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)

Recent evidence from this laboratory indicates that at least two isoenzymic forms of pyruvate dehydrogenase kinase (PDK1 and PDK2) may be involved in the regulation of enzymatic activity of mammalian pyruvate dehydrogenase complex by phosphorylation (Popov, K.M., Kedishvili, N.Y., Zhao, Y., Gudi, R., and Harris, R.A. (1994) J. Biol. Chem. 269, 29720-29724). The present study was undertaken to further explore the diversity of the pyruvate dehydrogenase kinase gene family. Here we report the deduced amino acid sequences of three isoenzymic forms of PDK found in humans. In terms of their primary structures, two isoenzymes identified in humans correspond to rat PDK1 and PDK2, whereas a third gene (PDK3) encodes for a new isoenzyme that shares 68% and 67% of amino acid identities with PDK1 and PDK2, respectively. PDK3 cDNA expressed in Eschierichia coli directs the synthesis of a polypeptide with a molecular mass of approximately 45,000 Da that possesses catalytic activity toward kinase-depleted pyruvate dehydrogenase. PDK3 appears to have the highest specific activity among the three isoenzymes tested as recombinant proteins. Tissue distribution of all three isoenzymes of human PDK was characterized by Northern blot analysis. The highest amount of PDK2 mRNA was found in heart and skeletal muscle, the lowest amount in placenta and lung. Brain, kidney, pancreas, and liver expressed an intermediate amount of PDK2 (brain > kidney = pancreas > liver). The tissue distribution of PDK1 mRNA differs markedly from PDK2. The message for PDK1 was expressed predominantly in heart with only modest levels of expression in other tissues (skeletal muscle > liver > pancreas > brain > placenta = lung > kidney). In contrast to PDk1 and PDK2, which are expressed in all tissues tested, the message for PDK3 was found almost exclusively in heart and skeletal muscle, indicating that PDK3 may serve specialized functions characteristic of muscle tissues. In all tissues tested thus far, the level of expression of PDK2 mRNA was essentially higher than that of PDK1 and PDK3, consistent with the idea that PDK2 is a major isoenzyme responsible for regulation of pyruvate dehydrogenase in human tissues.
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PMID:Diversity of the pyruvate dehydrogenase kinase gene family in humans. 749 31

The initial steps in insulin signal transduction occur at the plasma membrane and lead to the activation of phosphatidylinositide (PtdIns) 3-kinase and the formation of PtdIns(3,4,5,)P3 in the inner leaflet of the plasma membrane which is then converted to PtdIns(3,4)P2 by a specific phosphatase. Inhibitors of PtdIns 3-kinase suppress nearly all the metabolic actions of insulin indicating that PtdIns(3,4,5)P3 and/or PtdIns(3,4)P2 are key 'second messengers' for this hormone. A major effect of insulin is its ability to stimulate the synthesis of glycogen in skeletal muscle. By 'working backwards' from glycogen synthesis, we have dissected an insulin-stimulated protein kinase cascade which is triggered by the activation of PtdIns 3-kinase. The first enzyme in this cascade is termed 3-phosphoinositide-dependent protein kinase (PDK1), because it is only active in the presence of PtdIns(3,4,5)P3 or PtdIns(3,4)P2. PDK1 then activates protein kinase B (PKB) which, in turn, inactivates glycogen synthase kinase-3 (GSK3), leading to the dephosphorylation and activation of glycogen synthase and hence to an acceleration of glycogen synthesis. We review the evidence which indicates that the phosphorylation of other proteins by PKB and GSK3 is likely to mediate many of the intracellular actions of insulin.
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PMID:PDK1, one of the missing links in insulin signal transduction? 924 12

293 cells were transfected with wild-type GSK3beta (WT-GSK3beta) or a mutant in which the PKB phosphorylation site (Ser-9) was altered to Ala (A9-GSK3beta). Upon stimulation with IGF-1 or insulin, WT-GSK3beta was inhibited 75% or 60%, respectively, whereas the activity of the A9-GSK3beta mutant was unaffected. Incubation of WT-GSK3beta with PP2A1 (a Ser/Thr-specific phosphatase) completely reversed the IGF-1- or insulin-induced inhibition. IGF-1 stimulation did not induce any tyrosine dephosphorylation of WT-GSK3beta or A9-GSK3beta. Coexpression of WT-GSK3beta in 293 cells with either PKB alpha (also known as AKT) or PDK1 (the 'upstream' activator of PKB) mimicked the IGF-1- or insulin-induced phosphorylation of Ser-9 and inactivation of GSK3beta.
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PMID:Further evidence that the inhibition of glycogen synthase kinase-3beta by IGF-1 is mediated by PDK1/PKB-induced phosphorylation of Ser-9 and not by dephosphorylation of Tyr-216. 937 75

Tissue distribution and kinetic parameters for the four isoenzymes of pyruvate dehydrogenase kinase (PDK1, PDK2, PDK3 and PDK4) identified thus far in mammals were analysed. It appeared that expression of these isoenzymes occurs in a tissue-specific manner. The mRNA for isoenzyme PDK1 was found almost exclusively in rat heart. The mRNA for PDK3 was most abundantly expressed in rat testis. The message for PDK2 was present in all tissues tested but the level was low in spleen and lung. The mRNA for PDK4 was predominantly expressed in skeletal muscle and heart. The specific activities of the isoenzymes varied 25-fold, from 50nmol/min per mg for PDK2 to 1250nmol/min per mg for PDK3. Apparent Ki values of the isoenzymes for the synthetic analogue of pyruvate, dichloroacetate, varied 40-fold, from 0.2 mM for PDK2 to 8 mM for PDK3. The isoenzymes were also different with respect to their ability to respond to NADH and NADH plus acetyl-CoA. NADH alone stimulated the activities of PDK1 and PDK2 by 20 and 30% respectively. NADH plus acetyl-CoA activated these isoenzymes nearly 200 and 300%. Under comparable conditions, isoenzyme PDK3 was almost completely unresponsive to NADH, and NADH plus acetyl-CoA caused inhibition rather than activation. Isoenzyme PDK4 was activated almost 2-fold by NADH, but NADH plus acetyl-CoA did not activate above the level seen with NADH alone. These results provide the first evidence that the unique tissue distribution and kinetic characteristics of the isoenzymes of PDK are among the major factors responsible for tissue-specific regulation of the pyruvate dehydrogenase complex activity.
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PMID:Evidence for existence of tissue-specific regulation of the mammalian pyruvate dehydrogenase complex. 940 93

This study investigated whether conditions known to alter the activity and phosphorylation state of the pyruvate dehydrogenase complex have specific effects on the levels of isoenzymes of pyruvate dehydrogenase kinase (PDK) in rat heart. Immunoblot analysis revealed a remarkable increase in the amount of PDK4 in the hearts of rats that had been starved or rendered diabetic with streptozotocin. Re-feeding of starved rats and insulin treatment of diabetic rats very effectively reversed the increase in PDK4 protein and restored PDK enzyme activity to levels of chow-fed control rats. Starvation and diabetes also markedly increased the abundance of PDK4 mRNA, and re-feeding and insulin treatment reduced levels of the message to that of controls. In contrast with the findings for PDK4, little or no changes in the amounts of PDK1 and PDK2 protein and the abundance of their messages occurred in response to starvation and diabetes. The observed shift in the relative abundance of PDK isoenzymes probably explains previous studies of the effects of starvation and diabetes on heart PDK activity. The results indicate that control of the amount of PDK4 is important in long-term regulation of the activity of the pyruvate dehydrogenase complex in rat heart.
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PMID:Starvation and diabetes increase the amount of pyruvate dehydrogenase kinase isoenzyme 4 in rat heart. 940 94

Activation of the protein p70s6k by mitogens leads to increased translation of a family of messenger RNAs that encode essential components of the protein synthetic apparatus. Activation of the kinase requires hierarchical phosphorylation at multiple sites, culminating in the phosphorylation of the threonine in position 229 (Thr229), in the catalytic domain. The homologous site in protein kinase B (PKB), Thr308, has been shown to be phosphorylated by the phosphoinositide-dependent protein kinase PDK1. A regulatory link between p70s6k and PKB was demonstrated, as PDK1 was found to selectively phosphorylate p70s6k at Thr229. More importantly, PDK1 activated p70s6k in vitro and in vivo, whereas the catalytically inactive PDK1 blocked insulin-induced activation of p70s6k.
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PMID:Phosphorylation and activation of p70s6k by PDK1. 947 28

1321N1 astrocytoma cells have proved a valuable model system in which to study interactions between two major PtdIns (4,5) P2-utilizing signaling pathways, since they possess receptor populations which elicit independent activation of PI 3-kinase and a G-protein-dependent PLC respectively. Activation of PLC down-regulates PI 3-kinase by at least two mechanisms involving inhibition of IRS-1-associated PI 3-kinase and acute activation of a PtdIns (3,4,5) P3 5-phosphatase. PKB, which is an important early PI 3-kinase-dependent component of insulin signalling pathways, is also down-regulated by PLC-coupled agonists. The activation of PKB by insulin appears to involve a novel PtdIns (3,4,5) P3-dependent protein kinase, which we have named PDK1. The molecular mechanisms underlying PtdIns (3,4,5) P3-stimulated phosphorylation and activation of PKB by PDK1 are currently under investigation.
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PMID:Cross-talk between phospholipase C and phosphoinositide 3-kinase signalling pathways. 944 62

Although phosphorylation of Thr-197 in the activation loop of the catalytic subunit of cAMP-dependent protein kinase (PKA) is an essential step for its proper biological function, the kinase responsible for this reaction in vivo has remained elusive. Using nonphosphorylated recombinant catalytic subunit as a substrate, we have shown that the phosphoinositide-dependent protein kinase, PDK1, expressed in 293 cells, phosphorylates and activates the catalytic subunit of PKA. The phosphorylation of PKA by PDK1 is rapid and is insensitive to PKI, the highly specific heat-stable protein kinase inhibitor. A mutant form of the catalytic subunit where Thr-197 was replaced with Asp was not a substrate for PDK1. In addition, phosphorylation of the catalytic subunit can be monitored immunochemically by using antibodies that recognize Thr-197 phosphorylated enzyme but not unphosphorylated enzyme or the Thr197Asp mutant. PDK1, or one of its homologs, is thus a likely candidate for the in vivo PKA kinase that phosphorylates Thr-197. This finding opens a new dimension in our thinking about this ubiquitous protein kinase and how it is regulated in the cell.
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PMID:Phosphorylation and activation of cAMP-dependent protein kinase by phosphoinositide-dependent protein kinase. 970 64

Phosphorylation sites in members of the protein kinase A (PKA), PKG, and PKC kinase subfamily are conserved. Thus, the PKB kinase PDK1 may be responsible for the phosphorylation of PKC isotypes. PDK1 phosphorylated the activation loop sites of PKCzeta and PKCdelta in vitro and in a phosphoinositide 3-kinase (PI 3-kinase)-dependent manner in vivo in human embryonic kidney (293) cells. All members of the PKC family tested formed complexes with PDK1. PDK1-dependent phosphorylation of PKCdelta in vitro was stimulated by combined PKC and PDK1 activators. The activation loop phosphorylation of PKCdelta in response to serum stimulation of cells was PI 3-kinase-dependent and was enhanced by PDK1 coexpression.
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PMID:Protein kinase C isotypes controlled by phosphoinositide 3-kinase through the protein kinase PDK1. 974 66

Two maize cDNAs were isolated and sequenced that had open reading frames with approximately 37% amino acid identity to mammalian pyruvate dehydrogenase kinases. Both maize kinase sequences contain the five domains with conserved signature residues typical of procaryotic two-component histidine kinases. Sequence comparisons identified six other highly conserved motifs that are proposed to be specific to pyruvate dehydrogenase kinases. In addition, specific Trp and Cys residues are also invariant in these sequences. The maize cDNAs are 1332 (PDK1) and 1602 (PDK2) nucleotides in length, encoding polypeptides with calculated molecular masses of 38,867 and 41,327 Da that share 77% amino acid identity. Reverse transcriptase-polymerase chain reaction analysis with oligonucleotide-specific primers revealed a differential expression pattern for the two isoforms. PDK1 and PDK2 were expressed in Escherichia coli with N-terminal His6 tags to facilitate purification. The recombinant proteins migrated at 44 and 48 kDa, respectively, during SDS-polyacrylamide gel electrophoresis. Anti-PDK1 antibodies immunoprecipitated 75% of pyruvate dehydrogenase kinase activity from a maize mitochondrial matrix fraction, and recognized a matrix protein of 43 kDa. Recombinant PDK2, expressed as a fusion with the maltose-binding protein, inactivated kinase-depleted maize pyruvate dehydrogenase complex when incubated with MgATP, coincident with incorporation of 32P from [gamma-32P]ATP into the alpha subunit of pyruvate dehydrogenase.
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PMID:Molecular analysis of two pyruvate dehydrogenase kinases from maize. 975 1


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