国立情報学研究所で電子化したコンテンツを使用している。

Thesis (Ph. D.)--Cornell University, May, 2009. / Vita. Includes bibliographical references (leaves 163-186).

Contexte: KCNQ1: KCNE3 joue un rôle essentiel dans le mécanisme de sécrétion du Cl- dans le côlon distal. Ce canal K+ génère la force électromotrice nécessaire à la sécrétion apicale de Cl- par le recyclage basolatéral de K+. Il a précédemment été démontré que l'hormone stéroïde œstrogène (17β-œstradiol, E2) induit, spécifiquement chez la femelle un effet anti-sécrétoire dans les cryptes de côlon de rat via l'inhibition de KCNQ1:KCNE3. Cette thèse a pour but de déterminer les mécanismes moléculaires mise en jeu dans la régulation des fonctions du canal KCNQ1 par l'œstrogène, en particulier dans la sécrétion de Cl-, la prolifération et la migration des colonocytes. Cette thèse met en évidence la régulation de l'activité de KCNQ1 par l'œstrogène via l'endocytose et la dissociation du canal. Méthodes : Des cryptes isolées de côlon de rats ainsi que la lignée cellulaire HT29cl.19A ont été utilisées pour étudier les effets de l'œstrogène sur la sécrétion de Cl- et les fonctions du canal KCNQ1. Pour cela des techniques d'électrophysiologie, de biologie cellulaire et moléculaire ainsi que d'imagerie ont été utilisées. Résultats: Nous avons montré que l'œstrogène induit une rapide réduction de la sécrétion de Cl- et du courant KCNQ1; cette inhibition est maintenue au moins 2 heures. Nous avons aussi démontré que l'œstrogène induit une rapide internalisation du canal par la voie de signalisation suivante : PKCδ-AMPK-Nedd4.2. L'internalisation du canal est suivie d'un recyclage à la membrane qui présente un mécanisme bi-phasique; une phase rapide impliquant Rab4 et une phase plus lente via Rab11. L'œstrogène induit également une dissociation entre KCNQ1 et KCNE3 conduisant à la diminution de la conductance du canal. La thèse a également démontré le rôle de KCNQ1 dans la modulation de la migration des colonocytes induite par l'œstrogène. Conclusion : L'étude établit le rôle de l'œstrogène dans la régulation de la sécrétion d'électrolytes par la modulation de la densité de KCNQ1 à la membrane plasmique et la stabilité du complexe KCNQ1:KCNE3. Ici, est révélé un nouveau rôle pour KCNQ1 dans la modulation de la migration des colonocytes par l'œstrogène. Ainsi, l'œstrogène joue un rôle important dans l'homéostasie des cryptes de côlon par la régulation du taux de migration et de sécrétion des colonocytes. / Background : The KCNQ1:KCNE3 K+ channel is an essential component of the Cl- secretion machinery in the distal colon. This channel provides the driving force for apical Cl- secretion by basolateral recycling of K+. The steroid hormone estrogen (17β-estradiol, E2) has previously been reported to exert a female specific anti-secretory response in colonic crypts through the inhibition of the KCNQ1: KCNE3 channel. The purpose of this study was to uncover and describe molecular mechanisms of estrogen regulation of KCNQ1 channel function and its consequences for intestinal Cl- secretion, colonocyte proliferation and migration. The thesis reveals a novel estrogen regulation of KCNQ1:KCNE3 activity by channel endocytosis and complex dissociation. Methods : Isolated rat colonic crypts as well as the colonic cell line HT29cl19A (HT29) were used to investigate estrogen effects on Cl- secretion and KCNQ1 channel function using a combination of electrophysiological, cellular and molecular biology and imaging techniques. Results : The forskolin-stimulated Cl- secretion and KCNQ1 current in rat colon and HT29 epithelia were rapidly reduced following estrogen treatment (10nM) and remained inhibited over 2 hours after estrogen exposure. Our findings revealed a rapid estrogen-promoted retrieval of KCNQ1 from the plasma membrane via a PKCδ-AMPK-Nedd4 .2 signaling pathway, followed by the recycling of the channel. The mechanism underlying recycling was biphasic; a rapid recycling phase mediated by Rab4 and a slow recycling phase mediated by Rab11. Estrogen also causes dissociation of the KCNQ1:KCNE3 channel complex resulting in collapse of the K+ channel conductance and Cl- secretion. The thesis also demonstrated that KCNQ1 plays a role in E2-modulated colonocyte migration. Conclusion : This study establishes a role for estrogen in the regulation of colonic electrolyte secretion via modulation of KCNQ1 cell membrane surface abundance and KCNQ1:KCNE3 complex formation. Here, we highlighted a new role of KCNQ1 in colonocyte migration which is also modulated by estrogen through KCNQ1. Thus, estrogen plays an important role in colonic crypt homeostasis by regulating colonocyte secretion and migration rate.

Reproduction de : Thèse de doctorat : Médecine. Physiologie : Nantes : 2007. / Bibliogr.

Epithelial cells lining the upper airways are characterized by low sodium absorption and elevated chloride secretion. Together, the movement of these ions creates the osmotic drive to hydrate the airways. Recent studies indicate that influenza is capable of directly modulating the vectorial transport of sodium and chloride ions. However, the direct impact of influenza has not been studied with respect to potassium channels. This is significant because potassium conductance creates the driving force for chloride secretion. Disruptions to this process leads to edema formation in the lungs and can subsequently cause Acute Respiratory Distress Syndrome. Additionally, it has been demonstrated that the induction of pro-inflammatory cytokines in infected cells may contribute to altered ion channel function, further exacerbating edema formation. The purpose of this study was to assess the direct and indirect effects of influenza virus infection on potassium and chloride ion channel function in a secretory epithelial cell model. In order to assess the direct effects we exposed polarized epithelial cell monolayers to varying doses of H1N1 virus. Potassium and chloride channel function was measured by means of short-circuit current in an Ussing chamber. The immune response to viral infection was determined by RT-qPCR and Bioplex suspension array. Virus conditioned media (CM), and IL-8 were used to characterize the indirect effects on non-infected cells. We observed an increase in chloride secretion, consistent with edema formation, when 60% of the epithelium was infected, and after CM treatment. This observation correlated with increased potassium channel conductance through the calcium-activated (KCNN4) and cAMP-activated potassium channels (KCNQ1), which was ameliorated upon specific inhibition of these channels. The data suggest that the mixture of pro-inflammatory cytokines induced by viral infection directly up-regulate these potassium channels. However, treatment with IL-8 also appears to increase chloride secretion, although the underlying mechanism remains to be determined, as it is not mediated through KCNN4 and KCNQ1. We conclude that the strong induction of cytokines in infected cells act in a paracrine manner on non-infected cells to increase potassium channel conductance. This up-regulation of potassium channels subsequently drives an increase in chloride secretion, leading to fluid build-up in the lungs and edema formation.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

KCNE β-subunits modulate KCNQ1 (Q1) voltage-gate K+channels providing the current diversity required for Q1 channels to function in a wide variety of cell types and tissues. In the present thesis, the stoichiometry of KCNE1 (E1) β-subunits in functioning Q1 channels is investigated, along with the formation of heteromeric channel complexes, complexes containing 2 different KCNE β-subunits. The chemical approaches used to answer these questions were then expanded to generate a novel labeling reagent. To determine the stoichiometry of the Q1/E1 complex, I devised an iterative subunit counting approach that relies on a chemically releasable K+channel blocking reagent. The extracellularly applied reagent irreversibly blocks charybdotoxin (CTX) sensitive Q1 channels by chemically modifying E1 peptides that contain an N-terminal cysteine residue. Chemical release of the inhibitor and subsequent iterative applications of the reagent reported that Q1 channels partner with two KCNE β-subunits. To determine whether heteromeric Q1-KCNE complexes form, I synthesized a similar, but non-cleavable, K+channel blocking reagent that detects specific KCNE peptides in functioning complexes by irreversible channel inhibition. Using this “KCNE sensor”, heteromeric Q1/E1/E3, Q1/E1/E4 and Q1/E3/E4 complexes were shown to form, traffic to the cell surface and function. Using mathematical subtraction to visualize the irreversibly blocked current, the currents and gating kinetics of the different heteromeric complexes were revealed and a hierarchy of KCNE subunit modulation of Q1 channels was determined: E3>E1>>E4. Building on this technology, a chemically releasable K+ channel blocking reagent was created to specifically label KCNE β-subunits with biotin. The reagent delivers biotin to CTX sensitive Q1 channels and labeling occurs through free thiols provided by either cysteine residues or thiol modified sugars. This preliminary data demonstrates a novel strategy for labeling endogenous K+ channels in native cells.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13232号 / 論医博第2172号 / 新制||医||1036(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 山下 潤, 教授 江藤 浩之, 教授 木村 剛 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

Les canalopathies cardiaques congénitales constituent la principale hypothèse diagnostique dans les cas de mort subite inexpliquée chez les sujets de moins de 35 ans. Notre travail a eu pour objectif demettre au point une stratégie de détection post-mortem des mutations sur les gènes connus pour être impliqués dans les canalopathies cardiaques, applicable en routine, à partir de la principale source d’ADN post-mortem disponible en France à savoir les prélèvements fixés au formol et inclus en paraffine (FFIP). A partir d’une cohorte de 12 cas, deux techniques de détection de variants génétiques ont été évaluées, une technique de criblage par l’analyse des courbes de fusion haute résolution et une technique de génotypage par spectrométrie de masse MALDI-TOF, respectivement sur le gène KCNQ1 et le gène RyR2. Quelle que soit la technique utilisée, il n’est pas possible de s’affranchir du séquençage de type Sanger afin d’explorer les séquences d’intérêts qui n’ont pu être optimisées avec l’une ou l’autre des méthodes à la fois sur les prélèvements congelés et FFIP. L’arrivée des séquenceurs de nouvelles générations ouvrent ainsi de nouvelles perspectives dans ce domaine. / The congenital cardiac channelopathies constitute the principal diagnostic hypothesis in autopsynegative sudden unexplained death concerning people younger than 35 years old. The present study aimed to develop a strategy of mutations detection on known genes implicated in the cardiac channelopathies. This strategy of mutations detection had to be applicable to routine and has been studied on formalin-fixed and paraffin-embedded (FFPE) tissues which are the principal DNA source available in France. On a cohort of 12 cases, two technique of sequence variants detection wereevaluated: the screening method of High Resolution Melt and the genotyping method based on a MALDI-TOF mass spectrometry, respectively on KCNQ1 and RyR2 genes. Whatever the technique, there is a necessity of resorting to the Sanger sequencing to explore the sequence of interest none optimized with one or the other technology both on FFEP and frozen tissues. That’s why the next generation sequencing method should open new perspectives in the post-mortem diagnostic of cardiac channelopathies.

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