Recent Submissions

  • Journal Article

    Integrated Analyses of Microbiome and Longitudinal Metabolome Data Reveal Microbial-Host Interactions on Sulfur Metabolism in Parkinson’s Disease 

    Hertel, Johannes; Harms, Amy C.; Heinken, Almut; Baldini, Federico; Thinnes, Cyrille C.; Glaab, Enrico; Vasco, Daniel A.; Pietzner, Maik; Stewart, Isobel D.; Wareham, Nicholas J.; et al.
    Langenberg, ClaudiaTrenkwalder, ClaudiaKrüger, RejkoHankemeier, ThomasFleming, Ronan M.T.Mollenhauer, BritThiele, Ines
    Cell Reports 2019; 29(7): Art. 1777.e8
    Parkinson's disease (PD) exhibits systemic effects on the human metabolism, with emerging roles for the gut microbiome. Here, we integrate longitudinal metabolome data from 30 drug-naive, de novo PD patients and 30 matched controls with constraint-based modeling of gut microbial communities derived from an independent, drug-naive PD cohort, and prospective data from the general population. Our key results are (1) longitudinal trajectory of metabolites associated with the interconversion of methionine and cysteine via cystathionine differed between PD patients and controls; (2) dopaminergic medication showed strong lipidomic signatures; (3) taurine-conjugated bile acids correlated with the severity of motor symptoms, while low levels of sulfated taurolithocholate were associated with PD incidence in the general population; and (4) computational modeling predicted changes in sulfur metabolism, driven by A. muciniphila and B. wadsworthia, which is consistent with the changed metabolome. The multi-omics integration reveals PD-specific patterns in microbial-host sulfur co-metabolism that may contribute to PD severity.
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  • Journal Article

    Subcellular Targeting of VIP Boutons in Mouse Barrel Cortex is Layer-Dependent and not Restricted to Interneurons 

    Zhou, Xiaojuan; Rickmann, Michael; Hafner, Georg; Staiger, Jochen F.
    Cerebral Cortex 2017; 27(11) p.5353-5368
    Neocortical vasoactive intestinal polypeptide (VIP) expressing cells are a diverse subpopulation of GABAergic interneurons issuing distinct axonal projections. They are known to inhibit other types of interneurons as well as excitatory principal neurons and possess a disinhibitory net effect in cortical circuits. In order to elucidate their targeting specificity, the output connectivity of VIP interneurons was studied at the subcellular level in barrel cortex of interneuron-specific Cre-driver mice, using pre- and postembedding electron microscopy. Systematically sampling VIP boutons across all layers, we found a substantial proportion of the innervated subcellular structures were dendrites (80%), with somata (13%), and spines (7%) being much less targeted. In layer VI, a high proportion of axosomatic synapses was found (39%). GABA-immunopositive ratio was quantified among the targets using statistically validated thresholds: only 37% of the dendrites, 7% of the spines, and 26% of the somata showed above-threshold immunogold labeling. For the main target structure "dendrite", a higher proportion of GABAergic subcellular profiles existed in deep than in superficial layers. In conclusion, VIP interneurons innervate non-GABAergic excitatory neurons and interneurons at their subcellular domains with layer-dependent specificity. This suggests a diverse output of VIP interneurons, which predicts multiple functionality in cortical circuitry beyond disinhibition.
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  • Journal Article

    Efficacy of venlafaxine extended release in major depressive disorder patients 

    Lyndon, Gavin J.; Prieto, Rita; Wajsbrot, Dalia B.; Allgulander, Christer; Bandelow, Borwin
    International Clinical Psychopharmacology 2019; 34(3) p.110-118
    Effects of baseline anxiety on the efficacy of venlafaxine extended release versus placebo were examined in a post hoc pooled subgroup analysis of 1573 patients enrolled in eight short-term studies of major depressive disorder. Anxiety subgroups were defined based on baseline 17-item Hamilton Rating Scale for Depression Item 10 score <3 (low) versus ≥3 (high). Change from baseline to final visit in Montgomery-Åsberg Depression Rating Scale total score and Montgomery-Åsberg Depression Rating Scale response and remission rates were analyzed. Change from baseline in Montgomery-Åsberg Depression Rating Scale total score and response and remission rates was significantly greater for venlafaxine extended release versus placebo in both low and high anxiety subgroups (all P < 0.0001). A statistically significant baseline anxiety by treatment interaction was observed for Montgomery-Åsberg Depression Rating Scale total score only (P = 0.0152). The adjusted mean change from baseline in Montgomery-Åsberg Depression Rating Scale total score was significantly greater in the high anxiety subgroup versus low anxiety subgroup for patients treated with venlafaxine extended release (-6.27 versus -3.89; P = 0.0440) but not placebo. These results support the efficacy of venlafaxine extended release for major depressive disorder treatment in patients with anxiety symptoms.
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  • Journal Article

    Intracranial mechanical thrombectomy of large vessel occlusions in the posterior circulation using SAVE 

    Maus, Volker; Styczen, Hanna; Liman, Jan; Maier, Ilko; Brehm, Alex; Tsogkas, Ioannis; Psychogios, Marios-Nikos
    BMC Neurology 2019; 19(1): Art. 197
    BACKGROUND: Mechanical thrombectomy (MT) using stent retriever assisted vacuum-locked extraction (SAVE) is a promising method for anterior circulation strokes. We present our experience with SAVE for large vessel occlusions (LVO) of the posterior circulation. METHODS: We retrospectively analyzed 66 consecutive MT patients suffering from LVO of the posterior circulation. Primary endpoints were first-pass and overall complete/near complete reperfusion, defined as a modified thrombolysis in cerebral infarction (mTICI) score of 2c and 3. Secondary endpoints contained number of passes, time interval from groin puncture to reperfusion and rate of postinterventional symptomatic intracranial hemorrhage (sICH). RESULTS: Median age was 75 years (interquartile range (IQR) 54-81 years). Baseline median National Institutes of Health stroke scale (NIHSS) was 13 (IQR 8-21). Fifty-five (83%) patients had LVO of the basilar artery and 11 (17%) of the posterior cerebral artery. Eighteen (27%) patients were treated with SAVE and 21 (32%) with aspiration only. First pass mTICI2c or 3 and overall mTICI2c or 3 were documented in 11/18 (61%) and 14/18 (78%) with SAVE and in 4/21 (19%) and 13/21 (33%) with aspiration only. Median attempt was 1 (IQR 1-2) with SAVE and 2 (IQR 1-4) with aspiration (p = 0.0249). Median groin to reperfusion time did not differ significantly between groups. The rate of sICH was 5% without any complications in the SAVE cohort. CONCLUSION: Mechanical thrombectomy of posterior large vessel occlusions with SAVE is feasible, safe, and effective with high rates of near-complete and complete reperfusion.
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  • Journal Article

    Cation selectivity of the presequence translocase channel Tim23 is crucial for efficient protein import 

    Denkert, Niels; Schendzielorz, Alexander Benjamin; Barbot, Mariam; Versemann, Lennart; Richter, Frank; Rehling, Peter; Meinecke, Michael
    eLife 2017; 6: Art. eLife.28324
    Virtually all mitochondrial matrix proteins and a considerable number of inner membrane proteins carry a positively charged, N-terminal presequence and are imported by the TIM23 complex (presequence translocase) located in the inner mitochondrial membrane. The voltage-regulated Tim23 channel constitutes the actual protein-import pore wide enough to allow the passage of polypeptides with a secondary structure. In this study, we identify amino acids important for the cation selectivity of Tim23. Structure based mutants show that selectivity is provided by highly conserved, pore-lining amino acids. Mutations of these amino acid residues lead to reduced selectivity properties, reduced protein import capacity and they render the Tim23 channel insensitive to substrates. We thus show that the cation selectivity of the Tim23 channel is a key feature for substrate recognition and efficient protein import.
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  • Journal Article

    Mitochondrial respiratory chain deficiency inhibits lysosomal hydrolysis 

    Fernandez-Mosquera, Lorena; Yambire, King Faisal; Couto, Renata; Pereyra, Leonardo; Pabis, Kamil; Ponsford, Amy H.; Diogo, Cátia V.; Stagi, Massimiliano; Milosevic, Ira; Raimundo, Nuno
    Autophagy(27) p.1-20
    Mitochondria are key organelles for cellular metabolism, and regulate several processes including cell death and macroautophagy/autophagy. Here, we show that mitochondrial respiratory chain (RC) deficiency deactivates AMP-activated protein kinase (AMPK, a key regulator of energy homeostasis) signaling in tissue and in cultured cells. The deactivation of AMPK in RC-deficiency is due to increased expression of the AMPK-inhibiting protein FLCN (folliculin). AMPK is found to be necessary for basal lysosomal function, and AMPK deactivation in RC-deficiency inhibits lysosomal function by decreasing the activity of the lysosomal Ca2+ channel MCOLN1 (mucolipin 1). MCOLN1 is regulated by phosphoinositide kinase PIKFYVE and its product PtdIns(3,5)P2, which is also decreased in RC-deficiency. Notably, reactivation of AMPK, in a PIKFYVE-dependent manner, or of MCOLN1 in RC-deficient cells, restores lysosomal hydrolytic capacity. Building on these data and the literature, we propose that downregulation of the AMPK-PIKFYVE-PtdIns(3,5)P2-MCOLN1 pathway causes lysosomal Ca2+ accumulation and impaired lysosomal catabolism. Besides unveiling a novel role of AMPK in lysosomal function, this study points to the mechanism that links mitochondrial malfunction to impaired lysosomal catabolism, underscoring the importance of AMPK and the complexity of organelle cross-talk in the regulation of cellular homeostasis. Abbreviation: ΔΨm: mitochondrial transmembrane potential; AMP: adenosine monophosphate; AMPK: AMP-activated protein kinase; ATG5: autophagy related 5; ATP: adenosine triphosphate; ATP6V0A1: ATPase, H+ transporting, lysosomal, V0 subbunit A1; ATP6V1A: ATPase, H+ transporting, lysosomal, V0 subbunit A; BSA: bovine serum albumin; CCCP: carbonyl cyanide-m-chlorophenylhydrazone; CREB1: cAMP response element binding protein 1; CTSD: cathepsin D; CTSF: cathepsin F; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; EBSS: Earl's balanced salt solution; ER: endoplasmic reticulum; FBS: fetal bovine serum; FCCP: carbonyl cyanide-p-trifluoromethoxyphenolhydrazone; GFP: green fluorescent protein; GPN: glycyl-L-phenylalanine 2-naphthylamide; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MCOLN1/TRPML1: mucolipin 1; MEF: mouse embryonic fibroblast; MITF: melanocyte inducing transcription factor; ML1N*2-GFP: probe used to detect PtdIns(3,5)P2 based on the transmembrane domain of MCOLN1; MTORC1: mechanistic target of rapamycin kinase complex 1; NDUFS4: NADH:ubiquinone oxidoreductase subunit S4; OCR: oxygen consumption rate; PBS: phosphate-buffered saline; pcDNA: plasmid cytomegalovirus promoter DNA; PCR: polymerase chain reaction; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns(3,5)P2: phosphatidylinositol-3,5-bisphosphate; PIKFYVE: phosphoinositide kinase, FYVE-type zinc finger containing; P/S: penicillin-streptomycin; PVDF: polyvinylidene fluoride; qPCR: quantitative real time polymerase chain reaction; RFP: red fluorescent protein; RNA: ribonucleic acid; SDS-PAGE: sodium dodecyl sulfate polyacrylamide gel electrophoresis; shRNA: short hairpin RNA; siRNA: small interfering RNA; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; TMRM: tetramethylrhodamine, methyl ester, perchlorate; ULK1: unc-51 like autophagy activating kinase 1; ULK2: unc-51 like autophagy activating kinase 2; UQCRC1: ubiquinol-cytochrome c reductase core protein 1; v-ATPase: vacuolar-type H+-translocating ATPase; WT: wild-type.
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  • Journal Article

    Medial prefrontal cortex supports perceptual memory 

    Schwiedrzik, Caspar M.; Sudmann, Sandrin S.; Thesen, Thomas; Wang, Xiuyuan; Groppe, David M.; Mégevand, Pierre; Doyle, Werner; Mehta, Ashesh D.; Devinsky, Orrin; Melloni, Lucia
    Current Biology 2018; 28(18) p.R1094-R1095
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  • Journal Article

    IgSF9b regulates anxiety behaviors through effects on centromedial amygdala inhibitory synapses 

    Babaev, Olga; Cruces-Solis, Hugo; Piletti Chatain, Carolina; Hammer, Matthieu; Wenger, Sally; Ali, Heba; Karalis, Nikolaos; de Hoz, Livia; Schlüter, Oliver M.; Yanagawa, Yuchio; et al.
    Ehrenreich, HanneloreTaschenberger, HolgerBrose, NilsKrueger-Burg, Dilja
    Nature Communications 2018; 9(1): Art. 5400
    Abnormalities in synaptic inhibition play a critical role in psychiatric disorders, and accordingly, it is essential to understand the molecular mechanisms linking components of the inhibitory postsynapse to psychiatrically relevant neural circuits and behaviors. Here we study the role of IgSF9b, an adhesion protein that has been associated with affective disorders, in the amygdala anxiety circuitry. We show that deletion of IgSF9b normalizes anxiety-related behaviors and neural processing in mice lacking the synapse organizer Neuroligin-2 (Nlgn2), which was proposed to complex with IgSF9b. This normalization occurs through differential effects of Nlgn2 and IgSF9b at inhibitory synapses in the basal and centromedial amygdala (CeM), respectively. Moreover, deletion of IgSF9b in the CeM of adult Nlgn2 knockout mice has a prominent anxiolytic effect. Our data place IgSF9b as a key regulator of inhibition in the amygdala and indicate that IgSF9b-expressing synapses in the CeM may represent a target for anxiolytic therapies.
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  • Journal Article

    Mitochondrial biogenesis is transcriptionally repressed in lysosomal lipid storage diseases 

    Yambire, King Faisal; Fernandez-Mosquera, Lorena; Steinfeld, Robert; Mühle, Christiane; Ikonen, Elina; Milosevic, Ira; Raimundo, Nuno
    eLife 2019; 8: Art. e39598
    Perturbations in mitochondrial function and homeostasis are pervasive in lysosomal storage diseases, but the underlying mechanisms remain unknown. Here, we report a transcriptional program that represses mitochondrial biogenesis and function in lysosomal storage diseases Niemann-Pick type C (NPC) and acid sphingomyelinase deficiency (ASM), in patient cells and mouse tissues. This mechanism is mediated by the transcription factors KLF2 and ETV1, which are both induced in NPC and ASM patient cells. Mitochondrial biogenesis and function defects in these cells are rescued by the silencing of KLF2 or ETV1. Increased ETV1 expression is regulated by KLF2, while the increase of KLF2 protein levels in NPC and ASM stems from impaired signaling downstream sphingosine-1-phosphate receptor 1 (S1PR1), which normally represses KLF2. In patient cells, S1PR1 is barely detectable at the plasma membrane and thus unable to repress KLF2. This manuscript provides a mechanistic pathway for the prevalent mitochondrial defects in lysosomal storage diseases. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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  • Journal Article

    Investigating the feasibility of channelrhodopsin variants for nanoscale optogenetics 

    Stahlberg, Markus A.; Ramakrishnan, Charu; Willig, Katrin I.; Boyden, Edward S.; Deisseroth, Karl; Dean, Camin
    Neurophotonics 2019; 6(1): Art. 015007
    Optogenetics has revolutionized the study of circuit function in the brain, by allowing activation of specific ensembles of neurons by light. However, this technique has not yet been exploited extensively at the subcellular level. Here, we test the feasibility of a focal stimulation approach using stimulated emission depletion/reversible saturable optical fluorescence transitions-like illumination, whereby switchable light-gated channels are focally activated by a laser beam of one wavelength and deactivated by an overlapping donut-shaped beam of a different wavelength, confining activation to a center focal region. This method requires that activated channelrhodopsins are inactivated by overlapping illumination of a distinct wavelength and that photocurrents are large enough to be detected at the nanoscale. In tests of current optogenetic tools, we found that ChR2 C128A/H134R/T159C and CoChR C108S and C108S/D136A-activated with 405-nm light and inactivated by coillumination with 594-nm light-and C1V1 E122T/C167S-activated by 561-nm light and inactivated by 405-nm light-were most promising in terms of highest photocurrents and efficient inactivation with coillumination. Although further engineering of step-function channelrhodopsin variants with higher photoconductances will be required to employ this approach at the nanoscale, our findings provide a framework to guide future development of this technique.
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  • Journal Article

    An opposing function of paralogs in balancing developmental synapse maturation. 

    Favaro, Plinio D.; Huang, Xiaojie; Hosang, Leon; Stodieck, Sophia; Cui, Lei; Liu, Yu-Zhang; Engelhardt, Karl-Alexander; Schmitz, Frank; Dong, Yan; Löwel, Siegrid; et al.
    Schlüter, Oliver M.
    PLOS Biology 2018; 16(12): Art. e2006838
    The disc-large (DLG)-membrane-associated guanylate kinase (MAGUK) family of proteins forms a central signaling hub of the glutamate receptor complex. Among this family, some proteins regulate developmental maturation of glutamatergic synapses, a process vulnerable to aberrations, which may lead to neurodevelopmental disorders. As is typical for paralogs, the DLG-MAGUK proteins postsynaptic density (PSD)-95 and PSD-93 share similar functional domains and were previously thought to regulate glutamatergic synapses similarly. Here, we show that they play opposing roles in glutamatergic synapse maturation. Specifically, PSD-95 promoted, whereas PSD-93 inhibited maturation of immature α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate receptor (AMPAR)-silent synapses in mouse cortex during development. Furthermore, through experience-dependent regulation of its protein levels, PSD-93 directly inhibited PSD-95's promoting effect on silent synapse maturation in the visual cortex. The concerted function of these two paralogs governed the critical period of juvenile ocular dominance plasticity (jODP), and fine-tuned visual perception during development. In contrast to the silent synapse-based mechanism of adjusting visual perception, visual acuity improved by different mechanisms. Thus, by controlling the pace of silent synapse maturation, the opposing but properly balanced actions of PSD-93 and PSD-95 are essential for fine-tuning cortical networks for receptive field integration during developmental critical periods, and imply aberrations in either direction of this process as potential causes for neurodevelopmental disorders.
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  • Journal Article

    TORC1-mediated sensing of chaperone activity alters glucose metabolism and extends lifespan. 

    Perić, Matea; Lovrić, Anita; Šarić, Ana; Musa, Marina; Bou Dib, Peter; Rudan, Marina; Nikolić, Andrea; Sobočanec, Sandra; Mikecin, Ana-Matea; Dennerlein, Sven; et al.
    Milošević, IraVlahoviček, KristianRaimundo, NunoKriško, Anita
    Aging Cell 2017; 16(5) p.994-1005
    Protein quality control mechanisms, required for normal cellular functioning, encompass multiple functions related to protein production and maintenance. However, the existence of communication between proteostasis and metabolic networks and its underlying mechanisms remain elusive. Here, we report that enhanced chaperone activity and consequent improved proteostasis are sensed by TORC1 via the activity of Hsp82. Chaperone enrichment decreases the level of Hsp82, which deactivates TORC1 and leads to activation of Snf1/AMPK, regardless of glucose availability. This mechanism culminates in the extension of yeast replicative lifespan (RLS) that is fully reliant on both TORC1 deactivation and Snf1/AMPK activation. Specifically, we identify oxygen consumption increase as the downstream effect of Snf1 activation responsible for the entire RLS extension. Our results set a novel paradigm for the role of proteostasis in aging: modulation of the misfolded protein level can affect cellular metabolic features as well as mitochondrial activity and consequently modify lifespan. The described mechanism is expected to open new avenues for research of aging and age-related diseases.
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  • Journal Article

    Neurofeedback of Slow Cortical Potentials in Children with Attention-Deficit/Hyperactivity Disorder: A Multicenter Randomized Trial Controlling for Unspecific Effects. 

    Strehl, Ute; Aggensteiner, Pascal; Wachtlin, Daniel; Brandeis, Daniel; Albrecht, Björn; Arana, Maria; Bach, Christiane; Banaschewski, Tobias; Bogen, Thorsten; Flaig-Röhr, Andrea; et al.
    Freitag, Christine M.Fuchsenberger, YvonneGest, StephanieGevensleben, HolgerHerde, LauraHohmann, SarahLegenbauer, TanjaMarx, Anna-MariaMillenet, SabinaPniewski, BenjaminRothenberger, AribertRuckes, ChristianWörz, SonjaHoltmann, Martin
    Frontiers in human neuroscience 2017; 11: Art. 135
    Background: Neurofeedback (NF) in children with attention-deficit/hyperactivity disorder (ADHD) has been investigated in a series of studies over the last years. Previous studies did not unanimously support NF as a treatment in ADHD. Most studies did not control for unspecific treatment effects and did not demonstrate that self-regulation took place. The present study examined the efficacy of NF in comparison to electromyographic (EMG) feedback to control for unspecific effects of the treatment, and assessed self-regulation of slow cortical potentials (SCPs). Methods: A total of 150 children aged 7-9 years diagnosed with ADHD (82% male; 43% medicated) were randomized to 25 sessions of feedback of SCPs (NF) or feedback of coordination of the supraspinatus muscles (EMG). The primary endpoint was the change in parents' ratings of ADHD core symptoms 4 weeks after the end of treatment compared to pre-tests. Results: Children in both groups showed reduced ADHD-core symptoms (NF 0.3, 95% CI -0.42 to -0.18; EMG 0.13, 95% CI -0.26 to -0.01). NF showed a significant superiority over EMG (treatment difference 0.17, 95% CI 0.02-0.3, p = 0.02). This yielded an effect size (ES) of d = 0.57 without and 0.40 with baseline observation carried forward (BOCF). The sensitivity analysis confirmed the primary result. Successful self-regulation of brain activity was observed only in NF. As a secondary result teachers reported no superior improvement from NF compared to EMG, but within-group analysis revealed effects of NF on the global ADHD score, inattention, and impulsivity. In contrast, EMG feedback did not result in changes despite more pronounced self-regulation learning. Conclusions: Based on the primary parent-rated outcome NF proved to be superior to a semi-active EMG feedback treatment. The study supports the feasibility and efficacy of NF in a large sample of children with ADHD, based on both specific and unspecific effects. Trial Register: Current controlled trials ISRCTN76187185, registered 5 February 2009.
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  • Journal Article

    The BET/BRD inhibitor JQ1 improves brain plasticity in WT and APP mice. 

    Benito, E.; Ramachandran, B.; Schroeder, H.; Schmidt, G.; Urbanke, H.; Burkhardt, S.; Capece, V.; Dean, C.; Fischer, A.
    Translational psychiatry 2017-09-26; 7(9) p.e1239-e1239
    Histone acetylation is essential for memory formation and its deregulation contributes to the pathogenesis of Alzheimer's disease. Thus, targeting histone acetylation is discussed as a novel approach to treat dementia. The histone acetylation landscape is shaped by chromatin writer and eraser proteins, while readers link chromatin state to cellular function. Chromatin readers emerged novel drug targets in cancer research but little is known about the manipulation of readers in the adult brain. Here we tested the effect of JQ1-a small-molecule inhibitor of the chromatin readers BRD2, BRD3, BRD4 and BRDT-on brain function and show that JQ1 is able to enhance cognitive performance and long-term potentiation in wild-type animals and in a mouse model for Alzheimer's disease. Systemic administration of JQ1 elicited a hippocampal gene expression program that is associated with ion channel activity, transcription and DNA repair. Our findings suggest that JQ1 could be used as a therapy against dementia and should be further tested in the context of learning and memory.
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  • Journal Article

    TRPV1 regulates excitatory innervation of OLM neurons in the hippocampus 

    Hurtado-Zavala, Joaquin I.; Ramachandran, Binu; Ahmed, Saheeb; Halder, Rashi; Bolleyer, Christiane; Awasthi, Ankit; Stahlberg, Markus A.; Wagener, Robin J.; Anderson, Kristin; Drenan, Ryan M.; et al.
    Lester, Henry A.Miwa, Julie M.Staiger, Jochen F.Fischer, AndreDean, Camin
    Nature communications 2017; 8: Art. 15878
    TRPV1 is an ion channel activated by heat and pungent agents including capsaicin, and has been extensively studied in nociception of sensory neurons. However, the location and function of TRPV1 in the hippocampus is debated. We found that TRPV1 is expressed in oriens-lacunosum-moleculare (OLM) interneurons in the hippocampus, and promotes excitatory innervation. TRPV1 knockout mice have reduced glutamatergic innervation of OLM neurons. When activated by capsaicin, TRPV1 recruits more glutamatergic, but not GABAergic, terminals to OLM neurons in vitro. When TRPV1 is blocked, glutamatergic input to OLM neurons is dramatically reduced. Heterologous expression of TRPV1 also increases excitatory innervation. Moreover, TRPV1 knockouts have reduced Schaffer collateral LTP, which is rescued by activating OLM neurons with nicotine-via α2β2-containing nicotinic receptors-to bypass innervation defects. Our results reveal a synaptogenic function of TRPV1 in a specific interneuron population in the hippocampus, where it is important for gating hippocampal plasticity.
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  • Journal Article

    Capture of Dense Core Vesicles at Synapses by JNK-Dependent Phosphorylation of Synaptotagmin-4. 

    Bharat, Vinita; Siebrecht, Michael; Burk, Katja; Ahmed, Saheeb; Reissner, Carsten; Kohansal-Nodehi, Mahdokht; Steubler, Vicky; Zweckstetter, Markus; Ting, Jonathan T; Dean, Camin
    Cell reports 2017-11-21; 21(8) p.2118-2133
    Delivery of neurotrophins and neuropeptides via long-range trafficking of dense core vesicles (DCVs) from the cell soma to nerve terminals is essential for synapse modulation and circuit function. But the mechanism by which transiting DCVs are captured at specific sites is unknown. Here, we discovered that Synaptotagmin-4 (Syt4) regulates the capture and spatial distribution of DCVs in hippocampal neurons. We found that DCVs are highly mobile and undergo long-range translocation but switch directions only at the distal ends of axons, revealing a circular trafficking pattern. Phosphorylation of serine 135 of Syt4 by JNK steers DCV trafficking by destabilizing Syt4-Kif1A interaction, leading to a transition from microtubule-dependent DCV trafficking to capture at en passant presynaptic boutons by actin. Furthermore, neuronal activity increased DCV capture via JNK-dependent phosphorylation of the S135 site of Syt4. Our data reveal a mechanism that ensures rapid, site-specific delivery of DCVs to synapses.
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  • Journal Article

    EndophilinAs regulate endosomal sorting of BDNF-TrkB to mediate survival signaling in hippocampal neurons 

    Burk, Katja; Murdoch, John D.; Freytag, Siona; Koenig, Melanie; Bharat, Vinita; Markworth, Ronja; Burkhardt, Susanne; Fischer, Andre; Dean, Camin
    Scientific Reports 2017; 7(1): Art. 2149
    The sorting of activated receptors into distinct endosomal compartments is essential to activate specific signaling cascades and cellular events including growth and survival. However, the proteins involved in this sorting are not well understood. We discovered a novel role of EndophilinAs in sorting of activated BDNF-TrkB receptors into late endosomal compartments. Mice lacking all three EndophilinAs accumulate Rab7-positive late endosomes. Moreover, EndophilinAs are differentially localized to, co-traffic with, and tubulate, distinct endosomal compartments: In response to BDNF, EndophilinA2 is recruited to both early and late endosomes, EndophilinA3 is recruited to Lamp1-positive late endosomes, and co-trafficks with Rab5 and Rab7 in both the presence and absence of BDNF, while EndophilinA1 colocalizes at lower levels with endosomes. The absence of all three EndophilinAs caused TrkB to accumulate in EEA1 and Rab7-positive endosomes, and impaired BDNF-TrkB-dependent survival signaling cascades. In addition, EndophilinA triple knockout neurons exhibited increased cell death which could not be rescued by exogenous BDNF, in a neurotrophin-dependent survival assay. Thus, EndophilinAs differentially regulate activated receptor sorting via distinct endosomal compartments to promote BDNF-dependent cell survival.
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  • Journal Article

    A novel method for culturing stellate astrocytes reveals spatially distinct Ca2+ signaling and vesicle recycling in astrocytic processes. 

    Wolfes, Anne C.; Ahmed, Saheeb; Awasthi, Ankit; Stahlberg, Markus A.; Rajput, Ashish; Magruder, Daniel S.; Bonn, Stefan; Dean, Camin
    The Journal of general physiology 2017; 149(1) p.149-170
    Interactions between astrocytes and neurons rely on the release and uptake of glial and neuronal molecules. But whether astrocytic vesicles exist and exocytose in a regulated or constitutive fashion is under debate. The majority of studies have relied on indirect methods or on astrocyte cultures that do not resemble stellate astrocytes found in vivo. Here, to investigate vesicle-associated proteins and exocytosis in stellate astrocytes specifically, we developed a simple, fast, and economical method for growing stellate astrocyte monocultures. This method is superior to other monocultures in terms of astrocyte morphology, mRNA expression profile, protein expression of cell maturity markers, and Ca(2+) fluctuations: In astrocytes transduced with GFAP promoter-driven Lck-GCaMP3, spontaneous Ca(2+) events in distinct domains (somata, branchlets, and microdomains) are similar to those in astrocytes co-cultured with other glia and neurons but unlike Ca(2+) events in astrocytes prepared using the McCarthy and de Vellis (MD) method and immunopanned (IP) astrocytes. We identify two distinct populations of constitutively recycling vesicles (harboring either VAMP2 or SYT7) specifically in branchlets of cultured stellate astrocytes. SYT7 is developmentally regulated in these astrocytes, and we observe significantly fewer synapses in wild-type mouse neurons grown on Syt7(-/-) astrocytes. SYT7 may thus be involved in trafficking or releasing synaptogenic factors. In summary, our novel method yields stellate astrocyte monocultures that can be used to study Ca(2+) signaling and vesicle recycling and dynamics in astrocytic processes.
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  • Journal Article

    Acute and chronic mitochondrial respiratory chain deficiency differentially regulate lysosomal biogenesis 

    Fernández-Mosquera, Lorena; Diogo, Cátia V.; Yambire, King Faisal; Santos, Gabriela L.; Luna Sánchez, Marta; Bénit, Paule; Rustin, Pierre; Lopez, Luis Carlos; Milosevic, Ira; Raimundo, Nuno
    Scientific Reports 2017; 7: Art. 45076
    Mitochondria are key cellular signaling platforms, affecting fundamental processes such as cell proliferation, differentiation and death. However, it remains unclear how mitochondrial signaling affects other organelles, particularly lysosomes. Here, we demonstrate that mitochondrial respiratory chain (RC) impairments elicit a stress signaling pathway that regulates lysosomal biogenesis via the microphtalmia transcription factor family. Interestingly, the effect of mitochondrial stress over lysosomal biogenesis depends on the timeframe of the stress elicited: while RC inhibition with rotenone or uncoupling with CCCP initially triggers lysosomal biogenesis, the effect peaks after few hours and returns to baseline. Long-term RC inhibition by long-term treatment with rotenone, or patient mutations in fibroblasts and in a mouse model result in repression of lysosomal biogenesis. The induction of lysosomal biogenesis by short-term mitochondrial stress is dependent on TFEB and MITF, requires AMPK signaling and is independent of calcineurin signaling. These results reveal an integrated view of how mitochondrial signaling affects lysosomes, which is essential to fully comprehend the consequences of mitochondrial malfunction, particularly in the context of mitochondrial diseases.
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  • Journal Article

    Post-endocytic sorting of Plexin-D1 controls signal transduction and development of axonal and vascular circuits 

    Burk, Katja; Mire, Erik; Bellon, Anaïs; Hocine, Mélanie; Guillot, Jeremy; Moraes, Filipa; Yoshida, Yutaka; Simons, Michael; Chauvet, Sophie; Mann, Fanny
    Nature Communications 2017; 8: Art. 14508
    Local endocytic events involving receptors for axon guidance cues play a central role in controlling growth cone behaviour. Yet, little is known about the fate of internalized receptors, and whether the sorting events directing them to distinct endosomal pathways control guidance decisions. Here, we show that the receptor Plexin-D1 contains a sorting motif that interacts with the adaptor protein GIPC1 to facilitate transport to recycling endosomes. This sorting process promotes colocalization of Plexin-D1 with vesicular pools of active R-ras, leading to its inactivation. In the absence of interaction with GIPC1, missorting of Plexin-D1 results in loss of signalling activity. Consequently, Gipc1 mutant mice show specific defects in axonal projections, as well as vascular structures, that rely on Plexin-D1 signalling for their development. Thus, intracellular sorting steps that occur after receptor internalization by endocytosis provide a critical level of control of cellular responses to guidance signals.
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