Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.10.2 (focal adhesion kinase)
44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Growth factors and hormones activate protein translation by phosphorylation and inactivation of the translational repressors, the eIF4E-binding proteins (4E-BPs), through a wortmannin- and rapamycin-sensitive signaling pathway. The mechanism by which signals emanating from extracellular signals lead to phosphorylation of 4E-BPs is not well understood. Here we demonstrate that the activity of the serine/threonine kinase Akt/PKB is required in a signaling cascade that leads to phosphorylation and inactivation of 4E-BP1. PI 3-kinase elicits the phosphorylation of 4E-BP1 in a wortmannin- and rapamycin-sensitive manner, whereas activated Akt-mediated phosphorylation of 4E-BP1 is wortmannin resistant but rapamycin sensitive. A dominant negative mutant of Akt blocks insulin-mediated phosphorylation of 4E-BP1, indicating that Akt is required for the in vivo phosphorylation of 4E-BP1. Importantly, an activated Akt induces phosphorylation of 4E-BP1 on the same sites that are phosphorylated upon serum stimulation. Similar to what has been observed with serum and growth factors, phosphorylation of 4E-BP1 by Akt inhibits the interaction between 4E-BP1 and eIF-4E. Furthermore, phosphorylation of 4E-BP1 by Akt requires the activity of FRAP/mTOR. FRAP/mTOR may lie downstream of Akt in this signaling cascade. These results demonstrate that the PI 3-kinase-Akt signaling pathway, in concert with FRAP/mTOR, induces the phosphorylation of 4E-BP1.
...
PMID:4E-BP1, a repressor of mRNA translation, is phosphorylated and inactivated by the Akt(PKB) signaling pathway. 947 19

The FKBP12-rapamycin associated protein (FRAP, also RAFT, mTOR) belongs to a family of phosphatidylinositol kinase-related kinases. These kinases mediate cellular responses to stresses such as DNA damage and nutrient deprivation in a variety of eukaryotes from yeast to humans. FRAP regulates G(1) cell cycle progression and translation initiation in part by controlling the phosphorylation states of a number of translational and cell cycle regulators. Although FRAP is known to be phosphorylated in vivo and to phosphorylate several proteins (including itself) in vitro, FRAP's phosphorylation sites and substrate specificity are unknown. We report here the identification of a FRAP autophosphorylation site. This site, Ser-2481, is located in a hydrophobic region near the conserved carboxyl-terminal FRAP tail. We demonstrate that the COOH-terminal tail is required for FRAP kinase activity and for signaling to the translational regulator p70(s6k) (ribosomal subunit S6 kinase). Phosphorylation of wild-type but not kinase-inactive FRAP occurs at Ser-2481 in vivo, suggesting that Ser-2481 phosphorylation is a marker of FRAP autokinase activity in cells. FRAP autophosphorylation is blocked completely by wortmannin treatment but not by rapamycin treatment, amino acid deprivation, or serum withdrawal, treatments that lead to acute dephosphorylation of eIF4E-binding protein (4E-BP1) and p70(s6k). Ser-2481 phosphorylation increases slightly upon c-Akt/PKB activation and dramatically upon calyculin A treatment of T-cells. These results suggest that FRAP-responsive dephosphorylation of 4E-BP1 and p70(s6k) occurs through a mechanism other than inhibition of intrinsic FRAP kinase activity.
...
PMID:FKBP12-rapamycin-associated protein (FRAP) autophosphorylates at serine 2481 under translationally repressive conditions. 1070 16

Inhibitors of signalling pathways were used to dissect the mechanism of insulin action on expression of the gene encoding glucokinase in cultured rat hepatocytes. Wortmannin and LY 294002 completely prevented the insulin-induced increase in glucokinase mRNA seen in unhibited cells, indicating that the phosphoinositide 3-kinase module has a key role. A ligand inducible protein kinase B (PKB, also termed cAkt) fusion protein was expressed by using adenoviral transduction of hepatocytes in primary culture. The PKB activity of this protein was shown to be activated in transduced hepatocytes within 30 min of the addition of 4-hydroxytamoxifen and to stay high for 8 h, as a result of serine phosphorylation at position 473 of PKB. The increase in PKB activity was reflected in the hyperphosphorylation of phosphorylated, heat and acid stable regulated by insulin protein (PHAS-I; also termed 4E-BP1, for eukaryotic initiation factor 4E-binding protein 1), a protein involved in the regulation of translation initiation. These effects were comparable to the insulin-induced activation of endogenous PKB and phosphorylation of PHAS-I in non-transduced hepatocytes. The addition of tamoxifen to transduced hepatocytes resulted in an induction of glucokinase mRNA with kinetics and magnitude similar to those of insulin-induced mRNA accumulation. The effect of tamoxifen depended on stimulated PKB activity because it did not occur in hepatocytes that were transduced with a mutant PKB fusion protein that was refractory to activation with tamoxifen. These results establish that acute activation of PKB is sufficient to produce an insulin-like induction of glucokinase in isolated hepatocytes. Together with the inhibition by phosphoinositide 3-kinase inhibitors, they suggest that the activation of PKB might be critical in mediating the induction of glucokinase by insulin. In addition, experiments showed that PD98059 decreased by half the increase in glucokinase mRNA brought about by insulin, suggesting a contributory role of the mitogen-activated protein kinase cascade.
...
PMID:Activation of protein kinase B/cAkt in hepatocytes is sufficient for the induction of expression of the gene encoding glucokinase. 1104 16

Tumstatin is a 28-kilodalton fragment of type IV collagen that displays both anti-angiogenic and proapoptotic activity. Here we show that tumstatin functions as an endothelial cell-specific inhibitor of protein synthesis. Through a requisite interaction with alphaVbeta3 integrin, tumstatin inhibits activation of focal adhesion kinase (FAK), phosphatidylinositol 3-kinase (PI3-kinase), protein kinase B (PKB/Akt), and mammalian target of rapamycin (mTOR), and it prevents the dissociation of eukaryotic initiation factor 4E protein (eIF4E) from 4E-binding protein 1. These results establish a role for integrins in mediating cell-specific inhibition of cap-dependent protein synthesis and suggest a potential mechanism for tumstatin's selective effects on endothelial cells.
...
PMID:Tumstatin, an endothelial cell-specific inhibitor of protein synthesis. 1177 52

The phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA), a potent stimulator of Erk, leads to the phosphorylation of 4E-BP1 and its dissociation from eIF4E. In contrast to agonists such as insulin, this occurs independently of PKB activation. In this report, we investigate the mechanism by which TPA regulates 4E-BP1 phosphorylation. Treatment of HEK293 cells with TPA was found to result in the phosphorylation of 4E-BP1 at Ser(64), Thr(69), and Thr(36/45). The TPA-stimulated phosphorylation of all these sites is sensitive to inhibitors of MEK and to the inhibitor of mTOR, rapamycin, indicating that inputs from both mTOR and MEK are required for the regulation of 4E-BP1 phosphorylation by TPA. Indeed, evidence is presented that mTOR may initially be required for the phosphorylation of Thr(45) in a priming step, which is necessary for the subsequent phosphorylation of Ser(64) and Thr(69) through an Erk-dependent pathway. Overexpression of constitutively active MEK in HEK293 cells resulted both in the phosphorylation of 4E-BP1 at Ser(64) and Thr(36/45) and its release from eIF4E. In this case, the phosphorylation of these sites was also blocked by inhibitors of MEK or by rapamycin. In conclusion, the Erk pathway, via mechanisms also requiring mTOR, regulates the phosphorylation of multiple sites in 4E-BP1 in vivo and this is sufficient for the release of 4E-BP1 from eIF4E.
...
PMID:The extracellular signal-regulated kinase pathway regulates the phosphorylation of 4E-BP1 at multiple sites. 1179 19

The mechanisms by which insulin-like growth factor I (IGF-I) and insulin regulate eukaryotic initiation factor (eIF)4F formation were examined in the ovine fetus. Insulin infusion increased phosphorylation of eIF4E-binding protein (4E-BP1) in muscle and liver. IGF-I infusion did not alter 4E-BP1 phosphorylation in liver. In muscle, IGF-I increased 4E-BP1 phosphorylation by 27%; the percentage in the gamma-form in the IGF-I group was significantly lower than that in the insulin group. In liver, only IGF-I increased eIF4G. Both IGF-I and insulin increased eIF4E. eIF4G binding in muscle, but only insulin decreased the amount of 4E-BP1 associated with eIF4E. In liver, only IGF-I increased eIF4E. eIF4G binding. Insulin increased the phosphorylation of p70 S6 kinase (p70(S6k)) in both muscle and liver and protein kinase B (PKB/Akt) in muscle, two indicative signal proteins in the phosphatidylinositol (PI) 3-kinase pathway. IGF-I increased PKB/Akt phosphorylation in muscle but had no effect on p70(S6k) phosphorylation in muscle or liver. We conclude that insulin and IGF-I modulate eIF4F formation; however, the two hormones have different regulatory mechanisms. Insulin increases phosphorylation of 4E-BP1 and eIF4E. eIF4G binding in muscle, whereas IGF-I regulates eIF4F formation by increasing total eIF4G. Insulin, but not IGF-I, decreased 4E-BP1 content associated with eIF4E. Insulin regulates translation initiation via the PI 3-kinase-p70(S6k) pathway, whereas IGF-I does so mainly via mechanisms independent of the PI 3-kinase-p70(S6k) pathway.
...
PMID:IGF-I and insulin regulate eIF4F formation by different mechanisms in muscle and liver in the ovine fetus. 1216 54

Tumstatin and endostatin are two inhibitors of angiogenesis derived from precursor human collagen molecules known as alpha 3 chain of type IV collagen and alpha1 chain of type XVIII collagen, respectively. Although both these inhibitors are noncollagenous (NC1) domain fragments of collagens, they only share a 14% amino acid homology. In the present study we evaluated the functional receptors, mechanism of action, and intracellular signaling induced by these two collagen-derived inhibitors. Human tumstatin prevents angiogenesis via inhibition of endothelial cell proliferation and promotion of apoptosis with no effect on migration, whereas human endostatin prevents endothelial cell migration with no effect on proliferation. We demonstrate that human tumstatin binds to alpha v beta 3 integrin in a vitronectin/fibronectin/RGD cyclic peptide independent manner, whereas human endostatin competes with fibronectin/RGD cyclic peptide to bind alpha 5 beta 1 integrin. The activity of human tumstatin is mediated by alpha v beta 3 integrin, whereas the activity of human endostatin is mediated by alpha 5 beta 1 integrin. Additionally, although human tumstatin binding to alpha v beta 3 integrin leads to the inhibition of Cap-dependent translation (protein synthesis) mediated by focal adhesion kinase/phosphatidylinositol 3-kinase/Akt/mTOR/4E-BP1 pathway, human endostatin binding to alpha 5 beta 1 integrin leads to the inhibition of focal adhesion kinase/c-Raf/MEK1/2/p38/ERK1 mitogen-activated protein kinase pathway, with no effect on phosphatidylinositol 3-kinase/Akt/mTOR/4E-BP1 and Cap-dependent translation. Collectively, such distinct properties of human tumstatin and human endostatin provide the first insight into their diverse antiangiogenic actions and argue for combining them for targeting tumor angiogenesis.
...
PMID:Human tumstatin and human endostatin exhibit distinct antiangiogenic activities mediated by alpha v beta 3 and alpha 5 beta 1 integrins. 3174 8

Abnormal protein tyrosine kinases (PTKs) cause many human leukemias. For example, BCR/ABL causes chronic myelogenous leukemia (CML), whereas FLT3 mutations contribute to the pathogenesis of acute myelogenous leukemia. The ABL inhibitor Imatinib (Gleevec, STI571) has remarkable efficacy for treating chronic phase CML, and FLT3 inhibitors (e.g., PKC412) show similar promise in preclinical studies. However, resistance to PTK inhibitors is a major emerging problem that may limit long-term therapeutic efficacy. Development of rational combination therapies will probably be required to effect cures of these and other neoplastic disorders. Here, we report that the mTOR inhibitor rapamycin synergizes with Imatinib against BCR/ABL-transformed myeloid and lymphoid cells and increases survival in a murine CML model. Rapamycin/Imatinib combinations also inhibit Imatinib-resistant mutants of BCR/ABL, and rapamycin plus PKC412 synergistically inhibits cells expressing PKC412-sensitive or -resistant leukemogenic FLT3 mutants. Biochemical analyses raise the possibility that inhibition of 4E-BP1 phosphorylation may be particularly important for the synergistic effects of PTK inhibitor/rapamycin combinations. Addition of a mitogen-activated protein kinase kinase inhibitor to rapamycin or rapamycin plus PTK inhibitor further increases efficacy. Our results suggest that simultaneous targeting of more than one signaling pathway required by leukemogenic PTKs may improve the treatment of primary and relapsed CML and/or acute myelogenous leukemia caused by FLT3 mutations. Similar strategies may be useful for treating solid tumors associated with mutant and/or overexpressed PTKs.
...
PMID:Combination of rapamycin and protein tyrosine kinase (PTK) inhibitors for the treatment of leukemias caused by oncogenic PTKs. 1497 43

Acute alcohol intoxication impairs myocardial protein synthesis in rats, secondary to a diminished mRNA translational efficiency. Decreased mRNA translational efficiency occurs through altered regulation of peptide chain initiation. The purpose of the present set of experiments was to determine whether acute alcohol intoxication alters the phosphorylation state of eukaryotic initiation factor (eIF) 4G, eIF4G.eIF4E complex formation, and the mammalian target of rapamycin (mTOR) signaling pathway in the heart. Acute alcohol intoxication was induced by injection of alcohol (75 mmol/kg body wt ip). Control animals received an equal volume of saline. Alcohol administration enhanced phosphorylation of eIF4G (Ser(1108)) approximately threefold. Alcohol administration lowered formation of the active eIF4G.eIF4E complex by >90%, whereas it increased the abundance of the inactive 4E-binding protein 1 (4E-BP1).eIF4E complex by approximately 160%. Phosphorylation of mTOR on Ser(2448) and Ser(2481) was decreased by 50%. Reduced mTOR phosphorylation did not result from decreased phosphorylation of PKB. Phosphorylation of 4E-BP1 and S6 kinase 1 (Thr(389)), downstream targets of mTOR, were also reduced after acute alcohol administration. These data suggest that acute alcohol-induced impairments in myocardial mRNA translation initiation result, in part, from marked decreases in eIF4G.eIF4E complex formation, which appear to be independent of changes in phosphorylation of eIF4G but dependent on mTOR.
...
PMID:Acute alcohol intoxication enhances myocardial eIF4G phosphorylation despite reducing mTOR signaling. 1538 9

The protein TRB3 (tribbles 3), also called NIPK (neuronal cell death-inducible protein kinase), was recently identified as a protein-protein interaction partner and an inhibitor of PKB (protein kinase B). To explore the hypothesis that TRB3/NIPK might act as a negative regulator of insulin signalling in the liver, this protein was overexpressed by adenoviral transduction of primary cultures of rat hepatocytes, and various aspects of insulin action were investigated. The insulin-induced phosphorylation of Ser-473 and Thr-308 of PKB was found to be undiminished in transduced hepatocytes with a molar excess of TRB3/NIPK over PKB of more than 25-fold. Consistent with unimpaired insulin activation of PKB, the stimulation of Ser-21 and Ser-9 phosphorylation of glycogen synthase kinase 3-alpha and -beta, and the apparent phosphorylation level of 4E-BP1 (eukaryotic initiation factor 4-binding protein 1), were similar in transduced and control hepatocytes. The induction by insulin of the mRNAs encoding glucokinase and SREBF1 (sterol-regulatory-element-binding factor 1) were also normal in TRB3/NIPK hepatocytes. In contrast, the insulin-dependent induction of these two genes, as well as the activation of PKB, were shown to be suppressed in hepatocytes treated with the lipid ether compound PIA6 (phosphatidylinositol ether lipid analogue 6), a recently discovered specific inhibitor of PKB. Since TRB3/NIPK was reported to be increased in the liver of fasting mice, the effects of glucagon, glucocorticoids and insulin on the level of endogenous TRB3/NIPK mRNA in primary hepatocytes were investigated. No significant change in mRNA level occurred under any of the hormonal treatments. The present study does not support the hypothesis that the physiological role of TRB3/NIPK might be to put a brake on insulin signalling in hepatocytes.
...
PMID:Lack of evidence for a role of TRB3/NIPK as an inhibitor of PKB-mediated insulin signalling in primary hepatocytes. 1546 16


1 2 3 4 5 6 7 8 Next >>

---