Academic literature on the topic 'TMEM16B'

Notre système immunitaire assure la protection et régule l'homéostasie de l'organisme. Pour cela, il se compose d'une réponse immune innée et d'une réponse adaptative. Notre équipe a identifié TMEM176A et TMEM176B, deux protéines transmembranaires de structure et de fonction identiques. Ces protéines sont des canaux ioniques intracellulaires qui ont la particularité d'être fortement exprimés à la fois dans les cellules RORyt+ et dans les cellules dendritiques. La génération d'une souris déficiente pour ces deux gènes nous a permis d'étudier leur rôle. Nous avons mis en évidence que l'absence de Tmem176a et b n'impacte pas la génération des cellules RORyt+, ni leur capacité à sécréter des cytokines. L'étude de deux modèles de colite nous a permis de confirmer que Tmem176a et b ne semblent pas avoir un rôle majeur dans ces cellules. A l'inverse l'étude épigénétique des cellules dendritiques déficientes a mis en évidence une dérégulation de la voie de présentation du CMH de classe If. Nous avons mis en évidence une diminution de leur prolifération des lymphocytes T CD4*. En utilisant une technique de microscopie innovante, nous avons observé une localisation préférentielle de TMEM176A et B dans la voie endolysosomale et notamment dans le compartiment MIIC impliqué dans la présentation des antigènes par la voie du CMH de classe 11. Ainsi ces résultats suggèrent que dans les cellules dendritiques, Tmem176a et b participent à la présentation des antigènes et à l'activation des lymphocytes T CD4* naïfs<br>Our immune system provides protection and regulates the homeostasis of the organism. For this, it consists of an innate immune response and an adaptive response. Our team has identified TMEM176A and TMEM176B. These proteins are intracellular ion channels that are particularly expressed both in RORyt+ cells and in dendritic cells. The generation of a deficient mouse for these two genes allowed us to study their role. We have demonstrated that the absence of Tmem 176a and b does not affect the generation of RORyt+ cells, neither their ability to secrete cytokines. The study of two models of colitis allowed us to confirm that Tmem176a and b seem to be dispensable in these cells. However, the epigenetic study of deficient dendritic cells put in evidence a deregulation of the MHC class li presentation pathway. We have detected a decrease of the proliferation of CD4+ T. Using an innovative microscopy technique, we have observed a preferential localization of TMEM176A and B in the endo-lysosomal pathway and in particular in the MIIC compartment involved in the presentation of antigens by the MHC class li pathway. Thus, these results suggest that in dendritic cells, Tmem 176a and b are involved in the presentation of antigens and activation of naïve CD4* T cells

TMEM16A/Anoctamin1 is a novel calcium-­‐activated chloride channel involved in neuronal and cardiac excitation, vascular tone, pain perception and olfactory and sensory signal transduction and GI tract motility. It is also associated to diverse type of cancer including breast cancer malignancy. Alternative splicing (AS) of exons 6b, 13 and 15 generates functionally distinct TMEM16A isoforms with different electrophysiological properties. To study their splicing regulation, I performed in minigene system a systematic analysis of exonic and intronic regulatory elements followed by co-­‐transfection of a panel of splicing regulatory factors. Analysis of TMEM16A pre-­‐mRNA splicing supports a model in which each exon is regulated by different cis-­‐ and trans-­‐acting elements. Exon 6b inclusion is regulated primarily by SRSF9 and TRA2B, through a unique GAA-­‐rich ESE element. Exon 15 is enhanced only by TIA1 and FOX1 and this effect is mediated by downstream intronic sequences. On the other hand, the small exon 13, included in most human tissues, was mainly skipped in the minigene and only FOX1 and U2AF65 enhanced its inclusion. To understand if there is any preferential association between three AS exons, I have evaluated TMEM16A isoforms using a long range RT-­‐PCR assay that amplifies transcripts across the AS events. Coordination between distant alternative spliced exons in the same gene has been suggested to be an important mechanism to regulate gene expression but very few genes have been studied in detail. I observed that the selection of exons 6b and 15 is preferentially coordinated in several human normal tissues: mature transcripts that predominantly include exon 6b tend to exclude exon 15. Unexpectedly, this coordination was not conserved in mouse tissues. This was mainly due to the fact that exon 15 was largely and predominantly excluded in the mouse, a fact that suggest a peculiar evolutionary conservation of AS in this gene. To explore if changes in splicing coordination of the two major AS events are associated to cancer development I evaluated normal mammalian tissue and corresponding breast tumors of the same cohort, obtained from surgical excision (n=18). The distribution of individual AS events did not change between normal and tumor tissues. However, the TMEM16A splicing coordination increased significantly in tumors. Indeed, the splicing coordination was present in 50% of normal mammalian breast tissues and in 84% in tumors. In conclusion this study identifies several cis-­‐acting elements and trans-­‐acting factors involved in the regulation of TMEM16A Alternative Splicing and provides evidence of its intragenic splicing coordination. The increase of TMEM16A splicing coordination observed in breast tumor, might represent a common event in genes with multiple AS events.

Calcium-activated chloride channels (CaCCs) are a class of the ligand-gated channels involved in numerous cellular functions. In vascular smooth muscle, these ion channels couple agonist-induced calcium-release from the sarcoplasmic reticulum to membrane depolarisation and vasoconstriction. For this reason, CaCCs have been suggested as a potential molecular target to treat a range of vascular disorders. These ion channels, however, have not been yet explored as a drug target because their molecular identity has been elusive and their pharmacology has been restricted to compounds with low potency and poor specificity. The general aims of this work of thesis are: i) to define the molecular identity of CaCCs in vascular smooth muscle, ii) to investigate how the structural features of the identified channel relate to its functional properties and iii) to examine how drug binding modulates CaCC activity. The main findings are the following:1) By using RNA interference technology and patch-clamp analysis, the Tmem16A gene was found to encode for CaCCs in pulmonary artery smooth muscle. Furthermore, Tmem16A appeared to be expressed in other vascular smooth muscles suggesting that this ion channel may represent CaCCs in various vascular beds.2) To understand the physiology and pharmacology of TMEM16A channels it is of a fundamental importance to elucidate the molecular mechanisms by which channel gating and conductance are achieved. TMEM16A comprises eight putative transmembrane domains (TMs) with TM5 and TM6 flanking a putative re-entrant loop, which resembles the pore of other ion channels. Using a chimeric approach the role of this region was investigated. The re-entrant loop of TMEM16A was found to mediate a range of functional roles: it controlled the response of the channel to intracellular calcium, the permeation of anions and the expression of channels on the plasma membrane. Specifically, a non-canonical trafficking motif was identified within in a 38 amino acid region within the re-entrant loop.3) Drugs that modulate the function of TMEM16A channels are currently limited. The generic chloride channel blocker anthracene-9-carboxylic acid (A9C) was found to produce a bimodal effect on TMEM16A currents: low concentrations of A9C activated the channels, while doses higher than ~300 µM produced current inhibition. These two effects were mediated via A9C binding to two separate sites. Binding of A9C into the pore resulted in channel inhibition, while A9C binding to an extracellular site increased the open probability of the channel. To conclude, this work of thesis has revealed the molecular identity of CaCCs in vascular smooth muscle and elucidated the functional roles of the re-entrant loop of the TMEM16A channel protein. The identification of the activating and inhibiting A9C binding sites may help the development of selective blockers and activators of TMEM16A channels.

Meckel-Gruber syndrome (MKS) is a universally lethal heritable human disease characterised by CNS malformations, cystic kidney, polydactyly, and liver fibrosis. MKS is classed as one of the ciliopathies due to its association with dysfunctional primary cilia, signalling organelles found on most cells in the human body. Some of the symptoms of MKS can be explained as a consequence of disrupted developmental signalling through the primary cilium, other defects are harder to explain, and evidence now exists for non-ciliary influences on ciliopathies. The nature of these influences, and the implications they may have for our understanding of ciliary function and the aetiology of MKS, remain unclear. In this thesis, defects in cell-extracellular matrix (ECM) interaction in MKS are investigated to determine whether MKS proteins have a role in this process, and if so, whether this role may be involved in MKS pathology. A combination of transcriptomic, proteomic, and cell imaging approaches are used to demonstrate that MKS patient cells produce a defective extracellular matrix, and that the MKS protein TMEM67 is present at the cell surface at sites of cell-ECM interaction. It is shown that the full-length TMEM67 protein is required for correct ECM morphology, and it is further shown that the abnormal extracellular matrix morphology in MKS cells underlies other defects, including failure to build cilia and alterations to the actin cytoskeleton. This represents the first set of causal relationships identified between the cellular defects in this complex disease. It is further shown that treatment with developmental signalling pathway antagonists can rescue these defects, potentially revealing a new avenue of therapeutic intervention for MKS. Finally, possible upstream defects are investigated that might underlie the ECM defect, including alterations to cell spreading behaviour and cell deformation resistance.

Calcium-activated chloride channels (CaCCs) are ubiquitously expressed in a plethora of cell types and, consequently, are involved in numerous cellular processes as diverse as epithelial secretion, regulation of cardiac excitability and smooth muscle contraction. Current pharmacology of CaCCs is limited to compounds with low potency and poor selectivity. The lack of knowledge surrounding the molecular identity of the CaCC has greatly hindered the development of more specific drugs and has impaired our understanding of the channel physiology and biophysics. The recent discovery that the TMEM16A gene codes for CaCCs has offered hope for new developments in these areas. CaCCs have been suggested as possible targets to treat a variety of conditions including asthma as well as pulmonary and systemic hypertension. Due to the ubiquitous expression of CaCCs and the ability of the channel to interact with a number of pharmacological compounds with diverse chemical structures however, it was hypothesised that TMEM16A could be a possible source for off-target drug effects and may represent a concern for safety pharmacology. The principal aim of this thesis was to assess the functional significance of TMEM16A in the cardiovascular system, as this is one of the major systems of concern for safety pharmacology and accounts for the largest number of post-market drug withdrawals. The main findings of this study can be summarised as follows: 1) RT-PCR analysis revealed a ubiquitous expression of TMEM16A in tissues of the rat and human cardiovascular systems, including systemic and pulmonary arteries as well as cardiac tissue. Analysis also revealed the presence of multiple TMEM16A splice variants in all rat tissues examined, in addition to a number of other TMEM16x family members. 2) Myography experiments using the “classical” CaCC blocker niflumic acid and newly identified TMEM16A blockers confirmed a functional role for TMEM16A in phenylephrine-induced vascular smooth muscle contraction. 3) The suitability of currently available Cl- channel blockers for use as pharmacological tools for TMEM16A research was assessed using conventional whole-cell patch clamp and high-throughput electrophysiology techniques to respectively compare their potencies and selectivity over other cardiovascular ion channels. Of the compounds tested, DIDS and T16Ainh-A01 appeared the most suitable blockers; however all compounds had a degree of non-selectivity, raising concerns for their use in functional studies. In conclusion, these findings provide evidence for the ubiquitous expression and functional significance of TMEM16A within the cardiovascular system and support the hypothesis that TMEM16A is a concern for safety pharmacology and should be included into future pre-clinical safety assays. The inadequacy of current inhibitors however highlights the urgency for the development of novel potent and selective channel modulators for future TMEM16A research.

TMEM16A e TMEM16B sono proteine di membrana con funzione di canali del cloruro attivati da calcio. Attraverso la generazione di canali chimerici, e in particolare, sostituendo la regione carbossi-terminale di TMEM16A con la regione equivalente di TMEM16B, sono stati ottenuti dei canali dotati di una maggiore attività. Il progressivo accorciamento della regione chimerica ha permesso di restringere il “dominio attivante” a una corta sequenza di 14 aminoacidi localizzata vicino all’ultimo dominio transmembrana e ha generato proteine-canale TMEM16A dotate di un’attività molto alta anche a concentrazioni basse di calcio intracellulare. Per chiarire il meccanismo molecolare alla base di questo effetto, sono stati eseguiti esperimenti basati sulla generazione di doppie chimere, Forster resonance Energy transfer e cross-linking intermolecolare. Inoltre, è stato generato un modello tridimensionale teorico di TMEM16A basato sulla struttura di una proteina TMEM16 del fungo Nectria haematococca. I risultati ottenuti indicano che l’aumentata attività nei canali chimerici è causata da un’alterazione dell’interazione tra il carbossi-terminale e la prima ansa intracellulare di TMEM16A. L’identificazione di piccole molecole farmacologiche in grado di mimare questa perturbazione potrebbe rappresentare la base di un approccio farmacologico volto a stimolare il trasporto ionico TMEM16A-dipendente. L’attivazione farmacologica di TMEM16A potrebbe essere utile per stimolare la secrezione epiteliale nelle vie aeree, un effetto potenzialmente benefico in patologie quali la fibrosi cistica e altre malattie ostruttive croniche dell’apparato respiratorio

論文1ページ目の下部に著作権を表示すること。（© 2016, American Society for Microbiology. ）<br>Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(医科学)<br>甲第19634号<br>医科博第72号<br>新制||医科||5(附属図書館)<br>32670<br>京都大学大学院医学研究科医科学専攻<br>(主査)教授 近藤 玄, 教授 篠原 隆司, 教授 秋山 芳展<br>学位規則第4条第1項該当

Frontotemporal dementia is the second most common neurodegenerative disease in people younger than 65 years. Patients suffer from behavioral changes, language deficits and speech impairment. Unfortunately, there is no effective treatment available at the moment. Cytoplasmic inclusions of the DNA/RNA-binding protein TDP-43 are the pathological hallmark in the majority of FTLD cases, which are accordingly classified as FTLD-TDP. Mutations in GRN, the gene coding for the trophic factor progranulin, are responsible for the majority of familiar FTLD-TDP cases. The first genome-wide association study performed for FTLD-TDP led to the identification of risk variants in the so far uncharacterized gene TMEM106B. Initial cell culture studies revealed intracellular localization of TMEM106B protein in lysosomes but its neuronal function remained elusive. Based on these initial findings, I investigated the physiological function of TMEM106B in primary rat neurons during this thesis. I demonstrated that endogenous TMEM106B is localized to late endosomes and lysosomes in primary neurons, too. Notably, knockdown of the protein does neither impair general neuronal viability nor the protein level of FTLD associated proteins, such as GRN or TDP-43. However, shRNA-mediated knockdown of TMEM106B led to a pronounced withering of the dendritic arbor in developing and mature neurons. Moreover, the strong impairment of dendrite outgrowth and maintenance was accompanied by morphological changes and loss of dendritic spines. To gain mechanistic insight into the loss-of-function phenotypes, I searched for coimmunoprecipitating proteins by LC-MS/MS. I specifically identified the microtubule-binding protein MAP6 as interaction partner and was able to validate binding. Strikingly, overexpression of MAP6 in primary neurons phenocopied the TMEM106B knockdown effect on dendrites and loss of MAP6 restored dendritic branching in TMEM106B knockdown neurons, indicating functional interaction of the two proteins. The link between a lysosomal and a microtubule-binding protein made me study the microtubule dependent transport of dendritic lysosomes. Remarkably, live cell imaging studies revealed enhanced movement of dendritic lysosomes towards the soma in neurons devoid of TMEM106B. Again, MAP6 overexpression phenocopied and MAP6 knockdown rescued this effect, strengthening the functional link. The MAP6-independent rescue of dendrite outgrowth by enhancing anterograde lysosomal movement provided additional evidence that dendritic arborization is directly controlled by lysosomal trafficking. From these findings I suggest the following model: TMEM106B and MAP6 together act as a molecular brake for the retrograde transport of dendritic lysosomes. Knockdown of TMEM106B and (the presumably dominant negative) overexpression of MAP6 release this brake and enhance the retrograde movement of lysosomes. Subsequently, the higher protein turnover and the net loss of membranes in distal dendrites may cause the defect in dendrite outgrowth. The findings of this study suggest that lysosomal misrouting in TMEM106B risk allele carrier might further aggravate lysosomal dysfunction seen in patients harboring GRN mutations and thereby contribute to disease progression. Taken together, I discovered the first neuronal function for the FTLD-TDP risk factor TMEM106B: This lysosomal protein acts together with its novel, microtubule-associated binding partner MAP6 as molecular brake for the dendritic transport of lysosomes and thereby controls dendrite growth and maintenance.<br>Frontotemporale Demenz ist die zweithäufigste Form neurodegenerativer Erkrankungen bei Menschen unter 65 Jahren. Patienten leiden an Verhaltensauffälligkeiten und Sprach- sowie Artikulationsstörungen. Leider steht zurzeit keine wirksame medikamentöse Therapie zur Verfügung. Das pathologische Hauptmerkmal der meisten FTLD-Fälle sind zytoplasmatische Einschlüsse des DNA/RNA-bindenden Proteins TDP-43. Diese Fälle werden entsprechend als FTLD-TDP klassifiziert. Für einen Großteil der familiären FTLD-TDP Fälle sind Mutationen in GRN, dem für den Wachstumsfaktor Progranulin kodierenden Gen, verantwortlich. Die erste für FTLD-TDP durchgeführte genomweite Assoziationsstudie führte zur Entdeckung von genetischen Varianten im bis dato uncharakterisierten Gen TMEM106B. Diese Varianten sind mit einem erhöten Risiko an FTLD zu erkranken assoziiert. Initiale Studien in Zellkultur zeigten eine Lokalisierung des TMEM106B Proteins in Lysosomen, die Frage nach der neuronale Funktion des Proteins blieb allerdings bisher unbeantwortet. Auf diesen ersten Ergebnissen aufbauend untersuchte ich während meiner Dissertation die physiologische Funktion von TMEM106B in primären Ratten-neuronen. Ich konnte zeigen, dass endogenes TMEM106B auch in primären Neuronen in späten Endsosomen und Lysosomen lokalisiert ist. Beachtenswerterweise verminderte die Herunterregulierung (shRNA-vermittelter Gen-Knockdown) des Proteins weder das generelle Überleben der Neuronen noch die Level von anderen FTLD-assoziierten Proteinen, wie GRN oder TDP-43. Die Herunterregulierung von TMEM106B führte jedoch zu einem ausgeprägten Verlust von Dendriten in sich entwickelnden und ausgereiften Neuronen. Des Weiteren war die starke Beeinträchtigung dendritischen Wachstums und Aufrechterhaltung von einer morphologischen Veränderung und dem Verlust der Dornfortsätze begleitet. Um den Mechanismus dieser Phänotypen zu erklären, suchte ich nach TMEM106B coimmunopräzipitierenden Proteinen mittels Massenspektrometrie. Ich konnte das Mikrotubuli bindende Protein MAP6 als spezifischen Bindungspartner identifizieren und die Interaktion beider Proteine validieren. Hervorzuheben ist, dass die Überexpression von MAP6 in primären Neuronen den Effekt der Herunterregulation von TMEM106B auf die Dendriten kopierte und die Herunterregulation von MAP6 die dendritischen Verästelungen in TMEM106B depletierten Neuronen sogar wiederherstellen konnte. Diese Ergebnisse legen eine funktionelle Interaktion beider Proteine nahe. Die Verbindung zwischen einem lysosomalen und einem an die Mikrotubuli bindenden Protein brachte mich dazu, den Mikrotubuli abhängigen Transport von dendritischen Lysosomen zu untersuchen. Bemerkenswerterweise zeigten mittels Lebendzellmikroskopie erzeugte Aufnahmen eine erhöhte Bewegung dendritischer Lysosomen Richtung Zellsoma in TMEM106B depletierten Neuronen. Auch in diesem Kontext konnte die Überexpression von MAP6 den Effekt kopieren und die Herunterregulation von MAP6 den Effekt aufheben und somit die These einer funktionellen Interaktion festigen. Die MAP6 unabhängige Wiederherstellung des dendritischen Wachstums durch die Erhöhung des lysosomalen Transports in anterograder Richtung lieferte einen zusätzlichen Beweis dafür, dass das dendritische Wachstum direkt von lysosomalem Transport abhängt. Ausgehend von diesen Ergebnissen schlage ich folgendes Modell vor: TMEM106B und MAP6 wirken zusammen als molekulare Bremse für den retrograden Transport dendritischer Lysosomen. Die Herunterregulation von TMEM106B und die (wahrscheinlich dominant negative wirkende) Überexpression von MAP6 lösen diese Bremse und verstärken die retrograde Bewegung von Lysosomen. Daraufhin könnten der gestiegene Proteinumsatz und der Verlust von Plasmamembranbestandteilen zu einem Fehler im dendritischen Wachstum führen. Die Ergebnisse dieser Arbeit legen nahe, dass fehlerhafter, lysosomaler Transport in TMEM106B Risikoallelträgern zu einer Verstärkung der lysosomalen Fehlfunktion in Patienten mit GRN Mutation führt und dabei zur Krankheitsentwicklung beiträgt. Zusammengefasst habe ich die erste neuronale Funktion für den FTLD-TDP Risikofaktor TMEM106B entdeckt: Dieses lysosomale Protein wirkt zusammen mit seinem neuentdeckten, Mikrotubuli assoziierten Bindungspartner MAP6 als molekulare Bremse für den dendritischen Transport von Lysosomen und kontrolliert dadurch Wachstum und Aufrechterhaltung von Dendriten.