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Fluorescein derivatives potentiate CFTR by altering the ATP affinity and efficacy of channel gating

Fluorescein derivatives potentiate CFTR by altering the ATP ...

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2008北京国际生理科学学术大会

作者： MORAN Oscar SHEPPARD David N Istituto di Biofisica CNRVia DeMarini 616149 GenoaItaly Department of Physiology and Pharmacology University of BristolBristolBS8 1TDUK

The fluorescein derivative phloxine B is a potent modulator of the cystic fibrosis transmembrane conductance regulator(CFTR)Cl *** micromolar concentrations of phloxine B potentiate ATP-dependent channel gating,whereas higher concentrations occlude the channel *** determine whether fluorescein derivatives (FDs)affect the ATP affinity of CFTR and the efficacy of channel gating,we investigated the effects of FDs on the gating behaviour of CFTR using excised inside-out membrane patches from C127 cells expressing wild-type human *** employed a simple linear three-state scheme(C(?)C(?)O)to describe CFTR channel *** this scheme,C represents the long duration closed state separating channel openings,C the brief closures that interrupt channel openings,and O the open *** between the three states are described by the forward rate constantsβ,β and the backward rate constantsα andα.Given that CFTR is an agonist-activated channel gated by intracellular ATP and this scheme is reminiscent of the del Castillo-Katz mechanism,we can calculate the ATP affinity(α/β)and gating efficacy of CFTR(β/α).The FDs phloxine B(1μmol/L)and eosin Y(1μmol/L) augment channel gating by prolonging mean burst duration(MBD)without changing the interburst interval(IBI), whereas dichlorofluorescein(DCF;20μmol/L)decreases the IBI without changing MBD(n=4-15).Interestingly, phloxine B(1μmol/L)and DCF(20μmol/L)decreasedα/β(enhanced affinity),whereas only phloxine B(1μmol/L) elevatedβ/α(augmented gating efficacy).To understand better how FDs affect the relationship between the ATP affinity and gating efficacy,we examined the ATP-dependence of channel gating(n>5).Increasing ATP concentrations enhanced markedly both the ATP affinity and gating efficacy of ***,phloxine B(1μmol/L) augmented both the ATP affinity and gating efficacy of CFTR,particularly at low ATP *** interpret our results to suggest that the ATP affinity and gating efficacy of CFTR are t

关键词： CFTR channel gating ATP affinity gating efficacy

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A Cl--regulated structural switch that controls proton sensitivity of acid-sensing ion channels

A Cl--regulated structural switch that controls proton sensi...

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中国神经科学学会第九届全国学术会议暨第五次会员代表大会

作者： Wei-Guang LI~(1,2),Zhu-Dan ZHANG~(1,2),Hui CAO~1,Tian-Le XU~(1,3,*) 1 Institute of Neuroscience and State Key Laboratory of Neuroscience,Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences,Shanghai 200031 2 Graduate School of Chinese Academy of Sciences,Shanghai 200031,China 3 Institute of Medical Sciences,Shanghai Jiaotong University,Shanghai 200025

Acid-sensing ion channel(ASIC) has a prominent role in tissue pH-sensing and neuronal signaling,and participates in various pathological *** the availability of structures for chicken ASIC1 subunit, obtaining mechanistic insight into the function of these highly dynamic channel proteins using static crystallographic information is *** a series of mutational,chemical and functional approaches,we found that the extracellular CI-binding module shown in crystals of ASIC1 constitutes an indispensable component for ASIC1a *** gluconate-substitution of natural CI-binding enhanced whereas engineering a permanent anion into the CI-binding module inhibited channel activity,suggesting an essential role of CI-regulated domain flexibility but not the absolute charge state created by bound anion in channel ***-comparable anion substitution(F, Br-,or I) revealed a CI-dependent modulation of proton sensing function,supporting a structural role of dynamic association and dissociation of CI ion in coordinating conformational transition associated with proton sensing. Furthermore,charge reversal and swap as well as mutant cycle analysis of alanine substitutions of two counter-charged residues(K311,E315) in the CI-binding module show that they electrostatically interacted and energetically coupled, underpinning a structural switch controlling proton sensitivity of ASIC1a channels.

关键词： acid-sensing ion channel channel gating salt bridge

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Structural Mechanism of NMDA Receptor Inhibition, Activation and Allosteric Modulation

Structural Mechanism of NMDA Receptor Inhibition, Activation...

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中国神经科学学会第十二届全国学术会议

作者： Shujia ZHU Richard A.Stein Craig Yoshioka Chia-Hsueh Lee April Goehring Hassane S.Mchaourab Eric Gouaux Institute of Neuroscience Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Vollum Institute Oregon Health and Science University Department of Molecular Physiology and Biophysics Vanderbilt University

N-methyl-D-aspartate（NMDA） receptors are glutamate-gated, calciumpermeable ion channels that mediate synaptic transmission in the mammalian brain, have fundamental roles in brain development and function, and underpin learning and memory. NMDA receptor dysfunction is directly implicated in states of disease or injury ranging from seizure to ischemia and they are also targets of new rapid-acting therapeutic agents for the treatment of depression. Despite the fundamental importance of NMDA receptors in nervous system function and disease, there is little known about how the intact receptor transitions between inactive and active states, and how specific molecules antagonize or activate the receptor. Here we report single particle electron cryomicroscopy structures of the Glu N1/GluN2B NMDA receptor in 3 novel conformations: an antagonist-bound state, an agonist-bound conformation, and a complex with agonists and the allosteric inhibitor, Ro25-6981. Together with double electron-electron resonance experiments, we show how competitive antagonists dramatically rupture the ligandbinding domain gating ‘ring’, how agonists promote reassembly of the ‘ring’ into a dimer-of-dimers configuration, and how allosteric inhibitors, acting within the amino terminal domain, further stabilize the ligand-binding domain layer. These structural and spectroscopic studies illuminate how the ligand-binding domain gating ‘ring’ is fundamental to signal transduction and gating in NMDA receptors.

关键词： NMDA receptors channel gating allosteric modulation Cryo electron microscopy

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