scholarly journals Modulation of the slow/common gating of CLC channels by intracellular cadmium

2015 ◽  
Vol 146 (6) ◽  
pp. 495-508 ◽  
Author(s):  
Yawei Yu ◽  
Ming-Feng Tsai ◽  
Wei-Ping Yu ◽  
Tsung-Yu Chen
Keyword(s):  
Binding Site ◽  
Transmembrane Domain ◽  
Kinetic Studies ◽  
Dimer Interface ◽  
State Dependent ◽  
Fast Gating ◽  
Cl Channels ◽  
The Common ◽  
The Individual ◽  
Opening And Closing

Members of the CLC family of Cl− channels and transporters are homodimeric integral membrane proteins. Two gating mechanisms control the opening and closing of Cl− channels in this family: fast gating, which regulates opening and closing of the individual pores in each subunit, and slow (or common) gating, which simultaneously controls gating of both subunits. Here, we found that intracellularly applied Cd2+ reduces the current of CLC-0 because of its inhibition on the slow gating. We identified CLC-0 residues C229 and H231, located at the intracellular end of the transmembrane domain near the dimer interface, as the Cd2+-coordinating residues. The inhibition of the current of CLC-0 by Cd2+ was greatly enhanced by mutation of I225W and V490W at the dimer interface. Biochemical experiments revealed that formation of a disulfide bond within this Cd2+-binding site is also affected by mutation of I225W and V490W, indicating that these two mutations alter the structure of the Cd2+-binding site. Kinetic studies showed that Cd2+ inhibition appears to be state dependent, suggesting that structural rearrangements may occur in the CLC dimer interface during Cd2+ modulation. Mutations of I290 and I556 of CLC-1, which correspond to I225 and V490 of CLC-0, respectively, have been shown previously to cause malfunction of CLC-1 Cl− channel by altering the common gating. Our experimental results suggest that mutations of the corresponding residues in CLC-0 change the subunit interaction and alter the slow gating of CLC-0. The effect of these mutations on modulations of slow gating of CLC channels by intracellular Cd2+ likely depends on their alteration of subunit interactions.

scholarly journals Allosteric potentiation of a ligand-gated ion channel is mediated by access to a deep membrane-facing cavity

2018 ◽  
Vol 115 (42) ◽  
pp. 10672-10677 ◽  
Author(s):  
Stephanie A. Heusser ◽  
Marie Lycksell ◽  
Xueqing Wang ◽  
Sarah E. McComas ◽  
Rebecca J. Howard ◽  
...  
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Allosteric Modulation ◽  
Bacterial Protein ◽  
Detailed Model ◽  
Differential Motion ◽  
State Dependent ◽  
The Common ◽  
Pore Lining

Theories of general anesthesia have shifted in focus from bulk lipid effects to specific interactions with membrane proteins. Target receptors include several subtypes of pentameric ligand-gated ion channels; however, structures of physiologically relevant proteins in this family have yet to define anesthetic binding at high resolution. Recent cocrystal structures of the bacterial protein GLIC provide snapshots of state-dependent binding sites for the common surgical agent propofol (PFL), offering a detailed model system for anesthetic modulation. Here, we combine molecular dynamics and oocyte electrophysiology to reveal differential motion and modulation upon modification of a transmembrane binding site within each GLIC subunit. WT channels exhibited net inhibition by PFL, and a contraction of the cavity away from the pore-lining M2 helix in the absence of drug. Conversely, in GLIC variants exhibiting net PFL potentiation, the cavity was persistently expanded and proximal to M2. Mutations designed to favor this deepened site enabled sensitivity even to subclinical concentrations of PFL, and a uniquely prolonged mode of potentiation evident up to ∼30 min after washout. Dependence of these prolonged effects on exposure time implicated the membrane as a reservoir for a lipid-accessible binding site. However, at the highest measured concentrations, potentiation appeared to be masked by an acute inhibitory effect, consistent with the presence of a discrete, water-accessible site of inhibition. These results support a multisite model of transmembrane allosteric modulation, including a possible link between lipid- and receptor-based theories that could inform the development of new anesthetics.

scholarly journals Electrostatic Control and Chloride Regulation of the Fast Gating of ClC-0 Chloride Channels

2003 ◽  
Vol 122 (5) ◽  
pp. 641-651 ◽  
Author(s):  
Tsung-Yu Chen ◽  
Mei-Fang Chen ◽  
Chia-Wei Lin
Keyword(s):  
Chloride Channels ◽  
Electric Organ ◽  
Time Range ◽  
Gating Mechanism ◽  
Fast Gating ◽  
Cl Channels ◽  
The One ◽  
Opening And Closing ◽  
Chloride Regulation ◽  
Closing Rate

The opening and closing of chloride (Cl−) channels in the ClC family are thought to tightly couple to ion permeation through the channel pore. In the prototype channel of the family, the ClC-0 channel from the Torpedo electric organ, the opening-closing of the pore in the millisecond time range known as “fast gating” is regulated by both external and internal Cl− ions. Although the external Cl− effect on the fast-gate opening has been extensively studied at a quantitative level, the internal Cl− regulation remains to be characterized. In this study, we examine the internal Cl− effects and the electrostatic controls of the fast-gating mechanism. While having little effect on the opening rate, raising [Cl−]i reduces the closing rate (or increases the open time) of the fast gate, with an apparent affinity of >1 M, a value very different from the one observed in the external Cl− regulation on the opening rate. Mutating charged residues in the pore also changes the fast-gating properties—the effects are more prominent on the closing rate than on the opening rate, a phenomenon similar to the effect of [Cl−]i on the fast gating. Thus, the alteration of fast-gate closing by charge mutations may come from a combination of two effects: a direct electrostatic interaction between the manipulated charge and the negatively charged glutamate gate and a repulsive force on the gate mediated by the permeant ion. Likewise, the regulations of internal Cl− on the fast gating may also be due to the competition of Cl− with the glutamate gate as well as the overall more negative potential brought to the pore by the binding of Cl−. In contrast, the opening rate of the fast gate is only minimally affected by manipulations of [Cl−]i and charges in the inner pore region. The very different nature of external and internal Cl− regulations on the fast gating thus may suggest that the opening and the closing of the fast gate are not microscopically reversible processes, but form a nonequilibrium cycle in the ClC-0 fast-gating mechanism.

scholarly journals Involvement of Helices at the Dimer Interface in ClC-1 Common Gating

2003 ◽  
Vol 121 (2) ◽  
pp. 149-161 ◽  
Author(s):  
Michael Duffield ◽  
Grigori Rychkov ◽  
Allan Bretag ◽  
Michael Roberts
Keyword(s):  
Muscle Stiffness ◽  
Site Directed Mutagenesis ◽  
Open Probability ◽  
Dominant Form ◽  
Dimer Interface ◽  
Fast Gating ◽  
Muscle Disorder ◽  
The Common ◽  
Gating Process

ClC-1 is a dimeric, double-pored chloride channel that is present in skeletal muscle. Mutations of this channel can result in the condition myotonia, a muscle disorder involving increased muscle stiffness. It has been shown that the dominant form of myotonia often results from mutations that affect the so-called slow, or common, gating process of the ClC-1 channel. Mutations causing dominant myotonia are seen to cluster at the interface of the ClC-1 channel monomers. This study has investigated the role of the H, I, P, and Q helices, which lie on this interface, as well as the G helix, which is situated immediately behind the H and I helices, on ClC-1 gating. 11 mutant ClC-1 channels (T268M, C277S, C278S, S289A, T310M, S312A, V321S, T539A, S541A, M559T, and S572V) were produced using site-directed mutagenesis, and gating properties of these channels were investigated using electrophysiological techniques. Six of the seven mutations in G, H, and I, and two of the four mutations in P and Q, caused shifts of the ClC-1 open probability. In the majority of cases this was due to alterations in the common gating process, with only three of the mutants displaying any change in fast gating. Many of the mutant channels also showed alterations in the kinetics of the common gating process, particularly at positive potentials. The changes observed in common gating were caused by changes in the opening rate (e.g. T310M), the closing rate (e.g. C277S), or both rates. These results indicate that mutations in the helices forming the dimer interface are able to alter the ClC-1 common gating process by changing the energy of the open and/or closed channel states, and hence altering transition rates between these states.

The Red Neuronal Pigment in the Nervous System of the Mussel, Mytilus Edulis: Localization and Its Effect on Lateral Ciliary Activity with Spectral and Analytical Changes

1981 ◽  
Vol 39 ◽  
pp. 494-495
Author(s):  
Anthony A. Paparo ◽  
Judith A. Murphy
Keyword(s):  
Nervous System ◽  
Mytilus Edulis ◽  
Neuronal Cell ◽  
Ciliary Activity ◽  
Neuronal Cell Bodies ◽  
The Central Nervous System ◽  
Intracellular Organelles ◽  
The Common ◽  
The Individual ◽  
Cryostat Sections

The purpose of this study was to localize the red neuronal pigment in Mytilus edulis and examine its role in the control of lateral ciliary activity in the gill. The visceral ganglia (Vg) in the central nervous system show an over al red pigmentation. Most red pigments examined in squash preps and cryostat sec tions were localized in the neuronal cell bodies and proximal axon regions. Unstained cryostat sections showed highly localized patches of this pigment scattered throughout the cells in the form of dense granular masses about 5-7 um in diameter, with the individual granules ranging from 0.6-1.3 um in diame ter. Tissue stained with Gomori's method for Fe showed bright blue granular masses of about the same size and structure as previously seen in unstained cryostat sections.Thick section microanalysis (Fig.l) confirmed both the localization and presence of Fe in the nerve cell. These nerve cells of the Vg share with other pigmented photosensitive cells the common cytostructural feature of localization of absorbing molecules in intracellular organelles where they are tightly ordered in fine substructures.

What Can Economists Contribute to the Common Good Tradition?

2017 ◽  
Author(s):  
Andrew M. Yuengert
Keyword(s):  
Common Good ◽  
Common Pool Resources ◽  
Economic Approach ◽  
Public And Private ◽  
Private Provision ◽  
The Public ◽  
The Common Good ◽  
The Common ◽  
The Individual ◽  
Insight Into

Although most economists are skeptical of or puzzled by the Catholic concept of the common good, a rejection of the economic approach as inimical to the common good would be hasty and counterproductive. Economic analysis can enrich the common good tradition in four ways. First, economics embodies a deep respect for economic agency and for the effects of policy and institutions on individual agents. Second, economics offers a rich literature on the nature of unplanned order and how it might be shaped by policy. Third, economics offers insight into the public and private provision of various kinds of goods (private, public, common pool resources). Fourth, recent work on the development and logic of institutions and norms emphasizes sustainability rooted in the good of the individual.

Punk as Folk: Continuities and Tensions in the UK and Beyond

2020 ◽  
Author(s):  
Pete Dale
Keyword(s):  
Folk Music ◽  
Music Making ◽  
Collective Creativity ◽  
Living Tradition ◽  
Wide Range ◽  
The Us ◽  
The Common ◽  
The Individual ◽  
The Uk

Numerous claims have been made by a wide range of commentators that punk is somehow “a folk music” of some kind. Doubtless there are several continuities. Indeed, both tend to encourage amateur music-making, both often have affiliations with the Left, and both emerge at least partly from a collective/anti-competitive approach to music-making. However, there are also significant tensions between punk and folk as ideas/ideals and as applied in practice. Most obviously, punk makes claims to a “year zero” creativity (despite inevitably offering re-presentation of at least some existing elements in every instance), whereas folk music is supposed to carry forward a tradition (which, thankfully, is more recognized in recent decades as a subject-to-change “living tradition” than was the case in folk’s more purist periods). Politically, meanwhile, postwar folk has tended more toward a socialist and/or Marxist orientation, both in the US and UK, whereas punk has at least rhetorically claimed to be in favor of “anarchy” (in the UK, in particular). Collective creativity and competitive tendencies also differ between the two (perceived) genre areas. Although the folk scene’s “floor singer” tradition offers a dispersal of expressive opportunity comparable in some ways to the “anyone can do it” idea that gets associated with punk, the creative expectation of the individual within the group differs between the two. Punk has some similarities to folk, then, but there are tensions, too, and these are well worth examining if one is serious about testing out the common claim, in both folk and punk, that “anyone can do it.”

scholarly journals Kinetic Studies of Proton Transfer in the Microenvironment of a Binding Site

1982 ◽  
Vol 121 (3) ◽  
pp. 637-642 ◽  
Author(s):  
Menachem GUTMAN ◽  
Dan HUPPERT ◽  
Esther NACHLIEL
Keyword(s):  
Proton Transfer ◽  
Binding Site ◽  
Kinetic Studies

Can Communities Protect Autonomy? Ethical Dilemmas in HIV Preventative Drug Trials

1995 ◽  
Vol 4 (4) ◽  
pp. 516-523 ◽  
Author(s):  
Deborah Zion
Keyword(s):  
Advance Directive ◽  
Common Good ◽  
Ethical Dilemmas ◽  
Drug Trials ◽  
The Common Good ◽  
Gay Community ◽  
The Common ◽  
The Individual ◽  
Trial Participants

Before sailing past the sirens' “flowery meadow,” Ulysses instructed his sailors to lash him to the mast so that he would not succumb to the siren's singing. His advance directive demonstrated that he valued his dispositional or long-term autonomy over his unquestioned right to make decisions. He also indicated to his oarsmen that he understood the nature of temptation and his inability to resist it. Ideas of autonomy and sexual choice are central to this discussion of new AIDS treatments, especially the trials of preventative vaccines. Questions arise over the rights of individuals and the extent that these should be limited by concerns of the gay community. Should the gay community intervene in the risky decisions of individuals if no explicit advance directive exists? If so, how do they justify their paternalism? Could their aims not be better served through strengthening the individual dispositional autonomy of trial participants rather than making specific claims about the common good?

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