2-Hydroxyglutarate-Mediated Autophagy of the Endoplasmic Reticulum Leads to an Unusual Downregulation of Phospholipid Biosynthesis in Mutant IDH1 Gliomas.

Tumor metabolism is reprogrammed to meet the demands of proliferating cancer cells. In particular, cancer cells upregulate synthesis of the membrane phospholipids phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdE) in order to allow for rapid membrane turnover. Nonetheless, we show here that, in mutant isocitrate dehydrogenase 1 (IDHmut) gliomas, which produce the oncometabolite 2-hydroxyglutarate (2-HG), PtdCho and PtdE biosynthesis is downregulated and results in lower levels of both phospholipids when compared with wild-type IDH1 cells. 2-HG inhibited collagen-4-prolyl hydroxylase activity, leading to accumulation of misfolded procollagen-IV in the endoplasmic reticulum (ER) of both genetically engineered and patient-derived IDHmut glioma models. The resulting ER stress triggered increased expression of FAM134b, which mediated autophagic degradation of the ER (ER-phagy) and a reduction in the ER area. Because the ER is the site of phospholipid synthesis, ER-phagy led to reduced PtdCho and PtdE biosynthesis. Inhibition of ER-phagy via pharmacological or molecular approaches restored phospholipid biosynthesis in IDHmut glioma cells, triggered apoptotic cell death, inhibited tumor growth, and prolonged the survival of orthotopic IDHmut glioma-bearing mice, pointing to a potential therapeutic opportunity. Glioma patient biopsies also exhibited increased ER-phagy and downregulation of PtdCho and PtdE levels in IDHmut samples compared with wild-type, clinically validating our observations. Collectively, this study provides detailed and clinically relevant insights into the functional link between oncometabolite-driven ER-phagy and phospholipid biosynthesis in IDHmut gliomas.Significance: Downregulation of phospholipid biosynthesis via ER-phagy is essential for proliferation and clonogenicity of mutant IDH1 gliomas, a finding with immediate therapeutic implications. Cancer Res; 78(9); 2290-304. ©2018 AACR.

Live Cell Imaging of Endogenous mRNA Using RNA-Based Fluorescence "Turn-On" Probe.

Messenger RNA (mRNA) plays a critical role in cellular growth and development. However, there have been limited methods available to visualize endogenous mRNA in living cells with ease. We have designed RNA-based fluorescence "turn-on" probes that target mRNA by fusing an unstable form of Spinach with target-complementary sequences. These probes have been demonstrated to be selective, stable, and capable of targeting various mRNAs for live E. coli imaging.

Heavy water: a simple solution to increasing the brightness of fluorescent proteins in super-resolution imaging.

Photoactivatable fluorescent proteins (PA-FPs) are widely used in live single-molecule super-resolution imaging but emit substantially fewer photons than organic dyes do. Herein, we show that in heavy water (D2O) instead of H2O, common PA-FPs emit 26-54% more photons, effectively improving the localization precision in super-resolution imaging.

Locking high energy 1D chain of dichloromethane molecules containing abnormally short Cl···Cl contacts of 2.524 Å inside organic crystals.

1D helical channels can be created by "sticky" end-mediated formation of 1D helical stacks composed of short cavity-containing helices and are able to host 1D chains of dichloromethane molecules containing extraordinarily short intermolecular Cl···Cl contacts of 2.524 Å in length that computationally destabilize the host-guest complex by 14.94 kcal mol(-1).

Patterned recognition of amines and ammonium ions by a pyridine-based helical oligoamide host.

In response to binding to amine and ammonium guests of varying types, a pyridine-based folding oligomer displays fingerprint regions in its (1)H NMR spectra that allow for the easy identification and classification of the bound guests.

Synthesis, structural investigation and computational modelling of water-binding aquafoldamers.

Detailed studies on water-binding aquafoldamers are presented that illustrate the potential use of the elongated larger aquafoldamers for recognizing larger water clusters of diverse topologies. A novel self-trapping dimerization mode involving two tetramer molecules is proposed, which is consistent with the obtained varying experimental evidences.

Five-fold-symmetric macrocyclic aromatic pentamers: high-affinity cation recognition, ion-pair-induced columnar stacking, and nanofibrillation.

Described in this study is a conceptually new class of five-fold-symmetric cavity-containing planar pentameric macrocycles with their interior decorated by five convergently aligned, properly spaced carbonyl oxygen atoms. These cation-binding oxygens enclose a hydrophilic lumen of 2.85 Å in radius and thus display high-affinity binding toward alkali metal cations, and possibly many other cations, too. Arising from their high-affinity recognition of metal ions, these planar macrocycles form cation- or ion-pair-induced one-dimensional columnar aggregates, and subsequently fascinating fibrillation results.

Encapsulation of conventional and unconventional water dimers by water-binding foldamers.

Water-binding foldamers have been rarely studied. By orienting both H-bond donors and acceptors toward their interior, two pyridine-derived crescent-shaped folding oligoamides were found to be capable of trapping both conventional and unconventional water dimer clusters in their cavity (∼2.5 Å radius). In the unconventional water dimer cluster, the two water molecules stay in contact via an unusual H-H interaction (2.25 Å) rather than the typical H-bond.

Computational prediction and experimental verification of pyridine-based helical oligoamides containing four repeating units per helical turn.

Aided by high level ab initio computational modeling, we successfully designed and experimentally proved a new set of backbone-rigidified pyridine-based folding oligoamides that require approximately four repeating units to form a helical turn.

Highly selective one-pot synthesis of H-bonded pentagon-shaped circular aromatic pentamers.

One-pot, multi-molecular macrocyclization allows the highly selective preparation of pentagon-shaped circular aromatic pentamers mediated by an inward-pointing continuous hydrogen-bonding network.

Crystallographic evidence of an unusual, pentagon-shaped folding pattern in a circular aromatic pentamer.

Introduction of a continuous hydrogen-bonding network suppressed the conformational flexibility of an oligomeric backbone. Cyclization of a rigidified, suitably sized oligomer led to a circular aromatic pentamer. Its crystal structure determined by X-ray crystallography reveals a pseudo five-fold symmetric planarity in the solid state, which is quite unusual among all the previously described shape-persistent macrocycles and synthetic foldamers with biased conformations enforced by noncovalent forces.