The unique metabolic profile of cancer (aerobic glycolysis) might confer apoptosis resistance and be therapeutically targeted. Compared to normal cells, several human cancers have high mitochondrial membrane potential (DeltaPsim) and low expression of the K+ channel Kv1.5, both contributing to apoptosis resistance. Dichloroacetate (DCA) inhibits mitochondrial pyruvate dehydrogenase kinase (PDK), shifts metabolism from glycolysis to glucose oxidation, decreases DeltaPsim, increases mitochondrial H2O2, and activates Kv channels in all cancer, but not normal, cells; DCA upregulates Kv1.5 by an NFAT1-dependent mechanism. DCA induces apoptosis, decreases proliferation, and inhibits tumor growth, without apparent toxicity. Molecular inhibition of PDK2 by siRNA mimics DCA. The mitochondria-NFAT-Kv axis and PDK are important therapeutic targets in cancer; the orally available DCA is a promising selective anticancer agent.

Abstract:Regulation of cell volume is critical for many cellular and organismal functions, yet the molecular identity of a key player, the volume-regulated anion channel VRAC, has remained unknown. A genome-wide siRNA screen in mammalian cells identified LRRC8A as a VRAC component. LRRC8A formed heteromers with other LRRC8 multispan membrane proteins.Genomic disruption of LRRC8A ablated VRAC currents. Cells with disruption of all five LRRC8 genes required LRRC8A co-transfection with other LRRC8 isoforms to reconstitute VRAC currents. The isoform combination determined VRAC inactivation kinetics. Taurine flux and regulatory volume decrease also depended on LRRC8 proteins. Our work shows that VRAC defines a class of anion channels, suggests that VRAC is identical to the volumesensitive organic osmolyte/anion channel VSOAC, and explains the heterogeneity of native VRAC currents. One Sentence Summary:We show that the swelling-activated anion channel VRAC represents a structurally new class of anion channels that also conducts organic osmolytes. Main Text:Cells regulate their volume to counteract swelling or shrinkage caused by osmotic challenges and during processes like cell growth, division, and migration. As water transport across cellular membranes is driven by osmotic gradients, cell volume regulation requires appropriate changes of intracellular concentrations of ions or organic osmolytes like taurine (1, 2). Regulatory volume decrease (RVD) follows the extrusion of intracellular Cl -and K + and other osmolytes across the plasma membrane. A key player is the volume-regulated anion channel VRAC that mediates characteristic swelling-activated Cl --currents (I Cl(swell) ) and is ubiquitously expressed in vertebrate cells (3-5). Nearly inactive under resting conditions, VRAC slowly opens upon hypotonic swelling. The mechanism behind VRAC opening remains enigmatic. VRAC currents are outwardly rectifying (hence the alternative name VSOR for volume-stimulated outward rectifier (4, 5)) and show variable inactivation at insidepositive voltages. VRAC conducts iodide better than chloride and might also conduct organic osmolytes like taurine (6) (hence VSOAC, volume-stimulated organic osmolyte/anion channel (7)), but this notion is controversial (8-10). VRAC is believed to be important for cell volume regulation and swelling-induced exocytosis (11), and also for cell cycle regulation, proliferation and migration (1,3,4). It may play a role in apoptosis and various pathological (Fig. 1F). We hypothesized that VRAC contains LRRC8A as part of a heteromer and that LRRC8A overexpression led to a subunit stoichiometry that was incompatible with channel activity. LRRC8A has four closely related homologs (LRRC8B -LRRC8E) which all have four predicted transmembrane domains (19,20). EST databases suggested that all homologs were widely expressed.Immunocytochemistry of transfected HeLa cells ( fig. S4A) and of native HEK cells (Fig. 1, G and H) detected LRRC8A at the plasma membrane. Truncation of its carboxy-terminus as in a pat...

N-methyladenosine RNA (mA) is a prevalent messenger RNA modification in vertebrates. Although its functions in the regulation of post-transcriptional gene expression are beginning to be unveiled, the precise roles of mA during development of complex organisms remain unclear. Here we carry out a comprehensive molecular and physiological characterization of the individual components of the methyltransferase complex, as well as of the YTH domain-containing nuclear reader protein in Drosophila melanogaster. We identify the member of the split ends protein family, Spenito, as a novel bona fide subunit of the methyltransferase complex. We further demonstrate important roles of this complex in neuronal functions and sex determination, and implicate the nuclear YT521-B protein as a main mA effector in these processes. Altogether, our work substantially extends our knowledge of mA biology, demonstrating the crucial functions of this modification in fundamental processes within the context of the whole animal.