Chloride channel

Chloride channels are a superfamily of poorly understood ion channels specific for chloride. These channels may conduct many different ions, but are named for chloride because its concentration in vivo is much higher than other anions. Several families of voltage-gated channels and ligand-gated channels (e.g., the CaCC families) have been characterized in humans. Voltage-gated chloride channels perform numerous crucial physiological and cellular functions, such as controlling pH, volume homeostasis, transporting organic solutes, regulating cell migration, proliferation, and differentiation. Based on sequence homology the chloride channels can be subdivided into a number of groups. General functions Voltage-gated chloride channels are important for setting cell resting membrane potential and maintaining proper cell volume. These channels conduct or other anions such as . The structure of these channels are not like other known channels. The chloride channel subunits contai

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This course focuses on the cellular mechanisms of mammalian brain function. We will describe how neurons communicate through synaptic transmission in order to process sensory information ultimately leading to motor behavior.

Ce cours d'introduction à la corrosion veut familiariser l'étudiant avec les mécanismes réactionnels de la corrosion, avec les différentes formes de corrosion et avec les principes de la protection contre la corrosion.

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Simultaneous Optical Recording in Multiple Cells by Digital Holographic Microscopy of Chloride Current Associated to Activation of the Ligand-Gated Chloride Channel GABA(A) Receptor

Daniel Boss, Christian Depeursinge, Pascal Jourdain, Pierre Marquet, Corinne Moratal, Benjamin Rappaz

Chloride channels represent a group of targets for major clinical indications. However, molecular screening for chloride channel modulators has proven to be difficult and time-consuming as approaches essentially rely on the use of fluorescent dyes or invasive patch-clamp techniques which do not lend themselves to the screening of large sets of compounds. To address this problem, we have developed a non-invasive optical method, based on digital holographic microcopy (DHM), allowing monitoring of ion channel activity without using any electrode or fluorescent dye. To illustrate this approach, GABA(A) mediated chloride currents have been monitored with DHM. Practically, we show that DHM can non-invasively provide the quantitative determination of transmembrane chloride fluxes mediated by the activation of chloride channels associated with GABA(A) receptors. Indeed through an original algorithm, chloride currents elicited by application of appropriate agonists of the GABA(A) receptor can be derived from the quantitative phase signal recorded with DHM. Finally, chloride currents can be determined and pharmacologically characterized non-invasively simultaneously on a large cellular sampling by DHM.

Public Library of Science2012

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Digital Holographic Imaging for Label-Free Phenotypic Profiling, Cytotoxicity, and Chloride Channels Target Screening

Fabien Kuttler, Benjamin Rappaz, Gerardo Turcatti

Cellular assays using label-free Digital Holographic Microscopy (DHM) have been previously validated for cell viability assays in a drug screening context. Our automated DHM system allows performing fast and cost-effective screening assays for a wide range of applications for monitoring cell morphological changes and cell movements upon interaction with interfering compounds. In addition to these classic phenotypic assays, it has been demonstrated that target-based cellular assays can also be addressed by DHM for therapeutically relevant chloride channel receptors. Our DH-imaging (DHI) technology, potentially scalable for screening by imaging approaches in a high-throughput manner can also deliver highly informative data through long term experiments. Three examples of phenotypic screens are detailed in the present chapter: a label-free profiling approach, a cell proliferation assay, and methods for monitoring the activity of the GABAA chloride channel receptor.

Springer2015

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The human CFTR protein expressed in CHO cells activates aquaporin-3 in a cAMP-dependent pathway: study by digital holographic microscopy

Pascal Jourdain, Sylvain Eric Lengacher, Pierre Magistretti, Pierre Marquet

The transmembrane water movements during cellular processes and their relationship to ionic channel activity remain largely unknown. As an example, in epithelial cells it was proposed that the movement of water could be directly linked to cystic fibrosis transmembrane conductance regulator (CFTR) protein activity through a cAMP-stimulated aqueous pore, or be dependent on aquaporin. Here, we used digital holographic microscopy (DHM) an interferometric technique to quantify in situ the transmembrane water fluxes during the activity of the epithelial chloride channel, CFTR, measured by patch-clamp and iodide efflux techniques. We showed that the water transport measured by DHM is fully inhibited by the selective CFTR blocker CFTRinh172 and is absent in cells lacking CFTR. Of note, in cells expressing the mutated version of CFTR (F508del-CFTR), which mimics the most common genetic alteration encountered in cystic fibrosis, we also show that the water movement is profoundly altered but restored by pharmacological manipulation of F508del-CFTR-defective trafficking. Importantly, whereas activation of this endogenous water channel required a cAMP-dependent stimulation of CFTR, activation of CFTR or F508del-CFTR by two cAMP-independent CFTR activators, genistein and MPB91, failed to trigger water movements. Finally, using a specific small-interfering RNA against the endogenous aquaporin AQP3, the water transport accompanying CFTR activity decreased. We conclude that water fluxes accompanying CFTR activity are linked to AQP3 but not to a cAMP-stimulated aqueous pore in the CFTR protein.

Company of Biologists2014

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Canal ionique

Un canal ionique est une protéine membranaire qui permet le passage à grande vitesse d'un ou plusieurs ions. Il existe de nombreux types de canaux ioniques. Ils peuvent être sélectivement perméables

Potentiel électrochimique de membrane

Toute cellule biologique est entourée d'une membrane dite membrane plasmique. Cette membrane est relativement imperméable aux espèces électriquement chargées telles que les ions et aux molécules qui

Récepteur GABAA

Les récepteurs GABA de type A (GABAA) sont des récepteurs canaux des membranes des neurones qui sont activés par fixation de l'acide γ-aminobutyrique (GABA). Ces récepteurs ionotropes ont une grande