S4 Movement in a Mammalian HCN Channel

Sriharsha Vemana, Shilpi Pandey, Hans P Larsson

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

Hyperpolarization-activated, cyclic nucleotide-gated ion channels (HCN) mediate an inward cation current that contributes to spontaneous rhythmic firing activity in the heart and the brain. HCN channels share sequence homology with depolarization-activated Kv channels, including six transmembrane domains and a positively charged S4 segment. S4 has been shown to function as the voltage sensor and to undergo a voltage-dependent movement in the Shaker K+ channel (a Kv channel) and in the spHCN channel (an HCN channel from sea urchin). However, it is still unknown whether S4 undergoes a similar movement in mammalian HCN channels. In this study, we used cysteine accessibility to determine whether there is voltage-dependent S4 movement in a mammalian HCN1 channel. Six cysteine mutations (R247C, T249C, I251C, S253C, L254C, and S261C) were used to assess S4 movement of the heterologously expressed HCN1 channel in Xenopus oocytes. We found a state-dependent accessibility for four S4 residues: T249C and S253C from the extracellular solution, and L254C and S261C from the internal solution. We conclude that S4 moves in a voltage-dependent manner in HCN1 channels, similar to its movement in the spHCN channel. This S4 movement suggests that the role of S4 as a voltage sensor is conserved in HCN channels. In addition, to determine the reason for the different cAMP modulation and the different voltage range of activation in spHCN channels compared with HCN1 channels, we constructed a COOH-terminal-deleted spHCN. This channel appeared to be similar to a COOH-terminal-deleted HCN1 channel, suggesting that the main functional differences between spHCN and HCN1 channels are due to differences in their COOH termini or in the interaction between the COOH terminus and the rest of the channel protein in spHCN channels compared with HCN1 channels.

Original languageEnglish
Pages (from-to)21-32
Number of pages12
JournalJournal of General Physiology
Volume123
Issue number1
DOIs
StatePublished - Jan 1 2004
Externally publishedYes

Fingerprint

Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
Cysteine
Sea Urchins
Sequence Homology
Xenopus
Oocytes
Cations

Keywords

  • Cysteine accessibility
  • Hyperpolarization activated
  • SPIH
  • Voltage sensor

ASJC Scopus subject areas

  • Physiology

Cite this

S4 Movement in a Mammalian HCN Channel. / Vemana, Sriharsha; Pandey, Shilpi; Larsson, Hans P.

In: Journal of General Physiology, Vol. 123, No. 1, 01.01.2004, p. 21-32.

Research output: Contribution to journalArticle

Vemana, Sriharsha ; Pandey, Shilpi ; Larsson, Hans P. / S4 Movement in a Mammalian HCN Channel. In: Journal of General Physiology. 2004 ; Vol. 123, No. 1. pp. 21-32.
@article{9480b25b2c92409aa6d176904d7e6a3c,
title = "S4 Movement in a Mammalian HCN Channel",
abstract = "Hyperpolarization-activated, cyclic nucleotide-gated ion channels (HCN) mediate an inward cation current that contributes to spontaneous rhythmic firing activity in the heart and the brain. HCN channels share sequence homology with depolarization-activated Kv channels, including six transmembrane domains and a positively charged S4 segment. S4 has been shown to function as the voltage sensor and to undergo a voltage-dependent movement in the Shaker K+ channel (a Kv channel) and in the spHCN channel (an HCN channel from sea urchin). However, it is still unknown whether S4 undergoes a similar movement in mammalian HCN channels. In this study, we used cysteine accessibility to determine whether there is voltage-dependent S4 movement in a mammalian HCN1 channel. Six cysteine mutations (R247C, T249C, I251C, S253C, L254C, and S261C) were used to assess S4 movement of the heterologously expressed HCN1 channel in Xenopus oocytes. We found a state-dependent accessibility for four S4 residues: T249C and S253C from the extracellular solution, and L254C and S261C from the internal solution. We conclude that S4 moves in a voltage-dependent manner in HCN1 channels, similar to its movement in the spHCN channel. This S4 movement suggests that the role of S4 as a voltage sensor is conserved in HCN channels. In addition, to determine the reason for the different cAMP modulation and the different voltage range of activation in spHCN channels compared with HCN1 channels, we constructed a COOH-terminal-deleted spHCN. This channel appeared to be similar to a COOH-terminal-deleted HCN1 channel, suggesting that the main functional differences between spHCN and HCN1 channels are due to differences in their COOH termini or in the interaction between the COOH terminus and the rest of the channel protein in spHCN channels compared with HCN1 channels.",
keywords = "Cysteine accessibility, Hyperpolarization activated, SPIH, Voltage sensor",
author = "Sriharsha Vemana and Shilpi Pandey and Larsson, {Hans P}",
year = "2004",
month = "1",
day = "1",
doi = "10.1085/jgp.200308916",
language = "English",
volume = "123",
pages = "21--32",
journal = "Journal of General Physiology",
issn = "0022-1295",
publisher = "Rockefeller University Press",
number = "1",

}

TY - JOUR

T1 - S4 Movement in a Mammalian HCN Channel

AU - Vemana, Sriharsha

AU - Pandey, Shilpi

AU - Larsson, Hans P

PY - 2004/1/1

Y1 - 2004/1/1

N2 - Hyperpolarization-activated, cyclic nucleotide-gated ion channels (HCN) mediate an inward cation current that contributes to spontaneous rhythmic firing activity in the heart and the brain. HCN channels share sequence homology with depolarization-activated Kv channels, including six transmembrane domains and a positively charged S4 segment. S4 has been shown to function as the voltage sensor and to undergo a voltage-dependent movement in the Shaker K+ channel (a Kv channel) and in the spHCN channel (an HCN channel from sea urchin). However, it is still unknown whether S4 undergoes a similar movement in mammalian HCN channels. In this study, we used cysteine accessibility to determine whether there is voltage-dependent S4 movement in a mammalian HCN1 channel. Six cysteine mutations (R247C, T249C, I251C, S253C, L254C, and S261C) were used to assess S4 movement of the heterologously expressed HCN1 channel in Xenopus oocytes. We found a state-dependent accessibility for four S4 residues: T249C and S253C from the extracellular solution, and L254C and S261C from the internal solution. We conclude that S4 moves in a voltage-dependent manner in HCN1 channels, similar to its movement in the spHCN channel. This S4 movement suggests that the role of S4 as a voltage sensor is conserved in HCN channels. In addition, to determine the reason for the different cAMP modulation and the different voltage range of activation in spHCN channels compared with HCN1 channels, we constructed a COOH-terminal-deleted spHCN. This channel appeared to be similar to a COOH-terminal-deleted HCN1 channel, suggesting that the main functional differences between spHCN and HCN1 channels are due to differences in their COOH termini or in the interaction between the COOH terminus and the rest of the channel protein in spHCN channels compared with HCN1 channels.

AB - Hyperpolarization-activated, cyclic nucleotide-gated ion channels (HCN) mediate an inward cation current that contributes to spontaneous rhythmic firing activity in the heart and the brain. HCN channels share sequence homology with depolarization-activated Kv channels, including six transmembrane domains and a positively charged S4 segment. S4 has been shown to function as the voltage sensor and to undergo a voltage-dependent movement in the Shaker K+ channel (a Kv channel) and in the spHCN channel (an HCN channel from sea urchin). However, it is still unknown whether S4 undergoes a similar movement in mammalian HCN channels. In this study, we used cysteine accessibility to determine whether there is voltage-dependent S4 movement in a mammalian HCN1 channel. Six cysteine mutations (R247C, T249C, I251C, S253C, L254C, and S261C) were used to assess S4 movement of the heterologously expressed HCN1 channel in Xenopus oocytes. We found a state-dependent accessibility for four S4 residues: T249C and S253C from the extracellular solution, and L254C and S261C from the internal solution. We conclude that S4 moves in a voltage-dependent manner in HCN1 channels, similar to its movement in the spHCN channel. This S4 movement suggests that the role of S4 as a voltage sensor is conserved in HCN channels. In addition, to determine the reason for the different cAMP modulation and the different voltage range of activation in spHCN channels compared with HCN1 channels, we constructed a COOH-terminal-deleted spHCN. This channel appeared to be similar to a COOH-terminal-deleted HCN1 channel, suggesting that the main functional differences between spHCN and HCN1 channels are due to differences in their COOH termini or in the interaction between the COOH terminus and the rest of the channel protein in spHCN channels compared with HCN1 channels.

KW - Cysteine accessibility

KW - Hyperpolarization activated

KW - SPIH

KW - Voltage sensor

UR - http://www.scopus.com/inward/record.url?scp=0346041553&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0346041553&partnerID=8YFLogxK

U2 - 10.1085/jgp.200308916

DO - 10.1085/jgp.200308916

M3 - Article

C2 - 14676284

AN - SCOPUS:0346041553

VL - 123

SP - 21

EP - 32

JO - Journal of General Physiology

JF - Journal of General Physiology

SN - 0022-1295

IS - 1

ER -