Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of Lyn, a Src-related nonreceptor tyrosine kinase, in trophoblast cells is associated with trophoblast giant cell differentiation. The purpose of the present work was to use Lyn as a tool to identify signaling pathways regulating the endocrine differentiation of trophoblast cells. The Src homology 3 domain of Lyn was shown to display differentiation-dependent associations with other regulatory proteins, including phosphatidylinositol 3-kinase (PI3-K). PI3-K activation was dependent upon trophoblast giant cell differentiation. The downstream mediator of PI3-K, Akt/protein kinase B, also exhibited differentiation-dependent activation. Lyn is a potential regulator of the PI3-K/Akt signaling pathway, as are receptor tyrosine kinases. Protein tyrosine kinase profiling was used to identify two candidate regulators of the PI3-K/Akt pathway, fibroblast growth factor receptor-1 and Sky. At least part of the activation of Akt in differentiating trophoblast giant cells involves an autocrine growth arrest-specific-6-Sky signaling pathway. Inhibition of PI3-K activities via treatment with LY294002 disrupted Akt activation and interfered with the endocrine differentiation of trophoblast giant cells. In summary, activation of the PI3-K/Akt signaling pathway regulates the development of the differentiated trophoblast giant cell phenotype.
Mol Endocrinol 2002 Jul
PMID:The phosphatidylinositol 3-kinase/Akt signaling pathway modulates the endocrine differentiation of trophoblast cells. 1208 43

The Akt (or protein kinase B) and Cot (or Tpl-2) serine/threonine kinases are associated with cellular transformation. These kinases have also been implicated in the induction of NF-kappa B-dependent transcription. As a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, Cot can also activate MAP kinase signaling pathways that target AP-1 and NFAT family transcription factors. Here we show that Akt and Cot physically associate and functionally cooperate. Akt appears to function upstream of Cot, as Akt can enhance Cot induction of NF-kappa B-dependent transcription, and dominant-negative Cot blocks the activation of this element by Akt. Furthermore, deletion analysis shows that binding to Akt is critical for Cot function. The regulation of NF-kappa B-dependent transcription by Cot requires Akt-dependent phosphorylation of serine 400 (S400), near the carboxy terminus of Cot. However, phosphorylation at this site is not required for Cot kinase activity or AP-1 induction, suggesting it specifically regulates Cot effector function at the level of the NF-kappa B pathway. Mutation of S400 in Cot does indeed abolish its ability to activate I kappa B-kinase (IKK) complexes, but paradoxically it allows for increased Cot association with the IKK complex. This mutated form of Cot also acts as a dominant negative for T-cell antigen receptor/CD28- or Akt/phorbol myristate acetate-induced NF-kappa B induction, while having relatively little effect on tumor necrosis factor induction of NF-kappa B. These findings suggest that the activation of different signaling pathways by MAP3Ks may be regulated separately and may provide evidence for how such discrimination by one member of this kinase family occurs.
Mol Cell Biol 2002 Aug
PMID:Akt-dependent phosphorylation specifically regulates Cot induction of NF-kappa B-dependent transcription. 1213 5

Phosphatidylinositol 3-kinase (PI 3-kinase) and its target protein kinase B (Akt) are involved in various processes including internalization, chemotaxis and proliferation. We analysed the activation of Akt in J774 macrophages infected with virulent (pYV+) or avirulent (pYV-) Yersinia enterocolitica. During the early stage of infection with pYV+ and pYV- bacteria, Akt and its targets, glycogen synthase kinase 3 (GSK-3) and forkhead transcription factor (FKHRL1), became phosphorylated. This phosphorylation induction was inhibited by wortmannin and thus dependent on PI 3-kinase. When infection was carried out with pYV+ bacteria but not with pYV- bacteria, Akt and its targets became dephosphorylated at later time points. Using single knock-out mutants in bacterial effector genes, we have determined that the tyrosine phosphatase YopH was responsible for the inactivation of the PI 3-kinase cascade. In macrophages, this inactivation correlated with the downregulation of mRNA coding for monocyte chemoattractant protein 1 (MCP-1), suggesting that YopH inhibits recruitment of macrophages to lymph nodes. We also analysed the effects of Y. enterocolitica infection on the proliferation of T lymphocytes. Consistent with the observation that YopH inactivated the Akt pathway, YopH inhibited PI 3-kinase-dependent secretion of interleukin 2 and proliferation. These data reveal a new effect of YopH in Yersinia pathogenesis.
Mol Microbiol 2002 Aug
PMID:YopH prevents monocyte chemoattractant protein 1 expression in macrophages and T-cell proliferation through inactivation of the phosphatidylinositol 3-kinase pathway. 1213 25

Inhalation of toxic doses of ozone causes lung injury and inflammation in humans and experimental animals. Using a rodent model of ozone toxicity, we have previously demonstrated that macrophages recruited to the lung following exposure to this oxidant contribute to the pathogenesis of tissue injury. In the present studies we analyzed potential mechanisms regulating alveolar macrophage activity following ozone inhalation and the role of inflammatory mediators in toxicity. Treatment of mice with ozone (0.8 ppm, 3 h) resulted in increased expression of inducible nitric oxide synthase (iNOS) protein and production of nitric oxide (NO) and peroxynitrite by alveolar macrophages. In contrast, these effects were not observed in macrophages from transgenic mice with a targeted disruption of the gene for iNOS, or in mice overexpressing superoxide dismutase. Moreover, ozone toxicity, as measured by bronchoalveolar lavage protein levels and nitrotyrosine staining of the lung was prevented in both of these transgenic mouse strains. The promoter/enhancer region of the iNOS gene contains binding sites for the transcription factors NF-kappaB and STAT-1 which regulate the activity of the gene. Ozone inhalation resulted in a rapid and prolonged activation of NF-kappaB in alveolar macrophages. Phosphoinositide 3-kinase (PI 3-K) and its down stream target, protein kinase B (PKB), which are known to regulate NF-kappaB activity, also increased in alveolar macrophages following ozone inhalation. These data, together with our findings that inhibitors of PI 3-K block NO production, suggest that these proteins are important in controlling expression of iNOS. Furthermore, the fact that macrophages from NF-kappaB p50 knockout mice did not generate reactive nitrogen intermediates and that these mice were protected from ozone induced toxicity demonstrate the importance of the NF-kappaB signaling pathway in lung injury. We also found that STAT-1 nuclear binding activity and STAT-1 protein expression were upregulated in macrophages from ozone treated animals. Taken together, these data suggest that biochemical signaling pathways that control the expression of genes critical for the inflammatory process play a role in ozone toxicity.
Mol Cell Biochem
PMID:Upregulation of phosphoinositide 3-kinase and protein kinase B in alveolar macrophages following ozone inhalation. Role of NF-kappaB and STAT-1 in ozone-induced nitric oxide production and toxicity. 1216 64

The protein kinase B (PKB)/Akt family of serine kinases is rapidly activated following agonist-induced stimulation of phosphoinositide 3-kinase (PI3K). To probe the molecular events important for the activation process, we employed two distinct models of posttranslational inducible activation and membrane recruitment. PKB induction requires phosphorylation of two critical residues, threonine 308 in the activation loop and serine 473 near the carboxyl terminus. Membrane localization of PKB was found to be a primary determinant of serine 473 phosphorylation. PI3K activity was equally important for promoting phosphorylation of serine 473, but this was separable from membrane localization. PDK1 phosphorylation of threonine 308 was primarily dependent upon prior serine 473 phosphorylation and, to a lesser extent, localization to the plasma membrane. Mutation of serine 473 to alanine or aspartic acid modulated the degree of threonine 308 phosphorylation in both models, while a point mutation in the substrate-binding region of PDK1 (L155E) rendered PDK1 incapable of phosphorylating PKB. Together, these results suggest a mechanism in which 3' phosphoinositide lipid-dependent translocation of PKB to the plasma membrane promotes serine 473 phosphorylation, which is, in turn, necessary for PDK1-mediated phosphorylation of threonine 308 and, consequentially, full PKB activation.
Mol Cell Biol 2002 Sep
PMID:Multiple phosphoinositide 3-kinase-dependent steps in activation of protein kinase B. 1216 17

CD98, an early marker of T-cell activation, is an important regulator of integrin-mediated adhesion events. Previous studies suggest that CD98 is coupled to both cellular activation and transformation and is involved in the pathogenesis of viral infection, inflammatory disease, and cancer. Understanding of the molecular mechanisms underlying CD98 activity may have far-reaching practical applications in the development of novel therapeutic strategies in these disease states. Using small cell lung cancer cell lines, which are nonadherent, nonpolarized, and highly express CD98, we show that, in vitro, under physiological conditions, CD98 is constitutively associated with beta1 integrins regardless of activation status. Cross-linking CD98 with the monoclonal antibody 4F2 stimulated phosphatidylinositol (PI) 3-kinase, PI(3,4,5)P(3), and protein kinase B in the absence of integrin ligation or extracellular matrix engagement. Furthermore, cross-linking CD98 promoted anchorage-independent growth. Using fibroblasts derived from beta1 integrin null stem cells (GD25), wild-type GD25beta1, or GD25 cells expressing a mutation preventing beta1 integrin-dependent FAK phosphorylation, we demonstrate that a functional beta1 integrin is required for CD98 signaling. We propose that by cross-linking CD98, it acts as a "molecular facilitator" in the plasma membrane, clustering beta1 integrins to form high-density complexes. This results in integrin activation, integrin-like signaling, and anchorage-independent growth. Activation of PI 3-kinase may, in part, explain cellular transformation seen on overexpressing CD98. These results may provide a paradigm for events involved in such diverse processes as inflammation and viral-induced cell fusion.
Mol Biol Cell 2002 Aug
PMID:Cross-linking CD98 promotes integrin-like signaling and anchorage-independent growth. 1218 50

Overexpression of the growth factor receptor subunit c-erbB2, leading to its ligand-independent homodimerization and activation, has been implicated in the pathogenesis of mammary carcinoma. Here, we have examined the effects of c-erbB2 on the adhesive properties of a mammary epithelial cell line, HB2/tnz34, in which c-erbB2 homodimerization can be induced by means of a transfected hybrid "trk-neu" construct. trk-neu consists of the extracellular domain of the trkA nerve growth factor (NGF) receptor fused to the transmembrane and cytoplasmic domains of c-erbB2, allowing NGF-induced c-erbB2 homodimer signaling. Both spreading and adhesion on collagen surfaces were impaired on c-erbB2 activation in HB2/tnz34 cells. Antibody-mediated stimulation of alpha(2)beta(1) integrin function restored adhesion, suggesting a direct role for c-erbB2 in integrin inactivation. Using pharmacological inhibitors and transient transfections, we identified signaling pathways required for suppression of integrin function by c-erbB2. Among these was the MEK-ERK pathway, previously implicated in integrin inactivation. However, we could also show that downstream of phosphoinositide-3-kinase (PI3K), protein kinase B (PKB) acted as a previously unknown, potent inhibitor of integrin function and mediator of the disruptive effects of c-erbB2 on adhesion and morphogenesis. The integrin-linked kinase, previously identified as a PKB coactivator, was also found to be required for integrin inactivation by c-erbB2. In addition, the PI3K-dependent mTOR/S6 kinase pathway was shown to mediate c-erbB2-induced inhibition of adhesion (but not spreading) independently of PKB. Overexpression of MEK1 or PKB suppressed adhesion without requirement for c-erbB2 activation, suggesting that these two pathways partake in integrin inhibition by targeting common downstream effectors. These results demonstrate a major novel role for PI3K and PKB in regulation of integrin function.
Mol Biol Cell 2002 Aug
PMID:c-erbB2-induced disruption of matrix adhesion and morphogenesis reveals a novel role for protein kinase B as a negative regulator of alpha(2)beta(1) integrin function. 1218 54

Insulin-like growth factors (IGFs) are potent mitogenic and antiapoptotic factors for many cell types, including some normal and neoplastic lung cells in vitro. However, in this study we show that IGF-I, at concentrations of 10 ng/ml or greater, significantly inhibits DNA synthesis and cell proliferation in a human lung adenocarcinoma cell line, A549. Inhibition of DNA synthesis was completely reversed by an IGF-I receptor-neutralizing antibody, alphaIR-3, indicating that IGF-I receptor activation is involved in its inhibitory effect. Attenuation of the p44/42 mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3'-kinase (PI 3'-kinase) pathways downstream of the IGF-I receptor using the inhibitors PD98059 and LY294002, respectively, partially reversed IGF-I-induced inhibition. Acute (2-60 min) and chronic (24 h) exposure of A549 cells to 100 ng/ml IGF-I resulted in sustained phosphorylation of Akt/protein kinase B downstream of PI 3'-kinase, whereas p44/42 MAPK phosphorylation was decreased in response to chronic exposure to IGF-I. An IGF-I dose-dependent increase in the cyclin-dependent kinase inhibitor p21(Cip1/WAF1) was also observed over 24 h of treatment. Collectively, these data suggest that IGF-I is growth inhibitory to A549 cells, possibly via sustained activation of the PI 3'-kinase signaling pathway, and induction of p21(Cip1/WAF1).
Am J Respir Cell Mol Biol 2002 Sep
PMID:Insulin-like growth factor-I inhibits cell growth in the a549 non-small lung cancer cell line. 1220 96

Signaling events involving angiotensin IV (ANG IV)-mediated pulmonary artery endothelial cell (PAEC) proliferation were examined. ANG IV significantly increased upstream phosphatidylinositide (PI) 3-kinase (PI3K), PI-dependent kinase-1 (PDK-1), extracellular signal-related kinases (ERK1/2), and protein kinase B-alpha/Akt (PKB-alpha) activities, as well as downstream p70 ribosomal S6 kinase (p70S6K) activities and/or phosphorylation of these proteins. ANG IV also significantly increased 5-bromo-2'-deoxy-uridine incorporation into newly synthesized DNA in a concentration- and time-dependent manner. Pretreatment of cells with wortmannin and LY-294002, inhibitors of PI3K, or rapamycin, an inhibitor of the mammalian target of rapamycin kinase and p70S6K, diminished the ANG IV-mediated activation of PDK-1 and PKB-alpha as well as phosphorylation of p70S6K. Although an inhibitor of mitogen-activated protein kinase kinase, PD-98059, but not rapamycin, blocked ANG IV-induced phosphorylation of ERK1/2, both PD-98059 and rapamycin independently caused partial reduction in ANG IV-mediated cell proliferation. However, simultaneous treatment with PD-98059 and rapamycin resulted in total inhibition of ANG IV-induced cell proliferation. These results demonstrate that ANG IV-induced DNA synthesis is regulated in a coordinated fashion involving multiple signaling modules in PAEC.
Am J Physiol Lung Cell Mol Physiol 2002 Oct
PMID:Activation of multiple signaling modules is critical in angiotensin IV-induced lung endothelial cell proliferation. 1222 47

Resveratrol (RV), a polyphenolic substance found in grape skin, is proposed to account in part for the protective effect of red wine in the cardiovascular system. Angiotensin II (Ang II)-induced hypertrophy of vascular smooth muscle cells (VSMCs) is a pivotal step in the development of cardiovascular disease. The aims of this study were to test the hypothesis that RV may alter Ang II-mediated hypertrophic VSMC growth and to identify the putative underlying signaling pathways. We show that RV indeed potently inhibits Ang II-induced [(3)H]leucine incorporation in a concentration-dependent manner (50 microM RV, 71% inhibition). Western blot analysis reveals that phosphorylation of Akt/protein kinase B (PKB) and to a lesser extent the mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) 1/2, both essentially involved in Ang II-mediated hypertrophy, is dose dependently reduced by RV. Consistent with these results, we show that RV attenuates phosphorylation of the p70 ribosomal protein S6 kinase (p70(S6K)), a kinase downstream of the ERK 1/2 as well as the Akt pathway, that is implicated in Ang II-induced protein synthesis. Upstream of Akt/PKB RV seems to mediate its antihypertrophic effect by inhibiting phosphorylation of the phosphatidylinositol 3-kinase (PI(3)K) rather than by activating phosphatases. In summary, we demonstrate for the first time that RV inhibits Ang II-induced VSMC hypertrophy, possibly by interfering mainly with the PI(3)K/Akt and p70(S6K) but also with the ERK 1/2 signaling pathway. Thus, this study delivers important new insight in the molecular pathways that may contribute to the proposed beneficial effects of RV in cardiovascular disease.
Mol Pharmacol 2002 Oct
PMID:Resveratrol suppresses angiotensin II-induced Akt/protein kinase B and p70 S6 kinase phosphorylation and subsequent hypertrophy in rat aortic smooth muscle cells. 1223 23


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