Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P31749 (AKT)
 22,954 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cyclooxygenase (COX) 2 expression is regulated via the Ras signaling pathway, and induction of mutated Ras rapidly increases COX-2 levels in intestinal epithelial cells. Protein kinase B (Akt/PKB) is an important effector of Ras signaling and a critical component of Ras-mediated transformation. Here we investigate the role of Akt/PKB in K-Ras-mediated induction of COX-2. Rat intestinal epithelial cells (IEC-6) were transfected with an inducible K-RasVal12 cDNA (IEC-iK-Ras cells). Addition of 5 mM isopropyl-1-thio-beta-D-galactopyranoside induced the expression of K-RasVal12, followed by increased activity of extracellular signal-regulated kinase and Akt/PKB. COX-2 levels were dramatically increased after induction of K-RasVal12. Inhibition of MAPK/ERK kinase activity by PD 98059 completely blocked the K-Ras-mediated induction of COX-2, whereas inhibition of PI3K/Akt/PKB activity with LY 294002 or by expressing a dominant negative Akt (Akt-K179M) partially blocked the induction of COX-2 by K-Ras. Transient transfection of cells with phosphatidylinositol 3-kinase and Akt expression vectors revealed that PI3/Akt/PKB activity predominantly regulates the stability of COX-2 mRNA. Thus, Akt/PKB activity is involved in K-Ras-induced expression of COX-2 and stabilization of COX-2 mRNA largely depends on the activation of Akt/PKB.
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PMID:K-Ras-mediated increase in cyclooxygenase 2 mRNA stability involves activation of the protein kinase B1. 1128 46

Despite an improved understanding of the molecular mechanisms of insulin-like growth factor-I (IGF-I) signaling and the recognition that IGF-I mediates many effects in endothelial cells, some of which may be important for atherosclerosis, little is known about the signal transduction pathways that mediate the effects of IGF-I in endothelial cells. To that end, we examined the signaling pathways activated by IGF-I in endothelial cells and their contribution to IGF-I-stimulated endothelial cell migration and nuclear factor (NF)-kappaB-dependent transcription. Treatment of bovine pulmonary artery endothelial cells (PAEC) with IGF-I activated the mitogen-activated protein kinases extracellular signal-regulated kinase (ERK)1/2 and ERK5. In contrast, IGF-I had no effect on either c-Jun amino-terminal kinase or p38 kinase activity. IGF-I also activated phosphatidylinositol (PI) 3-kinase, as reflected by increased phosphorylation of AKT: There was no evidence of cross-talk between the ERK and PI 3-kinase pathways in PAEC. In PAEC transiently transfected with pTK81-NFkappaB-Luc, which contained four copies of the NF-kappaB DNA binding site 5' to a minimal promoter and the luciferase gene, treatment with 50 ng/ml IGF-I increased luciferase activity 1.8-fold. Inhibition of ERK activity using PD98059 and PI 3-kinase activity with LY 294002 abrogated the induction of NF-kappaB-dependent transcription by IGF-I, suggesting that both pathways contribute to the effect of IGF-I on NF-kappaBdependent transcription. In contrast to the effect of tumor necrosis factor-alpha on NF-kappaB activation, Western blot analyses demonstrated that IGF-I had no effect on IkappaB phosphorylation and degradation or nuclear translocation and DNA binding of NF-kappaB. These data suggest a direct of effect of IGF-I on nuclear NF-kappaB. IGF-I also increased endothelial cell migration approximately 2-fold, as demonstrated using a Boyden chamber apparatus. IGF-I-induced endothelial cell migration was inhibited, in part, by LY 294002 but not PD98059. Together, these studies demonstrate that IGF-I activates multiple signaling pathways in endothelial cells with little evidence for cross-talk between the pathways. Moreover, these pathways appear to mediate both overlapping and distinct effects in that activation of both PI 3-kinase and the ERKs contributed to the stimulation of NF-kappaB-dependent transcription by IGF-I, whereas only PI 3-kinase mediated IGF-I-stimulated endothelial cell migration.
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PMID:The role of phosphatidylinositol 3-kinase and the mitogen-activated protein kinases in insulin-like growth factor-I-mediated effects in vascular endothelial cells. 1131 33

Ionizing radiation is one of the agents inducing activation of DNA repair, cell cycle arrest, apoptosis and cell death. Here we report evidence for an enhanced activity of DNA polymerase beta, one of the repair enzymes, concomitant to the activation of the pathway phosphatidylinositol-3-kinase/AKT-1 (PI-3-kinase/AKT-1), which delivers a survival signal in Friend erythroleukemia cells exposed to 15 Gy. Significantly, the preincubation of the cellls with PI-3-kinase inhibitors wortmannin and LY 294002, disactivating this pathway, sensitizes the cells to ionizing radiation by further reducing the rate of proliferation without substantial variations of the number of dead cells. Thus, we suggest a role for these enzymes in maintaining survival programs upon exposure to ionizing radiation and in giving to these cells a chance to recover from this stress.
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PMID:Involvement of the pathway phosphatidylinositol-3-kinase/AKT-1 in the establishment of the survival response to ionizing radiation. 1136 19

Phosphatidylinositol 3'-kinase (PI3k) is implicated in a wide array of biological and pathophysiological responses. Thus, inhibiting molecules involved in its signal transduction pathway is a possible means of treating cancer. Our previous studies demonstrated that LY294002, a potent and selective PI3k inhibitor, decreases growth of ovarian carcinoma and ascites formation in an athymic mouse xenogeneic transplant model of ovarian cancer. However, the dose of LY294002 used to decrease tumor growth resulted in significant dermatological toxicity. We demonstrate herein that introduction of an active catalytic subunit of PI3k into an ovarian cancer cell line, and thus activation of the PI3k/AKT pathway, confers resistance to the effects of paclitaxel, one of the major drugs used in ovarian cancer therapy. The resistance to paclitaxel can be reversed in vitro by inhibition of PI3k. Therefore, we evaluated whether combined therapy with paclitaxel and LY294002 would result in increased efficacy and allow utilization of doses of LY294002 that do not induce dermatological toxicity. Two weeks after i.p. inoculation with OVCAR-3 ovarian cancer cells, mice were treated i.p. with LY294002 plus paclitaxel, each three times weekly on alternate days, for 4 weeks. Tumor burden in the LY294002 + paclitaxel, LY 294002 alone, and paclitaxel alone groups was reduced by 80% (P < 0.01), 38% (P < 0.05), and 51% (P < 0.05), respectively, compared with controls. Virtually no ascites developed in the combined treatment group; mean volume of ascites in the controls was 3.7 ml. Treatment with LY294002 alone reduced ascites by 70% (P < 0.01), whereas paclitaxel alone reduced ascites slightly but not significantly. No dermatological lesions or weight loss were observed in any treatment group. In vivo and in vitro morphological studies demonstrated that inhibition of PI3k enhanced paclitaxel-induced apoptosis in the human ovarian cancers. Our data suggest that a combination of a PI3k inhibitor and conventional chemotherapy may provide an effective approach to inhibiting tumor growth and ascites production in ovarian cancer with acceptable side effects.
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PMID:Inhibition of phosphatidylinositol 3'-kinase increases efficacy of paclitaxel in in vitro and in vivo ovarian cancer models. 1186 87

CKI p21 is a regulator of cellular responses to microtubule damage induced by drugs such as paclitaxel (PTX). It mediates the G1 4N arrest postactivation of the spindle assembly checkpoint and protects cancer cells against PTX-induced cytotoxicity. We demonstrated here that low doses of PTX that are unable to activate the spindle assembly checkpoint, upregulate p21 by a p53-dependent pathway and induce its translocation to the cytoplasm. This cytoplasmic accumulation of p21 resulted from an AKT-dependent p21 phosphorylation leading to an association of p21 with 14-3-3. Furthermore, the cytoplasmic p21 accumulation observed in PTX-treated cells was inhibited by LY 294002, a specific PI-3 kinase inhibitor or by the expression of a dominant-negative AKT mutant. However, the kinase activity of AKT was unchanged in PTX-treated cells, suggesting that low doses of PTX could regulate p21 phosphorylation via inhibition of its dephosphorylation. As a functional consequence, we found that cytoplasmic accumulation of the phosphorylated form of p21 prevents the inhibitory effect of p21, enabling these cells to escape to the p53-dependent Gl/S and G2/M checkpoints.
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PMID:Paclitaxel increases p21 synthesis and accumulation of its AKT-phosphorylated form in the cytoplasm of cancer cells. 1276 96

We have earlier reported that transforming growth factor-beta1 (TGF-beta1), a well-known inhibitor of hematopoiesis, stimulated colony formation from adult human bone marrow mononuclear cells (BM MNC) when used at low concentrations. We examined the possible molecular mechanism behind this bidirectional effect using CD34+ cells isolated from human BM for clonal assays and the KG1a cell line as a model system for analysis of proteins for signaling pathways by immunoblotting. We found that TGF-beta1 at low doses (picogram levels) stimulated the colony formation from CD34+ cells, indicating that these progenitors form the direct target of stimulatory action of TGF-beta1. CD34+ cells were found to be more sensitive to the TGF-beta1 concentration than the total MNC. We used the KG1a cell line as a model system for identification of mitogen-activated protein kinase (MAPK) and AKT signaling pathways involved in the process. Low doses strongly induced p44/42 MAPK phosphorylation, whereas high doses induced p38 activation. Use of specific p44/42 MAPK inhibitor PD 98059 in the colony assay abrogated the stimulatory effect of low TGF-beta1. On the other hand, use of p38 MAPK inhibitor SB 203580 along with low TGF-beta1 concentrations had a synergistic effect on stimulation of colony formation. Treatment of BM MNC with Anisomycin, which activates stress kinases, resulted in a dose-dependent inhibition of colony formation. This inhibition could not be rescued by stimulatory doses of TGF-beta1. Phosphorylation of AKT was found to occur in a dose-dependent way but declined slightly at the highest concentration used (10 ng/ml). Inhibition of the AKT pathway by LY 294002 strongly suppressed colony formation. These data indicate clearly that sustained activation of p44/42 MAPK perhaps forms the stimulatory signal induced by low TGF-beta1, whereas activation of p38 forms the inhibitory pathway.
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PMID:Differential activation of MAPK signaling pathways by TGF-beta1 forms the molecular mechanism behind its dose-dependent bidirectional effects on hematopoiesis. 1506 91

To determine whether Insulin-like growth factor (IGF-I) treatment represents a potential means of enhancing the survival of cardiac muscle cells from adriamycin (ADR)-induced cell death, the present study examined the ability of IGF-I to prevent cell death. The study was performed utilising the embryonic, rat, cardiac muscle cell line, H9C2. Incubating cardiac muscle cells in the presence of adriamycin increased cell death, as determined by MTT assay and annexin V-positive cell number. The addition of 100 ng/mL IGF-I, in the presence of adriamycin, decreased apoptosis. The effect of IGF-I on phosphorylation of PI, a substrate of phosphatidylinositol 3-kinase (PI 3-kinase) or protein kinase B (AKT), was also examined in H9C2 cardiac muscle cells. IGF-I increased the phosphorylation of ERK 1 and 2 and PKC zeta kinase. The use of inhibitors of PI 3-kinase (LY 294002), in the cell death assay, demonstrated partial abrogation of the protective effect of IGF-I. The MEK1 inhibitor-PD098059 and the PKC inhibitor-chelerythrine exhibited no effect on IGF-1-induced cell protection. In the regulatory subunit of PI3K-p85- dominant, negative plasmid-transfected cells, the IGF-1-induced protective effect was reversed. This data demonstrates that IGF-I protects cardiac muscle cells from ADR-induced cell death. Although IGF-I activates several signaling pathways that contribute to its protective effect in other cell types, only activation of PI 3-kinase contributes to this effect in H9C2 cardiac muscle cells.
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PMID:Signal transduction of the protective effect of insulin like growth factor-1 on adriamycin-induced apoptosis in cardiac muscle cells. 1508 39

Paf (1-o-alkyl-2-acetyl-sn-gylcero-3-phosphocholine) is a putative autocrine survival factor for the preimplantation embryo. It acts to induce receptor-mediated calcium transients in the early embryo. Inhibitors of 1-o-phosphatidylinositol-3-kinase (PI3kinase), such as wortmannin and LY 294002, blocked these calcium transients, implicating the generation of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in autocrine signal transduction in the early embryo. Perfusion of the embryo cytoplasm with a blocking antibody to PIP3 inhibited paf-induced calcium transients and hyperpolarization of the membrane potential. Furthermore, direct infusion of PIP3 into the embryo induced a nifedipine (10 micromol/L)- and diltiazem (10 micromol/L)-sensitive calcium current in the 2-cell embryo. PIP3 acts as a docking site on membranes for proteins that contain pleckstrin homology domains, such as the thymoma viral proto-oncogene protein (AKT) and phospholipase C gamma. The 2-cell embryo expressed three genes for AKT (Akt 1-3) and two genes for phospholipase C gamma (Plcg1 and Plcg2), and we confirmed the expression of both AKT and phospholipase C gamma 1 by immunolocalization. Paf induced increased accumulation of serine 473-phosphorylated AKT in the region of the plasma membrane, consistent with its recruitment to membrane PIP3. Inhibitors of PI3kinase, such as LY294002, and of AKT, e.g., deguelin and AKT-inhibitor, reduced zygote development in a dose-dependent manner, and this inhibition was partially reversed by the addition of paf to the culture medium. These results provide the first direct evidence that PIP3 and its responsive signaling pathways act in the 2-cell embryo. Since signal transduction via PI3kinase has important roles in governing the cell survival pathways, these results support the hypothesis that autocrine embryotropins, such as paf, act as survival factors.
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PMID:Direct evidence for the action of phosphatidylinositol (3,4,5)-trisphosphate-mediated signal transduction in the 2-cell mouse embryo. 1763 44

Inhibition of the forkhead transcription factor, FOXO3a, can promote the transition from primordial to primary follicle and subsequent follicle development in mammalian ovaries. Stem cell factor (SCF) initiates anti-apoptotic signaling from its membrane receptor, c-kit, to Bcl-2 family members through PI3K/AKT in oocytes of primordial follicles. However, whether FOXO3a mediates the apoptosis of naked oocytes and oocytes of primordial follicles remains unknown. In the present study, oocytes from nests and primordial follicles from neonatal rat ovaries were cultured, and oocyte apoptosis was examined using the TUNEL technique. The pro-apoptotic action of FOXO3a and the potential signal transduction pathways were investigated using RT-PCR, Western blot, and immunocytochemistry. Culturing oocytes in the presence of SCF did not affect the level of total FOXO3a protein, but rapidly elevated the level of phosphorylated FOXO3a (indicating functional suppression). As phosphorylated FOXO3a increased, oocyte apoptosis was inhibited. The specific PI3K/Akt inhibitor, LY 294002, abolished the phosphorylation of FOXO3a and the anti-apoptotic action of SCF. SCF down-regulated the expression of p27KIP1 and pro-apoptotic factors such as Bim, Bad, and Bax, and this activity was reversed by LY 294002. SCF up-regulated the expression of MnSOD, which was also inhibited by LY 294002. However, SCF had no effect on Bcl-2 protein. These results suggest that FOXO3a is involved in oocyte apoptosis in the neonatal rat ovary, and the SCF-PI3K/Akt-FOXO3a signaling pathway mediates oocyte apoptosis and primordial follicle formation.
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PMID:FOXO3a is involved in the apoptosis of naked oocytes and oocytes of primordial follicles from neonatal rat ovaries. 1925 7

Protein kinase B (PKB/Akt) plays a critical role in cell survival but the investigation of its involvement has been limited by the lack of specific pharmacological agents. In this study, using novel PKB inhibitors (VIII and XI), we investigated the role of PKB in cardioprotection of the rat and human myocardium, the location of PKB in relation to mitoK(ATP) channels and p38 mitogen-activated protein kinase (p38 MAPK), and whether the manipulation of PKB can overcome the unresponsiveness to protection of the diabetic myocardium. Myocardial slices from rat left ventricle and from the right atrial appendage of patients undergoing elective cardiac surgery were subjected to 90 min ischaemia/120 min reoxygenation at 37 degrees C. Tissue injury was assessed by creatine kinase (CK) released and determination of cell necrosis and apoptosis. The results showed that blockade of PKB activity caused significant reduction of CK release and cell death, a benefit that was as potent as ischaemic preconditioning and could be reproduced by blockade of phosphatidylinositol 3-kinase (PI-3K) with wortmannin and LY 294002. The protection was time dependent with maximal benefit seen when PKB and PI-3K were inhibited before ischaemia or during both ischaemia and reoxygenation. In addition, it was revealed that PKB is located downstream of mitoK(ATP) channels but upstream of p38 MAPK. PKB inhibition induced a similar degree of protection in the human and rat myocardium and, importantly, it reversed the unresponsiveness to protection of the diabetic myocardium. In conclusion, inhibition of PKB plays a critical role in protection of the mammalian myocardium and may represent a clinical target for the reduction of ischaemic injury.
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PMID:Selective blockade of protein kinase B protects the rat and human myocardium against ischaemic injury. 2040 80


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