An essential role of acetylcholine-glutamate synergy at habenular synapses in nicotine dependence

A great deal of interest has been focused recently on the habenula and its critical role in aversion, negative-reward and drug dependence. Using a conditional mouse model of the ACh-synthesizing enzyme choline acetyltransferase (Chat), we report that local elimination of acetylcholine (ACh) in medial habenula (MHb) neurons alters glutamate corelease and presynaptic facilitation. Electron microscopy and immuno-isolation analyses revealed colocalization of ACh and glutamate vesicular transporters in synaptic vesicles (SVs) in the central IPN. Glutamate reuptake in SVs prepared from the IPN was increased by ACh, indicating vesicular synergy. Mice lacking CHAT in habenular neurons were insensitive to nicotine-conditioned reward and withdrawal. These data demonstrate that ACh controls the quantal size and release frequency of glutamate at habenular synapses, and suggest that the synergistic functions of ACh and glutamate may be generally important for modulation of cholinergic circuit function and behavior

Suppression of peripheral pain by blockade of voltage-gated calcium 2.2 channels in nociceptors induces RANKL and impairs recovery from inflammatory arthritis in a mouse model

Objective: A hallmark of rheumatoid arthritis (RA) is the chronic pain that accompanies the inflammation and joint deformation. Patients with RA rate pain relief with highest priority, however, few studies have addressed the efficacy and safety of therapies directed specifically towards pain pathways. The conotoxin MVIIA (Prialt/Ziconotide) is used in humans to alleviate persistent pain syndromes because it specifically blocks the CaV 2.2 voltage-gated calcium channel, which mediates the release of neurotransmitters and proinflammatory mediators from peripheral nociceptor nerve terminals. The purpose of this study was to investigate whether block of CaV 2.2 can suppress arthritic pain, and to examine the progression of induced arthritis during persistent CaV 2.2 blockade. Methods: Transgenic mice (Tg-MVIIA) expressing a membrane-tethered form of the {Omega}-conotoxin MVIIA, under the control of a nociceptor-specific gene, were employed. These mice were subjected to unilateral induction of joint inflammation using the Antigen- and Collagen-Induced Arthritis (ACIA) model. Results: We observed that CaV 2.2-blockade mediated by t-MVIIA effectively suppressed arthritis-induced pain; however, in contrast to their wild-type littermates, which ultimately regained use of their injured joint as inflammation subsides, Tg-MVIIA mice showed continued inflammation with an up-regulation of the osteoclast activator RANKL and concomitant joint and bone destruction. Conclusion: Altogether, our results indicate that alleviation of peripheral pain by blockade of CaV 2.2- mediated calcium influx and signaling in nociceptor sensory neurons, impairs recovery from induced arthritis and point to the potentially devastating effects of using CaV 2.2 channel blockers as analgesics during inflammation

Habenular expression of rare missense variants of the β4 nicotinic receptor subunit alters nicotine consumption

The CHRNA5-CHRNA3-CHRNB4 gene cluster, encoding the {alpha}5, {alpha}3, and {beta}4 nicotinic acetylcholine receptor (nAChR) subunits, has been linked to nicotine dependence. The habenulo-interpeduncular (Hb-IPN) tract is particularly enriched in {alpha}3{beta}4 nAChRs. We recently showed that modulation of these receptors in the medial habenula (MHb) in mice altered nicotine consumption. Given that {beta}4 is rate-limiting for receptor activity and that single nucleotide polymorphisms (SNPs) in CHRNB4 have been linked to altered risk of nicotine dependence in humans, we were interested in determining the contribution of allelic variants of {beta}4 to nicotine receptor activity in the MHb. We screened for missense SNPs that had allele frequencies >0.0005 and introduced the corresponding substitutions in Chrnb4. Fourteen variants were analyzed by co-expression with {alpha}3. We found that {beta}4A90I and {beta}4T374I variants, previously shown to associate with reduced risk of smoking, and an additional variant {beta}4D447Y, significantly increased nicotine-evoked current amplitudes, while {beta}4R348C, the mutation most frequently encountered in sporadic amyotrophic lateral sclerosis (sALS), showed reduced nicotine currents. We employed lentiviruses to express {beta}4 or {beta}4 variants in the MHb. Immunoprecipitation studies confirmed that {beta}4 lentiviral-mediated expression leads to specific upregulation of {alpha}3{beta}4 but not {beta}2 nAChRs in the Mhb. Mice injected with the {beta}4-containing virus showed pronounced aversion to nicotine as previously observed in transgenic Tabac mice overexpressing Chrnb4 at endogenous sites including the MHb. Habenular expression of the {beta}4 gain-of-function allele T374I also resulted in strong aversion, while transduction with the {beta}4 loss-of function allele R348C failed to induce nicotine aversion. Altogether, these data confirm the critical role of habenular {beta}4 in nicotine consumption, and identify specific SNPs in CHRNB4 that modify nicotine-elicited currents and alter nicotine consumption in mice

EXD2 governs germ stem cell homeostasis and lifespan by promoting mitoribosome integrity and translation

Mitochondria are subcellular organelles critical for meeting the bioenergetic and biosynthetic needs of the cell. Mitochondrial function relies on genes and RNA species encoded both in the nucleus and mitochondria, as well as their coordinated translation, import and respiratory complex assembly. Here we describe the characterization of exonuclease domain like 2 (EXD2), a nuclear encoded gene that we show is targeted to the mitochondria and prevents the aberrant association of mRNAs with the mitochondrial ribosome. The loss of EXD2 resulted in defective mitochondrial translation, impaired respiration, reduced ATP production, increased reactive oxygen species and widespread metabolic abnormalities. Depletion of EXD2/CG6744 in D.melanogaster caused developmental delays and premature female germline stem cell attrition, reduced fecundity and a dramatic extension of lifespan that could be reversed with an anti-oxidant diet. Our results define a conserved role for EXD2 in mitochondrial translation that influences development and aging

Mitochondrial and cell cycle functions of SLIMP

[eng] The mitochondrial Seryl-tRNA Synthetase (SerRS2) is a member of the class II tRNA synthetase family. The mature enzyme catalyses the ligation of serine to tRNASer in mitochondria. During the process of constructing a model for human disorders caused by mitochondrial tRNA aminoacylation deficiencies in Drosophila melanogaster, a previously uncharacterized paralogue of SerRS2 named Seryl-tRNA synthetase-Like Insect Mitochondrial Protein (SLIMP) was identified. SLIMP is a new type of aminoacyl tRNA synthetase-like protein that has acquired an essential function in insects. This fast evolving paralogue is a mitochondrial RNA-binding protein which lacks tRNA aminoacylation activity. It has been previously demonstrated that mitochondrial SLIMP interacts with its homologue SerRS2 and also with LON protease. We confirmed these interactions and we described the function of SLIMP by depleting its protein levels in Drosophila melanogaster S2 cells, which led to severe defects in mitochondrial function and cell cycle arrest. We found that SLIMP simultaneously acts as a regulator of DNA replication and translation in the mitochondria and, as regulator of cell cycle progression. We show that SLIMP activates mitochondrial protein synthesis through its interaction with SerRS2 and regulates mitochondrial DNA levels by stimulating TFAM digestion by the protease LON. SLIMP was previously reported to be required for correct cell cycle progression. We showed that the depletion of a non-mitochondrial pool of SLIMP causes cell cycle arrest in G2 and the activation of E2F-related and G2/M check-point genes. Our results indicate that SLIMP activity provides an important protein for the communication between mitochondrial anabolism and cell cycle regulation.[cat] La Seril-ARNt Sintetasa mitocondrial (SerRS2) és membre de la família de ARNt sintetases de classe II. Aquest enzim es responsable de la lligació de l’aminoàcid serina al corresponent ARNtSer a la mitocòndria. En el procés de desenvolupament d’un model de malalties mitocondrials causades per deficiències en l’aminoacilació de ARNt en Drosophila melanogaster, es descobrí una proteïna paràleg de SerRS2 no caracteritzada fins el moment, anomenada Seril-ARNt sintetasa-Like Insect Mitochondrial Protein (SLIMP). SLIMP representa una nova classe de proteïna semblant a les ARNt sintetases que ha adquirit funcions essencials en insectes. Aquest paràleg ha evolucionat en poc temps i constitueix una proteïna amb unió a ARN però sense capacitat d’aminoacilació. Prèviament s’havia caracteritzat que SLIMP interacciona amb el seu homòleg SerRS2 i també amb la proteasa mitocondrial LON. Ara hem confirmat aquestes interaccions i hem descrit les funcions de SLIMP, caracteritzant l’efecte de la depleció dels seus nivells proteics en cèl·lules S2 de Drosophila melanogaster, que comportà severs defectes mitocondrials i un arrest del cicle cel·lular. Hem definit que SLIMP actua simultàniament com un regulador de la replicació del ADN i la traducció a la mitocòndria i, com a regulador de la progressió del cicle cel·lular. SLIMP activa la síntesis proteica mitocondrial gràcies a la interacció amb SerRS2, i a més regula els nivells de ADN mitocondrial, estimulant la degradació de TFAM per la proteasa LON. Anteriorment, es descrigué que SLIMP és necessari per la correcta progressió del cicle cel·lular. Hem trobat que la depleció d’una isoforma no mitocondrial de SLIMP arresta el cicle cel·lular en la fase G2 i activa la transcripció de gens relacionats amb E2F i amb el punt de control de G2/M. Aquests resultats indiquen la important tasca de SLIMP per la comunicació entre l’anabolisme mitocondrial i la regulació del cicle cel·lular

Identifizierung eines neuen synaptischen G-Protein gekoppelten Rezeptors, der Nikotin-Abhängigkeit und Entzug kontrolliert

This work identifies a novel synaptic G protein-coupled receptor, Gpr151, present only in habenular neurons in the human and mouse brain, as a novel target for the development of smoking cessation therapies. Therefore it provides new insights into the biology of this specific neuronal cell type and into the functional role of Gpr151. This study was prompted: first, by our discovery of the habenula as a key brain area controlling nicotine consumption and withdrawal (Frahm et al., 2011; Gorlich et al., 2013; Slimak et al., 2014) and second, by the identification of Gpr151 as highly and specifically enriched in cholinergic neurons of the medial habenula using the TRAP methodology when compared to previously collected TRAP data from different cell types in the CNS (Gorlich et al., 2013). Three main conclusions can be drawn from this work: First, I show that Gpr151 is exclusively localized at the axonal projections of habenular neurons where it plays a key role in regulating nicotine dependence and nicotine withdrawal. Gpr151-expressing neurons of the medial and lateral habenula project mainly to the interpeduncular nucleus (IPN), the rostromedial tegmental nucleus (RMTg) and the raphe nuclei. Respectively, the MHb-IPN tract modulates nicotine-related behaviors, the RMTg regulates negative reward and the raphe nuclei are responsible for releasing serotonin to other parts of the brain, suggesting that Gpr151 could modulate the nicotine addiction circuit, reinforcement learning, pain, stress and depression-like behavior among others. I demonstrate that Gpr151 deletion or shRNA-mediated downregulation increased the sensitivity to nicotine-conditioned reward. In addition, deletion of Gpr151 induced an anxiety-like response and an increase in the number of somatic signs in mice undergoing nicotine withdrawal, indicating that Gpr151 expression in habenular terminals attenuates physical and affective signs of nicotine withdrawal. Second, I show by electron microscopy that Gpr151 is localized at habenular presynaptic terminals in the interpeduncular nucleus, specifically at the plasma membrane close to the active zone and also in association with synaptic vesicles. These findings are critically important because they clearly identify Gpr151 as a novel presynaptic component in close proximity to the active zone and specific for habenular synapses. Further, the colocalization with the transporter VGlut1 in synaptic vesicles indicates that Gpr151 might be translocated from the synaptic vesicles to the plasma membrane when habenular neurons are depolarized and glutamate-filled synaptic vesicles are released. These results together with the behavioral analysis, suggest that Gpr151 at the plasma membrane of habenular presynaptic terminals may act as an inhibitory feedback regulator of habenula signaling. Third, analysis of the Gpr151 signaling pathway indicates that Gpr151 couples to the Gαi/o protein. I observed an increase of cAMP levels in the habenular terminals of Gpr151 knockout mice. Remarkably cAMP at the habenular terminals has been shown to modulate neurotransmitter release (Hu et al., 2012). Depletion of presynaptic cAMP levels in medial habenular neurons led to a reduction of protein kinase A activity and consequently to a suppression of glutamate release (Hu et al., 2012). These data together with the behavioral analysis suggest that increased levels of cAMP in the habenular terminals of Gpr151-KO mice facilitate nicotine-induced neurotransmitter release. Activation of the MHb-IPN pathway triggers an inhibitory motivational signal that limits nicotine intake (Fowler et al., 2011; Frahm et al., 2011). Therefore I hypothesize that increased levels of cAMP in the MHb terminals of Gpr151-KO increases the magnitude of this inhibitory signal, leading to increased sensitivity to nicotine-induced reinforcement responses and increased somatic and affective signs of nicotine withdrawal. Altogether these results highlight the importance of Gpr151 for smoking-related diseases. Current therapies for nicotine addiction are hampered by serious side effects since they act on nicotinic and/or dopamine targets in the mesocorticolimbic reward system. In addition the success rate of these therapies is less than 30% (Crooks et al., 2014). Thus alternative and more efficacious pharmacotherapies to target the negative states of withdrawal are required. Human genetics studies have identified several loci associated with heavy smoking and lung cancer in relation to nicotinic acetylcholine receptors. Importantly, although α4β2 and α7 nAChRs are the major subtypes present in the brain, genome wide association studies (GWAS) have not linked these genes to nicotine abuse. Rather, they have established a strong association between SNPs in the CHRNB4-A3-A5 gene cluster and smoking dependence, indicating that α3β4α5 nAChRs, which are mostly restricted to the MHb-IPN pathway in the CNS, are critical for acquisition of nicotine dependence and difficulties in smoking cessation. However because α3β4α5 receptors are also expressed in ganglia in the PNS, antagonists of these cholinergic receptors are expected to have undesired side effects. Therefore an ideal candidate for such therapies is Gpr151 as the habenula-interpeduncular nucleus tract has never been previously targeted. The studies presented here favor the hypothesis that a Gpr151 agonist would be a very valuable therapeutic target not only for smoking cessation, as it could decrease the magnitude of the negative states associated with nicotine withdrawal such as anxiety, but also as a deterrent to become nicotine dependent, since a Gpr151 agonist would decrease the sensitivity to nicotine reward.In dieser Arbeit wurde der neue G-Protein-gekoppelte Rezeptor Gpr151, der im Menschen- und Mäusehirn nur in Neuronen der Habenula zu finden ist, als neuer potentieller Angriffspunkt für die Rauchentwöhnungstherapie entdeckt. Damit bietet diese Arbeit neue Einblicke in die Biologie und die Funktion dieses spezifischen, neuronalen Zelltyps und von Gpr151. Als Grundlage für diese Arbeit dienen erstens Befunde welcher der Habenula Schlüsselfunktionen im Nikotinkonsum sowie Nikotinentzug zuweisen (Frahm et al., 2011; Görlich et al., 2013; Slimak et al., 2014), und zweitens Befunde aus vergleichenden TRAP- Analysen (Görlich et al., 2013), die Gpr151 als hoch prominent und spezifisch in cholinergen Neuronen der medialen Habenula ausweisen. Drei Hauptaussagen können aus dieser Arbeit getroffen werden: Erstens: Gpr151 ist ausschließlich in axonalen Projektionen der Habenula zu finden und spielt dort eine Schlüsselrolle in der Regulation von Nikotinabhängigkeit und Nikotinentzug. Gpr151 exprimierende Neurone der medialen und lateralen Habenula projizieren hauptsächlich zum interpeduncular nucleus (IPN), dem rostromedialen tegmental nucleus (RMTg) und den raphe Kernen. Verhalten, das mit Nikotinkosum in Bezug gesetzt wird, ist durch den MHb-IPN Signalweg, Vermeidungsverhalten durch den RMTg, und Serotonin-Ausschüttung von den raphe Kernen moduliert. Dies lässt vermuten, dass Gpr151 unter anderem Nikotinabhängigkeit, bestärkendes Lernen, Schmerz, Stress und depressives Verhalten beeinflusst. In dieser Arbeit konnte ich zeigen, dass eine Gpr151 Gendeletion oder eine shRNA-vermittelte Expressionsreduktion, die Sensitivität von Nikotin-konditioniertem Belohnungsverhalten erhöht. Zudem induziert die Gendeletion von Gpr151 in Mäusen ein Angst-ähnliches Verhalten sowie eine erhöhte Zahl an somatischen Symptomen im Nikotinentzug woraus zu schließen ist, dass die Gpr151 Expression in Terminalen der Habenula physische und somatische Entzugserscheinungen vermindert. Zweitens: Mit elektronenmikroskopischen Aufnahmen konnte ich zeigen, dass Gpr151 im IPN in Axonterminalen der Habenula vor allem an der Plasmamembran der aktiven Zone sowie vereinzelt an synaptische Vesikel assoziiert ist. Da diese Ergebnisse Gpr151 klar als neue präsynaptische Komponente in der aktiven Zone der habenula Terminalen zeigt, sind sie von besonderer Bedeutung, Da meine Ergebnisse zudem eine Kolokalisation von Gpr151 mit dem vesikulärem Glutamat Transporter VGlut1 in synaptischen Vesikeln zeigt, vermute ich, dass Gpr151 durch Depolarisation von Habenulaneuronen und folgender Glutamatausschüttung in die Plasmamembran eingebracht wird. Dies lässt zusammen mit meinen Verhaltensexperimenten vermuten, dass Gpr151 an der präsynaptischen Membran die Habenula-IPN Signalübertragung reguliert. Drittens: Meine Analysen deuten darauf hin, das Gpr151 mit dem Gαi Protein gekoppelt ist. In habenula Terminalen von Gpr151 knockout (KO) Mäusen konnte ich eine Erhöhung des cAMP Levels erkennen. Ein verringerter cAMP Spiegel in präsynaptischen Terminalen der medialen Habenula führt zu einer Reduktion der Proteinkinase A Aktivität und folglich zu einer verminderten Glutamatausschüttung (Hu et al., 2012). Zusammen mit meinen Verhaltensexperimenten deuten diese Ergebnisse darauf hin, dass ein erhöhter cAMP Level in habenula Terminalen von Gpr151-KO Tieren die nikotin-induzierte Neurotransmitterfreisetzung erhöht. Durch Aktivierung des MHb-IPN Trakts wird die Nikotin-Einnahme auf Grund Demotivation reduziert (Fowler et al., 2011; Frahm et al., 2011). Ich vermute daher, dass der erhöhte cAMP Level in MHb Terminalen von Gpr151-KO Mäusen inhibitorische Signale potenziert, somit die Reaktion auf Nikotin verstärkt und zu erhöhten somatischen und affektiven Signalen des Nikotinentzugs führt. Zusammengefasst unterstreichen meine Ergebnisse die wichtige Bedeutung von Gpr151 für durch Rauchen verursachte Krankheiten. Da derzeitige Therapien zur Rauchentwöhnung an nikotinergen und/oder dopaminergen Rezeptoren im mesocorticolimbischen System agieren, bedingen sie schwerwiegende Nebenwirkungen und sind daher unbefriedigend. Hinzu kommt, dass weniger als 30% der derzeitigen Therapien erfolgreich sind (Crooks et al., 2014). Alternative, effektivere pharmakologische Therapien mit reduzierten Nebenwirkungen sind notwendig. Humane Genanalysen haben starkes Rauchen und das Risiko an Lungenkrebs zu erkranken mit nikotinergen Acetylcholin Rezeptoren (nAChR) in Verbindung gebracht. Obwohl α4β2 und α7 nAChRs die Haupt-Rezeptoruntereinheiten des CNS sind, konnten sie in genomweiten Assoziationsstudien (GWAS) nicht mit Nikotinmissbrauch in Verbindung gesetzt werden. Nikotinabhängigkeit wurde vielmehr mit SNPs im CHRNB4-A3-A5 Gen-Cluster und damit mit α3β4α5 nAChRs welche vor allem im MHb- IPN Trakt im CNS vorkommen, assoziiert. Da α3β4α5 nAChRs auch in Ganglien des PNS exprimiert sind, ist zu vermuten, dass Antagonisten gegen diesen Rezeptor unerwünschte Nebeneffekte mit sich bringen. Die hier dargelegten Ergebnisse favorisieren die Hypothese, dass ein Gpr151 Agonist eine sehr nützliche Alternative zu derzeitig praktizierten Rauchentwöhnungstherapien seien kann. Da Gpr151 zudem die belohnenden Effekte von Nikotin verringert, ist ein Agonist auch als Präventionsmittel zur Nikotinabhängigkeit denkbar

Cost-effectiveness análisis ofmicro-dystrophin: a novel gene therapy for duchenne muscular dystrophy

Màster Universitari en Economia de la Salud i del Medicament. (UPF Barcelona School of Management) Curs 2017-2020Mentor: Aníbal Garcí

Novel heterojunction bipolar transistor architectures for the practical implementation of high-efficiency three-terminal solar cells

Practical device architectures are proposed here for the implementation of three-terminal heterojunction bipolar transistor solar cells (3T-HBTSCs). These photovoltaic devices, which have a potential efficiency similar to that of multijunction cells, exhibit reduced spectral sensitivity compared with monolithically and series-connected tandem solar cells. In addition, the simplified n-p-n (or p-np) structure does not require the use of tunnel junctions. In this framework, four architectures are proposed and discussed in this paper: 1) one in which the top cell is based on silicon and the bottom cell is based on a heterojunction between silicon and III-V nanomaterials; 2) one in which the top cell is made of amorphous silicon and the bottom cell is made of an amorphous silicon-silicon heterojunction; 3) one based on the use of III-V semiconductors aimed at space applications; and 4) one in which the top cell is based on a perovskite material and the bottom cell is made of a perovskitesilicon heterostructure

Reexposure to nicotine during withdrawal increases the pacemaking activity of cholinergic habenular neurons

The discovery of genetic variants in the cholinergic receptor nicotinic CHRNA5-CHRNA3-CHRNB4 gene cluster associated with heavy smoking and higher relapse risk has led to the identification of the midbrain habenula-interpeduncular axis as a critical relay circuit in the control of nicotine dependence. Although clear roles for {alpha}3, {beta}4, and {alpha}5 receptors in nicotine aversion and withdrawal have been established, the cellular and molecular mechanisms that participate in signaling nicotine use and contribute to relapse have not been identified. Here, using translating ribosome affinity purification (TRAP) profiling, electrophysiology, and behavior, we demonstrate that cholinergic neurons, but not peptidergic neurons, of the medial habenula (MHb) display spontaneous tonic firing of 2-10 Hz generated by hyperpolarization-activated cyclic nucleotide-gated (HCN) pacemaker channels and that infusion of the HCN pacemaker antagonist ZD7288 in the habenula precipitates somatic and affective signs of withdrawal. Further, we show that a strong, {alpha}3{beta}4-dependent increase in firing frequency is observed in these pacemaker neurons upon acute exposure to nicotine. No change in the basal or nicotine-induced firing was observed in cholinergic MHb neurons from mice chronically treated with nicotine. We observe, however, that, during withdrawal, reexposure to nicotine doubles the frequency of pacemaking activity in these neurons. These findings demonstrate that the pacemaking mechanism of cholinergic MHb neurons controls withdrawal, suggesting that the heightened nicotine sensitivity of these neurons during withdrawal may contribute to smoking relapse

DISC1, PDE4B, and NDE1 at the centrosome and synapse

International audienceDisrupted-In-Schizophrenia 1 (DISC1) is a risk factor for schizophrenia and other major mental illnesses. Its protein binding partners include the Nuclear Distribution Factor E Homologs (NDE1 and NDEL1), LIS1, and phosphodiesterases 4B and 4D (PDE4B and PDE4D). We demonstrate that NDE1, NDEL1 and LIS1, together with their binding partner dynein, associate with DISC1, PDE4B and PDE4D within the cell, and provide evidence that this complex is present at the centrosome. LIS1 and NDEL1 have been previously suggested to be synaptic, and we now demonstrate localisation of DISC1, NDE1, and PDE4B at syn-apses in cultured neurons. NDE1 is phosphorylated by cAMP-dependant Protein Kinase A (PKA), whose activity is, in turn, regulated by the cAMP hydrolysis activity of phosphodiesterases, including PDE4. We propose that DISC1 acts as an assembly scaffold for all of these proteins and that the NDE1/ NDEL1/LIS1/dynein complex is modulated by cAMP levels via PKA and PDE4