C-type inactivation of a voltage-gated K+ channel occurs by a cooperative mechanism

Panyi, György; Sheng, Zu-Fang; Deutsch, Carol

doi:10.1016/s0006-3495(95)79963-5

Cited by 159 publications

(175 citation statements)

References 16 publications

(27 reference statements)

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“…1, D-I. In the hKv1.3_V388C mutant channel in [160 3 The abbreviations used are: CTX, charybdotoxin; KTX, kaliotoxin; PDB, Protein Data Bank; TEA, tetraethylammonium; wt, wild type. (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…(Ϯ)-Verapamil was obtained as hydrochloride salt from Sigma-Aldrich. CTX 3 and KTX (Bachem, Bubendorf, Switzerland) were dissolved in external bath solution containing 0.1% BSA (SigmaAldrich). TEA chloride was purchased from Fluka (Taufkirchen, Germany) and dissolved in external bath solution to the respective final concentration.…”

Section: Methodsmentioning

confidence: 99%

“…The human voltage-gated potassium channel Kv1.3 is a member of the Shaker-related potassium channel family (1) and can be distinguished from the other members because of its characteristic C-type inactivation (2,3). With the crystal structure data on the hKv1.2 channel (4), another member of the Shaker-related family, we have a good picture about the architecture of the classical voltage-gated potassium channels.…”

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A Novel Current Pathway Parallel to the Central Pore in a Mutant Voltage-gated Potassium Channel

Prütting¹,

Grissmer²

2011

Journal of Biological Chemistry

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Voltage-gated potassium channels are proteins composed of four subunits consisting of six membrane-spanning segments S1-S6, with S4 as the voltage sensor. The region between S5 and S6 forms the potassium-selective ion-conducting central ␣-pore. Recent studies showed that mutations in the voltage sensor of the Shaker channel could disclose another ion permeation pathway through the voltage-sensing domain (S1-S4) of the channel, the -pore. In our studies we used the voltage-gated hKv1.3 channel, and the insertion of a cysteine at position V388C (Shaker position 438) generated a current through the ␣-pore in high potassium outside and an inward current at hyperpolarizing potentials carried by different cations like Na ؉ , Li ؉ , Cs ؉ , and NH 4 ؉ . The observed inward current looked similar to the -current described for the R1C/S Shaker mutant channel and was not affected by some pore blockers like charybdotoxin and tetraethylammonium but was inhibited by a phenylalkylamine blocker (verapamil) that acts from the intracellular side. Therefore, we hypothesize that the hKv1.3_V388C mutation in the P-region generated a channel with two ion-conducting pathways. One, the ␣-pore allowing K ؉ flux in the presence of K ؉ , and the second pathway, the -pore, functionally similar but physically distinct from the -pathway. The entry of this new pathway (-pore) is presumably located at the backside of Y395 (Shaker position 445), proceeds parallel to the ␣-pore in the S6 -S6 interface gap, ending between S5 and S6 at the intracellular side of one ␣-subunit, and is blocked by verapamil.The human voltage-gated potassium channel Kv1.3 is a member of the Shaker-related potassium channel family (1) and can be distinguished from the other members because of its characteristic C-type inactivation (2, 3). With the crystal structure data on the hKv1.2 channel (4), another member of the Shaker-related family, we have a good picture about the architecture of the classical voltage-gated potassium channels. The channels consist of four subunits composed of six membranespanning segments, termed S1-S6. The region between the segments S5 and S6, with the pore helix (P) in-between (S5-P-S6), forms, together with three other subunits, the central ion conduction pathway, the ␣-pore, which is potassium-selective. The S4 segment is known as the voltage sensor, and the helices S1-S4 form the voltage-sensing domain, which surrounds the pore domain and controls the gates (1, 5). Recent studies showed that mutations in the voltage sensor of the Shaker channel or of the voltage-gated sodium channel Na v 1.2 can disclose another ion permeation pathway, the -pore, a pathway through the voltage-sensing domain (S1-S4) of the channel (5-9). The substitution of the first S4 arginine (Arg-1) in the Shaker channel with smaller amino acids like serine or cysteine created a pathway for a leak current selective for monovalent cations, the -pore. This conductance pathway in the Shaker channel was located distinct from the central K ϩ -conducting ␣-pore and ran throu...

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“…1, D-I. In the hKv1.3_V388C mutant channel in [160 3 The abbreviations used are: CTX, charybdotoxin; KTX, kaliotoxin; PDB, Protein Data Bank; TEA, tetraethylammonium; wt, wild type. (Fig.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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A Novel Current Pathway Parallel to the Central Pore in a Mutant Voltage-gated Potassium Channel

Prütting¹,

Grissmer²

2011

Journal of Biological Chemistry

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“…N-type inactivation involves the binding of a tethered blocking particle, containing positively charged N-terminal amino acids to the cytoplasmic face of the channel (46,47). The exact mechanisms of C-type inactivation (containing C-terminal amino acids) are unknown, but may involve a constriction of the outer mouth of the pore, preventing conduction (48,49). The mechanisms of inactivation for I AP remain to be determined.…”

Section: Discussionmentioning

confidence: 99%

A transient outward-rectifying K ⁺ channel current down-regulated by cytosolic Ca ²⁺ in Arabidopsis thaliana guard cells

Pei

Baizabal-Aguirre²,

Allen³

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

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A BSTR ACTSustained (noninactivating) outwardrectifying K ؉ channel currents have been identified in a variety of plant cell types and species. Here, in Arabidopsis thaliana guard cells, in addition to these sustained K ؉ currents, an inactivating outward-rectifying K ؉ current was characterized (plant A-type current: I AP ). I AP activated rapidly with a time constant of 165 ms and inactivated slowly with a time constant of 7.2 sec at ؉40 mV. I AP was enhanced by increasing the duration (from 0 to 20 sec) and degree (from ؉20 to ؊100 mV) of prepulse hyperpolarization. Ionic substitution and relaxation (tail) current recordings showed that outward I AP was mainly carried by K ؉ ions. In contrast to the sustained outward-rectifying K ؉ currents, cytosolic alkaline pH was found to inhibit I AP and extracellular K ؉ was required for I AP activity. Furthermore, increasing cytosolic free Ca 2؉ in the physiological range strongly inhibited I AP activity with a half inhibitory concentration of Ϸ 94 nM. We present a detailed characterization of an inactivating K ؉ current in a higher plant cell. Regulation of I AP by diverse factors including membrane potential, cytosolic Ca 2؉ and pH, and extracellular K ؉ and Ca 2؉ implies that the inactivating I AP described here may have important functions during transient depolarizations found in guard cells, and in integrated signal transduction processes during stomatal movements.

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“…Currently, there are two hypotheses to explain the molecular mechanisms responsible for slow inactivation in Na v s. The first is that slow inactivation is due to conformational change in P-loops between S5 and S6 of Na v s. This may be a mechanism similar to that occurring in C-type inactivation in K ϩ channels (15,19,25,31). Support for this hypothesis comes from studies showing that methanethiosulfonate (MTS) modification in the D3 P-loop of the cysteine-substituted mutant F1236C in rat skeletal muscle Na v 1.4 (rNa v 1.4) increases with some depolarization protocols (27), and that disulfide bond formation between cysteines is enhanced during slow inactivation in the double-cysteine mutant K1237C ϩ W1531C in rNa v 1.4 (4).…”

mentioning

confidence: 99%

Relative resistance to slow inactivation of human cardiac Na⁺ channel hNa_v1.5 is reversed by lysine or glutamine substitution at V930 in D2-S6

Chancey¹,

Shockett²,

O’Reilly³

2007

American Journal of Physiology-Cell Physiology

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Chancey JH, Shockett PE, O'Reilly JP. Relative resistance to slow inactivation of human cardiac Na ϩ channel hNav1.5 is reversed by lysine or glutamine substitution at V930 in D2-S6. Am J Physiol Cell Physiol 293: C1895-C1905, 2007. First published October 10, 2007; doi:10.1152/ajpcell.00377.2007.-Transmembrane segment 6 is implicated in slow inactivation (SI) of voltage-gated Na ϩ channels (Na vs). To further study its role and understand differences between SI phenotypes of different Nav isoforms, we analyzed several domain 2-segment 6 (D2-S6) mutants of the human cardiac hNa v1.5, which is relatively resistant to SI. Mutants were examined by transient HEK cell transfection and patch-clamp recording of whole cell Na ϩ currents. Substitutions with lysine (K) included N927K, V930K, and L931K. We show recovery from short (100 ms) depolarization to 0 mV in N927K and L931K is comparable to wild type, whereas recovery in V930K is delayed and biexponential, suggesting rapid entry into a slow-inactivated state. SI protocols confirm enhanced SI phenotype (rapid development, hyperpolarized steady state, slowed recovery) for V930K, contrasting with the resistant phenotype of wild-type hNav1.5. This enhancement, not found in N927K or L931K, suggests that the effect in V930K is site specific. Glutamine (Q) substituted at V930 also exhibits an enhanced SI phenotype similar to that of V930K. Therefore, K or Q substitution eliminates hNav1.5 resistance to SI. Alanine (A) or cysteine (C) substitution at V930 shows no enhancement of SI, and in fact, V930A and V930C, as well as L931K, exhibit a resistance to SI, demonstrating that characteristics of specific amino acids (e.g., size, hydrophobicity) differentially affect SI gating. Thus V930 in D2-S6 appears to be an important structural determinant of SI gating in hNa v1.5. We suggest that conformational change involving D2-S6 is a critical component of SI in Na vs, which may be differentially regulated between isoforms by other isoformspecific determinants of SI phenotype. sodium channel; voltage gating; site-directed mutagenesis

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C-type inactivation of a voltage-gated K+ channel occurs by a cooperative mechanism

Cited by 159 publications

References 16 publications

A Novel Current Pathway Parallel to the Central Pore in a Mutant Voltage-gated Potassium Channel

A Novel Current Pathway Parallel to the Central Pore in a Mutant Voltage-gated Potassium Channel

A transient outward-rectifying K ⁺ channel current down-regulated by cytosolic Ca ²⁺ in Arabidopsis thaliana guard cells

Relative resistance to slow inactivation of human cardiac Na⁺ channel hNa_v1.5 is reversed by lysine or glutamine substitution at V930 in D2-S6

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C-type inactivation of a voltage-gated K+ channel occurs by a cooperative mechanism

Cited by 159 publications

References 16 publications

A Novel Current Pathway Parallel to the Central Pore in a Mutant Voltage-gated Potassium Channel

A Novel Current Pathway Parallel to the Central Pore in a Mutant Voltage-gated Potassium Channel

A transient outward-rectifying K + channel current down-regulated by cytosolic Ca 2+ in Arabidopsis thaliana guard cells

Relative resistance to slow inactivation of human cardiac Na+ channel hNav1.5 is reversed by lysine or glutamine substitution at V930 in D2-S6

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A transient outward-rectifying K ⁺ channel current down-regulated by cytosolic Ca ²⁺ in Arabidopsis thaliana guard cells

Relative resistance to slow inactivation of human cardiac Na⁺ channel hNa_v1.5 is reversed by lysine or glutamine substitution at V930 in D2-S6