Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.2 (PDK1)
 2,238 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The protein kinase Akt/PKB is stimulated by the phosphorylation of two regulatory residues, Thr 309 of the activation segment and Ser 474 of the hydrophobic motif (HM), that are structurally and functionally conserved within the AGC kinase family. To understand the mechanism of PKB regulation, we determined the crystal structures of activated kinase domains of PKB in complex with a GSK3beta-peptide substrate and an ATP analog. The activated state of the kinase was generated by phosphorylating Thr 309 using PDK1 and mimicking Ser 474 phosphorylation either with the S474D substitution or by replacing the HM of PKB with that of PIFtide, a potent mimic of a phosphorylated HM. Comparison with the inactive PKB structure indicates that the role of Ser 474 phosphorylation is to promote the engagement of the HM with the N-lobe of the kinase domain, promoting a disorder-to-order transition of the alphaC helix. The alphaC helix, by interacting with pThr 309, restructures and orders the activation segment, generating an active kinase conformation. Analysis of the interactions between PKB and the GSK3beta-peptide explains how PKB selects for protein substrates distinct from those of PKA.
Nat Struct Biol 2002 Dec
PMID:Crystal structure of an activated Akt/protein kinase B ternary complex with GSK3-peptide and AMP-PNP. 1243 48

Dichloroacetic acid (DCA), chlorofluoroacetic acid (CFA), and difluoroacetic acid (DFA) are inhibitors of pyruvate dehydrogenase kinase. DCA is used for the clinical management of congenital lactic acidosis. Glutathione transferase zeta (GSTZ1-1) catalyzes the biotransformation of DCA and CFA, and DCA is a mechanism-based inactivator of GSTZ1-1. In rodents, DCA causes multiorgan toxicities and is hepatocarcinogenic. The toxic effects of CFA, which is an excellent substrate but a poor inactivator of GSTZ1-1, have not been investigated. The objective of this study was to investigate the nephrotoxicity of CFA. Rats given a single dose of 1.5 mmol/kg CFA became anuric and died within 24 h. Urinalysis and light microscopic analysis showed that rats given 0.6-1.2 mmol/kg CFA developed polyuria, glycosuria, and renal proximal tubular damage. Electron microscopic analysis indicated a role for apoptosis in CFA-induced cell death. The nephrotoxicity of CFA was associated with a dose-dependent increase in inorganic fluoride excretion. Treatment of rats with DCA for 5 days to inactivate GSTZ1-1 failed to prevent metabolism of CFA to fluoride and did not block CFA-induced renal damage. A role for GSTZ1-1-catalyzed release of fluoride from CFA is proposed but a role for other enzymes cannot be excluded. DFA, which is not metabolized to fluoride by GSTZ1-1, was given to rats as a control and was also nephrotoxic: rats given 1.2 mmol DFA/kg/day for 5 days had normal urine volumes but showed proximal and distal tubular damage; fluoride excretion was not elevated. The mechanism of DFA-induced nephrotoxicity is not known but appears to differ from that of CFA.
Toxicol Sci 2002 Dec
PMID:Nephrotoxicity of chlorofluoroacetic acid in rats. 1244 71

In nutrient-deprived cells autophagy recycles cytoplasmic constituents by engulfing and degrading them in membrane-bound autophagic vacuoles. The regulation of autophagic vacuole formation is poorly understood, but here we show this process is under strict cell-cycle control in cultured animal cells. We found strong inhibition of autophagic vacuole accumulation in nocodazole-arrested pseudo-prometaphase cells, and also in metaphase and anaphase cells generated on release from the nocodazole arrest. Autophagic vacuoles reappeared after closure of the nuclear envelope in telophase/G1. Treatment with phosphoinositide 3(PI3)-kinase inhibitors wortmannin, LY294002 and 3-methyladenine (known to inhibit the autophagic response in interphase cells) rescued autophagy in mitotic cells without inducing reassembly of vesiculated ER and Golgi compartments. The autophagy induced in mitotic cells was inhibited by amino acids, and the resulting autophagosomes contained proteins LC3 and Lamp1, known to be associated with autophagosomes in interphase cells. The mitotic inhibition of autophagy was not relieved by rapamycin treatment or in PDK1-/- embryonic stem cells, by microinjection of inhibitory antibodies against the class III PI3 kinase VPS34, or in cell lines lacking the p85 regulatory subunits of class IA PI3 kinases. Our results show that autophagy is under strict mitotic control and indicate a novel role for phosphoinositide 3-kinases or other wortmannin/LY294002-sensitive kinases in mitotic membrane traffic regulation.
Traffic 2002 Dec
PMID:Inhibition of autophagy in mitotic animal cells. 1245 51

We determined basal and insulin-stimulated responses on signaling intermediates in soleus skeletal muscle from male Wistar and diabetic Goto-Kakizaki (GK) rats. Rats were infused with glucose (5 or 20 mm) for 3 h, followed by a continuous infusion of saline or insulin (3 U/kg.h) for 20 min. Under euglycemic and hyperglycemic conditions, basal and insulin-stimulated action on phosphatidylinositol (PI) 3-kinase, protein kinase B/Akt, and ERK were reduced in GK rats, whereas insulin-stimulated protein kinase C (PKC)zeta activity was not altered. Interestingly, basal PKCzeta activity was increased under hyperglycemic conditions in GK and Wistar rats. This finding of increased PKCzeta activity was confirmed in vitro in isolated soleus muscle exposed to high extracellular glucose, and occurred concomitant with an increase in PI-dependent kinase 1 (PDK-1) activity. The glucose effects were not specific to PKCzeta, because an increase in phosphorylation of PKCalpha/beta and PKCdelta, but not PKCtheta, in isolated soleus muscle exposed to 25 mm glucose was observed. In conclusion, insulin signaling defects in diabetic GK rats are not corrected by an acute normalization of glycemia. Interestingly, acute hyperglycemia leads to a parallel increase in PDK-1, PKCalpha/beta, PKCdelta, and PKCzeta phosphorylation/activity via a PI 3-kinase-protein kinase B/Akt-independent mechanism. The long-term consequence of elevated PDK-1 and PKC phosphorylation/activity should be considered in the context of diabetes mellitus, as hyperglycemia is a clinical feature of this disease.
Endocrinology 2003 Dec
PMID:Effect of hyperglycemia on signal transduction in skeletal muscle from diabetic Goto-Kakizaki rats. 1296 81

Huntington's disease features the loss of striatal neurons that stems from a disease process that is initiated by mutant huntingtin. Early events in the disease cascade, which predate overt pathology in Hdh CAG knock-in mouse striatum, implicate enhanced N-methyl-D-aspartate (NMDA) receptor activation, with excitotoxity caused by aberrant Ca2+ influx. Here we demonstrate in precise genetic Huntington's disease mouse and striatal cell models that these early phenotypes are associated with activation of the Akt pro-survival signaling pathway. Elevated levels of activated Ser(P)473-Akt are detected in extracts of Hdh(Q111/Q111) striatum and cultured mutant STHdh(Q111/Q111) striatal cells, compared with their wild type counterparts. Akt activation in mutant striatal cells is associated with increased Akt signaling via phosphorylation of GSK3beta at Ser9. Consequent decreased turnover of transcription co-factor beta-catenin leads to increased levels of beta-catenin target gene cyclin D1. Akt activation is phosphatidylinositol 3-kinase dependent, as demonstrated by increased levels of Ser(P)241-PDK1 kinase and decreased Ser(P)380-PTEN phosphatase. Moreover, Akt activation can be normally stimulated by treatment with insulin growth factor-1 and blocked by treatment with the phosphatidylinositol 3-kinase inhibitor LY294002. However, in contrast to wild type cells, Akt activation in mutant striatal cells can be blocked by the addition of the NMDA receptor antagonist MK-801. Akt activation in mutant striatal cells is Ca(2+)-dependent, because treatment with EGTA reduces levels of Ser(P)473-Akt. Thus, consistent with excitotoxicity early in the disease process, activation of the Akt pro-survival pathway in mutant knock-in striatal cells predates overt pathology and reflects mitochondrial dysfunction and enhanced NMDA receptor signaling.
J Biol Chem 2003 Dec 12
PMID:Enhanced Akt signaling is an early pro-survival response that reflects N-methyl-D-aspartate receptor activation in Huntington's disease knock-in striatal cells. 1452 59

PDC (pyruvate dehydrogenase complex) catalyses the oxidative decarboxylation of pyruvate, linking glycolysis to the tricarboxylic acid cycle. Regulation of PDC determines and reflects substrate preference and is critical to the 'glucose-fatty acid cycle', a concept of reciprocal regulation of lipid and glucose oxidation to maintain glucose homoeostasis developed by Philip Randle. Mammalian PDC activity is inactivated by phosphorylation by the PDKs (pyruvate dehydrogenase kinases). PDK inhibition by pyruvate facilitates PDC activation, favouring glucose oxidation and malonyl-CoA formation: the latter suppresses LCFA (long-chain fatty acid) oxidation. PDK activation by the high mitochondrial acetyl-CoA/CoA and NADH/NAD(+) concentration ratios that reflect high rates of LCFA oxidation causes blockade of glucose oxidation. Complementing glucose homoeostasis in health, fuel allostasis, i.e. adaptation to maintain homoeostasis, is an essential component of the response to chronic changes in glycaemia and lipidaemia in insulin resistance. We develop the concept that the PDKs act as tissue homoeostats and suggest that long-term modulation of expression of individual PDKs, particularly PDK4, is an essential component of allostasis to maintain homoeostasis. We also describe the intracellular signals that govern the expression of the various PDK isoforms, including the roles of the peroxisome proliferator-activated receptors and lipids, as effectors within the context of allostasis.
Biochem Soc Trans 2003 Dec
PMID:Regulation of pyruvate dehydrogenase complex activity by reversible phosphorylation. 1464 Oct 14

PDH (pyruvate dehydrogenase) is a key enzyme controlling the rate of glucose oxidation, and the availability of gluconeogenic precursors. Activation of PDH in skeletal muscle and liver may increase glucose uptake and reduce glucose production. This study describes the properties of AZD7545, a novel, small-molecule inhibitor of PDHK (PDH kinase). In the presence of PDHK2, AZD7545 increased PDH activity with an EC(50) value of 5.2 nM. In rat hepatocytes, the rate of pyruvate oxidation was stimulated 2-fold (EC(50) 105 nM). A single dose of AZD7545 to Wistar rats increased the proportion of liver PDH in its active, dephosphorylated form in a dose-related manner from 24.7 to 70.3% at 30 mg/kg; and in skeletal muscle from 21.1 to 53.3%. A single dose of 10 mg/kg also significantly elevated muscle PDH activity in obese Zucker (fa/fa) rats. Obese, insulin-resistant, Zucker rats show elevated postprandial glucose levels compared with their lean counterparts (8.7 versus 6.1 mM at 12 weeks old). AZD7545 (10 mg/kg) twice daily for 7 days markedly improved the 24-h glucose profile, by eliminating the postprandial elevation in blood glucose. These results suggest that PDHK inhibitors may be beneficial agents for improving glucose control in the treatment of type 2 diabetes.
Biochem Soc Trans 2003 Dec
PMID:AZD7545, a novel inhibitor of pyruvate dehydrogenase kinase 2 (PDHK2), activates pyruvate dehydrogenase in vivo and improves blood glucose control in obese (fa/fa) Zucker rats. 1464 Oct 18

The PDH (pyruvate dehydrogenase) multi-enzyme complex catalyses a key regulatory step in oxidative glycolysis. Phosphorylation of the E1 subunit of the complex on serine residues results in the inactivation of enzyme activity. A family of four dedicated PDH kinase isoenzymes exists, each of which displays a distinct tissue-specific expression profile. AZD7545 is one of a series of PDH kinase inhibitors developed for the treatment of type 2 diabetes. The isoenzyme-selectivity profile of AZD7545 and related compounds is described and the consequences for their in vivo mode of action are discussed.
Biochem Soc Trans 2003 Dec
PMID:AZD7545 is a selective inhibitor of pyruvate dehydrogenase kinase 2. 1464 Oct 19

During exercise in human skeletal muscle, the proportion of carbohydrate derived acetyl-CoA is determined at least in part by the activity of the PDH (pyruvate dehydrogenase) complex. Inhibition of the complex is achieved through reversible phosphorylation of the E1 subunit by a family of PDH kinase isoforms (PDK1-4) while dephosphorylation and activation of the complex is catalysed by a pair of intrinsic PDH phosphatases (PDP1 and 2). In general, the relative activity of the kinases and phosphatases is determined by a host of intramitochondrial effectors which signal energy charge, substrate and product accumulation, muscle contraction and nutritional status. This review focuses on advances in our understanding in human skeletal muscle of the regulatory signals and changes in gene expression which are important during acute exercise and exercise training, as well as in prolonged situations of altered nutritional status.
Biochem Soc Trans 2003 Dec
PMID:Regulation of PDH activity and isoform expression: diet and exercise. 1464 Oct 42

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.
Mol Cell Biol 2003 Dec
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


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