. Immunofluorescence microscopy demonstrated that p38 MAP kinase is present in both the nucleus and cytoplasm of activated cells. Together, these data establish that p38 is a member of the mammalian MAP kinase group.

Animals↗

PubMed1995

The MAP kinase signal transduction pathway is activated by the endogenous cannabinoid anandamide.

Anandamide is an endogenous ligand for delta 9-tetrahydrocannabinol (THC) receptors. Incubation of cultured cells with anandamide or THC causes increased arachidonic acid release and eicosanoid biosynthesis. Here we demonstrate that the MAP kinase signal transduction pathway contributes to this response. Treatment of WI-38 fibroblasts with anandamide causes increased MAP kinase activity and increased phosphorylation of the arachidonate-specific cytoplasmic phospholipase A2 (cPLA2). Significantly, MAP kinase phosphorylates and activates cPLA2 [Lin, et al., Cell, 72 (1993) 269-278]. The MAP kinase signal transduction pathway may therefore mediate the effects of anadamide on cPLA2 activation and arachidonic acid release.

Arachidonic Acid↗

PubMed1995

Independent human MAP-kinase signal transduction pathways defined by MEK and MKK isoforms.

Mammalian mitogen-activated protein (MAP) kinases include extracellular signal-regulated protein kinase (ERK), c-Jun amino-terminal kinase (JNK), and p38 subgroups. These MAP kinase isoforms are activated by dual phosphorylation on threonine and tyrosine. Two human MAP kinase kinases (MKK3 and MKK4) were cloned that phosphorylate and activate p38 MAP kinase. These MKK isoforms did not activate the ERK subgroup of MAP kinases, but MKK4 did activate JNK. These data demonstrate that the activators of p38 (MKK3 and MKK4), JNK (MKK4), and ERK (MEK1 and MEK2) define independent MAP kinase signal transduction pathways.

Amino Acid Sequence↗

PubMed1995

Transcription factor ATF2 regulation by the JNK signal transduction pathway.

Treatment of cells with pro-inflammatory cytokines or ultraviolet radiation causes activation of the c-Jun NH2-terminal protein kinase (JNK). Activating transcription factor-2 (ATF2) was found to be a target of the JNK signal transduction pathway. ATF2 was phosphorylated by JNK on two closely spaced threonine residues within the NH2-terminal activation domain. The replacement of these phosphorylation sites with alanine inhibited the transcriptional activity of ATF2. These mutations also inhibited ATF2-stimulated gene expression mediated by the retinoblastoma (Rb) tumor suppressor and the adenovirus early region 1A (E1A) oncoprotein. Furthermore, expression of dominant-negative JNK inhibited ATF2 transcriptional activity. Together, these data demonstrate a role for the JNK signal transduction pathway in transcriptional responses mediated by ATF2.

Activating Transcription Factor 2↗