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Pyruvate Dehydrogenase Complex (pyruvate + dehydrogenase_complex)
Selected AbstractsApparent mitochondrial asymmetry in Xenopus eggsDEVELOPMENTAL DYNAMICS, Issue 4 2003Natalia Volodina Abstract Cell polarity is manifest along the animal/vegetal axis in eggs of the frog, Xenopus laevis. Along this axis, maternal cytoplasmic components are asymmetrically distributed and are thought to underlie specification of distinct cell fates. To ascertain the molecular identities of such cytoplasmic components, we have used a monoclonal antibody that specifically stains the vegetal hemisphere of Xenopus eggs. The antigenic protein Vp67 (vegetal protein of 67 kDa) was identified through purification and cloning as a Xenopus homolog of the mitochondrial protein dihydrolipoamide acetyltransferase, a component of the pyruvate dehydrogenase complex. The identification of Vp67 as a mitochondrial protein could indicate that populations of mitochondria are asymmetrically distributed in Xenopus eggs. Developmental Dynamics 226:654,662, © 2003 Wiley-Liss, Inc. [source] Decreased activities of mitochondrial respiratory chain complexes in non-mitochondrial respiratory chain diseasesDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 2 2006Joannie Hui MBBS The aim of this study was to illustrate the difficulties in establishing a diagnosis of mitochondrial respiratory chain (MRC) disorders based on clinical grounds in combination with intermediate activities of the MRC enzyme complexes. We reviewed retrospectively all medical and laboratory records of patients initially considered likely to have MRC disorders on clinical grounds, and subsequently diagnosed with other disorders (n=20; 11 males, 9 females). Data were retrieved from hospital records, referral letters, and results of enzymatic analysis at a reference laboratory. Clinical symptoms included developmental delay, epilepsy, hypotonia, movement disorder, spastic quadriplegia, tetany, microcephaly, visual problems, carpopedal spasms, dysmorphism, hearing loss, muscle weakness and rhabdomyolysis, and fulminant hepatitis. Blood and cerebrospinal fluid lactate levels were elevated in 13/20 and 9/20 respectively. One or more MRC complex activities (expressed as ratios relative to citrate synthase and/or complex II activity) were less than 50% of control mean activity in 11/20 patients (including patients with deficiencies of pyruvate dehydrogenase complex, pantothenate kinase, holocarboxylase synthetase, long-chain hydroxy acyl-CoA dehydrogenase, molybdenum co-factor, and neonatal haemochromatosis). One patient had a pattern suggestive of mitochondrial proliferation. We conclude that intermediate results of MRC enzymes should be interpreted with caution and clinicians should be actively looking for other underlying diagnoses. [source] Phosphorylation status of pyruvate dehydrogenase distinguishes metabolic phenotypes of cultured rat brain astrocytes and neuronsGLIA, Issue 10 2010Nader D. Halim Abstract Glucose metabolism in nervous tissue has been proposed to occur in a compartmentalized manner with astrocytes contributing largely to glycolysis and neurons being the primary site of glucose oxidation. However, mammalian astrocytes and neurons both contain mitochondria, and it remains unclear why in culture neurons oxidize glucose, lactate, and pyruvate to a much larger extent than astrocytes. The objective of this study was to determine whether pyruvate metabolism is differentially regulated in cultured neurons versus astrocytes. Expression of all components of the pyruvate dehydrogenase complex (PDC), the rate-limiting step for pyruvate entry into the Krebs cycle, was determined in cultured astrocytes and neurons. In addition, regulation of PDC enzymatic activity in the two cell types via protein phosphorylation was examined. We show that all components of the PDC are expressed in both cell types in culture, but that PDC activity is kept strongly inhibited in astrocytes through phosphorylation of the pyruvate dehydrogenase alpha subunit (PDH,). In contrast, neuronal PDC operates close to maximal levels with much lower levels of phosphorlyated PDH,. Dephosphorylation of astrocytic PDH, restores PDC activity and lowers lactate production. Our findings suggest that the glucose metabolism of astrocytes and neurons may be far more flexible than previously believed. © 2010 Wiley-Liss, Inc. [source] Covalent modification as a mechanism for the breakdown of immune tolerance to pyruvate dehydrogenase complex in the mouseHEPATOLOGY, Issue 6 2004Jeremy M. Palmer The autoimmune liver disease primary biliary cirrhosis (PBC) is characterized by the breakdown of normal immune self tolerance to pyruvate dehydrogenase complex (PDC). How tolerance is broken to such a central and highly conserved self antigen in the initiation of autoimmunity remains unclear. One postulated mechanism is that reactivity arises to an altered form of self antigen with subsequent cross-reactivity to native self. In this murine study, we set out to examine whether sensitization with a covalently modified form of self PDC can give rise to the pattern of breakdown of B-cell and T-cell tolerance to self PDC seen in PBC patients. The notion that altered self can lead to tolerance breakdown was studied by sensitizing SJL/J mice with a covalently modified (biotinylated) preparation of self murine PDC (mP/O-B). Subsequently, antibody and T-cell reactivities to unmodified self mP/O were studied. Sensitization with mP/O-B elicited high-titre, high-affinity antibody responses reactive with both the mP/O-B immunogen and, importantly, native mP/O. In addition, significant MHC class II restricted splenic T-cell responses to native mP/O (i.e., true autoimmune responses) were seen in mP/O-B sensitized animals. The breakdown of T-cell self tolerance to mP/O was not seen in animals sensitized with irrelevant biotinylated antigens. In conclusion, this study provides evidence to support the concept that exposure to covalently modified self PDC can, in the correct proimmune environment, replicate the full breakdown of B-cell and T-cell immune tolerance to PDC seen in PBC. One potential etiological pathway in PBC therefore could be the breakdown of tolerance to self PDC occurring after exposure to self antigen covalently modified in the metabolically active environment of the liver. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html). (HEPATOLOGY 2004;39:1583,1592.) [source] Bacterial motif DNA as an adjuvant for the breakdown of immune self-tolerance to pyruvate dehydrogenase complexHEPATOLOGY, Issue 3 2002David E. J. Jones Bacterial DNA containing unmethylated CpG dinucleotide motifs is immunostimulatory to mammals, skewing CD4+ T-cell responses toward the Th1 phenotype. Autoreactive T-cell responses seen in primary biliary cirrhosis (PBC) are typically of the Th1 phenotype, raising the possibility that bacterial DNA might play a role in the generation of pathologic autoimmunity. We therefore studied the effects of CpG motif-containing oligodeoxynucleotides (ODN) on responses to pyruvate dehydrogenase complex (PDC, the autoantigen in PBC) in a murine model. Sensitization of SJL/J mice with non,self-PDC has been shown to result in induction of autoreactive T-cell responses to PDC sharing characteristics with those seen in patients with PBC. Administration of CpG ODN to SJL/J mice at the time of sensitization with PDC resulted in a significant skewing of splenic T-cell response to self-PDC, with significant augmentation of the Th1 cytokine response (interleukin [IL] 2 and interferon [IFN] gamma) and reduction of the Th2 response (IL-4 and IL-10). In fact, CpG ODN seemed to be more effective at biasing the response phenotype and as effective at inducing liver histologic change as complete Freund's adjuvant (CFA), the standard adjuvant used for induction of Th1 responses in murine autoimmune and infectious immunity models. In conclusion, our findings raise the possibility that bacteria play a role in the development of autoimmunity (in PBC at least) through the potential of their DNA to shift the T-cell responses toward the phenotype associated with autoimmune damage. Moreover, this study suggests caution in the therapeutic use of CpG ODN as vaccine adjuvants. [source] Primary biliary cirrhosis: an orchestrated immune response against epithelial cellsIMMUNOLOGICAL REVIEWS, Issue 1 2000M. Eric Gershwin Summary: Primary biliary cirrhosis (PBC) is an organ-specific autoimmune disease that predominantly affects women and is characterized by chronic progressive destruction of small intrahepatic bile ducts with portal inflammation and ultimately fibrosis. The serologic hallmark of PBC is the presence of antibodies to mitochondria, especially to the E2 component of the pyruvate dehydrogenase complex. The mechanisms by which (and if) such antibodies produce liver tissue injury are unknown. However, the presence of these antibodies has allowed detailed immunological definition of the antigenic epitopes, the nature of reactive autoantibodies and the characterization of T-cell responses. Several mechanisms may now be proposed regarding the immune-mediated bile duct damage in PBC, including the possible role of T-cell-mediated cytotoxicity and intracellular interaction between the IgA class of antimitochondrial antibodies and mitochondrial autoantigens. There are major questions which remain unanswered, including, of course, etiology, but also the reasons for female predominance, the absence of PBC in children, the relative ineffectiveness of immunosuppressive drugs, and the specific role of mitochondrial antigens. The data so far provide suggestive evidence that PBC is a mucosal disease; this thesis provides a basis for discussion of etiology via the enterohepatic circulation of toxins and/or infection. [source] Experimental autoimmune cholangitis: a mouse model of immune-mediated cholangiopathyLIVER INTERNATIONAL, Issue 5 2000David E. J. Jones Abstract:Background: Primary biliary cirrhosis (PBC) is characterised by intra-hepatic immune-mediated cholangiopathy (non-suppurative destructive cholangitis (NSDC)). Although auto-reactive immune responses against pyruvate dehydrogenase complex (PDC) have been characterised in PBC, the lack of an animal model of the disease has limited study of the mechanisms of disease induction and the development of novel approaches to therapy. Aims: To develop and validate a mouse model of immune-mediated cholangiopathy relevant for future use in the study of the aetio-pathogenesis and therapy of PBC. Methods: Female SJL/J, C57BL/6, NOD and BALB/c mice were sensitised with PDC, its purified E2/E3BP component, and a PDC-E2 derived peptide p163 (a dominant T-cell epitope in humans) in complete Freund's adjuvant (CFA). Morphological changes were assessed under light microscopy by a hepatic histopathologist blinded to the experimental details. Antibody responses to PDC were studied by ELISA and PDC inhibition assay. Results: An initial series of experiments was performed to survey the susceptibility of female mice of a range of strains to the induction of NSDC by i.p. sensitisation with PDC, PDC-E2/E3BP or p163 in CFA. Although each animal showed a specific antibody response following sensitisation, it was found that NSDC development (assessed at 30 weeks post-sensitisation) was restricted to SJL/J mice following sensitisation with any of the mitochondrial antigen preparations. A subsequent series of experiments was performed to examine the specificity and aetiology of this disease. Significant bile duct lesions were only seen in SJL/J animals following sensitisation with CFA containing PDC, and were absent from CFA only and un-sensitised controls. Kinetic analysis revealed that this pathology developed slowly, but a high incidence of animals with severe lesions was observed after 30 weeks. Conclusions: We have described a model of experimental autoimmune cholangitis (EAC) with immunological (anti-PDC antibodies) and histological (immune-mediated cholangiopathy) features suggestive of PBC. This model may be useful in further defining the role of self-tolerance breakdown in the development of this condition. [source] Strange organelles ,Plasmodium mitochondria lack a pyruvate dehydrogenase complexMOLECULAR MICROBIOLOGY, Issue 1 2005Stuart A. Ralph Summary Our understanding of the Plasmodium mitochondrion and apicoplast has been greatly assisted by the genome sequence project. Sequence data have seeded recent research showing that the apicoplast is ,the ,site ,of ,several ,anabolic ,pathways ,including fatty acid synthesis. The discovery of an active apicoplast pyruvate dehydrogenase complex implies this enzyme generates the acetyl-CoA needed for fatty acid synthesis. However, the absence of a corresponding mitochondrial complex suggests that energy generation in Plasmodium is considerably different from pathways described in other eukaryotes. [source] Temporal changes in the involvement of pyruvate dehydrogenase complex in muscle lactate accumulation during lipopolysaccharide infusion in ratsTHE JOURNAL OF PHYSIOLOGY, Issue 6 2008N. Alamdari A characteristic manifestation of sepsis is muscle lactate accumulation. This study examined any putative (causative) association between pyruvate dehydrogenase complex (PDC) inhibition and lactate accumulation in the extensor digitorum longus (EDL) muscle of rats infused with lipopolysaccharide (LPS), and explored the involvement of increased transcription of muscle-specific pyruvate dehydrogenase kinase (PDK) isoenzymes. Conscious, male Sprague,Dawley rats were infused i.v. with saline (0.4 ml h,1, control) or LPS (150 ,g kg,1 h,1) for 2 h, 6 h or 24 h (n= 6,8). Muscle lactate concentration was elevated after 2, 6 and 24 h LPS infusion. Muscle PDC activity was the same at 2 h and 6 h, but was 65% lower after 24 h of LPS infusion (P < 0.01), when there was a 47% decrease in acetylcarnitine concentration (P < 0.05), and a 24-fold increase in PDK4 mRNA expression (P < 0.001). These changes were preceded by marked increases in tumour necrosis factor-, and interleukin-6 mRNA expression at 2 h. The findings indicate that the early (2 and 6 h) elevation in muscle lactate concentration during LPS infusion was not attributable to limited muscle oxygen availability or ATP production (evidenced by unchanged ATP and phosphocreatine (PCr) concentrations) or to PDC inhibition, whereas after 24 h, muscle lactate accumulation appears to have resulted from PDC activation status limiting pyruvate flux, most probably due to cytokine-mediated up-regulation of PDK4 transcription. [source] A new case of pyruvate dehydrogenase deficiency due to a novel mutation in the pdx1 geneANNALS OF NEUROLOGY, Issue 2 2003Runu Dey PhD We report a case of neonatal congenital lactic acidosis associated with pyruvate dehydrogenase E3-binding protein deficiency in a newborn girl. She had a severe encephalopathy, and magnetic resonance imaging of the brain showed large subependymal cysts and no basal ganglia lesions. She died 35 days after birth. We detected a novel homozygous deletion (620delC) in the PDX1 gene, which encodes for the E3BP subunit of the pyruvate dehydrogenase complex. [source] Crystallization and preliminary crystallographic studies of the catalytic subunits of human pyruvate dehydrogenase phosphatase isoforms 1 and 2ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010Junko Kato Pyruvate dehydrogenase phosphatase (PDP) is a mitochondrial serine phosphatase that activates phosphorylated pyruvate dehydrogenase complex by dephosphorylation. In humans, two PDP isoforms (1 and 2) have been identified. PDP1 is composed of a catalytic subunit (PDP1c) and a regulatory subunit (PDP1r), whereas PDP2 consists of only a catalytic subunit (PDP2c). Both PDP1c and PDP2c have been crystallized individually and complete X-ray diffraction data sets have been collected to 2.45 and 2.0,Å resolution, respectively. The PDP1c crystals belonged to space group P41212 or P43212, with unit-cell parameters a = b = 65.1, c = 216.1,Å. The asymmetric unit is expected to contain one molecule, with a Matthews coefficient VM of 2.56,Å3,Da,1. The PDP2c crystals belonged to space group P212121, with unit-cell parameters a = 53.6, b = 69.1, c = 109.7,Å. The asymmetric unit is expected to contain one molecule, with a Matthews coefficient VM of 1.91,Å3,Da,1. [source] Doubling the catabolic reducing power (NADH) output of Escherichia coli fermentation for production of reduced productsBIOTECHNOLOGY PROGRESS, Issue 1 2010Shengde Zhou Abstract Homofermentative production of reduced products requires additional reducing power output (NADH) from glucose catabolism. Anaerobic expression of the pyruvate dehydrogenase complex (PDH, encoded by aceEF-lpd, a normal aerobic operon) is able to provide the additional NADH required for production of reduced products in Escherichia coli fermentation. The multiple promoters (pflBp(1,7)) of pyruvate formate lyase (pflB) were evaluated for anaerobic expression of the aceEF-lpd operon. Four chromosomal constructs, pflBp(1,7)-aceEF-lpd, pflBp(1,6)-aceEF-lpd, pflBp(6,7)-aceEF-lpd, and pflBp6-aceEF-lpd efficiently expressed the PDH complex in anaerobically grown cells. Doubling the reducing power output was achieved when glucose was oxidized to acetyl-CoA through glycolysis and pyruvate oxidation by the anaerobically expressed PDH complex (glucose ,2 acetyl-CoA + 4 NADH). This additional reducing power output can be used for production of reduced products in anaerobic E. coli fermentation. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | |||||||||||||||||||||||||