Biophysical properties of gap junction channels formed by mouse connexin40 in induced pairs of transfected human HeLa cells

Bukauskas, Feliksas F.; Elfgang, Claudia; Willecke, Klaus; Weingart, Robert

doi:10.1016/s0006-3495(95)80411-x

Cited by 200 publications

(208 citation statements)

References 23 publications

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“…NIH-PA Author Manuscript NIH-PA Author Manuscript opened, increased current was seen in the cell held at a more positive potential and decreased (more negative) current was seen in the other cell, but the sum of the currents clamping the two cells remained constant [7]. Thus, there was no change in the current flowing into the extracellular space, and the hemichannels were closed before opening to form a cell-cell channel.…”

Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

“…The permeability and/or currents are inhibited by gap-junction blockers [10][11][12][13][14] (although most of the blockers are of dubious specificity). The pathway is permeable to larger molecules than is the 'normal' surface membrane, as are gap-junction channels [10][11][12][13][14] (but there are P2X 7 receptors and mechanosensitive channels that let through larger molecules, including several of the gap-junction-permeant species [20,21]). The volume of this evidence is substantial, but it is still possible to doubt the existence of hemichannels.…”

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

“…Now, refined methods of labeling indicate that new channels are transported to the surface in an undirected manner and reach existing junctions by lateral diffusion, where they form new channels at their periphery [29,30]; channels being retired are removed from the interior of the junction [29]. This picture does not address the question of the initial formation of junctions [7]. Remarkably, gap junctions are internalized, piecemeal or in their entirety, with both junctional faces entering one of the cells.…”

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

“…What is striking about these observations is that significant release was observed at Ca 2+ levels that might well occur under conditions of ischemia, seizures or spreading depression. It will be of interest to evaluate Cx43-deficient astrocytes for glutamate release, but the other obvious suspects, reverse operation of the uptake system and P2X 7 receptors, have been excluded pharmacologically. A low-Ca 2+ solution was shown to induce release of glutamate from optic nerve (which contains astrocytes and axons but no neuronal cell bodies or synaptic terminals).…”

Section: Hemichannels In the Cnsmentioning

confidence: 99%

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New roles for astrocytes: Gap junction hemichannels have something to communicate

Bennett

Contreras

Bukauskas

et al. 2003

Trends in Neurosciences

376

279

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Gap junctions are clusters of aqueous channels that connect the cytoplasm of adjoining cells. Each cell contributes a hemichannel, or connexon, to each cell-cell channel. The cell-cell channels are permeable to relatively large molecules, and it was thought that opening of hemichannels to the extracellular space would kill cells through loss of metabolites, collapse of ionic gradients and influx of Ca 2+ . Recent findings indicate that specific non-junctional hemichannels do open under both physiological and pathological conditions, and that opening is functional or deleterious depending on the situation. Most of these studies utilized cells in tissue culture that expressed a specific gap junction protein, connexin 43. Several such examples are reviewed here, with a particular focus on astrocytes.Gap junctions mediate intercellular communication by providing ultrastructural cytoplasmic continuity, and they are integral to formation of the functional syncytium of astrocytes. Each of the joined cells contributes a hemichannel or connexon to each cell-cell channel ( Figure 1; Box 1). Each hemichannel comprises a hexamer of connexins arranged around a central pore, and the cell-cell channels are gated by several stimuli, including transjunctional voltage, low pH and various pharmacological agents. Connexins are encoded by a gene family with at least 20 members in mammals [1].Gap-junction pores are nominally 1.0-1.5 nm in diameter and are permeable to molecules of 1 kDa [2]. Junctions formed from connexin 43 (Cx43), the predominant connexin in astrocytes, are permeable to Lucifer Yellow (443 Da, −2 charge) and propidium (420 Da, +2 charge). Other connexins appear to be more charge selective: Cx32 is more permeable to anions and Cx45 is more permeable to cations [2]. Single-channel conductance varies widely, from ~15 pS for Cx36 [3] and 110 pS for Cx43 [4] to ~375 pS for Cx37 [5]. The maximum size of permeant species also varies. Such diversity in selectivity and conductance are likely to account for the expansion of the connexin family. Why shouldn't hemichannels be open?Given the permeability and conductance of gap junctions, and the expectation that an open hemichannel would have twice the conductance and permeability of a cell-cell channel (in terms of ion or molecular flux, rather than selectivity), it was thought unlikely that hemichannels in the non-junctional membrane would open [6]. Direct evidence for this was provided by measurements during formation of the first channel between a newly apposed pair of cells. Each cell was held at a different potential, and then when the first channel NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript opened, increased current was seen in the cell held at a more positive potential and decreased (more negative) current was seen in the other cell, but the sum of the currents clamping the two cells remained constant [7]. Thus, there was no change in the current flowing into the extracellular space, and the hemichannels were closed before openin...

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Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

Section: Hemichannels In the Cnsmentioning

confidence: 99%

See 2 more Smart Citations

New roles for astrocytes: Gap junction hemichannels have something to communicate

Bennett

Contreras

Bukauskas

et al. 2003

Trends in Neurosciences

376

279

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show abstract

“…When individually expressed in transfected cells, gap junction channels composed of each connexin isotype display diverse functional properties [1,15,25].…”

Section: Introductionmentioning

confidence: 99%

Functional consequences of co-expressing connexin40 or connexin45 with connexin43 on intercellular electrical coupling

Thomas

Gray

Fry

et al. 2017

Biochemical and Biophysical Research Communications

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The functional characteristics of the co-expression of connexin43, connexin40, and connexin45 proteins in human myocardium are thought to play an important role in governing normal propagation of the cardiac electrical impulse and in generating the myocardial substrate for some arrhythmias and conduction disturbances.A rat liver epithelial cell line, that endogenously expresses connexin43, was used to induce also expression of connexin40 or connexin45 after stable transfection using an inducible ecdysone system. Electrical coupling was estimated from measurement of the input resistance of transfected cells using an intracellular microelectrode to inject current and record changes to membrane potential.However, varied expression of the transfected connexin40 or connexin45 did not change electrical coupling, although connexin43/40 co-expression led to better coupling than connexin43/45 co-expression. Quantification of endogenous connexin43 expression, at both mRNA and protein levels, showed that it was altered in a manner dependent on the transfected connexin isotype.The data using rat liver epithelial cells indicate an increased electrical coupling upon expression of connexin40 and connexin43 but decreased coupling with connexin45 and connexin43 co-expression.

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Functional properties, developmental regulation, and chromosomal localization of murine connexin36, a gap‐junctional protein expressed preferentially in retina and brain

et al. 2000

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Retinal neurons of virtually every type are coupled by gap-junctional channels whose pharmacological and gating properties have been studied extensively. We have begun to identify the molecular composition and functional properties of the connexins that form these 'electrical synapses,' and have cloned several that constitute a new subclass (gamma) of the connexin family expressed predominantly in retina and brain. In this paper, we present a series of experiments characterizing connexin36 (Cx36), a member of the gamma subclass that was cloned from a mouse retinal cDNA library. Cx36 has been localized to mouse chromosome 2, in a region syntenic to human chromosome 5, and immunocytochemistry showed strong labeling in the ganglion cell and inner nuclear layers of the mouse retina. Comparison of the developmental time course of Cx36 expression in mouse retina with the genesis of the various classes of retinal cells suggests that the expression of Cx36 occurs primarily after cellular differentiation is complete. Because photic stimulation can affect the gap-junctional coupling between retinal neurons, we determined whether lighting conditions might influence the steady state levels of Cx36 transcript in the mouse retina. Steady-state levels of Cx36 transcript were significantly higher in animals reared under typical cyclic-light conditions; exposure either to constant darkness or to continuous illumination reduced the steady-state level of mRNA approximately 40%. Injection of Cx36 cRNA into pairs of Xenopus oocytes induced intercellular conductances that were relatively insensitive to transjunctional voltage, a property shared with other members of the gamma subclass of connexins. Like skate Cx35, mouse Cx36 was unable to form heterotypic gap-junctional channels when paired with two other rodent connexins. In addition, mouse Cx36 failed to form voltage-activated hemichannels, whereas both skate and perch Cx35 displayed quinine-sensitive hemichannel activity. The conservation of intercellular channel gating contrasts with the failure of Cx36 to make hemichannels, suggesting that the voltage-gating mechanisms of hemichannels may be distinct from those of intact intercellular channels.

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Biophysical properties of gap junction channels formed by mouse connexin40 in induced pairs of transfected human HeLa cells

Cited by 200 publications

References 23 publications

New roles for astrocytes: Gap junction hemichannels have something to communicate

New roles for astrocytes: Gap junction hemichannels have something to communicate

Functional consequences of co-expressing connexin40 or connexin45 with connexin43 on intercellular electrical coupling

Functional properties, developmental regulation, and chromosomal localization of murine connexin36, a gap‐junctional protein expressed preferentially in retina and brain

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