Molecular determinants of electrical rectification of single channel conductance in gap junctions formed by connexins 26 and 32

Seunghoon Oh, Joshua B. Rubin, Michael V. L. Bennett, Vytautas Verselis, Thaddeus A. Bargiello

Research output: Contribution to journalArticle

110 Citations (Scopus)

Abstract

The fully open state of heterotypic gap junction channels formed by pairing cells expressing connexin 32 (Cx32) with those expressing connexin 26 (Cx26) rectifies in a way that cannot be predicted from the current-voltage (I-V) relation of either homotypic channel. Using a molecular genetic analysis, we demonstrate that charged amino acids positioned in the amino terminus (M1 and D2) and first extracellular loop (E42) are major determinants of the current-voltage relation of the fully open state of homotypic and heterotypic channels formed by Cx26 and Cx32. The observed I-V relations of wild-type and mutant channels were closely approximated by those obtained with the electro-diffusive model of Chen and Eisenberg (Chen, D., and R. Eisenberg. 1993. Biophys. J. 64:1405-1421), which solves the Poisson- Nernst-Plank equations in one dimension using charge distribution models inferred from the molecular analyses. The rectification of the Cx32/Cx26 heterotypic channel results from the asymmetry in the number and position of charged residues. The model required the incorporation of a partial charge located near the channel surface to approximate the linear I-V relation observed for the Cx32*Cx26E1 homotypic channel. The best candidate amino acid providing this partial charge is the conserved tryptophan residue (W3). Incorporation of the partial charge of residue W3 and the negative charge of the Cx32E41 residue into the charge profile used in the Poisson-Nernst-Plank model of homotypic Cx32 and heterotypic Cx26/Cx32 channels resulted in I-V relations that closely resembled the observed I-V relations of these channels. We further demonstrate that some channel substates rectify. We suggest that the conformational changes associated with transjunctional voltage (V(j))-dependent gating to these substates involves a narrowing of the cytoplasmic entry of the channel that increases the electrostatic effect of charges in the amino terminus. The rectification that is observed in the Cx32/Cx26 heterotypic channel is similar although less steep than that reported tot some rectifying electrical synapses. We propose that a similar electrostatic mechanism, which results in rectification through the open and substates of heterotypic channels, is sufficient to explain the properties of steeply rectifying electrical synapses.

Original languageEnglish (US)
Pages (from-to)339-364
Number of pages26
JournalJournal of General Physiology
Volume114
Issue number3
DOIs
StatePublished - 1999

Fingerprint

Gap Junctions
Electrical Synapses
Static Electricity
Amino Acids
Molecular Models
connexin 32
Connexin 26
Tryptophan
Molecular Biology

Keywords

  • Electrical rectification
  • Gap junctions
  • Ion channel
  • Poisson-Nernst-Plank
  • Rectifying electrical synapses

ASJC Scopus subject areas

  • Physiology

Cite this

Molecular determinants of electrical rectification of single channel conductance in gap junctions formed by connexins 26 and 32. / Oh, Seunghoon; Rubin, Joshua B.; Bennett, Michael V. L.; Verselis, Vytautas; Bargiello, Thaddeus A.

In: Journal of General Physiology, Vol. 114, No. 3, 1999, p. 339-364.

Research output: Contribution to journalArticle

@article{d553cf85d5e14417a9aa325d6a12afed,
title = "Molecular determinants of electrical rectification of single channel conductance in gap junctions formed by connexins 26 and 32",
abstract = "The fully open state of heterotypic gap junction channels formed by pairing cells expressing connexin 32 (Cx32) with those expressing connexin 26 (Cx26) rectifies in a way that cannot be predicted from the current-voltage (I-V) relation of either homotypic channel. Using a molecular genetic analysis, we demonstrate that charged amino acids positioned in the amino terminus (M1 and D2) and first extracellular loop (E42) are major determinants of the current-voltage relation of the fully open state of homotypic and heterotypic channels formed by Cx26 and Cx32. The observed I-V relations of wild-type and mutant channels were closely approximated by those obtained with the electro-diffusive model of Chen and Eisenberg (Chen, D., and R. Eisenberg. 1993. Biophys. J. 64:1405-1421), which solves the Poisson- Nernst-Plank equations in one dimension using charge distribution models inferred from the molecular analyses. The rectification of the Cx32/Cx26 heterotypic channel results from the asymmetry in the number and position of charged residues. The model required the incorporation of a partial charge located near the channel surface to approximate the linear I-V relation observed for the Cx32*Cx26E1 homotypic channel. The best candidate amino acid providing this partial charge is the conserved tryptophan residue (W3). Incorporation of the partial charge of residue W3 and the negative charge of the Cx32E41 residue into the charge profile used in the Poisson-Nernst-Plank model of homotypic Cx32 and heterotypic Cx26/Cx32 channels resulted in I-V relations that closely resembled the observed I-V relations of these channels. We further demonstrate that some channel substates rectify. We suggest that the conformational changes associated with transjunctional voltage (V(j))-dependent gating to these substates involves a narrowing of the cytoplasmic entry of the channel that increases the electrostatic effect of charges in the amino terminus. The rectification that is observed in the Cx32/Cx26 heterotypic channel is similar although less steep than that reported tot some rectifying electrical synapses. We propose that a similar electrostatic mechanism, which results in rectification through the open and substates of heterotypic channels, is sufficient to explain the properties of steeply rectifying electrical synapses.",
keywords = "Electrical rectification, Gap junctions, Ion channel, Poisson-Nernst-Plank, Rectifying electrical synapses",
author = "Seunghoon Oh and Rubin, {Joshua B.} and Bennett, {Michael V. L.} and Vytautas Verselis and Bargiello, {Thaddeus A.}",
year = "1999",
doi = "10.1085/jgp.114.3.339",
language = "English (US)",
volume = "114",
pages = "339--364",
journal = "Journal of General Physiology",
issn = "0022-1295",
publisher = "Rockefeller University Press",
number = "3",

}

TY - JOUR

T1 - Molecular determinants of electrical rectification of single channel conductance in gap junctions formed by connexins 26 and 32

AU - Oh, Seunghoon

AU - Rubin, Joshua B.

AU - Bennett, Michael V. L.

AU - Verselis, Vytautas

AU - Bargiello, Thaddeus A.

PY - 1999

Y1 - 1999

N2 - The fully open state of heterotypic gap junction channels formed by pairing cells expressing connexin 32 (Cx32) with those expressing connexin 26 (Cx26) rectifies in a way that cannot be predicted from the current-voltage (I-V) relation of either homotypic channel. Using a molecular genetic analysis, we demonstrate that charged amino acids positioned in the amino terminus (M1 and D2) and first extracellular loop (E42) are major determinants of the current-voltage relation of the fully open state of homotypic and heterotypic channels formed by Cx26 and Cx32. The observed I-V relations of wild-type and mutant channels were closely approximated by those obtained with the electro-diffusive model of Chen and Eisenberg (Chen, D., and R. Eisenberg. 1993. Biophys. J. 64:1405-1421), which solves the Poisson- Nernst-Plank equations in one dimension using charge distribution models inferred from the molecular analyses. The rectification of the Cx32/Cx26 heterotypic channel results from the asymmetry in the number and position of charged residues. The model required the incorporation of a partial charge located near the channel surface to approximate the linear I-V relation observed for the Cx32*Cx26E1 homotypic channel. The best candidate amino acid providing this partial charge is the conserved tryptophan residue (W3). Incorporation of the partial charge of residue W3 and the negative charge of the Cx32E41 residue into the charge profile used in the Poisson-Nernst-Plank model of homotypic Cx32 and heterotypic Cx26/Cx32 channels resulted in I-V relations that closely resembled the observed I-V relations of these channels. We further demonstrate that some channel substates rectify. We suggest that the conformational changes associated with transjunctional voltage (V(j))-dependent gating to these substates involves a narrowing of the cytoplasmic entry of the channel that increases the electrostatic effect of charges in the amino terminus. The rectification that is observed in the Cx32/Cx26 heterotypic channel is similar although less steep than that reported tot some rectifying electrical synapses. We propose that a similar electrostatic mechanism, which results in rectification through the open and substates of heterotypic channels, is sufficient to explain the properties of steeply rectifying electrical synapses.

AB - The fully open state of heterotypic gap junction channels formed by pairing cells expressing connexin 32 (Cx32) with those expressing connexin 26 (Cx26) rectifies in a way that cannot be predicted from the current-voltage (I-V) relation of either homotypic channel. Using a molecular genetic analysis, we demonstrate that charged amino acids positioned in the amino terminus (M1 and D2) and first extracellular loop (E42) are major determinants of the current-voltage relation of the fully open state of homotypic and heterotypic channels formed by Cx26 and Cx32. The observed I-V relations of wild-type and mutant channels were closely approximated by those obtained with the electro-diffusive model of Chen and Eisenberg (Chen, D., and R. Eisenberg. 1993. Biophys. J. 64:1405-1421), which solves the Poisson- Nernst-Plank equations in one dimension using charge distribution models inferred from the molecular analyses. The rectification of the Cx32/Cx26 heterotypic channel results from the asymmetry in the number and position of charged residues. The model required the incorporation of a partial charge located near the channel surface to approximate the linear I-V relation observed for the Cx32*Cx26E1 homotypic channel. The best candidate amino acid providing this partial charge is the conserved tryptophan residue (W3). Incorporation of the partial charge of residue W3 and the negative charge of the Cx32E41 residue into the charge profile used in the Poisson-Nernst-Plank model of homotypic Cx32 and heterotypic Cx26/Cx32 channels resulted in I-V relations that closely resembled the observed I-V relations of these channels. We further demonstrate that some channel substates rectify. We suggest that the conformational changes associated with transjunctional voltage (V(j))-dependent gating to these substates involves a narrowing of the cytoplasmic entry of the channel that increases the electrostatic effect of charges in the amino terminus. The rectification that is observed in the Cx32/Cx26 heterotypic channel is similar although less steep than that reported tot some rectifying electrical synapses. We propose that a similar electrostatic mechanism, which results in rectification through the open and substates of heterotypic channels, is sufficient to explain the properties of steeply rectifying electrical synapses.

KW - Electrical rectification

KW - Gap junctions

KW - Ion channel

KW - Poisson-Nernst-Plank

KW - Rectifying electrical synapses

UR - http://www.scopus.com/inward/record.url?scp=0032888052&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032888052&partnerID=8YFLogxK

U2 - 10.1085/jgp.114.3.339

DO - 10.1085/jgp.114.3.339

M3 - Article

C2 - 10469726

AN - SCOPUS:0032888052

VL - 114

SP - 339

EP - 364

JO - Journal of General Physiology

JF - Journal of General Physiology

SN - 0022-1295

IS - 3

ER -