Regulation of Connexin Degradation as a Mechanism to Increase Gap Junction Assembly and Function

Anisotropy is the property of directional dependence. In cardiac tissue, conduction velocity is anisotropic and its orientation is determined by myocyte direction. Cell shape and size, excitability, myocardial fibrosis, gap junction distribution and function are all considered to contribute to anisotropic conduction. In disease states, anisotropic conduction may be enhanced, and is implicated, in the genesis of pathological arrhythmias. The principal mechanism responsible for enhanced anisotropy in disease remains uncertain. Possible contributors include changes in cellular excitability, changes in gap junction distribution or function and cellular uncoupling through interstitial fibrosis. It has recently been demonstrated that myocyte orientation may be identified using diffusion tensor magnetic resonance imaging in explanted hearts, and multisite pacing protocols have been proposed to estimate myocyte orientation and anisotropic conduction in vivo. These tools have the potential to contribute to the understanding of the role of myocyte disarray and anisotropic conduction in arrhythmic states.

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GJA1 Depletion Causes Ciliary Defects by Affecting Rab11 Trafficking to the Ciliary Base

10.1101/2020.11.13.381764 ◽

2020 ◽

Author(s):

Dong Gil Jang ◽

Keun Yeong Kwon ◽

Yeong Cheon Kweon ◽

Byung-gyu Kim ◽

Kyungjae Myung ◽

...

Keyword(s):

Gap Junction ◽

Primary Cilium ◽

Transport Channel ◽

Junction Protein ◽

Complex Functions ◽

Mother Centriole ◽

Pericentriolar Material ◽

Gap Junction Protein ◽

And Function ◽

Distinct Distribution

AbstractThe gap junction complex functions as a transport channel across the membrane. Among gap junction subunits, gap junction protein alpha 1 (GJA1) is the most commonly expressed subunit. However, the roles of GJA1 in the formation and function of cilia remain unknown. Here, we examined GJA1 functions during ciliogenesis in vertebrates. GJA1 was localized to the motile ciliary axonemes or pericentriolar material (PCM) around the primary cilium. GJA1 depletion caused the severe malformation of both primary cilium and motile cilia. Interestingly, GJA1 depletion caused strong delocalization of BBS4 from the PCM and basal body and distinct distribution as cytosolic puncta. Further, CP110 removal from the mother centriole was significantly reduced by GJA1 depletion. Importantly, Rab11, key regulator during ciliogenesis, was immunoprecipitated with GJA1 and GJA1 knockdown caused the mis-localization and mis-accumulation of Rab11. These findings suggest that GJA1 is necessary for proper ciliogenesis by regulating the Rab11 pathway.

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Involvement of the Gap Junction Protein, Connexin43, in the Formation and Function of Invadopodia in the Human U251 Glioblastoma Cell Line

Cells ◽

10.3390/cells9010117 ◽

2020 ◽

Vol 9 (1) ◽

pp. 117 ◽

Cited By ~ 3

Author(s):

Amandine Chepied ◽

Zeinaba Daoud-Omar ◽

Annie-Claire Meunier-Balandre ◽

Dale W. Laird ◽

Marc Mesnil ◽

...

Keyword(s):

Gap Junction ◽

Molecular Mechanisms ◽

Glioblastoma Cells ◽

Dynamic Interactions ◽

Cx43 Expression ◽

Junction Protein ◽

Gap Junction Protein ◽

And Function ◽

Low Cell Density ◽

Invadopodia Formation

The resistance of glioblastomas to treatments is mainly the consequence of their invasive capacities. Therefore, in order to better treat these tumors, it is important to understand the molecular mechanisms which are responsible for this behavior. Previous work suggested that gap junction proteins, the connexins, facilitate the aggressive nature of glioma cells. Here, we show that one of them—connexin43 (Cx43)—is implicated in the formation and function of invadopodia responsible for invasion capacity of U251 human glioblastoma cells. Immunofluorescent approaches—combined with confocal analyses—revealed that Cx43 was detected in all the formation stages of invadopodia exhibiting proteolytic activity. Clearly, Cx43 appeared to be localized in invadopodia at low cell density and less associated with the establishment of gap junctions. Accordingly, lower extracellular matrix degradation correlated with less mature invadopodia and MMP2 activity when Cx43 expression was decreased by shRNA strategies. Moreover, the kinetics of invadopodia formation could be dependent on Cx43 dynamic interactions with partners including Src and cortactin. Interestingly, it also appeared that invadopodia formation and MMP2 activity are dependent on Cx43 hemichannel activity. In conclusion, these results reveal that Cx43 might be involved in the formation and function of the invadopodia of U251 glioblastoma cells.

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Zinc Modulation of Hemi-Gap-Junction Channel Currents in Retinal Horizontal Cells

Journal of Neurophysiology ◽

10.1152/jn.90581.2008 ◽

2009 ◽

Vol 101 (4) ◽

pp. 1774-1780 ◽

Cited By ~ 21

Author(s):

Ziyi Sun ◽

Dao-Qi Zhang ◽

Douglas G. McMahon

Keyword(s):

Gap Junction ◽

Inhibitory Action ◽

Divalent Cations ◽

Horizontal Cells ◽

Visual Signals ◽

Histidine Residues ◽

Gap Junction Channel ◽

And Function ◽

Channel Currents

Hemi-gap-junction (HGJ) channels of retinal horizontal cells (HCs) function as transmembrane ion channels that are modulated by voltage and calcium. As an endogenous retinal neuromodulator, zinc, which is coreleased with glutamate at photoreceptor synapses, plays an important role in shaping visual signals by acting on postsynaptic HCs in vivo. To understand more fully the regulation and function of HC HGJ channels, we examined the effect of Zn2+ on HGJ channel currents in bass retinal HCs. Hemichannel currents elicited by depolarization in Ca2+-free medium and in 1 mM Ca2+ medium were significantly inhibited by extracellular Zn2+. The inhibition by Zn2+ of hemichannel currents was dose dependent with a half-maximum inhibitory concentration of 37 μM. Compared with other divalent cations, Zn2+ exhibited higher inhibitory potency, with the order being Zn2+ > Cd2+ ≈ Co2+ > Ca2+ > Ba2+ > Mg2+. Zn2+ and Ca2+ were found to modulate HGJ channels independently in additivity experiments. Modification of histidine residues with N-bromosuccinimide suppressed the inhibitory action of Zn2+, whereas modification of cysteine residues had no significant effect on Zn2+ inhibition. Taken together, these results suggest that zinc acts on HGJ channels in a calcium-independent way and that histidine residues on the extracellular domain of HGJ channels mediate the inhibitory action of zinc.

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Analysis of Trafficking, Stability and Function of Human Connexin 26 Gap Junction Channels with Deafness-Causing Mutations in the Fourth Transmembrane Helix

PLoS ONE ◽

10.1371/journal.pone.0070916 ◽

2013 ◽

Vol 8 (8) ◽

pp. e70916 ◽

Cited By ~ 15

Author(s):

Cinzia Ambrosi ◽

Amy E. Walker ◽

Adam D. DePriest ◽

Angela C. Cone ◽

Connie Lu ◽

...

Keyword(s):

Gap Junction ◽

Transmembrane Helix ◽

Connexin 26 ◽

Gap Junction Channels ◽

And Function

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Cx50 requires an intact PDZ-binding motif and ZO-1 for the formation of functional intercellular channels

Molecular Biology of the Cell ◽

10.1091/mbc.e11-05-0438 ◽

2011 ◽

Vol 22 (23) ◽

pp. 4503-4512 ◽

Cited By ~ 18

Author(s):

Zhifang Chai ◽

Daniel A. Goodenough ◽

David L. Paul

Keyword(s):

Gap Junction ◽

Hela Cells ◽

Pdz Domain ◽

Cell Communication ◽

Normal Function ◽

Scaffolding Protein ◽

Binding Motif ◽

Interacting Protein ◽

And Function

The three connexins expressed in the ocular lens each contain PDZ domain–binding motifs directing a physical association with the scaffolding protein ZO-1, but the significance of the interaction is unknown. We found that Cx50 with PDZ-binding motif mutations did not form gap junction plaques or induce cell–cell communication in HeLa cells, whereas the addition of a seven–amino acid PDZ-binding motif restored normal function to Cx50 lacking its entire C-terminal cytoplasmic domain. C-Terminal deletion had a similar although weaker effect on Cx46 but little if any effect on targeting and function of Cx43. Furthermore, small interfering RNA knockdown of ZO-1 completely inhibited the formation of gap junctions by wild-type Cx50 in HeLa cells. Thus both a PDZ-binding motif and ZO-1 are necessary for Cx50 intercellular channel formation in HeLa cells. Knock-in mice expressing Cx50 with a PDZ-binding motif mutation phenocopied Cx50 knockouts. Furthermore, differentiating lens fibers in the knock-in displayed extensive intracellular Cx50, whereas plaques in mature fibers contained only Cx46. Thus normal Cx50 function in vivo also requires an intact PDZ domain–binding motif. This is the first demonstration of a connexin-specific requirement for a connexin-interacting protein in gap junction assembly.

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Expression and function of the neuronal gap junction protein connexin 36 in developing mammalian retina

The Journal of Comparative Neurology ◽

10.1002/cne.20759 ◽

2005 ◽

Vol 493 (2) ◽

pp. 309-320 ◽

Cited By ~ 28

Author(s):

Kristi A. Hansen ◽

Christine L. Torborg ◽

Justin Elstrott ◽

Marla B. Feller

Keyword(s):

Gap Junction ◽

Connexin 36 ◽

Junction Protein ◽

Mammalian Retina ◽

Gap Junction Protein ◽

And Function

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Gap junction structure and function

Trends in Biochemical Sciences ◽

10.1016/0968-0004(77)90251-1 ◽

1977 ◽

Vol 2 (2) ◽

pp. 26-31 ◽

Cited By ~ 13

Author(s):

Camillo Peracchia

Keyword(s):

Gap Junction ◽

Structure And Function ◽

And Function ◽

Junction Structure

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Asymmetry of an intracellular scaffold at vertebrate electrical synapses

10.1101/173955 ◽

2017 ◽

Author(s):

Audrey J Marsh ◽

Jennifer Carlisle Michel ◽

Anisha P Adke ◽

Emily L Heckman ◽

Adam C Miller

Keyword(s):

Gap Junction ◽

Synapse Formation ◽

Neural Circuit ◽

Electrical Synapse ◽

Electrical Synapses ◽

Gap Junction Channels ◽

Junction Protein ◽

Chemical Synapses ◽

And Function

AbstractNeuronal synaptic connections are electrical or chemical and together are essential to dynamically defining neural circuit function. While chemical synapses are well known for their biochemical complexity, electrical synapses are often viewed as comprised solely of neuronal gap junction channels that allow direct ionic and metabolic communication. However, associated with the gap junction channels are structures observed by electron microscopy called the Electrical Synapse Density (ESD). The ESD has been suggested to be critical for the formation and function of the electrical synapse, yet the biochemical makeup of these structures is poorly understood. Here we find that electrical synapse formation in vivo requires an intracellular scaffold called Tight Junction Protein 1b (Tjp1b). Tjp1b is localized to electrical synapses where it is required for the stabilization of the gap junction channels and for electrical synapse function. Strikingly, we find that Tjp1b protein localizes and functions asymmetrically, exclusively on the postsynaptic side of the synapse. Our findings support a novel model in which there is molecular asymmetry at the level of the intracellular scaffold that is required for building the electrical synapse. ESD molecular asymmetries may be a fundamental motif of all nervous systems and could support functional asymmetry at the electrical synapse.

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Gap junction Heterogeneity in Liver, Heart, and Lens

Physiology ◽

10.1152/physiologyonline.1988.3.5.206 ◽

1988 ◽

Vol 3 (5) ◽

pp. 206-211

Author(s):

PG FitzGerald

Keyword(s):

Gap Junctions ◽

Gap Junction ◽

Molecular Analysis ◽

Tissue Specificity ◽

Structure And Function ◽

Junctional Proteins ◽

And Function ◽

Junction Structure

Gap junctions are nearly ubiquitous structures that ionically and metabolically couple adjacent cells. Molecular analysis of junctional proteins is establishing the presence of families of unique but homologous junctional proteins, opening the door to an explanation of tissue specificity in gap junction structure and function.

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