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- 저자 : Refaeli, Bosmat (검색결과 4 건)
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Kornilov, Polina,Peretz, Asher,Lee, Yoonji,Son, Karam,Lee, Jin Hee,Refaeli, Bosmat,Roz, Netta,Rehavi, Moshe,Choi, Sun,Attali, Bernard The Federation of American Societies for Experimen 2014 The FASEB Journal Vol.28 No.6
<P>Some of the fascinating features of voltage-sensing domains (VSDs) in voltage-gated cation channels (VGCCs) are their modular nature and adaptability. Here we examined the VSD sensitivity of different VGCCs to 2 structurally related nontoxin gating modifiers, NH17 and NH29, which stabilize K<SUB>v</SUB>7.2 potassium channels in the closed and open states, respectively. The effects of NH17 and NH29 were examined in Chinese hamster ovary cells transfected with transient receptor potential vanilloid 1 (TRPV1) or K<SUB>v</SUB>7.2 channels, as well as in dorsal root ganglia neurons, using the whole-cell patch-clamp technique. NH17 and NH29 exert opposite effects on TRPV1 channels, operating, respectively, as an activator and a blocker of TRPV1 currents (EC<SUB>50</SUB> and IC<SUB>50</SUB> values ranging from 4 to 40 μM). Combined mutagenesis, electrophysiology, structural homology modeling, molecular docking, and molecular dynamics simulation indicate that both compounds target the VSDs of TRPV1 channels, which, like vanilloids, are involved in π-π stacking, H-bonding, and hydrophobic interactions. Reflecting their promiscuity, the drugs also affect the lone VSD proton channel mVSOP. Thus, the same gating modifier can promiscuously interact with different VGCCs, and subtle differences at the VSD-ligand interface will dictate whether the gating modifier stabilizes channels in either the closed or the open state.—Kornilov, P., Peretz, A., Lee, Y., Son, K., Lee, J. H., Refaeli, B., Roz, N., Rehavi, M., Choi, S., Attali, B. Promiscuous gating modifiers target the voltage sensor of K<SUB>v</SUB>7.2, TRPV1, and H<SUB>v</SUB>1 cation channels.</P>
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Giladi, Moshe,Lee, Su Youn,Refaeli, Bosmat,Hiller, Reuben,Chung, Ka Young,Khananshvili, Daniel Elsevier 2019 Biochimica et biophysica acta, Bioenergetics Vol.1860 No.3
<P><B>Abstract</B></P> <P>The cell membrane (NCX) and mitochondrial (NCLX) Na<SUP>+</SUP>/Ca<SUP>2+</SUP> exchangers control Ca<SUP>2+</SUP> homeostasis. Eleven (out of twelve) ion-coordinating residues are highly conserved among eukaryotic and prokaryotic NCXs, whereas in NCLX, nine (out of twelve) ion-coordinating residues are different. Consequently, NCXs exhibit high selectivity for Na<SUP>+</SUP> and Ca<SUP>2+</SUP>, whereas NCLX can exchange Ca<SUP>2+</SUP> with either Na<SUP>+</SUP> or Li<SUP>+</SUP>. However, the underlying molecular mechanisms and physiological relevance remain unresolved. Here, we analyzed the NCX_Mj-derived mutant NCLX_Mj (with nine substituted residues) imitating the ion selectivity of NCLX. Site-directed fluorescent labeling and ion flux assays revealed the nearly symmetric accessibility of ions to the extracellular and cytosolic vestibules in NCLX_Mj (K<SUB>int</SUB> = 0.8–1.4), whereas the extracellular vestibule is predominantly accessible to ions (K<SUB>int</SUB> = 0.1–0.2) in NCX_Mj. HDX-MS (hydrogen-deuterium exchange mass-spectrometry) identified symmetrically rigidified core helix segments in NCLX_Mj, whereas the matching structural elements are asymmetrically rigidified in NCX_Mj. The HDX-MS analyses of ion-induced conformational changes and the mutational effects on ion fluxes revealed that the “Ca<SUP>2+</SUP>-site” (S<SUB>Ca</SUB>) of NCLX_Mj binds Na<SUP>+</SUP>, Li<SUP>+</SUP>, or Ca<SUP>2+</SUP>, whereas one or more additional Na<SUP>+</SUP>/Li<SUP>+</SUP> sites of NCLX_Mj are incompatible with the Na<SUP>+</SUP> sites (S<SUB>ext</SUB> and S<SUB>int</SUB>) of NCX_Mj. Thus, the replacement of ion-coordinating residues in NCLX_Mj alters not only the ion selectivity of NCLX_Mj, but also the capacity and affinity for Na<SUP>+</SUP>/Li<SUP>+</SUP> (but not for Ca<SUP>2+</SUP>) binding, bidirectional ion-accessibility, the response of the ion-exchange to membrane potential changes, and more. These structure-controlled functional features could be relevant for differential contributions of NCX and NCLX to Ca<SUP>2+</SUP> homeostasis in distinct sub-cellular compartments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Distinct structural elements control ion selectivity in the Na<SUP>+</SUP>/Ca<SUP>2+</SUP> exchanger. </LI> <LI> Residue-based changes in ion-selectivity specifically alter conformational patterns. </LI> <LI> Structure-dynamic variances at distinct sites are reflected in functional diversity. </LI> <LI> Conformational dynamics of apo-protein predefines a degree of functional asymmetry. </LI> <LI> The loss in ion selectivity has relatively small effects on the transport rates. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Haythem Bany Salameh,Ghaleb El Refae 한국통신학회 2022 ICT Express Vol.8 No.1
Cognitive radio (CR) is a key technology that can enable opportunistic spectrum access, which enables secondary users (SUs) to dynamically exploit the under-utilized channels in the licensed spectrum, owned by primary radio networks (PRNs), referred to as dominant firms. Such sharing is subject to interference, SU QoS and cost constraints, in which SUs should not introduce harmful interference to PR users, achieve QoS rate demand and pay a price for using the licensed PR spectrum. The price of accessing idle PR channels depends on the level of channel utilization and price paid by PRs to access the channels, while the amount of needed spectrum to serve the rate demand of each SU heavily depends on the link-quality of the various channels. In this paper, the spectrum assignment problem in a CR network (CRN), referred to as follower firm, is investigated with the target of serving the largest possible number of SUs with the least possible total price paid to the PRNs (highest CRN profit) while being aware of the time-varying achieved transmission rate and level of utilization of the various PR channels. The problem is mathematically expressed as an optimization problem with the goal of maximizing the number of served SUs and the profit made by the CRN, which has been shown to be a binary linear programming (BLP) problem. Due to the high complexity of solving such optimization, we use the well-known sequential-fixing optimization method to obtain sub-optimal solutions. Simulation results indicate that our channel-assignment optimization significantly increases the CRN profit by reducing the price paid to the PRNs while achieving comparable performance offered by previous price-unaware protocols.
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