Chapter 8: Membrane Potential Dependence of Gap Junctions in Vertebrates

Barrio, Luis C.; Revilla, Ana; Gómez‐Hernández, Juan M.; Miguel, Marta de; González, Daniel

doi:10.1016/s0070-2161(08)61012-6

Cited by 6 publications

(11 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The G jss ͞V m relation for G242stop-WT junctions was well fit by a single Boltzmann function with parameters close to those used in the squared Boltzmann relation to describe the behavior of homotypic WT junctions (Table 1). This result suggests that the V m dependence of the hybrid junctions was due to the single V m gate contributed by the WT hemichannels, a conclusion previously reported for other hybrid junctions (10,14). Taken together, these results strongly suggest that the CT region between 242-257 contains residues required for V m dependence of RCx43 junctions.…”

Section: Localization Of Molecular Determinants For Vm Gating In the supporting

confidence: 82%

“…In the V m protocols, g jss was normalized to its value at a holding potential of Ϫ100 mV to give G jss , which was plotted as a function of V m . To analyze the V m data, we assumed two independent V j gates in series, one per hemichannel (5,10,14). We also assumed that each gate could be either open or completely closed and that for each gate the steady state probability that it was open, p oss , was given by a Boltzmann relation of the form:…”

Section: Methodsmentioning

confidence: 99%

“…The model presented here may be applicable in whole or in part to other V m -and V j -sensitive gap junctions of vertebrates (11,14). The dependence on V m in some vertebrate junctions is sufficiently great that intercellular coupling could be directly regulated by the membrane potential, a parameter that is always present and that varies, particularly in excitable cells.…”

Section: A Novel Gating Model For Connexin Channels With Combined Vj mentioning

confidence: 99%

“…More recently, g j dependence of V m has also been demonstrated in junctions formed of vertebrate connexins in exogenous expression systems (9)(10)(11) as well as in native cells (12,13). Junctions comprised of different connexin isoforms have divergent properties of V m dependence, varying in their polarity of closing, voltage sensitivity, and kinetics (14).…”

mentioning

confidence: 98%

“…There is increasing evidence that separate gates mediate V m and V j dependence, a hypothesis supported by the striking differences in the gating induced by the two types of potential (14) and by the divergent evolution of their properties among Cx45 junctions in different vertebrate classes (10). Because the junctional conductance of rat Cx43 channels shows sensitivity to V m as well as V j , we chose to study the molecular determinants for V m regulation in these channels.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Molecular determinants of membrane potential dependence in vertebrate gap junction channels

Revilla

Bennett²,

Barrio

2000

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

Self Cite

View full text Add to dashboard Cite

The conductance, gj, of many gap junctions depends on voltage between the coupled cells (transjunctional voltage, Vj) with little effect of the absolute membrane potential (V m) in the two cells; others show combined Vj and Vm dependence. We examined the molecular determinants of V m dependence by using rat connexin 43 expressed in paired Xenopus oocytes. These junctions have, in addition to V j dependence, Vm dependence such that equal depolarization of both cells decreases gj. The dependence of gj on Vm was abolished by truncation of the C-terminal domain (CT) at residue 242 but not at 257. There are two charged residues between 242 and 257. In full-length Cx43, mutations neutralizing either one of these charges, Arg243Gln and Asp245Gln, decreased and increased Vm dependence, respectively, suggesting that these residues are part of the V m sensor. Mutating both residues together abolished Vm dependence, although there is no net change in charge. The neutralizing mutations, together or separately, had no effect on V j dependence. Thus, the voltage sensors must differ. However, V j gating was somewhat modulated by Vm, and Vm gating was reduced when the Vj gate was closed. These data suggest that the two forms of voltage dependence are mediated by separate but interacting domains. G ap junction channels are unique among ionic channels in that they span two cell membranes. They are composed of two hemichannels, one in each membrane, that are tightly docked head to head to form a pore that directly connects the cytoplasm of two cells (1). In vertebrates, gap junctions are formed by connexins (Cx), a gene family of protein subunits (2). Given their architecture, gap junction channels are subject to the influence of two types of voltage, that between the two cell interiors termed transjunctional voltage (V j ), and that between the interior and exterior or the membrane potential (V m ), which can differ between the cells and thus along the lumen of the channel connecting the cells. Many gap junctions are sensitive to V j with little effect of V m , whereas others show combined V j and V m dependence. The eponymous gap is accessible to small ions and because there is negligible leak through the channel wall, the potential in the gap is likely to be close to that in the bathing medium (3). V m dependence of junctional conductance (g j ) was initially described in invertebrate (deuterostome) gap junctions (4-7), which are formed by innexins, a family of proteins unrelated to connexins (8). More recently, g j dependence of V m has also been demonstrated in junctions formed of vertebrate connexins in exogenous expression systems (9-11) as well as in native cells (12,13). Junctions comprised of different connexin isoforms have divergent properties of V m dependence, varying in their polarity of closing, voltage sensitivity, and kinetics (14).V j dependence of vertebrate gap junctions has been extensively analyzed by site-directed mutagenesis (15-18), but the molecular basis of V m gating remains unknown. There is increasin...

show abstract

Section: Localization Of Molecular Determinants For Vm Gating In the supporting

confidence: 82%

Section: Methodsmentioning

confidence: 99%

Section: A Novel Gating Model For Connexin Channels With Combined Vj mentioning

confidence: 99%

mentioning

confidence: 98%

mentioning

confidence: 99%

See 3 more Smart Citations

Molecular determinants of membrane potential dependence in vertebrate gap junction channels

Revilla

Bennett²,

Barrio

2000

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

Self Cite

View full text Add to dashboard Cite

show abstract

Molecular basis of voltage dependence of connexin channels: An integrative appraisal

González

Gómez‐Hernández

Barrio

2007

Progress in Biophysics and Molecular Biology

108

110

View full text Add to dashboard Cite

The importance of electrical and molecular signaling through connexin (Cx) channels is now widely recognized. The transfer of ions and other small molecules between adjacent cells is regulated by multiple stimuli, including voltage. Indeed, Cx channels typically exhibit complex voltage sensitivity. Most channels are sensitive to the voltage difference between the cell interiors (or transjunctional voltage, V(j)), while other channels are also sensitive to absolute inside-outside voltage (i.e., the membrane potential, V(m)). The first part of this review is focused on the description of the distinct forms of voltage sensitivity and the gating mechanisms that regulate hemichannel activity, both individually and as components of homotypic and heterotypic gap junctions. We then provide an up to date and precise picture of the molecular and structural aspects of how V(j) and V(m) are sensed, and how they, therefore, control channel opening and closing. Mutagenic strategies coupled with structural, biochemical and electrophysical studies are providing significant insights into how distinct forms of voltage dependence are brought about. The emerging picture indicates that Cx channels can undergo transitions between multiple conductance states driven by distinct voltage-gating mechanisms. Each hemichannel may contain a set of two V(j) gates, one fast and one slow, which mediate the transitions between the main open state to the residual state and to the fully closed state, respectively. Eventually, a V(m) gate regulates channel transitions between the open and closed states. Clusters of charged residues within separate domains of the Cx molecule have been identified as integral parts of the V(j) and V(m) sensors. The charges at the first positions of the amino terminal cytoplasmic domain determine the magnitude and polarity of the sensitivity to fast V(j)-gating, as well as contributing to the V(j)-rectifying properties of ion permeation. Additionally, important advances have been made in identifying the conformational rearrangements responsible for fast V(j)-gating transitions to the residual state in the Cx43 channel. These changes involve an intramolecular particle-receptor interaction between the carboxy terminal domain and the cytoplasmic loop.

show abstract

Molecular Dissection of Transjunctional Voltage Dependence in the Connexin-32 and Connexin-43 Junctions

Revilla¹,

Castro²,

Barrio³

1999

Biophysical Journal

Self Cite

103

View full text Add to dashboard Cite

Most gap junction channels are sensitive to the voltage difference between the two cellular interiors, termed the transjunctional voltage (V(j)). In several junctions, the conductance transitions induced by V(j) show more than one kinetic component. To elucidate the structural basis of the fast and slow components that characterize the V(j )dependence of connexin-32 (Cx32) and connexin-43 (Cx43) junctions, we created deletions of both connexins, where most of the carboxy-terminal (CT) domain was removed. The wild-type and "tailless" mutants were expressed in paired Xenopus oocytes, and the macroscopic gating properties were analyzed using the dual voltage clamp technique. Truncation of the CT domain of Cx32 and Cx43 abolished the fast mechanism of conductance transitions and induced novel gating properties largely attributable to the slow mechanism of gating. The formation of hybrid junctions comprising wild-type and truncated hemichannels allowed us to infer that the fast and slow components of gating reside in each hemichannel and that both gates close at a negative V(j) on the cytoplasmic side. Thus we conclude that the two kinetic components of V(j)-sensitive conductance are a result of the action of two different gating mechanisms. They constitute separate structures in the Cx32 and Cx43 molecules, the CT domain being an integral part of fast V(j) gating.

show abstract

Chapter 8: Membrane Potential Dependence of Gap Junctions in Vertebrates

Cited by 6 publications

References 35 publications

Molecular determinants of membrane potential dependence in vertebrate gap junction channels

Molecular determinants of membrane potential dependence in vertebrate gap junction channels

Molecular basis of voltage dependence of connexin channels: An integrative appraisal

Molecular Dissection of Transjunctional Voltage Dependence in the Connexin-32 and Connexin-43 Junctions

Contact Info

Product

Resources

About