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:2.7.11.2 (PDK1)
2,238 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The p70 S6 kinase (p70 S6K) was the first signaling element in mammalian cells shown to be inhibited by rapamycin. The activity of the p70 S6K in mammalian cell is upregulated by extracellular amino acids (especially leucine) and by signals from receptor tyrosine kinases (RTKs), primarily through activation of the type 1A PI-3 kinase. The amino acid-/rapamycin-sensitive input and the PI-3 kinase input are co-dominant but largely independent, in that deletion of the amino-terminal and carboxy-terminal noncatalytic sequences flanking the p70 S6K catalytic domain renders the kinase insensitive to inhibition by both rapamycin and by withdrawal of amino acids, whereas this p70 S6K mutant remains responsive to activation by RTKs and to inhibition by wortmannin. At a molecular level, this dual control of p70 S6K activity is attributable to phosphorylation of the two p70 S6K sites: The Ptd Ins 3,4,5P3-dependent kinasel (PDK1) phosphorylates p70 S6K at a Thr on the activation loop, whereas mTOR phosphorylates a Thr located in a hydrophobic motif carboxyterminal to the catalytic domain. Together these two phosphorylations engender a strong, positively cooperative activation of p70 S6K, so that each is indispensable for physiologic regulation. Like RTKs, the p70 S6K appears early in metazoan evolution and comes to represent an important site at which the more ancient, nutrient-responsive TOR pathway converges with the RTK/PI-3 kinase pathway in the control of cell growth. Dual regulation of p70 S6K is seen in Drosophila; however, this convergence is not yet evident in Caenorhabditis elegans, wherein nutrient activation of the insulin receptor (InsR) pathway negatively regulates dauer development and longevity, whereas the TOR pathway regulates overall mRNA translation through effectors distinct from p70 S6K, as in yeast. The C. elegans TOR and InsR pathways show none of the cross- or convergent regulation seen in mammalian cells. The nature of the elements that couple nutrient sufficiency to TOR activity remain to be discovered, and the mechanisms by which RTKs influence TOR activity in mammalian cells require further study. One pathway for RTK control involves the tuberous sclerosis complex, which is absent in C. elegans, but of major importance in Drosophila and higher metazoans.
...
PMID:TOR action in mammalian cells and in Caenorhabditis elegans. 1456 Sep 55

Recent evidence indicates that mutations in the gene encoding the WNK1 [with no K (lysine) protein kinase-1] results in an inherited hypertension syndrome called pseudohypoaldosteronism type II. The mechanisms by which WNK1 is regulated or the substrates it phosphorylates are currently unknown. We noticed that Thr-60 of WNK1, which lies N-terminal to the catalytic domain, is located within a PKB (protein kinase B) phosphorylation consensus sequence. We found that PKB phosphorylated WNK1 efficiently compared with known substrates, and both peptide map and mutational analysis revealed that the major PKB site of phosphorylation was Thr-60. Employing a phosphospecific Thr-60 WNK1 antibody, we demonstrated that IGF1 (insulin-like growth factor) stimulation of HEK-293 cells induced phosphorylation of endogenously expressed WNK1 at Thr-60. Consistent with PKB mediating this phosphorylation, inhibitors of PI 3-kinase (phosphoinositide 3-kinase; wortmannin and LY294002) but not inhibitors of mammalian target of rapamycin (rapamycin) or MEK1 (mitogen-activated protein kinase kinase-1) activation (PD184352), inhibited IGF1-induced phosphorylation of endogenous WNK1 at Thr-60. Moreover, IGF1-induced phosphorylation of endogenous WNK1 did not occur in PDK1-/- ES (embryonic stem) cells, in which PKB is not activated. In contrast, IGF1 still induced normal phosphorylation of WNK1 in PDK1(L155E/L155E) knock-in ES cells in which PKB, but not S6K (p70 ribosomal S6 kinase) or SGK1 (serum- and glucocorticoid-induced protein kinase 1), is activated. Our study provides strong pharmacological and genetic evidence that PKB mediates the phosphorylation of WNK1 at Thr-60 in vivo. We also performed experiments which suggest that the phosphorylation of WNK1 by PKB is not regulating its kinase activity or cellular localization directly. These results provide the first connection between the PI 3-kinase/PKB pathway and WNK1, suggesting a mechanism by which this pathway may influence blood pressure.
...
PMID:WNK1, the kinase mutated in an inherited high-blood-pressure syndrome, is a novel PKB (protein kinase B)/Akt substrate. 1461 43

Previously it has been reported that caveolin-1 (cav-1) has antiapoptotic activities in prostate cancer cells and functions downstream of androgenic stimulation. In this study, we demonstrate that cav-1 overexpression significantly reduced thapsigargin (Tg)-stimulated apoptosis. Examination of the phosphatidylinositol 3-kinase (PI3-K)/Akt signaling cascade revealed higher activities of PDK1 and Akt but not PI3-K in cav-1-stimulated cells compared to control cells. We subsequently found that cav-1 interacts with and inhibits serine/threonine protein phosphatases PP1 and PP2A through scaffolding domain binding site interactions. Deletion of the cav-1 scaffolding domain significantly reduces phosphorylated Akt and cell viability compared with wild-type cav-1. Analysis of potential substrates for PP1 and PP2A revealed that cav-1-mediated inhibition of PP1 and PP2A leads to increased PDK1, Akt, and ERK1/2 activities. We demonstrate that increased Akt activities are largely responsible for cav-1-mediated cell survival using dominant-negative Akt mutants and specific inhibitors to MEK1/MEK and show that cav-1 increases the half-life of phosphorylated PDK1 and Akt after inhibition of PI3-K by LY294002. We further demonstrate that cav-1-stimulated Akt activities lead to increased phosphorylation of multiple Akt substrates, including GSK3, FKHR, and MDM2. In addition, overexpression of cav-1 significantly increases translocation of phosphorylated androgen receptor to nucleus. Our studies therefore reveal a novel mechanism of Akt activation in prostate cancer and potentially other malignancies.
...
PMID:Caveolin-1 maintains activated Akt in prostate cancer cells through scaffolding domain binding site interactions with and inhibition of serine/threonine protein phosphatases PP1 and PP2A. 1464 48

The small molecule UCN-01 is a cyclin-dependent kinase (CDK) modulator shown to have antiproliferative effects against several in vitro and in vivo cancer models currently being tested in human clinical trials. Although UCN-01 may inhibit several serine-threonine kinases, the exact mechanism by which it promotes cell cycle arrest is still unclear. We have reported previously that UCN-01 promotes G(1)-S cell cycle arrest in a battery of head and neck squamous cancer cell lines. The arrest is accompanied by an increase in both p21(waf1/cip1) and p27(kip1) CDK inhibitors leading to loss in G(1) CDK activity. In this report, we explore the role and the mechanism for the induction of these endogenous CDK inhibitors. We observed that p21 was required for the cell cycle effects of UCN-01, as HCT116 lacking p21 (HCT116 p21(-/-)) was refractory to the cell cycle effects of UCN-01. Moreover, UCN-01 promoted the accumulation of p21 at the mRNA level in the p53-deficient HaCaT cells without increase in the p21 mRNA half-life, suggesting that UCN-01 induced p21 at the transcriptional level. To study UCN-01 transcriptional activation of p21, we used several p21(waf1/cip1) promoter-driven luciferase reporter plasmids and observed that UCN-01 activated the full-length p21(waf1/cip1) promoter and a construct lacking p53 binding sites. The minimal promoter region required for UCN-01 (from -110 bp to the transcription start site) was the same minimal p21(waf1/cip1) promoter region required for Ras enhancement of p21(waf1/cip1) transcription. Neither protein kinase C nor PDK1/AKT pathways were relevant for the induction of p21 by UCN-01. In contrast, the activation of mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK)/extracellular signal-regulated kinase mitogen-activated protein kinase pathways was required for p21 induction as UCN-01 activated this pathway, and genetic or chemical MEK inhibitors blunted p21 accumulation. These results demonstrated for the first time that p21 is required for UCN-01 cell cycle arrest. Moreover, we showed that the accumulation of p21 is transcriptional via activation of the MEK pathway. This novel mechanism, by which UCN-01 exerts its antiproliferative effect, represents a promising strategy to be exploited in future clinical trials.
...
PMID:UCN-01-induced cell cycle arrest requires the transcriptional induction of p21(waf1/cip1) by activation of mitogen-activated protein/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase pathway. 1515 Jan 22

The hematopoietic class III receptor tyrosine kinase (RTK) Flt3 (Flk2, STK1) has recently received much attention as a potential drug target. Activation of Flt3 by different types of mutations plays an important role for proliferation, resistance to apoptosis, and prevention of differentiation of leukemic blasts in acute myeloid leukemia (AML). At least one type of such mutations - an internal tandem duplication in the Flt3 juxtamembrane domain (Flt3-ITD) - has been associated with an unfavorable prognosis. Signal transduction of Flt3 involves activation of several conserved pathways, including the RAS/MAP-Kinase and the phosphoinositide-3-kinase/Akt signaling cascades. Transforming versions of Flt3 exhibit altered signaling, for example a very pronounced activation of STAT5, ultimately resulting in alternate profiles of gene expression and cell transformation. Selective inhibitors of Flt3 tyrosine kinase activity have the potential to suppress aberrant Flt3 signaling. Although highly homologous to other class III RTKs, Flt3 is resistant to the phenylaminopyrimidine STI571 (Gleevec, Imatinib), a potent inhibitor of other RTKs in the family, such as the PDGFbeta-receptor or c-Kit. STI571 binding to Flt3 is prevented by the phenylalanine 691 side-chain in the ATP binding center and mutating this site to threonine renders the corresponding Flt3 mutant sensitive to STI571. Compounds of several other structural families, including the quinoxaline AG1296, the bis(1H-2-indolyl)-1-methanone D-65476, the indolinones SU5416 and SU11248, the indolocarbazoles PKC412 and CEP-701, and the piperazonyl quinazoline CT53518, are potent inhibitors of Flt3 kinase. They exhibit different selectivity profiles, both with respect to other kinases and among wildtype Flt3 and its activated versions. These compounds hold promise as novel drugs against AML and as probes for understanding activation mechanisms and signaling pathways in the class III RTK family.
...
PMID:Flt3 receptor tyrosine kinase as a drug target in leukemia. 1518 May 25

Most of the protein kinase inhibitors being developed are directed toward the adenosine triphosphate (ATP) binding site that is highly conserved in many kinases. A major issue with these inhibitors is the specificity for a given kinase. Structure determination of several kinases has shown that protein kinases adopt distinct conformations in their inactive state, in contrast to their strikingly similar conformations in their active states. Hence, alternative assay formats that can identify compounds targeting the inactive form of a protein kinase are desirable. The authors describe the development and optimization of an Immobilized Metal Assay for Phosphochemicals (IMAP)-based couple d assay using PDK1 and inactive Akt-2 enzymes. PDK1 phosphorylates Akt-2 at Thr 309 in the catalytic domain, leading to enzymatic activation. Activation of Akt by PDK1 is measured by quantitating the phosphorylation of Akt-specific substrate peptide using the IMAP assay format. This IMAP-coupled assay has been formatted in a 384-well microplate format with a Z' of 0.73 suitable for high-throughput screening. This assay was evaluated by screening the biologically active sample set LOPAC trade mark and validated with the protein kinase C inhibitor staurosporine. The IC(50) value generated was comparable to the value obtained by the radioactive (33)P-gamma-ATP flashplate transfer assay. This coupled assay has the potential to identify compounds that target the inactive form of Akt and prevent its activation by PDK1, in addition to finding inhibitors of PDK1 and activated Akt enzymes.
...
PMID:Development of a fluorescence polarization bead-based coupled assay to target different activity/conformation states of a protein kinase. 1519 48

Akt (= protein kinase B), a subfamily of the AGC serine/threonine kinases, plays critical roles in survival, proliferation, glucose metabolism, and other cellular functions. Akt activation requires the recruitment of the enzyme to the plasma membrane by interacting with membrane-bound lipid products of phosphatidylinositol 3-kinase. Membrane-bound Akt is then phosphorylated at two sites for its full activation; Thr-308 in the activation loop of the kinase domain is phosphorylated by 3-phosphoinositide-dependent kinase-1 (PDK1) and Ser-473 in the C-terminal hydrophobic motif by a putative kinase PDK2. The identity of PDK2 has been elusive. Here we present evidence that conventional isoforms of protein kinase C (PKC), particularly PKCbetaII, can regulate Akt activity by directly phosphorylating Ser-473 in vitro and in IgE/antigen-stimulated mast cells. By contrast, PKCbeta is not required for Ser-473 phosphorylation in mast cells stimulated with stem cell factor or interleukin-3, in serum-stimulated fibroblasts, or in antigen receptor-stimulated T or B lymphocytes. Therefore, PKCbetaII appears to work as a cell type- and stimulus-specific PDK2.
...
PMID:Protein kinase C betaII regulates Akt phosphorylation on Ser-473 in a cell type- and stimulus-specific fashion. 1536 15

Saccharomyces cerevisiae Pkh1 and Pkh2 (orthologues of mammalian protein kinase, PDK1) are functionally redundant. These kinases activate three AGC family kinases involved in the maintenance of cell wall integrity: Ypk1 and Ypk2, two closely related, functionally redundant enzymes (orthologues of mammalian protein kinase SGK), and Pkc1 (orthologue of mammalian protein kinase PRK2). Pkh1 and Pkh2 activate Ypk1, Ypk2 and Pkc1 by phosphorylating a Thr in a conserved sequence motif (PDK1 site) within the activation loop of these proteins. A fourth protein kinase involved in growth control and stress response, Sch9 (orthologue of mammalian protein kinase c-Akt/PKB), also carries the conserved activation loop motif. Like other AGC family kinases, Ypk1, Ypk2, Pkc1 and Sch9 also carry a second conserved sequence motif situated in a region C-terminal to the catalytic domain, called the hydrophobic motif (PDK2 site). Currently, there is still controversy surrounding the identity of the enzyme responsible for phosphorylating this second site and the necessity for phosphorylation at this site for in vivo function. Here, genetic and biochemical methods have been used to investigate the physiological consequences of phosphorylation at the PDK1 and PDK2 sites of Ypk1, Pkc1 and Sch9. It was found that phosphorylation at the PDK1 site in the activation loop is indispensable for the essential functions of all three kinases in vivo, whereas phosphorylation at the PDK2 motif plays a non-essential and much more subtle role in modulating the ability of these kinases to regulate the downstream processes in which they participate.
...
PMID:Differential roles of PDK1- and PDK2-phosphorylation sites in the yeast AGC kinases Ypk1, Pkc1 and Sch9. 1547 Jan 9

Degeneration of neurons is a key problem in Alzheimer's disease (AD) and neuroprotection is a possible way to safeguard neurons from neurodegeneration. Polysaccharides isolated from Chinese medicinal herbs have been investigated extensively for their anti-tumor and immune stimulating effects. Yet, little is known about the effects of polysaccharides in neurons. Recently, two pure polysaccharides isolated from the flowers of Nerium indicum were shown to stimulate proliferation and differentiation of PC12 pheochromocytoma cells, an effect similar to that observed from nerve growth factor. In this notion, it is hypothesized that polysaccharides isolated from the flowers of N. indicum could exhibit beneficial effects in neurons. In this study, we isolated, characterized and investigated two new polysaccharides from the flowers of N. indicum for their neuroprotective effects on neurons against serum-deprivation and beta-amyloid (Abeta) peptide toxicity in primary rat cortical neuronal cultures. Pretreatment of the polysaccharides significantly reduced the number of apoptotic neurons revealed by DAPI staining when neurons were exposed to serum-free medium. Besides, the polysaccharides could also decrease the activity of caspase-3 triggered by Abeta peptides. Western blot analysis indicated that polysaccharides stimulated the phosphorylation of PDK-1 (Serine 241) and Akt (Threonine 308). In conclusion, the polysaccharides J2, J3 and J4 isolated from N. indicum provide a lead for future development of neuroprotective agent against neuronal death in neurodegenerative diseases and the neuroprotective mechanism may primarily rely on activation of Akt survival signaling pathway.
...
PMID:Characterization of polysaccharides from the flowers of Nerium indicum and their neuroprotective effects. 1549 66

The molecular mechanisms by which the anti-HER2 antibodies trastuzumab and its murine equivalent 4D5 inhibit tumor growth and potentiate chemotherapy are not fully understood. Inhibition of signaling through the phosphatidylinositol 3-kinase (PI3K)-AKT pathway may be particularly important. Treatment of breast cancer cells that overexpress HER2 with trastuzumab inhibited HER2-HER3 association, decreased PDK1 activity, reduced Thr-308 and Ser-473 phosphorylation of AKT, and reduced AKT enzymatic activity. To place the role of PI3K-AKT in perspective, gene expression was studied by using Affymetrix microarrays and real time reverse transcription-PCR. Sixteen genes were consistently down-regulated 2.0-4.9-fold in two antibody-treated breast cancer cell lines. Fourteen of the 16 genes were involved in three major functional areas as follows: 7 in cell cycle regulation, particularly of the G(2)-M; 5 in DNA repair/replication; and 2 in modifying chromatin structure. Of the 16 antibody-regulated genes, 64% had roles in cell growth/maintenance and 52% contributed to the cell cycle. Direct inhibition of PI3K with an inhibitor markedly reduced expression of 14 genes that were also affected by the antibody. Constitutive activation of AKT1 blocked the effect of the anti-HER2 antibody on cell cycle arrest and on eight differentially expressed genes. The antibody enhanced docetaxel-induced growth inhibition but did not increase the fraction of apoptotic cells induced with docetaxel alone. In contrast, the antibody plus docetaxel markedly down-regulated two genes, HEC and DEEPEST, required for passage through G(2)-M. Thus, anti-HER2 antibody preferentially affects genes contributing to cell cycle progression and cell growth/maintenance, in part through the PI3K-AKT signaling. Transcriptional regulation by anti-HER2 antibody through PI3K-AKT pathway may potentiate the growth inhibitory activity of docetaxel by affecting cell cycle progression.
...
PMID:Genes affecting the cell cycle, growth, maintenance, and drug sensitivity are preferentially regulated by anti-HER2 antibody through phosphatidylinositol 3-kinase-AKT signaling. 1550 38


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---