Connexin-43 Hemichannels Opened by Metabolic Inhibition

John, Scott A.; Kondo, Richard P.; Wang, Shengyong; Goldhaber, Joshua I.; Weiss, James N.

doi:10.1074/jbc.274.1.236

Cited by 244 publications

(300 citation statements)

References 23 publications

Supporting

Mentioning

286

Contrasting

Unclassified

Order By: Relevance

“…Macroscopically, the existence of hemichannels was initially inferred from a non-selective conductance that depended on exogenous expression of Cx46 in Xenopus oocytes. Now, there are many other examples in which cells expressing connexins endogenously or by transfection develop permeability or macroscopic currents consistent with expression of hemichannels [10][11][12][13][14]. Conversely, cells from connexin knockout animals do not show these properties, even though wild-type cells do [12,14].…”

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

“…(However, connexin transfection can induce changes in the expression of many other genes [15], and connexins have binding partners and might transport other channel molecules to the cell surface [16][17][18][19].) 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]).…”

Section: So Are These Really Hemichannel Currents?mentioning

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%

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

377

279

View full text Add to dashboard Cite

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...

show abstract

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

Section: So Are These Really Hemichannel Currents?mentioning

confidence: 99%

See 1 more Smart Citation

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

Bennett

Contreras

Bukauskas

et al. 2003

Trends in Neurosciences

377

279

View full text Add to dashboard Cite

show abstract

“…Saez et al [11] reported that hypertonic stimulation induced Cx43 hemichannels opening. They indicated that Cx43 hemichannels were opened when the isomotic pressure between the internal and the external cells lost their balance; on the contrary, the hemichannels were closed when the isomotic pressure between the internal and the external cells reached balance [20] .…”

Section: Discussionmentioning

confidence: 99%

Hypertonic stimulation induces synthesis and release of glutamate in cultured rat hypothalamic astrocytes and C6 cells

et al. 2008

View full text Add to dashboard Cite

Objective To investigate whether hypertonic saline (HS) can induce the synthesis and release of glutamate in cultured hypothalamic astrocytes or C6 cell line. Methods Astrocytes were isolated, cultured, purified and identified from the hypothalamus of newborn rat (1 day). The astrocytes were randomly divided into five groups: isotonic (IS) and HS groups, astrocytes were incubated by IS and HS (320 mOsm NaCl) medium, respectively, for 1, 3, 5, 10 or 15 min; carbenoxolone (CBX) +IS and CBX+HS groups, astrocytes were pre-treated with CBX (100 mmol/L) for 1 h at 37 ºC in a 5% CO2 / 95% atmosphere, then removed to IS and HS medium, respectively, for 1, 3, 5, 10 or 15 min; Ca 2+ +HS group, astrocytes were pre-incubated with Ca 2+ (1 000 μmol/L) for 1 h at 37 ºC in a 5% CO 2 / 95% atmosphere, followed by a wash with isotonic FBS/DMEM, and then removed to hypertonic saline for 1, 3, 5, 10 or 15 min. The media of five groups were collected to analyze the medium glutamate concentration with high performance liquid chromatography. The astrocytes were fixed and double immunofluorescent stained with anti-glial fibrillary acidic protein (GFAP) and anti-glutamate. The C6 cells were divided into four groups: IS, HS, CBX+IS and CBX+HS groups, and used for quantitative measurement of glutamate in cells by flow cytometry (FCM). Results (1) Anti-GFAP immunofluorescent signal revealed no significant difference among various time points in each group, or among the five groups. (2) The anti-glutamate immunofluorescent signal was increased in HS group and peaked at 5 min, and decreased and returned to the level of IS group at 15 min (P < 0.01 vs the 5 min of HS group). In CBX+HS group, the glutamate intensity was higher than that in CBX+IS and HS groups. (3) The medium glutamate concentration had no change after treatment with HS for 1 and 3 min, while increased markedly after treatment for 5 min to 15 min (P < 0.01 vs 1 min and 3 min). On the contrary, the medium glutamate concentrations in the CBX+HS or Ca 2+ +HS group were significant lower than that in the HS group (P < 0.01). (4) FCM showed HS and CBX+HS induced glutamate increase in C6 cells. Conclusion HS induced cultured rat hypothalamic astrocytes or C6 cells to synthesize and release glutamate; CBX could block glutamate release, but could not disrupt glutamate synthesis.

show abstract

“…Specifically, Cx43 hemichannels have been suggested to form large conductance anion channels in myoblasts (4) and to constitute a class of "suicide channels" in macrophages (5). Cx43 hemichannels have been considered responsible for dye uptake and increased cell death upon metabolic inhibition of astrocytes (6) and cardiac myocytes (7). Additionally, Cx43 hemichannels have been reported to provide pores for ATP release (8) as well as glutamate and aspartate efflux in astrocytes (9).…”

Section: Introductionmentioning

confidence: 99%

Following Tracks of Hemichannels

Dermietzel

Meier

Bukauskas

et al. 2003

Cell Communication & Adhesion

View full text Add to dashboard Cite

It has been suggested that plasma membrane-bound hemichannels perform physiological and pathophysiological functions per se. Such functions require the presence of hemichannels on the cell surface and their accessibility to the extracellular environment for at least some limited period of time. We have previously shown that hemichannels can be labeled by means of antibodies directed to an external loop domain of connexin (Cx) 43 (1). We now provide evidence that trafficking of hemichannel vesicles can be visualized upon binding of a labeled homophilic peptide corresponding to a region of the first extracellular loop (EL1) of Cx43.In vivo imaging was performed after labeling hemichannels from the extracellular site with a mimetic peptide tagged with a fluorochrome (Alexa-546). Using a Cx43-CFP transfected HeLa cell line for incubation with the mimetic peptide, a significant number of double-labeled vesicles were found inside the cells. This double labeling indicates that a portion of Cx43 within the cell had accessed the cell surface as hemichannels where it bound to the peptide and was subsequently endocytosed. Pulse labeling with the peptide showed a decrease in the number of dual-labeled vesicles over time, indicating degradation and/or concurrent recycling of hemichannel vesicles.

show abstract

Connexin-43 Hemichannels Opened by Metabolic Inhibition

Cited by 244 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

Hypertonic stimulation induces synthesis and release of glutamate in cultured rat hypothalamic astrocytes and C6 cells

Following Tracks of Hemichannels

Contact Info

Product

Resources

About