Victor Chang Cardiac Research Institute

About: Victor Chang Cardiac Research Institute is a nonprofit organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Mechanosensitive channels & Heart failure. The organization has 708 authors who have published 1599 publications receiving 70035 citations.

Migration of Small Ribosomal Subunits on the 5' Untranslated Regions of Capped Messenger RNA.

Abstract: Several control mechanisms of eukaryotic gene expression target the initiation step of mRNA translation. The canonical translation initiation pathway begins with cap-dependent attachment of the small ribosomal subunit (SSU) to the messenger ribonucleic acid (mRNA) followed by an energy-dependent, sequential 'scanning' of the 5' untranslated regions (UTRs). Scanning through the 5'UTR requires the adenosine triphosphate (ATP)-dependent RNA helicase eukaryotic initiation factor (eIF) 4A and its efficiency contributes to the specific rate of protein synthesis. Thus, understanding the molecular details of the scanning mechanism remains a priority task for the field. Here, we studied the effects of inhibiting ATP-dependent translation and eIF4A in cell-free translation and reconstituted initiation reactions programmed with capped mRNAs featuring different 5'UTRs. An aptamer that blocks eIF4A in an inactive state away from mRNA inhibited translation of capped mRNA with the moderately structured β-globin sequences in the 5'UTR but not that of an mRNA with a poly(A) sequence as the 5'UTR. By contrast, the nonhydrolysable ATP analogue β,γ-imidoadenosine 5'-triphosphate (AMP-PNP) inhibited translation irrespective of the 5'UTR sequence, suggesting that complexes that contain ATP-binding proteins in their ATP-bound form can obstruct and/or actively block progression of ribosome recruitment and/or scanning on mRNA. Further, using primer extension inhibition to locate SSUs on mRNA ('toeprinting'), we identify an SSU complex which inhibits primer extension approximately eight nucleotides upstream from the usual toeprinting stop generated by SSUs positioned over the start codon. This '-8 nt toeprint' was seen with mRNA 5'UTRs of different length, sequence and structure potential. Importantly, the '-8 nt toeprint' was strongly stimulated by the presence of the cap on the mRNA, as well as the presence of eIFs 4F, 4A/4B and ATP, implying active scanning. We assembled cell-free translation reactions with capped mRNA featuring an extended 5'UTR and used cycloheximide to arrest elongating ribosomes at the start codon. Impeding scanning through the 5'UTR in this system with elevated magnesium and AMP-PNP (similar to the toeprinting conditions), we visualised assemblies consisting of several SSUs together with one full ribosome by electron microscopy, suggesting direct detection of scanning intermediates. Collectively, our data provide additional biochemical, molecular and physical evidence to underpin the scanning model of translation initiation in eukaryotes.

Improved poststorage cardiac function by poly (ADP-ribose) polymerase inhibition: role of phosphatidylinositol 3-kinase Akt pathway.

Abstract: BACKGROUND Inhibition of poly(ADP-ribose) polymerase 1 (PARP) has been shown to be effective in minimizing cardiac ischemia reperfusion injury. We investigated the cardioprotective effect of the PARP inhibitor, INO-1153, in isolated working rat hearts after 6 hr of hypothermic storage in Celsior. METHODS Hearts were treated with 1 muM INO-1153 before hypothermic storage, at cardioplegia and storage or after hypothermic storage. Hearts not exposed to INO-1153 served as controls. Another group was pretreated with the phosphatidylinositol 3-kinase inhibitor Wortmannin (0.1 muM) before storage in INO-1153-supplemented Celsior. After baseline measurement of aortic flow, heart rate, coronary flow, and cardiac output were obtained, hearts were arrested and stored in Celsior at 2-3 degrees C for 6 hr. After storage, hearts were reperfused for 15 min before performing work for a further 30 min, at which time poststorage indices of cardiac function were remeasured then heart tissue was stored at -80 degrees C for Western blot analysis. RESULTS The presence of INO-1153 during prestorage perfusion or during cardioplegia and storage significantly improved poststorage cardiac function. Functional improvements produced by INO-1153 were completely abolished by Wortmnanin pretreatment. Western blots showed a significant increase in phospho-Akt in presence of INO-1153, which was inhibited by Wortmannin. CONCLUSION Activation of the prosurvival phosphatidylinositol 3-kinase-Akt pathway was involved in the protective action of PARP inhibition in this model of donor heart procurement and hypothermic storage. Importantly for the logistics of clinical organ procurement, maximum protection is observed when the PARP inhibitor is included in the cardioplegic storage solution.

Triheptanoin alters [U-13C6]-glucose incorporation into glycolytic intermediates and increases TCA cycling by normalizing the activities of pyruvate dehydrogenase and oxoglutarate dehydrogenase in a chronic epilepsy mouse model.

Abstract: Triheptanoin is anticonvulsant in several seizure models. Here, we investigated changes in glucose metabolism by triheptanoin interictally in the chronic stage of the pilocarpine mouse epilepsy model. After injection of [U-13C6]-glucose (i.p.), enrichments of 13C in intermediates of glycolysis and the tricarboxylic acid (TCA) cycle were quantified in hippocampal extracts and maximal activities of enzymes in each pathway were measured. The enrichment of 13C glucose in plasma was similar across all groups. Despite this, we observed reductions in incorporation of 13C in several glycolytic intermediates compared to control mice suggesting glucose utilization may be impaired and/or glycogenolysis increased in the untreated interictal hippocampus. Triheptanoin prevented the interictal reductions of 13C incorporation in most glycolytic intermediates, suggesting it increased glucose utilization or - as an additional astrocytic fuel - it decreased glycogen breakdown. In the TCA cycle metabolites, the incorporation of 13C was reduced in the interictal state. Triheptanoin restored the correlation between 13C enrichments of pyruvate relative to most of the TCA cycle intermediates in "epileptic" mice. Triheptanoin also prevented the reductions of hippocampal pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase activities. Decreased glycogen breakdown and increased glucose utilization and metabolism via the TCA cycle in epileptogenic brain areas may contribute to triheptanoin's anticonvulsant effects.