Functional Role of the Carboxyl Terminal Domain of Human Connexin 50 in Gap Junctional Channels

Xu, Xiaorong; Berthoud, Viviana M.; Beyer, Eric C.; Ebihara, Lisa

doi:10.1007/s00232-001-0139-5

Cited by 43 publications

(55 citation statements)

References 46 publications

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“…As previously reported (9,30,40), Cx50 channels are among the most CO 2 -sensitive connexin channels tested. Indeed, G j drops by as much as 78% with exposures to just 30% CO 2 , corresponding to a drop in pH i to 6.83.…”

Section: Discussionsupporting

confidence: 80%

“…2D, the fitted function for control conditions departs somewhat from the data points at V j Ͼ40 mV. This is also observed in other V j records of Cx50 (4,29,40) and in those of Cx40 (1, 13) and Cx38 (36). The voltage sensitivity under control condition is slightly lower than that reported by an earlier study on Cx50 expressed in oocytes (39), but higher than those reported for Cx50 expressed in N2A cells (29,40).…”

Section: Homotypic Cx50 Channelssupporting

confidence: 48%

“…2D). This divergence is also seen in other records of Cx50 channels (4,29,40) and in those of Cx40 (1,13) and Cx38 (36) channels, but not in records of Cx32 (36) and Cx45 (21) channels. Because Cx50, Cx40, and Cx38 channels are positive gaters, whereas Cx32, Cx45, and Cx50-D3N channels are negative gaters, this phenomenon may also be related to gating polarity.…”

Section: Discussionmentioning

confidence: 70%

“…To test this hypothesis, the present study has monitored the CO 2 sensitivity of V j gating in Cx50 channels (positive gaters; 4,8,35) and in channels made of a Cx50 mutant (Cx50-D3N) in which the third residue, aspartate (D), is replaced with asparagine (N). Cx50 is a connexin expressed in eye lens fibers whose high gating sensitivity to cytosolic acidification (9,30,40) has been proposed to play a role in the function of differentiating fibers (2).…”

Section: For Review)mentioning

confidence: 99%

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Inversion of both gating polarity and CO₂ sensitivity of voltage gating with D3N mutation of Cx50

Peracchia¹,

Peracchia²

2005

American Journal of Physiology-Cell Physiology

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The effect of CO 2-induced acidification on transjunctional voltage (Vj) gating was studied by dual voltage-clamp in oocytes expressing mouse connexin 50 (Cx50) or a Cx50 mutant (Cx50-D3N), in which the third residue, aspartate (D), was mutated to asparagine (N). This mutation inverted the gating polarity of Cx50 from positive to negative. CO2 application greatly decreased the Vj sensitivity of Cx50 channels, and increased that of Cx50-D3N channels. CO2 also affected the kinetics of Vj dependent inactivation of junctional current (Ij), decreasing the gating speed of Cx50 channels and increasing that of Cx50-D3N channels. In addition, the D3N mutation increased the CO2 sensitivity of chemical gating such that even CO2 concentrations as low as 2.5% significantly lowered junctional conductance (Gj). With Cx50 channels Gj dropped by 78% with a drop in intracellular pH (pHi) to 6.83, whereas with Cx50-D3N channels Gj dropped by 95% with a drop in pHi to just 7.19. We have previously hypothesized that the way in which Vj gating reacts to CO2 might be related to connexin's gating polarity. This hypothesis is confirmed here by evidence that the D3N mutation inverts the gating polarity as well as the effect of CO2 on Vj gating sensitivity and speed. cell communication; lens; gap junctions; chemical gating; channel gating; Xenopus oocytes GAP JUNCTIONS are regions of cell contact that mediate the exchange of small cytosolic molecules via cell-cell channels. A gap junction channel results from the extracellular interaction of two hemichannels (connexons), each a hexamer of connexin proteins. Connexins (Cx) contain four transmembrane domains, two extracellular loops, a cytoplasmic loop, a short NH 2 terminus (NT), and a COOH terminus of variable length. The sequences of cytoplasmic loop and COOH terminus vary significantly among the members of the connexin family, whereas those of the other domains are relatively well conserved (see Ref. 14 for review).Gap junction channels are gated by transjunctional voltage (V j ; 27) and increased intracellular [Ca 2ϩ ] (10, 25) or [H ϩ ] i (28, 33) via molecular mechanisms that are still poorly defined (see Ref. 12 for review). At least two V j -sensitive gates have been identified: fast and slow. On the basis of their behavior at the single channel level, fast V j gate and chemical gate are believed to be distinct: the former closes rapidly (Ͻ1 ms) but incompletely, leaving a 20 -30% residual conductance, whereas the latter closes slowly (8 -10 ms) but completely (5). In contrast, slow V j gate and chemical gate are likely to be the same (5,17,20). Slow and fast V j gates are in series, and each hemichannel appears to have both gates. The slow gate closes at the negative side of V j in all connexin channels tested, whereas the polarity of the fast V j gating mechanism varies among connexin channels (see Ref. 8 for review).In the past, chemical and V j gating have been studied almost exclusively by testing chemicals and V j gradients, respectively, whereas minimal attention has been ...

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Section: Discussionsupporting

confidence: 80%

Section: Homotypic Cx50 Channelssupporting

confidence: 48%

Section: Discussionmentioning

confidence: 70%

Section: For Review)mentioning

confidence: 99%

See 2 more Smart Citations

Inversion of both gating polarity and CO₂ sensitivity of voltage gating with D3N mutation of Cx50

Peracchia¹,

Peracchia²

2005

American Journal of Physiology-Cell Physiology

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“…Analogous to its role in tight junctions, ZO-1 was originally thought to link Cxs to the actin cytoskeleton, but now appears to be involved in the formation, assembly, distribution, turnover, and function of GJ channels (28,33,(40)(41)(42)(43). Our results indicate that ZO-1 is prominent at electrical synapses composed of Cx35.…”

Section: Discussionmentioning

confidence: 99%

Interaction between connexin35 and zonula occludens-1 and its potential role in the regulation of electrical synapses

Flores

Bennett

et al. 2008

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

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Although regulation of chemical transmission is known to involve the interaction of receptors with scaffold proteins, little is known about the existence of protein-protein interactions in regulating gap junction-mediated electrical synapses. The scaffold protein zonulaoccludens-1 (ZO-1), a member of the MAGUK family of proteins, was reported to interact with several connexins (Cxs). We show here that ZO-1 extensively colocalizes with Cx35 at identifiable ''mixed'' (electrical and chemical) contacts on goldfish Mauthner cells, a model synapse for the study of vertebrate electrical transmission where it is possible to correlate physiological properties with molecular composition. Further, our analysis indicates that these proteins directly interact at goldfish electrical synapses. In contrast to Cx43, which interacts with ZO-1 via the PDZ2 domain, Cx35 interacts with ZO-1 via the PDZ1 domain, and this association is of lower affinity. The properties of the ZO-1/Cx35 association suggest the existence of a more dynamic relation between these two proteins, possibly including a role of ZO-1 in regulating gap junctional conductance at these highly modifiable electrical synapses. The interaction of ZO-1 with conserved regions of the C termini of Cx35/Cx36 orthologs may have a common function at electrical synapses of mammals and other vertebrates.gap junction ͉ Mauthner cell ͉ PDZ ͉ postsynaptic density-95 protein ͉ synaptic plasticity M ost electrical synaptic transmission is mediated by clusters of ion channels, known as gap junctions (GJs), that provide a low-resistance pathway between the interiors of coupled cells and permit the spread of electrical currents between them (1). Although regulation of chemical transmission is known to involve the action of multiple interacting proteins at both presynaptic and postsynaptic sites (2), little is known about the existence of protein interactions in regulating electrical synapses. Direct interactions of ligand-gated ion channels with several scaffold proteins play an essential role in the regulation of synaptic strength at chemical synapses by facilitating channel insertion, anchoring, or removal from the plasma membrane (3-9). We show here one candidate protein, zonula occludens-1 (ZO-1), for regulation at electrical synapses.Auditory afferents terminating as single large myelinated club endings (CEs) on the distal portion of the lateral dendrite of the goldfish Mauthner cells (M-cells) are identifiable ''mixed'' (electrical and chemical) synaptic terminals. These synapses constitute a valuable model for the study of vertebrate electrical transmission where structure, biochemical composition, and physiology of individual contacts are more readily characterized than at mammalian electrical synapses (10). Electrical transmission at each terminal is mediated by Ϸ100 clusters or plaques of GJ channels (11) formed by connexin35 (Cx35) (12), the fish ortholog of mammalian Cx36 (13). The junctional conductance at these synapses is dynamically regulated by activity, and both ele...

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Gap Junctions

Nielsen,

Nygaard Axelsen,

Sorgen

et al. 2012

Comprehensive Physiology

380

365

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Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell‐cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981‐2035, 2012.

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Functional Role of the Carboxyl Terminal Domain of Human Connexin 50 in Gap Junctional Channels

Cited by 43 publications

References 46 publications

Inversion of both gating polarity and CO₂ sensitivity of voltage gating with D3N mutation of Cx50

Inversion of both gating polarity and CO₂ sensitivity of voltage gating with D3N mutation of Cx50

Interaction between connexin35 and zonula occludens-1 and its potential role in the regulation of electrical synapses

Gap Junctions

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Functional Role of the Carboxyl Terminal Domain of Human Connexin 50 in Gap Junctional Channels

Cited by 43 publications

References 46 publications

Inversion of both gating polarity and CO2 sensitivity of voltage gating with D3N mutation of Cx50

Inversion of both gating polarity and CO2 sensitivity of voltage gating with D3N mutation of Cx50

Interaction between connexin35 and zonula occludens-1 and its potential role in the regulation of electrical synapses

Gap Junctions

Contact Info

Product

Resources

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Inversion of both gating polarity and CO₂ sensitivity of voltage gating with D3N mutation of Cx50

Inversion of both gating polarity and CO₂ sensitivity of voltage gating with D3N mutation of Cx50