Gap junctions in several tissues share antigenic determinants with liver gap junctions.

Dermietzel, Rolf; Leibstein, A.; Frixen, U.; Janssen-Timmen, U.; Traub, Otto; Willecke, Klaus

doi:10.1002/j.1460-2075.1984.tb02124.x

Cited by 118 publications

(75 citation statements)

References 26 publications

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“…In mammals, such a dominant negative effect of point mutations of connexin genes will be more pronounced with connexin genes other than the Cx32 gene; since the Cx32 gene is on the X-chromosome, no such effect will be seen in males and one of the two alleles is silent anyway in females (Migeon, 1994). In most cell types, several species of connexin genes are expressed (Dermietzel et al, 1984;Dermietzel and Spray, 1993;Nicholson et al, 1987). It has recently been reported that two different types of connexins can form chimeric connexons in insects (Stauffer, 1995).…”

Section: Discussionmentioning

confidence: 99%

“…The connexins belong to a multigene family, containing at least 12 members, whose cDNAs have been isolated from mammalian genomes (Kumar and Gilula, 1992). The expression pattern of each Cx species is different among tissues and changes during differentiation or development (Dermietzel et al, 1984;Dermietzel and Spray, 1993;Nicholson et al, 1987). Depending on the precise combination of connexins, connexons composed of one type may be able to form functional gap junctions with another connexon composed of other types (heterotypic) (Elfgang et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Connexin 32 mutations from X-linked Charcot-Marie-Tooth disease patients: functional defects and dominant negative effects.

Omori

Mesnil

Yamasaki

1996

MBoC

165

120

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We have characterized the function of connexin (Cx) 32 gene mutations found in X-linked dominant Charcot-Marie-Tooth disease with respect to their ability to form functional gap junctions among themselves and to inactivate wild-type Cx32 by a dominant negative mechanism. We prepared four types of Cx32 mutant cDNAs and transfected them into HeLa cells, which do not show detectable levels of gap junctional intercellular communication (GJIC), nor expression of any connexins examined. Cells transfected with the wild-type Cx32 gene, but not those transfected with three different base substitution mutations (i.e. Cys 60 to Phe, Val 139 to Met, and Arg 215 to Trp), restored GJIC. Unexpectedly, in cells transfected with a nonsense mutant at codon 220, there was also restored GJIC. When we double-transfected these mutant constructs into the HeLa cells that had already been transfected with the wild-type Cx32 gene and thus were GJIC proficient, three base substitution mutants inhibited GJIC, suggesting that these three mutants can eliminate the function of wild-type Cx32 in a dominant negative manner. The nonsense mutation at codon 220 did not show such a dominant negative effect. Since both mutant and wild-type Cx32 mRNAs were detected, but only poor Cx32 protein expression at cell-cell contact areas was observed in the double transfectants, it is suggested that certain mutants form nonfunctional chimeric connexons with wild-type connexins, which are not properly inserted into the cytoplasmic membrane.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Connexin 32 mutations from X-linked Charcot-Marie-Tooth disease patients: functional defects and dominant negative effects.

Omori

Mesnil

Yamasaki

1996

MBoC

165

120

View full text Add to dashboard Cite

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“…Labeling of Cx4O and Cx43 proteins for immunofluorescence was performed on cultured HeLa cells grown on round glass coverslips as described previously (Dermietzel et al, 1984 Bukauskas and Weingart, 1994). In the other case, the two pipettes were connected to the cells of a cell pair spontaneously formed in culture (preformed cell pairs).…”

Section: Immunofluorescence Analysismentioning

confidence: 99%

Incompatibility of connexin 40 and 43 Hemichannels in gap junctions between mammalian cells is determined by intracellular domains.

Haubrich

Schwarz

Bukauskas

et al. 1996

MBoC

104

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Murine connexin 40 (Cx4O) and connexin 43 (Cx43) do not form functional heterotypic gap junction channels. This property may contribute to the preferential propagation of action potentials in murine conductive myocardium (expressing Cx4O) which is surrounded by working myocardium, expressing Cx43. When mouse Cx4O and Cx43 were individually expressed in cocultured human HeLa cells, no punctate immunofluorescent signals were detected on apposed plasma membranes between different transfectants, using antibodies specific for each connexin, suggesting that Cx40 and Cx43 hemichannels do not dock to each other. We wanted to identify domains in these connexin proteins which are responsible for the incompatibility. Thus, we expressed in HeLa cells several chimeric gene constructs in which different extracellular and intracellular domains of Cx43 had been spliced into the corresponding regions of Cx4O. We found that exchange of both extracellular loops (El and E2) in this system (Cx40*43E1,2) was required for formation of homotypic and heterotypic conductive channels, although the electrical properties differed from those of Cx4O or Cx43 channels. Thus, the extracellular domains of Cx43 can be directed to form functional homo-and heterotypic channels. Another chimeric construct in which both extracellular domains and the central cytoplasmic loop (El, E2, and C2) of Cx43 were spliced into Cx4O (Cx4O*43E1,2,C2) led to heterotypic coupling only with Cx43 and not with Cx4O transfectants. Thus, the central cytoplasmic loop of Cx43 contributed to selectivity. A third construct, in which only the C-terminal domain (C3) of Cx43 was spliced into Cx4O, i.e., Cx4O*43C3, showed neither homotypic nor heterotypic coupling with Cx4O and Cx43 transfectants, suggesting that the Cterminal region of Cx43 determined incompatibility.

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“…After fixation, the tissue blocks were washed in PBS (three times for 15 min), then treated with 0.5 mg/ml sodium borohydride, and freshly dissolved in PBS (three times for 15 rain) to reduce free aldehyde groups. Small pieces of the fixed tissue were either immersed in 2.3 M sucrose in PBS and then processed for ultracryotomy on an ultracryotome (model FC-4D, Reichert Jung, Vienna, Austria) (18) or the tissue samples were embedded in LR-White (London Resin Co., Woking, United Kingdom) at 4°C as described in detail previously (22). Polymerization was performed in closed gelatine capsules at 4°C with UV light (360 nm).…”

Section: Immunoelectron Microscopymentioning

confidence: 99%

“…Ultrathin sections of the resin-embedded tissue were collected on water and retrieved to gold grids. Antibody labeling of the grids and processing for EM was done at room temperature exactly as described in previous papers (18,22,68). All affinity-purified primary antibodies were used at an IgG concentration of 10-50 Ixg/ml.…”

Section: Immunoelectron Microscopymentioning

confidence: 99%

Organization of the actin filament cytoskeleton in the intestinal brush border: a quantitative and qualitative immunoelectron microscope study.

Drenckhahn

Dermietzel

1988

The Journal of Cell Biology

229

134

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Abstract. In the present study we have used immunogold labeling of ultrathin sections of the intact chicken and human intestinal epithelium to obtain further insight into the molecular structure of the brushborder cytoskeleton. Actin, villin, and fimbrin were found within the entire microvillus filament bundle, from the tip to the basal end of the rootlets, but were virtually absent from the space between the rootlets. This suggests that the bulk of actin in the brush border is kept in a polymerized and cross-linked state and that horizontally deployed actin filaments are virtually absent. About 70% of the label specific for the ll0-kD protein that links the microvillus core bundle to the lipid bilayer was found overlying the microvilli. The remaining label was associated with rootlets and the interrooflet space, where some label was regularly observed in association with vesicles. Since the terminal web did not contain any significant amounts of tubulin and microtubules, the present findings would support a recently proposed hypothesis that the 110-kD protein (which displays properties of an actinactivated, myosin-like ATPase) might also be involved in the transport of vesicles through the terminal web. Label specific for myosin and a-actinin was confined to the interrootlet space and was absent from the rootlets. About 10-15% of the myosin label and 70-80% of the ~t-actinin label was observed within the circumferential band of actin filaments at the zonula adherens, where myosin and ct-actinin displayed a clustered, interrupted pattern that resembles the spacing of these proteins observed in other contractile systems. This circular filament ring did not contain villin, fimbrin, or the ll0-kD protein. Finally, actin-specific label was observed in close association with the cytoplasmic aspect of the zonula occludens, suggesting that tight junctions are structurally connected to the microfilament system.T HE resorptive surface of the intestinal epithelium, called brush border, is increased 15-30-fold by numerous microvilli that are 1-2 lxm long and 100 nm in diameter (64). Each microvillus is supported by an axial bundle of actin filaments that are in parallel alignment and display identical polarity (51, 53, 59; for review see references 8, 52). The microvillus core bundle is attached to the surrounding membrane by periodically arranged lateral bridges that consist of a complex of a rod-shaped ll0-kD protein and calmodulin (13,31,37,46,47,69). The actin filament core bundle is extensively cross-linked by two proteins, fimbrin (68 kD) and villin (95 kD; 2, 4, 5, 6, 25, 55). In the presence of Ca ++ (>10 -6 M), villin causes fragmentation of the core bundle whereas the bundling activity of fimbrin appears to be independent of Ca++ (9,17,48,49,55). Villin is also present in the rootlets (23). In contrast to the core bundle, the rootlets contain tropomyosin (21). There is a report indicating that the muscular Z-line protein, ~t-actinin, may also be present in the rootlets and absent from the microvilli (27).The spac...

show abstract

Gap junctions in several tissues share antigenic determinants with liver gap junctions.

Cited by 118 publications

References 26 publications

Connexin 32 mutations from X-linked Charcot-Marie-Tooth disease patients: functional defects and dominant negative effects.

Connexin 32 mutations from X-linked Charcot-Marie-Tooth disease patients: functional defects and dominant negative effects.

Incompatibility of connexin 40 and 43 Hemichannels in gap junctions between mammalian cells is determined by intracellular domains.

Organization of the actin filament cytoskeleton in the intestinal brush border: a quantitative and qualitative immunoelectron microscope study.

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