Discovery of CLC transport proteins: cloning, structure, function and pathophysiology

Jentsch, Thomas J.

doi:10.1113/jphysiol.2014.270043

Cited by 28 publications

(38 citation statements)

References 178 publications

(131 reference statements)

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“…The CLC family plays a wide variety of physiological functions in organisms ranging from bacteria to humans [1][2][3][4][5][6][7]. This family of membrane proteins is composed of both channels and H + /Cl − exchange transporters that share a structurally unique homodimeric architecture [8,9].…”

Section: Introductionmentioning

confidence: 99%

Dynamical model of the CLC-2 ion channel exhibits a two-step gating mechanism

McKiernan

Koster

Maduke

et al. 2017

Preprint

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AbstractThis work reports a dynamical Markov state model of CLC-2 “fast” (pore) gating, based on 600 microseconds of molecular dynamics (MD) simulation. In the starting conformation of our CLC-2 model, both outer and inner channel gates are closed. The first conformational change in our dataset involves rotation of the inner-gate backbone along residues S168-G169-I170. This change is strikingly similar to that observed in the cryo-EM structure of the bovine CLC-K channel, though the volume of the intracellular (inner) region of the ion conduction pathway is further expanded in our model. From this state (inner gate open and outer gate closed), two additional states are observed, each involving a unique rotameric flip of the outer-gate residue GLUex. Both additional states involve conformational changes that orient GLUex away from the extracellular (outer) region of the ion conduction pathway. In the first additional state, the rotameric flip of GLUex results in an open, or near-open, channel pore. The equilibrium population of this state is low (∼1%), consistent with the low open probability of CLC-2 observed experimentally in the absence of a membrane potential stimulus (0 mV). In the second additional state, GLUex rotates to occlude the channel pore. This state, which has a low equilibrium population (∼1%), is only accessible when GLUex is protonated. Together, these pathways model the opening of both an inner and outer gate within the CLC-2 selectivity filter, as a function of GLUex protonation. Collectively, our findings are consistent with published experimental analyses of CLC-2 gating and provide a high-resolution structural model to guide future investigations.Author summaryIn the brain, the roles and mechanisms of sodium-, potassium-, and calcium-selective ion channels are well established. In contrast, chloride-selective channels have been studied much less and are not sufficiently understood, despite known associations of chloride-channel defects with brain disorders. The most broadly expressed voltage-activated chloride channel in the brain is CLC-2 (one of 9 human CLC homologs). In this work, we use simulations to model the conformational dynamics of the CLC-2 chloride ion channel selectivity filter (SF), which is the part of the protein that controls whether the channel is in an ion-conducting or non-conducting state. Our analysis identifies four primary conformational states and a specific progression through these states. Our results are consistent with structural and functional data in the literature and provide a high-resolution model for guiding further studies of CLC-2. These results will inform our understanding of how CLC-2 governs electrical activity and ion homeostasis in the brain.

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Section: Introductionmentioning

confidence: 99%

Dynamical model of the CLC-2 ion channel exhibits a two-step gating mechanism

McKiernan

Koster

Maduke

et al. 2017

Preprint

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“…CLCs are a family of membrane proteins that is present in all eukaryotic and prokaryotic organisms. In eukaryotes, CLC proteins can be localized in intracellular membranes and at the plasma membrane (Jentsch, 2015). So far, all intracellular CLCs were found to be anion/H + exchangers, while the plasma membrane CLCs are anion channels.…”

Section: Vacuolar Anion Transport During Stomatal Movementmentioning

confidence: 99%

Ion Transport at the Vacuole during Stomatal Movements

Eisenach

Angeli

2017

Plant Physiol.

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Plant gas exchange with the environment is facilitated by stomata, small pores found on most aerial surfaces of land plants. Stomatal pores are formed between a pair of specialized guard cells. In C3 plants, open stomata allow the uptake of CO 2 for photosynthesis during the day and at the same time the loss of water vapor, maintaining the transpiration stream. At night and during drought, plants close their stomata to conserve water, while they open them in response to low CO 2 and at high temperatures to allow for evaporative cooling. The opening and closure of stomata depends on guard cell turgor, which, in turn, relies on fluxes of osmotically active solutes in and out of the guard cell. During stomatal opening, osmotically active solutes enter guard cells via the plasma membrane or are produced inside the cell and ultimately are stored in the vacuole (Roelfsema and Hedrich, 2005;Kollist et al., 2014;Santelia and Lawson, 2016). This causes water influx, a concomitant increase in turgor and swelling of the guard cell pair, resulting in the opening of the stomatal pore. K + and its charge-balancing anions Cl 2 , NO 3 2 , and malate (Mal 22 ), as well as sugars, are the osmotica accumulating in guard cell vacuoles for stomatal opening. The ions are transported across the vacuolar membrane (also, the tonoplast) by ion channels and secondary active transporters, while vacuolar proton pumps generate the necessary proton motive force and acidify the vacuolar lumen.With the dawn of the patch-clamp technique, many ion channels were characterized in the 1980s and 1990s. A lot of these early studies were conducted with the broad bean Vicia faba and the monocotyledon dayflower plant Commelina communis because of the large size of their guard cells. It was only with the era of molecular genetics that the proteins responsible for the characterized transport were identified in Arabidopsis (Arabidopsis thaliana), and this review focuses almost exclusively on vacuolar transport proteins of this species with a role in stomatal physiology (Table I; Fig. 1).Nevertheless, many discoveries about guard cell function were made using V. faba, C. communis, and other species but were carried over into Arabidopsis guard cell research and now shape our reasoning. For example, Mal 22 is often listed as an important osmoticum. This is true for some species such as V. faba (Outlaw and Lowry, 1977;Outlaw and Kennedy, 1978; Raschke, 1978a, 1978b) and in certain growth conditions (Raschke and Schnabl, 1978;Van Kirk and Raschke, 1978a). But in Arabidopsis guard cells, on average, K + is charge balanced to 50% by Cl 2 and only to 5% by Mal 22 , with Mal 22 concentrations in the range of 1 to 2 mM

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“…CLCN2 encodes for a transmembrane protein that regulates chloride ion homeostasis in various cells controlling their volumes that in turn, may affect several essential biological functions in which osmoregulation is relevant (Jentsch, 2015). SLC12A9 is included Fig.…”

Section: Selective Sweep Analysis In Cultivated European Sea Bassmentioning

confidence: 99%

Whole genome semiconductor based sequencing of farmed European sea bass (Dicentrarchus labrax) Mediterranean genetic stocks using a DNA pooling approach

et al. 2016

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European sea bass (Dicentrarchus labrax) is an important marine species for commercial and sport fisheries and aquaculture production. Recently, the European sea bass genome has been sequenced and assembled. This resource can open new opportunities to evaluate and monitor variability and identify variants that could contribute to the adaptation to farming conditions. In this work, two DNA pools constructed from cultivated European sea bass were sequenced using a next generation semiconductor sequencing approach based on Ion Proton sequencer. Using the first draft version of the D. labrax genome as reference, sequenced reads obtained a total of about 1.6 million of single nucleotide polymorphisms (SNPs), spread all over the chromosomes. Transition/transversion (Ti/Tv) was equal to 1.28, comparable to what was already reported in Salmon species. A pilot homozygosity analysis across the D. labrax genome using DNA pool sequence datasets indicated that this approach can identify chromosome regions with putative signatures of selection, including genes involved in ion transport and chloride channel functions, amino acid metabolism and circadian clock and related neurological systems. This is the first study that reported genome wide polymorphisms in a fish species obtained with the Ion Proton sequencer. Moreover, this study provided a methodological approach for selective sweep analysis in this species.

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Discovery of CLC transport proteins: cloning, structure, function and pathophysiology

Cited by 28 publications

References 178 publications

Dynamical model of the CLC-2 ion channel exhibits a two-step gating mechanism

Dynamical model of the CLC-2 ion channel exhibits a two-step gating mechanism

Ion Transport at the Vacuole during Stomatal Movements

Whole genome semiconductor based sequencing of farmed European sea bass (Dicentrarchus labrax) Mediterranean genetic stocks using a DNA pooling approach

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