Essentiality of fatty acid synthase in the 2D to anchorage-independent growth transition in transforming cells

Upregulation of fatty acid synthase (FASN) is a common event in cancer, although its mechanistic and potential therapeutic roles are not completely understood. In this study, we establish a key role of FASN during transformation. FASN is required for eliciting the anaplerotic shift of the Krebs cycle observed in cancer cells. However, its main role is to consume acetyl-CoA, which unlocks isocitrate dehydrogenase (IDH)-dependent reductive carboxylation, producing the reductive power necessary to quench reactive oxygen species (ROS) originated during the switch from two-dimensional (2D) to three-dimensional (3D) growth (a necessary hallmark of cancer). Upregulation of FASN elicits the 2D-to-3D switch; however, FASN's synthetic product palmitate is dispensable for this process since cells satisfy their fatty acid requirements from the media. In vivo, genetic deletion or pharmacologic inhibition of FASN before oncogenic activation prevents tumor development and invasive growth. These results render FASN as a potential target for cancer prevention studies.M.Q.F. is a recipient of the following grants: FIS PI13/00430 and FIS PI16/00354 funded by the Instituto de Salud Carlos III (ISCIII) and co-funded by the European Regional Development Fund (ERDF) and AECC Scientific Foundation (Beca de Retorno 2010). R.C. is a recipient of the following grants: FIS PI11/00832 and FIS PI14/00726 funded by the Instituto de Salud Carlos III (ISCIII) and co-funded by the European Regional Development Fund (ERDF), II14/00009 and PIE15/00068 from the Ministerio de Sanidad, Spain. N.S.C. is a recipient of an NIH grant (5R35CA197532). O.Y.T. is a recipient of the grants BFU2014-57466 from the Ministerio de Economia y Competitividad (MINECO). J.P.B. is funded by MINECO (SAF2016-78114-R), Instituto de Salud Carlos III (RD12/0043/0021), Junta de Castilla y Leon (Escalera de Excelencia CLU-2017-03), Ayudas Equipos Investigacion Biomedicina 2017 Fundacion BBVA, and Fundacion Ramon Areces. This study was partially supported by the generous donations from Fundacion CRIS Contra el Cancer and AVON Spain. We thank Drs. Erwin Wagner and Nabil Djouder for their critical review of the paper.S

Aberrant upregulation of the glycolytic enzyme PFKFB3 in CLN7 neuronal ceroid lipofuscinosis

CLN7 neuronal ceroid lipofuscinosis is an inherited lysosomal storage neurodegenerative disease highly prevalent in children. CLN7/MFSD8 gene encodes a lysosomal membrane glycoprotein, but the biochemical processes affected by CLN7-loss of function are unexplored thus preventing development of potential treatments. Here, we found, in the Cln7∆ex2 mouse model of CLN7 disease, that failure in autophagy causes accumulation of structurally and bioenergetically impaired neuronal mitochondria. In vivo genetic approach reveals elevated mitochondrial reactive oxygen species (mROS) in Cln7∆ex2 neurons that mediates glycolytic enzyme PFKFB3 activation and contributes to CLN7 pathogenesis. Mechanistically, mROS sustains a signaling cascade leading to protein stabilization of PFKFB3, normally unstable in healthy neurons. Administration of the highly selective PFKFB3 inhibitor AZ67 in Cln7∆ex2 mouse brain in vivo and in CLN7 patients-derived cells rectifies key disease hallmarks. Thus, aberrant upregulation of the glycolytic enzyme PFKFB3 in neurons may contribute to CLN7 pathogenesis and targeting PFKFB3 could alleviate this and other lysosomal storage diseases

Abrogating mitochondrial ROS in neurons or astrocytes reveals cell-specific impact on mouse behaviour.

Cells naturally produce mitochondrial reactive oxygen species (mROS), but the in vivo pathophysiological significance has long remained controversial. Within the brain, astrocyte-derived mROS physiologically regulate behaviour and are produced at one order of magnitude faster than in neurons. However, whether neuronal mROS abundance differentially impacts on behaviour is unknown. To address this, we engineered genetically modified mice to down modulate mROS levels in neurons in vivo. Whilst no alterations in motor coordination were observed by down modulating mROS in neurons under healthy conditions, it prevented the motor discoordination caused by the pro-oxidant neurotoxin, 3-nitropropionic acid (3-NP). In contrast, abrogation of mROS in astrocytes showed no beneficial effect against the 3-NP insult. These data indicate that the impact of modifying mROS production on mouse behaviour critically depends on the specific cell-type where they are generated

Astrocytic mitochondrial ROS modulate brain metabolism and mouse behaviour

International audienceTo satisfy its high energetic demand , the brain depends on the metabolic cooperation of various cell types. For example, astrocytic-derived lactate sustains memory consolidation by serving both as an oxidizable energetic substrate for neurons and as a signalling molecule. Astrocytes and neurons also differ in the regulation of glycolytic enzymes and in the organization of their mitochondrial respiratory chain. Unlike neurons, astrocytes rely on glycolysis for energy generation and, as a consequence, have a loosely assembled mitochondrial respiratory chain that is associated with a higher generation of mitochondrial reactive oxygen species (ROS). However, whether this abundant natural source of mitochondrial ROS in astrocytes fulfils a specific physiological role is unknown. Here we show that astrocytic mitochondrial ROS are physiological regulators of brain metabolism and neuronal function. We generated mice that inducibly overexpress mitochondrialtagged catalase in astrocytes and show that this overexpression decreases mitochondrial ROS production in these cells during adulthood. Transcriptomic, metabolomic, biochemical, immunohistochemical and behavioural analysis of these mice revealed alterations in brain redox, carbohydrate, lipid and amino acid metabolic pathways associated with altered neuronal function and mouse behaviour. We found that astrocytic mitochondrial ROS regulate glucose utilization via the pentose-phosphate pathway and glutathione metabolism, which modulates the redox status and potentially the survival of neurons. Our data provide further molecular insight into the metabolic cooperation between astrocytes and neurons and demonstrate that mitochondrial ROS are important regulators of organismal physiology in vivo