Formation of gap junctions by expression of connexins in Xenopus oocyte pairs

Swenson, Kirsten G.; Jordan, John R.; Beyer, Eric C.; Paul, David L.

doi:10.1016/0092-8674(89)90180-3

Cited by 313 publications

(226 citation statements)

References 52 publications

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“…Paired oocytes often exhibited high levels of endogenous coupling. Junctional conductance between water-injected oocytes sometimes reached 25 gS at 24-48 hr after pairing, 2 orders of magnitude higher than previously reported (6,11,12,27) but close to that between pairs injected with rat Cx43 in one oocyte and with water into the other (12), where endogenous Cx38 is presumably expressed by the water-injected cell. Endogenous gj was voltage dependent and, as in amphibian blastomeres, was only affected by transjunctional voltage; gj decreased symmetrically for depolarizing and hyperpolarizing steps applied to either cell.…”

supporting

confidence: 61%

“…The value of z is the same as that for Cx26/Cx26 junctions, which would be expected if transjunctional voltage dependence closed the series gate on the positive side, as seen in other systems (12,30), and if slow gating of the Cx26 hemichannel were similar to that in homotypic Cx26/Cx26 junctions. Also, the VO is closer to that of Cx26/Cx26 junctions than to that of Cx32/Cx32 junctions.…”

mentioning

confidence: 57%

“…In several invertebrate cases gj is sensitive to both Vi, and Vj (15,21 (6,11,12). It has also been used to indicate that heterotypic junctions can be formed, in particular between rat Cx43 and Xenopus Cx38 (11,12).…”

mentioning

confidence: 99%

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Gap junctions formed by connexins 26 and 32 alone and in combination are differently affected by applied voltage.

Barrio

Suchyna

Bargiello

et al. 1991

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

322

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confidence: 61%

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confidence: 57%

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Gap junctions formed by connexins 26 and 32 alone and in combination are differently affected by applied voltage.

Barrio

Suchyna

Bargiello

et al. 1991

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

322

202

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“…Methods for oocyte isolation, injection and pairing were essentially as previously described (Swenson et al, 1989;Phelan et al, 1998a). Cells were preinjected with 20 ng Cx38 DNA antisense oligonucleotides (5Ј-CTGACTGCTCGTCTGTCCACACAG-3Ј), 24 h before the injection of 2-20 ng innexin mRNA in 18.4 nl H 2 O or H 2 O only (Barrio et al, 1991).…”

Section: Expression In the Paired Xenopus Oocyte Systemmentioning

confidence: 99%

“…This raises the possibility that innexins, like connexins, form mixed junctions with a different type of hemi-channel in each membrane (heterotypic channels) (Swenson et al, 1989;Werner et al, 1989;Barrio et al, 1991; reviewed in Bruzzone et al, 1996) or with more than one type of innexin in each hemi-channel (heteromeric channels) (Stauffer, 1995;Jiang and Goodenough, 1996;Lee and Rhee, 1998; Ebihara et al, 1999;He et al, 1999). In view of the large number of innexins identified and the overlapping expression patterns of those that have been investigated so far (Crompton et al, 1995;Curtin et al, 1999), the occurrence of mixed channels seems likely.…”

Section: Introductionmentioning

confidence: 99%

TwoDrosophilaInnexins Are Expressed in Overlapping Domains and Cooperate to Form Gap-Junction Channels

Stebbings

Todman

Phelan

et al. 2000

MBoC

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Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes, Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notably in epidermal cells bordering each segment. We also explore the gap-junction-forming capabilities of the encoded proteins. In paired Xenopus oocytes, the injection of Dm-inx2 mRNA results in the formation of voltage-sensitive channels in only ϳ 40% of cell pairs. In contrast, Dm-Inx3 never forms channels. Crucially, when both mRNAs are coexpressed, functional channels are formed reliably, and the electrophysiological properties of these channels distinguish them from those formed by Dm-Inx2 alone. We relate these in vitro data to in vivo studies. Ectopic expression of Dm-inx2 in vivo has limited effects on the viability of Drosophila, and animals ectopically expressing Dm-inx3 are unaffected. However, ectopic expression of both transcripts together severely reduces viability, presumably because of the formation of inappropriate gap junctions. We conclude that Dm-Inx2 and Dm-Inx3, which are expressed in overlapping domains during embryogenesis, can form oligomeric gap-junction channels. INTRODUCTIONGap-junction channels allow small molecules and ions to pass between cells, thus mediating processes such as electrical coupling, maintenance of homeostasis, and cell-cell signaling (reviewed in Bruzzone et al., 1996). In vertebrates, these channels are composed of proteins called connexins. Six connexins associate to form a hexameric ring structure (connexon) in the plasma membrane that intercellularly docks with a corresponding connexon in an adjacent cell to form a continuous channel linking the cytoplasms (Yeager and Nicholson, 1996;Unger et al., 1999). Despite the fact that gap junctions are also found throughout invertebrate tissues, no connexins have been identified in the Caenorhabditis elegans or Drosophila genomes, for which near complete sequence data are available (Wilson, 1999; Flybase website: http://fly.ebi.ac.uk:7081/).It has recently been shown that invertebrate gap-junction channels are composed of proteins now named innexins (Phelan et al., 1998a,b;Landesman et al., 1999; reviewed in Phelan, 2000). These bear no sequence homology to the connexins but possess an identical predicted topology of four transmembrane domains and intracellular N-and Ctermini (Crompton et al., 1995;Starich et al., 1996).Innexin genes have been identified in several invertebrates. C. elegans has at least 24 innexins (Barnes and Hekimi, 1997), but few of these genes have been investigated in detail. Mutations in the unc-7 and unc-9 genes result in uncoordinated phenotypes (Starich et al., 1993(Starich et al., , 1996Barnes and Hekimi, 1997), and in eat-5 mutants electrical and dye coupling are abolished between some pharyngeal muscle cells, leading to feeding defects (Avery, 1993;Starich et al., 1996). In Drosophila, five innexi...

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Gap junctions in the adult cerebral cortex: Regional differences in their distribution and cellular expression of connexins

et al. 1996

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Gap junctions are membrane channels that mediate electrical and metabolic coupling between adjacent cells. Immunocytochemical analysis by using a panel of anti-connexin antibodies, as well as electron microscopy of thin sections and freeze-fracture replicas, has shown that gap junctions and their constituent proteins are abundant in the cerebral cortex of the adult rat. Their frequency and distribution vary in different cortical regions, which may reflect differences in the cellular and functional organization of these areas of the cortex. Gap junctions were identified between glial cells and, less frequently, between neuronal elements. Heterologous junctions were also identified between astrocytes and oligodendrocytes and between neurons and glia; the latter category included abundant junctions between astrocytic processes and neurons. Double-antibody labelling experiments in tissue sections and in acutely dissociated cells showed that connexin 32 was expressed in neurons and oligodendrocytes, whereas connexin 43, widely believed to be expressed only in astrocytes, was also localized in a population of cortical neurons. These results show that gap junctions can provide a major nonsynaptic means of communication between cortical cell types.

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Formation of gap junctions by expression of connexins in Xenopus oocyte pairs

Cited by 313 publications

References 52 publications

Gap junctions formed by connexins 26 and 32 alone and in combination are differently affected by applied voltage.

Gap junctions formed by connexins 26 and 32 alone and in combination are differently affected by applied voltage.

TwoDrosophilaInnexins Are Expressed in Overlapping Domains and Cooperate to Form Gap-Junction Channels

Gap junctions in the adult cerebral cortex: Regional differences in their distribution and cellular expression of connexins

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