Kinetic Analysis of Block of Open Sodium Channels by a Peptide Containing the Isoleucine, Phenylalanine, and Methionine (IFM) Motif from the Inactivation Gate

Eaholtz, Galen; Zagotta, William N.; Catterall, William A.

doi:10.1085/jgp.111.1.75

Cited by 26 publications

(27 citation statements)

References 33 publications

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“…Inactivation is completely blocked in I1488Q-F1489Q-M1490Q (IFM/QQQ, corresponds to I1303Q-F1304Q-M1305Q in Na v 1.4), but mutant F1489Q alone considerably slows inactivation (502) as does the equivalent F1304Q in muscle channels (Na v 1.4) for which kinetic modeling led to the assumption of three inactivated states (328). Inactivation is restored by adding short peptides containing IFM (KIFMK-amide) to the intracellular side (117,118) or in channels in which inactivation is slowed by external application of ␣-toxin of the scorpion Leiurus quinquestriatus (116). SCAM experiments with the mutant F1489C show that F becomes inaccessible to MTSET on inactivation, suggesting that IFM serves as a hydrophobic latch for a hinged lid formed by the D3-D4 linker (216).…”

Section: B Localization Of the Gate Mediating Fast Inactivationmentioning

confidence: 99%

Sodium Channel Inactivation: Molecular Determinants and Modulation

Ulbricht

2005

Physiological Reviews

268

222

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Voltage-gated sodium channels open (activate) when the membrane is depolarized and close on repolarization (deactivate) but also on continuing depolarization by a process termed inactivation, which leaves the channel refractory, i.e., unable to open again for a period of time. In the "classical" fast inactivation, this time is of the millisecond range, but it can last much longer (up to seconds) in a different slow type of inactivation. These two types of inactivation have different mechanisms located in different parts of the channel molecule: the fast inactivation at the cytoplasmic pore opening which can be closed by a hinged lid, the slow inactivation in other parts involving conformational changes of the pore. Fast inactivation is highly vulnerable and affected by many chemical agents, toxins, and proteolytic enzymes but also by the presence of beta-subunits of the channel molecule. Systematic studies of these modulating factors and of the effects of point mutations (experimental and in hereditary diseases) in the channel molecule have yielded a fairly consistent picture of the molecular background of fast inactivation, which for the slow inactivation is still lacking.

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Section: B Localization Of the Gate Mediating Fast Inactivationmentioning

confidence: 99%

Sodium Channel Inactivation: Molecular Determinants and Modulation

Ulbricht

2005

Physiological Reviews

268

222

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“…This cluster, containing isoleucine 1488, phenylalanine 1489 and methionine 1490 (IFM) has been identified as a fragment required for sodium channel inactivation (West et al 1992). More recently it has been shown that small peptides containing this IFM sequence are sufficient to restore fast inactivation of sodium channels with mutations in IDIII-IV connecting loop, leading to the hypothesis that the IFM motif binds within the pore of the sodium channel and blocks it during the inactivation (Eaholtz et al 1998). This hypothesis implies the presence of amino acid residues in the intracellular mouth of the pore of the sodium channel that are involved in conformational changes which couple activation to inactivation and bind the IFM motif to result in an inactivated state.…”

Section: The Inner Vestibule and Inactivation Gatementioning

confidence: 99%

Structure, function and pharmacology of voltage-gated sodium channels

Denac¹,

Mevissen²,

Scholtysik³

2000

Naunyn-Schmiedeberg's Archives of Pharmacology

142

108

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Voltage-gated sodium channels (VGSCs) are responsible for the initial inwards current during the depolarisation phase of action potential in excitable cells. Therefore, VGSCs are crucial for cardiac and nerve function, since the action potential of nerves and muscle cannot occur without them. Their importance in generation and transmission of signals has been known for more than 40 years but the more recent introduction of new electrophysiological methods and application of molecular biology techniques has led to an explosion of research on many different ion channels, including VGSCs. Their extraordinary biological importance makes them logical and obvious targets for toxins produced by animals and plants for attack or defence. The action of these and similar substances modulating the function of the VGSCs is interesting with respect to their possible use in medicine or use as tools in the study of these molecules. This review summarises recent progress in this research field and, in particular, considers what is known about the relationship of the structure to function, including a current understanding of the pharmacological modulation of VGSCs.

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“…Application of this peptide to the intracellular surface of patches containing Na ϩ channels with a mutation in the critical Phe of the intrinsic IFM motif (F1489Q) reduces the peak Na ϩ current and produces current decay during the pulse that resembles fast inactivation from closed and open states, respectively (19,41) (Fig. 9A).…”

Section: Effects Of the Inactivation Gate Peptide Kifmk On Decay Of Namentioning

confidence: 99%

A Critical Role for the S4-S5 Intracellular Loop in Domain IV of the Sodium Channel α-Subunit in Fast Inactivation

McPhee

Ragsdale

Scheuer

et al. 1998

Journal of Biological Chemistry

Self Cite

182

159

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Na؉ channel fast inactivation is thought to involve the closure of an intracellular inactivation gate over the channel pore. Previous studies have implicated the intracellular loop connecting domains III and IV and a critical IFM motif within it as the inactivation gate, but amino acid residues at the intracellular mouth of the pore required for gate closure and binding have not been positively identified. The short intracellular loops connecting the S4 and S5 segments in each domain of the Na ؉ channel ␣-subunit are good candidates for this role in the Na ؉ channel inactivation process. In this study, we used scanning mutagenesis to examine the role of the IVS4-S5 region in fast inactivation. Mutations F1651A, near the middle of the loop, and L1660A and N1662A, near the COOH-terminal end, substantially disrupted Na ؉ channel fast inactivation. The mutant F1651A conducted Na ؉ currents that decayed very slowly, while L1660A and N1662A had large sustained Na ؉ currents at the end of 30-ms depolarizing pulses. Inactivation of macroscopic Na؉ currents was nearly abolished by the N1662A mutation and the combination of the F1651A/L1660A mutations. Single channel analysis revealed frequent reopenings for all three mutants during 40-ms depolarizing pulses, indicating a substantial impairment of the stability of the inactivated state compared with wild type (WT). The F1651A and N1662A mutants also had increased mean open times relative to WT, indicating a slowed rate of entry into the inactivated state. In addition to these effects on inactivation of open Na ؉ channels, mutants F1651A, L1660A, and N1662A also impaired fast inactivation of closed Na In neurons and muscle cells, activation of voltage-gated Na ϩ channels leads to inward Na ϩ current which initiates the action potential (1). Within milliseconds after membrane depolarization, Na ϩ channels pass through a series of nonconducting closed states, enter an ion-conducting open state, and finally convert into a nonconducting inactivated state. Inactivated channels recover rapidly upon membrane repolarization and are thus available for reactivation by subsequent depolarizing stimuli. As inactivation exerts crucial control over Na ϩ channel activity, understanding the molecular basis of this process is an important step toward determining how Na ϩ channels function. Three subunits comprise the brain Na ϩ channel: ␣ of 260 kDa, ␤1 of 36 kDa, and ␤2 of 33 kDa (2

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Kinetic Analysis of Block of Open Sodium Channels by a Peptide Containing the Isoleucine, Phenylalanine, and Methionine (IFM) Motif from the Inactivation Gate

Cited by 26 publications

References 33 publications

Sodium Channel Inactivation: Molecular Determinants and Modulation

Sodium Channel Inactivation: Molecular Determinants and Modulation

Structure, function and pharmacology of voltage-gated sodium channels

A Critical Role for the S4-S5 Intracellular Loop in Domain IV of the Sodium Channel α-Subunit in Fast Inactivation

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