Journal articles on the topic 'Gap junctions'
To see the other types of publications on this topic, follow the link: Gap junctions.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Gap junctions.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Spray, D. C., R. L. White, F. Mazet, and M. V. Bennett. "Regulation of gap junctional conductance." American Journal of Physiology-Heart and Circulatory Physiology 248, no. 6 (June 1, 1985): H753—H764. http://dx.doi.org/10.1152/ajpheart.1985.248.6.h753.
Full textAbstract:
Gap junctional conductance is regulated by the number of channels between coupled cells (the balance between formation and loss of these channels) and by the fraction of these channels that are open (gating mechanisms). A variety of treatments are known to affect junction formation. Adenosine 3',5'-cyclic monophosphate (cAMP) is involved in some cases, and protein synthesis may be required but precursor molecules can also exist. Junction removal occurs both by dispersion of particles and by internalization of junctional membrane. Factors promoting removal are not well understood. A variety of gating mechanisms exist. Coupling may be controlled by changes in conductance of nonjunctional membranes. Several kinds of voltage dependence of junctional conductance are known, but rat ventricular junctions at least are electrically linear. Cytoplasmic acidification decreases conductance of most gap junctions. Sensitivity in rat ventricular myocytes allows modulation of coupling by moderate changes near normal internal pH. Increasing intracellular Ca also decreases junctional conductance, but in the better studied cases sensitivity is much lower to Ca than H. A few data support low sensitivity to Ca in cardiac cells, but quantitative studies are lacking. Higher alcohols such as octanol block junctional conductance in a wide range of tissues including rat ventricular myocytes. An antibody to liver gap junctions blocks junctions between rat ventricular myocytes. Cross reactivity indicates at least partial homology between many gap junctions. Although differences among gap junctions are known, a general physiology is being developed, which may have considerable relevance to normal cardiac function and also to conduction disorders of that tissue.
2
Lo, W. K., and T. S. Reese. "Multiple structural types of gap junctions in mouse lens." Journal of Cell Science 106, no. 1 (September 1, 1993): 227–35. http://dx.doi.org/10.1242/jcs.106.1.227.
Full textAbstract:
Gap junctions in the epithelium and superficial fiber cells from young mice were examined in lenses prepared by rapid-freezing, and processed for freeze-substitution and freeze-fracture electron microscopy. There appeared to be three structural types of gap junction: one type between epithelial cells and two types between fiber cells. Epithelial gap junctions seen by freeze-substitution were approximately 20 nm thick and consistently associated with layers of dense material lying along both cytoplasmic surfaces. Fiber gap junctions, in contrast, were 15–16 nm (type 1) or 17–18 nm thick (type 2), and had little associated cytoplasmic material. Type 1 fiber gap junctions were extensive in flat expanses of cell membrane and had a thin, discontinuous central lamina, whereas type 2 fiber gap junctions were associated with the ball-and-socket domains and exhibited a dense, continuous central lamina. Both types of fiber gap junction had a diffuse arrangement of junctional intramembrane particles, whereas particles and pits of epithelial gap junctions were in a tight, hexagonal configuration. The type 2 fiber gap junctions, however, had a larger particle size (approximately 9 nm) than the type 1 (approximately 7.5 nm). In addition, a large number of junctional particles typified the E-faces of both fiber types but not the epithelial type of gap junction. Gap junctions between fiber and epithelial cells had structural features of type 1 fiber gap junctions.(ABSTRACT TRUNCATED AT 250 WORDS)
3
Naus, Christian CG. "Gap junctions and tumour progression." Canadian Journal of Physiology and Pharmacology 80, no. 2 (February 1, 2002): 136–41. http://dx.doi.org/10.1139/y02-009.
Full textAbstract:
Gap junctional intercellular communication has been implicated in growth control and differentiation. The mechanisms by which connexins, the gap junction proteins, act as tumor suppressors are unclear. In this review, several different mechanisms are considered. Since transformation results in a loss of the differentiated state, one mechanism by which gap junctions may control tumour progression is to promote or enhance differentiation. Processes of differentiation and growth control are mediated at the genetic level. Thus, an alternative or complimentary mechanism of tumour suppression could involve the regulation of gene expression by connexins and gap junctional coupling. Finally, gap junction channels form a conduit between cells for the exchange of ions, second messengers, and small metabolites. It is clear that the sharing of these molecules can be rather selective and may be involved in growth control processes. In this review, examples will be discussed that provide evidence for each of these mechanisms. Taken together, these findings point to a variety of mechanims by which connexins and the gap junction channels that they form may control tumour progression.Key words: gap junctions, connexin, cancer.
4
Verheule, Sander, Marjan J. A. van Kempen, Sjoerd Postma, Martin B. Rook, and Habo J. Jongsma. "Gap junctions in the rabbit sinoatrial node." American Journal of Physiology-Heart and Circulatory Physiology 280, no. 5 (May 1, 2001): H2103—H2115. http://dx.doi.org/10.1152/ajpheart.2001.280.5.h2103.
Full textAbstract:
In comparison to the cellular basis of pacemaking, the electrical interactions mediating synchronization and conduction in the sinoatrial node are poorly understood. Therefore, we have taken a combined immunohistochemical and electrophysiological approach to characterize gap junctions in the nodal area. We report that the pacemaker myocytes in the center of the rabbit sinoatrial node express the gap junction proteins connexin (Cx)40 and Cx46. In the periphery of the node, strands of pacemaker myocytes expressing Cx43 intermingle with strands expressing Cx40 and Cx46. Biophysical properties of gap junctions in isolated pairs of pacemaker myocytes were recorded under dual voltage clamp with the use of the perforated-patch method. Macroscopic junctional conductance ranged between 0.6 and 25 nS with a mean value of 7.5 nS. The junctional conductance did not show a pronounced sensitivity to the transjunctional potential difference. Single-channel recordings from pairs of pacemaker myocytes revealed populations of single-channel conductances at 133, 202, and 241 pS. With these single-channel conductances, the observed average macroscopic junctional conductance, 7.5 nS, would require only 30–60 open gap junction channels.
5
Churchill, D., S. Coodin, R. R. Shivers, and S. Caveney. "Rapid de novo formation of gap junctions between insect hemocytes in vitro: a freeze-fracture, dye- transfer and patch-clamp study." Journal of Cell Science 104, no. 3 (March 1, 1993): 763–72. http://dx.doi.org/10.1242/jcs.104.3.763.
Full textAbstract:
Gap junctions form between insect hemocytes (blood cells) when they encapsulate foreign objects in the hemocoel (body cavity). In this study we show that hemocytes from cockroach (Periplaneta americana) form gap-junctions rapidly in vitro. Freeze-fracture replicas of hemocyte aggregates fixed 5 minutes after bleeding contain gap-junctional plaques. Dye passage was detected between carboxyfluorescein diacetate- labelled and unlabelled hemocytes within 3 minutes of bleeding, when the cells made contact as they flattened rapidly onto coverslips. When double whole-cell voltage-clamp was used to measure gap-junction formation between cells which were pushed together, electrical coupling was detected within one second of cell-cell contact. To prevent extensive flattening, cells were plated onto lipophorin-coated coverslips. Junctional conductance increased in staircase fashion with steps corresponding to an average single channel conductance of 345 pS. Assuming all channels to have this conductance, the maximal accretion rate of channels to the growing junction was one channel per second. Junctional currents and dye-coupling were detected in the absence of Ca2+, indicating that involvement of Ca2+-dependent adhesion molecules is not a prerequisite for gap-junction formation in hemocytes. Hemocytes from distantly related insects (cockroach and moth) form functional gap junctions with each other, suggesting sequence homology among gap- junction proteins in insects. The function of rapid gap-junction formation between hemocytes during encapsulation and wound healing in vivo are discussed.
6
Rook, M. B., A. C. van Ginneken, B. de Jonge, A. el Aoumari, D. Gros, and H. J. Jongsma. "Differences in gap junction channels between cardiac myocytes, fibroblasts, and heterologous pairs." American Journal of Physiology-Cell Physiology 263, no. 5 (November 1, 1992): C959—C977. http://dx.doi.org/10.1152/ajpcell.1992.263.5.c959.
Full textAbstract:
Cultures of neonatal rat heart cells contain predominantly myocytes and fibroblastic cells. Most abundant are groups of synchronously contracting myocytes, which are electrically well coupled through large gap junctions. Cardiac fibroblasts may be electrically coupled to each other and to adjacent myocytes, be it with low intercellular conductances. Nevertheless, synchronously beating myocytes interconnected via a fibroblast were present, demonstrating that nonexcitable cardiac cells are capable of passive impulse conduction. In fibroblast pairs as well as in myocyte-fibroblast cell pairs, no sensitivity to junctional voltage could be detected when transjunctional conductance was > 1-2 nS. However, in pairs coupled by a conductance of < 1 nS, complex voltage-dependent gating was evident; gap junction channel open probability decreased with increasing junctional voltage but a nongated residual conductance remained at all voltages tested. Single gap junction channel conductance between fibroblasts was approximately 21 pS, very similar to an approximately 18-pS channel conductance that was found between myocytes next to the major conductance of 43 pS. Single-channel conductance in heterologous myocyte-fibroblast gap junctions was approximately 32 pS, which matches the theoretical value of 29 pS for gap junction channels composed of a fibroblast connexon and the major myocyte connexon. A site-directed antibody against rat heart gap junction protein connexin43 recognized gap junctions between neonatal cardiomyocytes, as demonstrated by immunocytochemical labeling. In contrast, junctions between fibroblasts showed no labeling, while in myocyte-fibroblast junctions labeling occasionally was present. Our results suggest the existence of two gap junction proteins between neonatal rat cardiocytes, connexin43 and another yet unidentified connexin. An alternative explanation (cell-specific regulation of the conductance of connexin43 channels) is discussed.
7
Warner, Anne E. "The role of gap junctions in amphibian development." Development 89, Supplement (November 1, 1985): 365–80. http://dx.doi.org/10.1242/dev.89.supplement.365.
Full textAbstract:
The possibility that communication through gap junctions may be important during embryonic development has often been raised since gap junctions were first described between early embryonic cells. It is now known that this direct cell-to-cell communication pathway disappears between groups of embryonic cells with different developmental fates as the embryo progresses through development, suggesting that transfer through the gap junctional pathway may play some part in controlling events during development. Supportive evidence for a role for gap junctions comes from experiments demonstrating that the properties of gap junctions differ at the border separating each segment in insect epidermis. Recently it has been shown that the ability to exchange small dyes between cells in the amphibian embryo depends on the position of each cell with respect to the grey crescent. When communication through gap junctions is prevented, by injecting antibodies to gap junctions protein, pattern formation is severely disturbed in the non-communicating region. The paper describes experiments on the pattern of junctional communication at early stages of development of the amphibian embryo and illustrates how anti-gap junction antibodies are being used to determine when and where communication through gap junctions may play an important role during development.
8
Boitano, Scott, Zeenat Safdar, Donald G. Welsh, Jahar Bhattacharya, and Michael Koval. "Cell-cell interactions in regulating lung function." American Journal of Physiology-Lung Cellular and Molecular Physiology 287, no. 3 (September 2004): L455—L459. http://dx.doi.org/10.1152/ajplung.00172.2004.
Full textAbstract:
Tight junction barrier formation and gap junctional communication are two functions directly attributable to cell-cell contact sites. Epithelial and endothelial tight junctions are critical elements of the permeability barrier required to maintain discrete compartments in the lung. On the other hand, gap junctions enable a tissue to act as a cohesive unit by permitting metabolic coupling and enabling the direct transmission of small cytosolic signaling molecules from one cell to another. These components do not act in isolation since other junctional elements, such as adherens junctions, help regulate barrier function and gap junctional communication. Some fundamental elements related to regulation of pulmonary barrier function and gap junctional communication were presented in a Featured Topic session at the 2004 Experimental Biology Conference in Washington, DC, and are reviewed in this summary.
9
FitzGerald, PG. "Gap junction Heterogeneity in Liver, Heart, and Lens." Physiology 3, no. 5 (October 1, 1988): 206–11. http://dx.doi.org/10.1152/physiologyonline.1988.3.5.206.
Full textAbstract:
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.
10
Ko, Kevin, Pamela Arora, Wilson Lee, and Christopher McCulloch. "Biochemical and functional characterization of intercellular adhesion and gap junctions in fibroblasts." American Journal of Physiology-Cell Physiology 279, no. 1 (July 1, 2000): C147—C157. http://dx.doi.org/10.1152/ajpcell.2000.279.1.c147.
Full textAbstract:
Despite their significance in wound healing, little is known about the molecular determinants of cell-to-cell adhesion and gap junctional communication in fibroblasts. We characterized intercellular adherens junctions and gap junctions in human gingival fibroblasts (HGFs) using a novel model. Calcein-labeled donor cells in suspension were added onto an established, Texas red dextran (10 kDa)-labeled acceptor cell monolayer. Cell-to-cell adhesion required Ca2+ and was >30-fold stronger than cell-to-fibronectin adhesion at 15 min. Electron micrographs showed rapid formation of adherens junction-like structures at ∼15 min that matured by ∼2–3 h; distinct gap junctional complexes were evident by ∼3 h. Immunoblotting showed that HGF expressed β-catenin and that cadherins and connexin43 were recruited to the Triton-insoluble cytoskeletal fraction in confluent cultures. Confocal microscopy localized the same molecules to intercellular contacts of acceptor and donor cells. There was extensive calcein dye transfer in a cohort of Texas red dextran-labeled cells, but this was almost completely abolished by the gap junction inhibitor β-glycyrrhetinic acid and the connexin43 mimetic peptide GAP 27. This donor-acceptor cell model allows large numbers (>105) of cells to form synchronous cell-to-cell contacts, thereby enabling the simultaneous functional and molecular studies of adherens junctions and gap junctions.
11
Ek-Vitorín, Jose F., and Janis M. Burt. "Quantification of gap junction selectivity." American Journal of Physiology-Cell Physiology 289, no. 6 (December 2005): C1535—C1546. http://dx.doi.org/10.1152/ajpcell.00182.2005.
Full textAbstract:
Gap junctions, which are essential for functional coordination and homeostasis within tissues, permit the direct intercellular exchange of small molecules. The abundance and diversity of this exchange depends on the number and selectivity of the comprising channels and on the transjunctional gradient for and chemical character of the permeant molecules. Limited knowledge of functionally significant permeants and poor detectability of those few that are known have made it difficult to define channel selectivity. Presented herein is a multifaceted approach to the quantification of gap junction selectivity that includes determination of the rate constant for intercellular diffusion of a fluorescent probe (k2-DYE) and junctional conductance ( gj) for each junction studied, such that the selective permeability (k2-DYE/ gj) for dyes with differing chemical characteristics or junctions with differing connexin (Cx) compositions (or treatment conditions) can be compared. In addition, selective permeability can be correlated using single-channel conductance when this parameter is also measured. Our measurement strategy is capable of detecting 1) rate constants and selective permeabilities that differ across three orders of magnitude and 2) acute changes in that rate constant. Using this strategy, we have shown that 1) the selective permeability of Cx43 junctions to a small cationic dye varied across two orders of magnitude, consistent with the hypothesis that the various channel configurations adopted by Cx43 display different selective permeabilities; and 2) the selective permeability of Cx37 vs. Cx43 junctions was consistently and significantly lower.
12
Miller, Leigh-Anne D., Melissa L. Farquhar, John S. Greenwood, and Steven R. Scadding. "Gap junctions in the limb regeneration blastema of the axolotl, Ambystoma mexicanum, are not distributed uniformly and are regulated by retinoic acid." Canadian Journal of Zoology 77, no. 6 (October 10, 1999): 902–9. http://dx.doi.org/10.1139/z99-045.
Full textAbstract:
Gap junctions are thought to play a role in pattern formation during limb development and regeneration by controlling the movement of small regulatory molecules between cells. An anteroposterior gradient of gap junctional communication that is higher posteriorly has been reported in the developing chick limb bud. In both the developing chick limb bud and the amphibian regenerating limb, an anteroposterior retinoic acid gradient is present, and this is also higher posteriorly. On the basis of these observations, we decided to examine the role of gap junctional communication in the regenerating amphibian limb. Gap junctions were observed in both the axolotl, Ambystoma mexicanum, limb regeneration blastema and cardiac tissue (as a positive control), using immunohistochemical labelling and laser scanning confocal microscopy. The scrape-loading/dye transfer technique for tracing the movement of a gap junction permeable dye, Lucifer yellow, showed that in blastemal epidermis there were nonuniform distributions of gap junctions in both the dorsoventral and anteroposterior axes of the blastema. Retinoic acid was found to increase gap junctional permeability in blastemal epidermis 48 h after injection and in blastemal mesenchyme 76 h after injection. The potential role of gap junctions during pattern formation in limb regeneration is discussed based on these results.
13
Koval, Michael. "Sharing signals: connecting lung epithelial cells with gap junction channels." American Journal of Physiology-Lung Cellular and Molecular Physiology 283, no. 5 (November 1, 2002): L875—L893. http://dx.doi.org/10.1152/ajplung.00078.2002.
Full textAbstract:
Gap junction channels enable the direct flow of signaling molecules and metabolites between cells. Alveolar epithelial cells show great variability in the expression of gap junction proteins (connexins) as a function of cell phenotype and cell state. Differential connexin expression and control by alveolar epithelial cells have the potential to enable these cells to regulate the extent of intercellular coupling in response to cell stress and to regulate surfactant secretion. However, defining the precise signals transmitted through gap junction channels and the cross talk between gap junctions and other signaling pathways has proven difficult. Insights from what is known about roles for gap junctions in other systems in the context of the connexin expression pattern by lung cells can be used to predict potential roles for gap junctional communication between alveolar epithelial cells.
14
Saffitz, Jeffrey E., Karen G. Green, William J. Kraft, Kenneth B. Schechtman, and Kathryn A. Yamada. "Effects of diminished expression of connexin43 on gap junction number and size in ventricular myocardium." American Journal of Physiology-Heart and Circulatory Physiology 278, no. 5 (May 1, 2000): H1662—H1670. http://dx.doi.org/10.1152/ajpheart.2000.278.5.h1662.
Full textAbstract:
Gap junction number and size vary widely in cardiac tissues with disparate conduction properties. Little is known about how tissue-specific patterns of intercellular junctions are established and regulated. To elucidate the relationship between gap junction channel protein expression and the structure of gap junctions, we analyzed Cx43 +/− mice, which have a genetic deficiency in expression of the major ventricular gap junction protein, connexin43 (Cx43). Quantitative confocal immunofluorescence microscopy revealed that diminished Cx43 signal in Cx43 +/− mice was due almost entirely to a reduction in the number of individual gap junctions (226 ± 52 vs. 150 ± 32 individual gap junctions/field in Cx43 +/+ and +/− ventricles, respectively; P < 0.05). The mean size of an individual gap junction was the same in both groups. Immunofluorescence results were confirmed with electron microscopic morphometry. Thus when connexin expression is diminished, ventricular myocytes become interconnected by a reduced number of large, normally sized gap junctions, rather than a normal number of smaller junctions. Maintenance of large gap junctions may be an adaptive response supporting safe ventricular conduction.
15
Mitra, Shalini, Lakshmanan Annamalai, Souvik Chakraborty, Kristen Johnson, Xiao-Hong Song, Surinder K. Batra, and Parmender P. Mehta. "Androgen-regulated Formation and Degradation of Gap Junctions in Androgen-responsive Human Prostate Cancer Cells." Molecular Biology of the Cell 17, no. 12 (December 2006): 5400–5416. http://dx.doi.org/10.1091/mbc.e06-04-0280.
Full textAbstract:
The constituent proteins of gap junctions, called connexins (Cxs), have a short half-life. Despite this, the physiological stimuli that control the assembly of Cxs into gap junctions and their degradation have remained poorly understood. We show here that in androgen-responsive human prostate cancer cells, androgens control the expression level of Cx32—and hence the extent of gap junction formation—post-translationally. In the absence of androgens, a major fraction of Cx32 is degraded presumably by endoplasmic reticulum–associated degradation, whereas in their presence, this fraction is rescued from degradation. We also show that Cx32 and Cx43 degrade by a similar mechanism. Thus, androgens regulate the formation and degradation of gap junctions by rerouting the pool of Cxs, which normally would have been degraded from the early secretory compartment, to the cell surface, and enhancing assembly into gap junctions. Androgens had no significant effect on the formation and degradation of adherens and tight junction–associated proteins. The findings that in a cell culture model that mimics the progression of human prostate cancer, degradation of Cxs, as well as formation of gap junctions, are androgen-dependent strongly implicate an important role of junctional communication in the prostate morphogenesis and oncogenesis.
16
Evans, W. H., and S. Boitano. "Connexin mimetic peptides: specific inhibitors of gap-junctional intercellular communication." Biochemical Society Transactions 29, no. 4 (August 1, 2001): 606–12. http://dx.doi.org/10.1042/bst0290606.
Full textAbstract:
Intercellular co-operation is a fundamental and widespread feature in tissues and organs. An important mechanism ensuring multicellular homoeostasis involves signalling between cells via gap junctions that directly connect the cytosolic contents of adjacent cells. Cell proliferation and intercellular communication across gap junctions are closely linked, and a number of pathologies in which communication is disrupted are known where connexins, the gap-junctional proteins, are modified. The proteins of gap junctions thus emerge as therapeutic targets inviting the development and exploitation of chemical tools and drugs that specifically influence intercellular communication. Connexin mimetic peptides that correspond to short specific sequences in the two extracellular loops of connexins are a class of benign, specific and reversible inhibitors of gap-junctional communication that have been studied recently in a broad range of cells, tissues and organs. This review summarizes the properties and uses of these short synthetic peptides, and compares their probable mechanism of action with those of a wide range of other less specific traditional gap-junction inhibitors.
17
Beckmann, Anja, Johanna Recktenwald, Alice Ferdinand, Alexander Grißmer, and Carola Meier. "First Responders to Hyperosmotic Stress in Murine Astrocytes: Connexin 43 Gap Junctions Are Subject to an Immediate Ultrastructural Reorganization." Biology 10, no. 12 (December 9, 2021): 1307. http://dx.doi.org/10.3390/biology10121307.
Full textAbstract:
In a short-term model of hyperosmotic stress, primary murine astrocytes were stimulated with a hyperosmolar sucrose solution for five minutes. Astrocytic gap junctions, which are mainly composed of Connexin (Cx) 43, displayed immediate ultrastructural changes, demonstrated by freeze–fracture replica immunogold labeling: their area, perimeter, and distance of intramembrane particles increased, whereas particle numbers per area decreased. Ultrastructural changes were, however, not accompanied by changes in Cx43 mRNA expression. In contrast, transcription of the gap junction regulator zonula occludens (ZO) protein 1 significantly increased, whereas its protein expression was unaffected. Phosphorylation of Serine (S) 368 of the Cx43 C–terminus has previously been associated with gap junction disassembly and reduction in gap junction communication. Hyperosmolar sucrose treatment led to enhanced phosphorylation of Cx43S368 and was accompanied by inhibition of gap junctional intercellular communication, demonstrated by a scrape loading-dye transfer assay. Taken together, Cx43 gap junctions are fast reacting elements in response to hyperosmolar challenges and can therefore be considered as one of the first responders to hyperosmolarity. In this process, phosphorylation of Cx43S368 was associated with disassembly of gap junctions and inhibition of their function. Thus, modulation of the gap junction assembly might represent a target in the treatment of brain edema or trauma.
18
Beyer, E. C., J. Kistler, D. L. Paul, and D. A. Goodenough. "Antisera directed against connexin43 peptides react with a 43-kD protein localized to gap junctions in myocardium and other tissues." Journal of Cell Biology 108, no. 2 (February 1, 1989): 595–605. http://dx.doi.org/10.1083/jcb.108.2.595.
Full textAbstract:
Rat heart and other organs contain mRNA coding for connexin43, a polypeptide homologous to a gap junction protein from liver (connexin32). To provide direct evidence that connexin43 is a cardiac gap junction protein, we raised rabbit antisera directed against synthetic oligopeptides corresponding to two unique regions of its sequence, amino acids 119-142 and 252-271. Both antisera stained the intercalated disc in myocardium by immunofluorescence but did not react with frozen sections of liver. Immunocytochemistry showed anti-connexin43 staining of the cytoplasmic surface of gap junctions in isolated rat heart membranes but no reactivity with isolated liver gap junctions. Both antisera reacted with a 43-kD polypeptide in isolated rat heart membranes but did not react with rat liver gap junctions by Western blot analysis. In contrast, an antiserum to the conserved, possibly extracellular, sequence of amino acids 164-189 in connexin32 reacted with both liver and heart gap junction proteins on Western blots. These findings support a topological model of connexins with unique cytoplasmic domains but conserved transmembrane and extracellular regions. The connexin43-specific antisera were used by Western blots and immunofluorescence to examine the distribution of connexin43. They demonstrated reactivity consistent with gap junctions between ovarian granulosa cells, smooth muscle cells in uterus and other tissues, fibroblasts in cornea and other tissues, lens and corneal epithelial cells, and renal tubular epithelial cells. Staining with the anti-connexin43 antisera was never observed to colocalize with antibodies to other gap junctional proteins (connexin32 or MP70) in the same junctional plaques. Because of limitations in the resolution of the immunofluorescence, however, we were not able to determine whether individual cells ever simultaneously express more than one connexin type.
19
Stains, Joseph P., and Roberto Civitelli. "Gap Junctions Regulate Extracellular Signal-regulated Kinase Signaling to Affect Gene Transcription." Molecular Biology of the Cell 16, no. 1 (January 2005): 64–72. http://dx.doi.org/10.1091/mbc.e04-04-0339.
Full textAbstract:
Osteoblasts are highly coupled by gap junctions formed by connexin43. Overexpression of connexin45 in osteoblasts results in decreased chemical and electrical coupling and reduces gene transcription from connexin response elements (CxREs) in the osteocalcin and collagen Iα1 promoters. Here, we demonstrate that transcription from the gap junction-dependent osteocalcin CxRE is regulated by extracellular signal-regulated protein kinase (ERK) and phosphatidylinositol 3-kinase (PI3K) cascades. Overexpression of a constitutively active mitogen-activated protein kinase kinase (MEK), Raf, or Ras can increase transcription more than twofold of the CxRE, whereas inhibition of MEK or PI3K can decrease transcription threefold from the osteocalcin CxRE. Importantly, disruption of gap junctional communication by overexpression of connexin45 or treatment with pharmacological inhibitors of gap junctions results in reduced Raf, ERK, and Akt activation. The consequence of attenuated gap junction-dependent signal cascade activation is a decrease in Sp1 phosphorylation by ERK, resulting in decreased Sp1 recruitment to the CxRE and inhibited gene transcription. These data establish that ERK/PI3K signaling is required for the optimal elaboration of transcription from the osteocalcin CxRE, and that disruption of gap junctional communication attenuates the ability of cells to respond to an extracellular cue, presumably by limiting the propagation of second messengers among adjacent cells by connexin43-gap junctions.
20
Fujimoto, K., A. Nagafuchi, S. Tsukita, A. Kuraoka, A. Ohokuma, and Y. Shibata. "Dynamics of connexins, E-cadherin and alpha-catenin on cell membranes during gap junction formation." Journal of Cell Science 110, no. 3 (February 1, 1997): 311–22. http://dx.doi.org/10.1242/jcs.110.3.311.
Full textAbstract:
We examined the dynamics of connexins, E-cadherin and alpha-catenin during gap-junction disassembly and assembly in regeneration hepatocytes by immunofluorescence microscopy, and immunogold-electron microscopy using SDS-digested freeze-replicas. The present findings suggest that during the disappearance of gap junctions most of the gap junction plaques are broken up into smaller aggregates, and then the gap junction proteins may be removed from the cell membrane, but some of the connexons or connexins remain dispersed in the plane of membrane as pure morphologically indistinguishable intramembrane proteins. Double-immunogold electron microscopy using a polyclonal antibody for connexins and a monoclonal antibody for E-cadherin or alpha-catenin revealed co-localization of these molecules at cell-to-cell contact sites during the reappearance of gap junction plaques. This implies that, at least in regenerating hepatocytes, the cadherin-catenin complex-mediated cell-to-cell contact sites act as foci for gap junction formation. In addition, connexin-immunoreactivity was also observed along tight junctional strands, suggesting that the gap junction may also form along the tight junctions.
21
Becker, David L., Catherine Leclerc-David, and Anne Warner. "The relationship of gap junctions and compaction in the preimplantation mouse embryo." Development 116, Supplement (April 1, 1992): 113–18. http://dx.doi.org/10.1242/dev.116.supplement.113.
Full textAbstract:
In the mouse embryo, gap junctions first appear at the 8-cell stage as compaction is about to take place. Compaction of the embryo is important for the differentiation of the first two cell types; the inner cell mass and the trophectoderm. Our studies examine the contribution of gap junctional communication at this stage of development We have characterised the normal sequence of appearance of gap junction protein and its distribution. The extent of communication as shown by the passage of dye between cells has been recorded in both normal embryos and embryos treated with drugs that influence gap junctional communication. Comparisons have been made with embryos that express a lethal gap junction defect and attempts were made to rescue such embryos by increasing their gap junction communication.
22
Musil, L. S., B. A. Cunningham, G. M. Edelman, and D. A. Goodenough. "Differential phosphorylation of the gap junction protein connexin43 in junctional communication-competent and -deficient cell lines." Journal of Cell Biology 111, no. 5 (November 1, 1990): 2077–88. http://dx.doi.org/10.1083/jcb.111.5.2077.
Full textAbstract:
Connexin43 is a member of the highly homologous connexin family of gap junction proteins. We have studied how connexin monomers are assembled into functional gap junction plaques by examining the biosynthesis of connexin43 in cell types that differ greatly in their ability to form functional gap junctions. Using a combination of metabolic radiolabeling and immunoprecipitation, we have shown that connexin43 is synthesized in gap junctional communication-competent cells as a 42-kD protein that is efficiently converted to a approximately 46-kD species (connexin43-P2) by the posttranslational addition of phosphate. Surprisingly, certain cell lines severely deficient in gap junctional communication and known cell-cell adhesion molecules (S180 and L929 cells) also expressed 42-kD connexin43. Connexin43 in these communication-deficient cell lines was not, however, phosphorylated to the P2 form. Conversion of S180 cells to a communication-competent phenotype by transfection with a cDNA encoding the cell-cell adhesion molecule L-CAM induced phosphorylation of connexin43 to the P2 form; conversely, blocking junctional communication in ordinarily communication-competent cells inhibited connexin43-P2 formation. Immunohistochemical localization studies indicated that only communication-competent cells accumulated connexin43 in visible gap junction plaques. Together, these results establish a strong correlation between the ability of cells to process connexin43 to the P2 form and to produce functional gap junctions. Connexin43 phosphorylation may therefore play a functional role in gap junction assembly and/or activity.
23
Reed, Anamika M., Thomas Kolodecik, Sohail Z. Husain, and Fred S. Gorelick. "Low pH enhances connexin32 degradation in the pancreatic acinar cell." American Journal of Physiology-Gastrointestinal and Liver Physiology 307, no. 1 (July 1, 2014): G24—G32. http://dx.doi.org/10.1152/ajpgi.00010.2014.
Full textAbstract:
Decreased extracellular pH is observed in a number of clinical conditions and can sensitize to the development and worsen the severity of acute pancreatitis. Because intercellular communication through gap junctions is pH-sensitive and modulates pancreatitis responses, we evaluated the effects of low pH on gap junctions in the rat pancreatic acinar cell. Decreasing extracellular pH from 7.4 to 7.0 significantly inhibited gap junctional intracellular communication. Acidic pH also significantly reduced levels of connexin32, the predominant gap junction protein in acinar cells, and altered its localization. Increased degradation through the proteasomal, lysosomal, and autophagic pathways mediated the decrease in connexin32 under low-pH conditions. These findings provide the first evidence that low extracellular pH can regulate gap junctional intercellular communication by enhancing connexin degradation.
24
ZAHS, KATHLEEN R., and PAUL W. CEELEN. "Gap junctional coupling and connexin immunoreactivity in rabbit retinal glia." Visual Neuroscience 23, no. 1 (January 2006): 1–10. http://dx.doi.org/10.1017/s0952523806231018.
Full textAbstract:
Gap junctions provide a pathway for the direct intercellular exchange of ions and small signaling molecules. Gap junctional coupling between retinal astrocytes and between astrocytes and Müller cells, the principal glia of vertebrate retinas, has been previously demonstrated by the intercellular transfer of gap-junction permeant tracers. However, functional gap junctions have yet to be demonstrated between mammalian Müller cells. In the present study, when the gap-junction permeant tracers Neurobiotin and Lucifer yellow were injected into a Müller cellviaa patch pipette, the tracers transferred to at least one additional cell in more than half of the cases examined. Simultaneous whole-cell recordings from pairs of Müller cells in the isolated rabbit retina revealed electrical coupling between closely neighboring cells, confirming the presence of functional gap junctions between rabbit Müller cells. The limited degree of this coupling suggests that Müller cell–Müller cell gap junctions may coordinate the functions of small ensembles of these glial cells. Immunohistochemistry and immunoblotting were used to identify the connexins in rabbit retinal glia. Connexin30 (Cx30) and connexin43 (Cx43) immunoreactivities were associated with astrocytes in the medullary ray region of the retinas of both pigmented and albino rabbits. Connexin43 was also found in Müller cells, but antibody recognition differed between astrocytic and Müller cell connexin43.
25
Bell, Cheryl, Teresa Shakespeare, Amber Smith, and Sandra Murray. "Visualization of Annular Gap Junction Vesicle Processing: The Interplay Between Annular Gap Junctions and Mitochondria." International Journal of Molecular Sciences 20, no. 1 (December 22, 2018): 44. http://dx.doi.org/10.3390/ijms20010044.
Full textAbstract:
It is becoming clear that in addition to gap junctions playing a role in cell–cell communication, gap junction proteins (connexins) located in cytoplasmic compartments may have other important functions. Mitochondrial connexin 43 (Cx43) is increased after ischemic preconditioning and has been suggested to play a protective role in the heart. How Cx43 traffics to the mitochondria and the interactions of mitochondria with other Cx43-containing structures are unclear. In this study, immunocytochemical, super-resolution, and transmission electron microscopy were used to detect cytoplasmic Cx43-containing structures and to demonstrate their interactions with other cytoplasmic organelles. The most prominent cytoplasmic Cx43-containing structures—annular gap junctions—were demonstrated to form intimate associations with lysosomes as well as with mitochondria. Surprisingly, the frequency of associations between mitochondria and annular gap junctions was greater than that between lysosomes and annular gap junctions. The benefits of annular gap junction/mitochondrial associations are not known. However, it is tempting to suggest, among other possibilities, that the contact between annular gap junction vesicles and mitochondria facilitates Cx43 delivery to the mitochondria. Furthermore, it points to the need for investigating annular gap junctions as more than only vesicles destined for degradation.
26
Lee, Y. C., C. E. Yellowley, Z. Li, H. J. Donahue, and D. E. Rannels. "Expression of functional gap junctions in cultured pulmonary alveolar epithelial cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 272, no. 6 (June 1, 1997): L1105—L1114. http://dx.doi.org/10.1152/ajplung.1997.272.6.l1105.
Full textAbstract:
Recent observations suggest that cell-cell interactions may modulate the response of the alveolar epithelium to injury. Expression and function of gap junctions were thus evaluated in isolated alveolar type II cells. Freshly isolated (day 0) type II cells expressed mRNAs for gap junctional connexins 26, 32, and 43. Whereas connexin 26 mRNA declined approximately 40% in cultured cells, connexin 32 message decreased rapidly and was not detectable on day 1. In contrast, connexin 43 expression increased 10-fold by day 3 compared with day 0. Western blot confirmed a 30-fold elevation in connexin 43 protein. Connexin 45 mRNA was not detected. Functional gap junction-mediated calcium signal propagation was monitored using fura 2, a calcium-sensitive dye. Membrane deformation in a single type II cell increased intracellular calcium; the signal spread rapidly to neighboring cells by octanol-sensitive pathways. Transfer of Lucifer yellow between cells also was inhibited by octanol. These observations demonstrate functional gap junctions between cultured alveolar epithelial cells and suggest that gap junctional expression and gap junction-mediated cell-cell coupling are regulated with time in culture.
27
MacKenzie, L. W., and R. E. Garfield. "Effects of tamoxifen citrate and cycloheximide on estradiol induction of rat myometrial gap junctions." Canadian Journal of Physiology and Pharmacology 64, no. 6 (June 1, 1986): 703–6. http://dx.doi.org/10.1139/y86-117.
Full textAbstract:
Longitudinal muscle of myometrial tissues from immature rats were examined by quantitative thin section electron microscopy for the presence of gap junctions after treatment with estradiol with and without tamoxifen, and cycloheximide for 1–6 days. Gap junctions were present between myometrial cells on days 4, 5, and 6 after treatment with estradiol (500 μg/day). Tamoxifen administered concomitantly with estradiol over the 6-day period completely prevented induction of the junctions. Gap junctions were not detected in the myometrium after treatment with tamoxifen alone. Administration of cycloheximide together with estradiol on day 0 of the 6-day period had no effect on gap junction frequency but resulted in a reduction in gap junction size in the myometrium after continued treatment with the hormone. Treatment with cycloheximide on day 1, however, significantly suppressed the effect of further estradiol treatment on the induction of gap junctions in the myometrium. Junctions were not visible in the tissues from animals treated with cycloheximide alone or in the control groups treated with sesame oil. These results indicate that estradiol influences the presence of gap junctions in the myometrium by regulating the synthesis of gap junction proteins through the steroid receptor mechanism.
28
Goodenough, D. A., and D. L. Paul. "Gap Junctions." Cold Spring Harbor Perspectives in Biology 1, no. 1 (July 1, 2009): a002576. http://dx.doi.org/10.1101/cshperspect.a002576.
Full text
29
Shimizu, Kazumichi, and Mark Stopfer. "Gap junctions." Current Biology 23, no. 23 (December 2013): R1026—R1031. http://dx.doi.org/10.1016/j.cub.2013.10.067.
Full text
30
Peters, Nicholas S. "Gap Junctions." Circulation Research 99, no. 11 (November 24, 2006): 1156–58. http://dx.doi.org/10.1161/01.res.0000251936.26233.0d.
Full text
31
Heyman, Nathanael S., David T. Kurjiaka, Jose F. Ek Vitorin, and Janis M. Burt. "Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin 43." American Journal of Physiology-Heart and Circulatory Physiology 297, no. 1 (July 2009): H450—H459. http://dx.doi.org/10.1152/ajpheart.00287.2009.
Full textAbstract:
Expression of connexin 40 (Cx40) and Cx43 in cardiovascular tissues varies as a function of age, injury, and development with unknown consequences on the selectivity of junctional communication and its acute regulation. We investigated the PKC-dependent regulation of charge selectivity in junctions composed of Cx43, Cx40, or both by simultaneous assessment of junctional permeance rate constants (Bdye) for dyes of similar size but opposite charge, N, N, N-trimethyl-2-[methyl-(7-nitro-2,1,3-benzoxadiol-4-yl)amino]ethanaminium (NBD-M-TMA; +1) and Alexa 350 (−1). The ratio of dye rate constants (BNBD-M-TMA/BAlexa 350) indicated that Cx40 junctions are cation selective (10.7 ± 0.5), whereas Cx43 junction are nonselective (1.22 ± 0.14). In coexpressing cells, a broad range of junctional selectivities was observed with mean cation selectivity increasing as the Cx40 to Cx43 expression ratio increased. PKC activation reduced or eliminated dye permeability of Cx43 junctions without altering their charge selectivity, had no effect on either permeability or charge selectivity of Cx40 junctions, and significantly increased the cation selectivity of junctions formed by coexpressing cells (approaching charge selectivity of Cx40 junctions). Junctions composed of Cx43 truncated at residue 257 (Cx43tr) were also not charge selective, but when Cx43tr was coexpressed with Cx40, a broad range of junctional selectivities that was unaffected by PKC activation was observed. Thus, whereas the charge selectivities of homomeric/homotypic Cx43 and Cx40 junctions appear invariant, the selectivities of junctions formed by cells coexpressing Cx40 and Cx43 vary considerably, reflecting both their relative expression levels and phosphorylation-dependent regulation. Such regulation could represent a mechanism by which coexpressing cells such as vascular endothelium and atrial cells regulate acutely the selective intercellular communication mediated by their gap junctions.
32
Beckmann, Anja, Nadine Hainz, Thomas Tschernig, and Carola Meier. "Facets of Communication: Gap Junction Ultrastructure and Function in Cancer Stem Cells and Tumor Cells." Cancers 11, no. 3 (March 1, 2019): 288. http://dx.doi.org/10.3390/cancers11030288.
Full textAbstract:
Gap junction proteins are expressed in cancer stem cells and non-stem cancer cells of many tumors. As the morphology and assembly of gap junction channels are crucial for their function in intercellular communication, one focus of our review is to outline the data on gap junction plaque morphology available for cancer cells. Electron microscopic studies and freeze-fracture analyses on gap junction ultrastructure in cancer are summarized. As the presence of gap junctions is relevant in solid tumors, we exemplarily outline their role in glioblastomas and in breast cancer. These were also shown to contain cancer stem cells, which are an essential cause of tumor onset and of tumor transmission into metastases. For these processes, gap junctional communication was shown to be important and thus we summarize, how the expression of gap junction proteins and the resulting communication between cancer stem cells and their surrounding cells contributes to the dissemination of cancer stem cells via blood or lymphatic vessels. Based on their importance for tumors and metastases, future cancer-specific therapies are expected to address gap junction proteins. In turn, gap junctions also seem to contribute to the unattainability of cancer stem cells by certain treatments and might thus contribute to therapeutic resistance.
33
Gourdie, R. G., C. R. Green, and N. J. Severs. "Gap junction distribution in adult mammalian myocardium revealed by an anti-peptide antibody and laser scanning confocal microscopy." Journal of Cell Science 99, no. 1 (May 1, 1991): 41–55. http://dx.doi.org/10.1242/jcs.99.1.41.
Full textAbstract:
A polyclonal antiserum, raised against a synthetic peptide matching part of the sequence of connexin43 (a rat cardiac gap-junctional protein), was used in combination with laser scanning confocal microscopy to investigate gap junction distribution in cardiac tissues from a range of mammalian species. Comparison of the localised punctate staining patterns obtained in ventricular tissue with the distribution of intercalated disks as viewed by conventional light microscopy and electron microscopy, and with the staining observed by standard light-microscope immunofluorescence using the same anti-serum, demonstrated highly specific labelling of clearly resolved individual gap junctions. Laser scanning confocal microscopy of ventricular myocardium showed the immunostained gap junctions to be confined to well-defined intercalated disks bisecting the long axis of the muscle fibre, whereas in the atrial myocardium, gap junctions were commonly distributed widely over the lateral surfaces of the myocyte body. Rat atrial gap junctions were significantly larger (as measured by the longest axial lengths of fluorescent spots), and showed a narrower spread of sizes, than their counterparts in the ventricle. Ventricular myocardium from six mammalian species including man gave similar immunostaining patterns, indicating conservation both of the epitope(s) detected by the antiserum, and of the general organisation of the cell-to-cell pathways for electrical propagation, in the mammalian heart. Optical section series obtained by laser scanning confocal microscopy permitted the quantification and mapping of the three-dimensional distribution of gap junctions in ventricular intercalated disks with high clarity over substantial specimen depths. A consistent feature of gap junction organisation within disks of ventricular myocardium in all species studied was the presence of a conspicuous ring of large gap junctions around the periphery of the disk. Immunostained gap junctions lying within the interior zone delineated by the peripheral junctions generally occurred at lower numerical densities and were significantly smaller. In all species, less than 3% of all immunolabelled gap junctions measured were greater than 2 microns in maximal length, though a small proportion (0.06%) exceeded 4 microns. The numerical density of immunolabelled gap junctions in the disk was similar between species; however, within species there was a significant decrease in numerical density with increasing disk size. The new features of intercalated disk structure revealed in this study may have an important part to play in the intercellular communication and electrical propagation properties of the mammalian heart.
34
Lan, Wei-Ren, Charles Jia-Yin Hou, Chih-Hsuan Yen, Bing-Fu Shih, An-Mei Wang, Tzung-Yi Lee, Cheng-Ho Tsai, and Hung-I. Yeh. "Effects of carbenoxolone on flow-mediated vasodilatation in healthy adults." American Journal of Physiology-Heart and Circulatory Physiology 301, no. 3 (September 2011): H1166—H1172. http://dx.doi.org/10.1152/ajpheart.00967.2010.
Full textAbstract:
Gap junctions play a key role in maintaining the functional integrity of the vascular wall. Using carbenoxolone (CBX) as a gap junction blocker, we aimed to assess the contribution of gap junctions in the vascular wall to flow-mediated vasodilatation (FMD) in healthy adults. Percentage FMD (%FMD) and circulating vasoactive molecules/activity, including atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), aldosterone, cortisol, plasma renin activity (PRA), and endothelin (ET-1), were measured in 25 healthy volunteers (mean age: 30.1 ± 5.4 yr; 14 males) before and after oral administration of CBX (100 mg). %FMD decreased after ingestion of CBX (9.71 ± 3.1 vs. 3.40 ± 2.0%; P < 0.0001). The levels of ANP, BNP, cortisol, and ET-1 remained stationary, while both PRA and aldosterone decreased ( P < 0.005) after CBX ingestion. Blood pressure and heart rate were minimally changed by CBX. Inhibition of gap junctional communication by CBX impairs FMD in healthy persons, suggesting that physiologically, vascular gap junctions participate in the maintenance of FMD. CBX does not induce the release of vasoconstricting molecules or enhance vasoconstriction, suggesting that inhibition of gap junctional communication by CBX underlies the impairment of FMD. Therefore, administering CBX in FMD examination can be a way to follow the effect of gap junctions on endothelial function, but further work remains to verify the specificity of CBX effect.
35
Peters, Nicholas S. "New Insights into Myocardial Arrhythmogenesis: Distribution of Gap-Junctional Coupling in Normal, Ischaemic and Hypertrophied Human Hearts." Clinical Science 90, no. 6 (June 1, 1996): 447–52. http://dx.doi.org/10.1042/cs0900447.
Full textAbstract:
1. Ischaemic and hypertrophic heart diseases are associated with ventricular arrhythmias, in which abnormal cellular coupling is implicated as having a causative role. The aim of this series of studies was to characterize gap-junctional organization in normal human ventricular myocardium, and to investigate the hypothesis that alterations in the quantity and patterns of expression of myocardial gap junctions occur in ischaemic and hypertrophic myocardial disease. 2. An antibody raised against connexin43 was used for immunohistochemical labelling of myocardium examined by confocal laser scanning microscopy, permitting highly sensitive and quantifiable immunofluorescent imaging of gap junctions through volumes of intact cardiac tissue. 3. Connexin43 gap junctions in normal adult human ventricular myocardium are highly organized into clusters of fluorescent label confined to the intercalated disks as a peripheral ring of larger junctions, with smaller junctions centrally, and occupy a surface area of 0.005 μm2/μm3 myocyte volume. 4. Neonatal human myocardium has a punctate distribution of connexin43 over the entire surface of the ventricular myocytes, with a progressive polarization of the gap junctions towards the positions of the mature intercalated disks, reaching the adult pattern at about 6 years. 5. At the myocardial interface with the scar of a healed infarct, connexin43 gap junction distribution is grossly disturbed, being strewn in longitudinally orientated arrays along the lateral interfaces between degenerated but viable myocytes, which may be due to a redistribution of the pre-existing population of junctions. This altered distribution is present as early as 4 days after coronary occlusion in a canine model, in which it defines the location of circuits causing ventricular tachycardia. 6. Myocardium distant from infarction in patients with ischaemic heart disease has a normal pattern of connexin43 gap junction distribution, but has a 47% reduction in gap junction surface area per unit cell volume, and a 30% reduction per cell. 7. In hypertrophied myocardium from chronically pressure-loaded human left ventricles, connexin43 gap junction expression per myocyte is not significantly different from normal, but is reduced by 40% per unit volume of myocyte. 8. The early phases of the hypertrophic response of myocardium to renovascular hypertension in guinea pigs revealed a substantially increased connexin43 gap junction expression compared with controls, both when measured per cell (increased by 45%) and per unit volume of myocyte (increased by 30%), and therefore showed an alteration apparently contrary to that observed in chronically hypertrophied human ventricular myocardium. 9. In this series of studies, normal adult human ventricular myocardium and the post-natal developmental changes have been characterized with respect to connexin43 gap junction content, and the observed alterations of both distribution and quantity in ischaemic and hypertrophied hearts would be expected to influence myocardial conduction and the arrhythmogenic substrate.
36
Bauer, Reinhard, Corinna Lehmann, Julia Martini, Franka Eckardt, and Michael Hoch. "Gap Junction Channel Protein Innexin 2 Is Essential for Epithelial Morphogenesis in the Drosophila Embryo." Molecular Biology of the Cell 15, no. 6 (June 2004): 2992–3004. http://dx.doi.org/10.1091/mbc.e04-01-0056.
Full textAbstract:
Direct communication of neighboring cells by gap junction channels is essential for the development of tissues and organs in the body. Whereas vertebrate gap junctions are composed of members of the connexin family of transmembrane proteins, in invertebrates gap junctions consist of Innexin channel proteins. Innexins display very low sequence homology to connexins. In addition, very little is known about their cellular role during developmental processes. In this report, we examined the function and the distribution of Drosophila Innexin 2 protein in embryonic epithelia. Both loss-of-function and gain-of-function innexin 2 mutants display severe developmental defects due to cell death and a failure of proper epithelial morphogenesis. Furthermore, immunohistochemical analyses using antibodies against the Innexins 1 and 2 indicate that the distribution of Innexin gap junction proteins to specific membrane domains is regulated by tissue specific factors. Finally, biochemical interaction studies together with genetic loss- and gain-of-function experiments provide evidence that Innexin 2 interacts with core proteins of adherens and septate junctions. This is the first study, to our knowledge, of cellular distribution and protein–protein interactions of an Innexin gap junctional channel protein in the developing epithelia of Drosophila.
37
Moore, L. K., E. C. Beyer, and J. M. Burt. "Characterization of gap junction channels in A7r5 vascular smooth muscle cells." American Journal of Physiology-Cell Physiology 260, no. 5 (May 1, 1991): C975—C981. http://dx.doi.org/10.1152/ajpcell.1991.260.5.c975.
Full textAbstract:
Recent evidence suggest that coordination of blood flow in the microcirculation involves cell-to-cell coupling via gap junctions. In this study, using A7r5 cells as a model of vascular smooth muscle, we have characterized the gap junctions in terms of the unitary conductances of the observed channels, the responses to second messengers, and subunit protein composition. The cells were typically well coupled several hours after plating, with junctional conductances on the order 20-40 nS. Channels with mean conductances of 36 and 89 pS were observed in low-conductance cell pairs and in cell pairs whose macroscopic conductance was reduced by exposure to halothane. Connexin43 was the only known gap junction sequence detected by Northern blots (low and high stringency), immunoblots, or immunohistochemical studies. Junctional conductance was reduced 15% by 8-bromoadenosine 3',5'-cyclic monophosphate; 8-bromoguanosine 3',5'-cyclic monophosphate had no effect. The results suggest that connexin43 can form stable channels of at least two distinct conductances and gap junctions with differing responses to second messengers.
38
Zampighi, G., M. Kreman, F. Ramón, A. L. Moreno, and S. A. Simon. "Structural characteristics of gap junctions. I. Channel number in coupled and uncoupled conditions." Journal of Cell Biology 106, no. 5 (May 1, 1988): 1667–78. http://dx.doi.org/10.1083/jcb.106.5.1667.
Full textAbstract:
Gap junctions between crayfish lateral axons were studied by combining anatomical and electrophysiological measurements to determine structural changes associated during uncoupling by axoplasmic acidification. In basal conditions, the junctional resistance, Rj, was approximately 60-80 k omega and the synapses appeared as two adhering membranes; 18-20-nm overall thickness, containing transverse densities (channels) spanning both membranes and the narrow extracellular gap (4-6 nm). In freeze-fracture replicas, the synapses contained greater than 3 X 10(3) gap junction plaques having a total of approximately 3.5 X 10(5) intramembrane particles. "Single" gap junction particles represented approximately 10% of the total number of gap junction particles present in the synapse. Therefore, in basal conditions, most of the gap junction particles were organized in plaques. Moreover, correlations of the total number of gap junction particles with Rj suggested that most of the junctional particles in plaques corresponded to conducting channels. Upon acidification of the axoplasm to pH 6.7-6.8, the junctional resistance increased to approximately 300 k omega and action potentials failed to propagate across the septum. Morphological measurements showed that the total number of gap junction particles in plaques decreased approximately 11-fold to 3.1 X 10(4) whereas the number of single particles dispersed in the axolemmae increased significantly. Thin sections of these synapses showed that the width of the extracellular gap increased from 4-6 nm in basal conditions to 10-20 nm under conditions where axoplasmic pH was 6.7-6.8. These observations suggest that single gap junction particles dispersed in the synapse most likely represent hemi-channels produced by the dissasembly of channels previously arranged in plaques.
39
Zhou, Cheng-Jie, Sha-Na Wu, Jiang-Peng Shen, Dong-Hui Wang, Xiang-Wei Kong, Angeleem Lu, Yan-Jiao Li, Hong-Xia Zhou, Yue-Fang Zhao, and Cheng-Guang Liang. "The beneficial effects of cumulus cells and oocyte-cumulus cell gap junctions depends on oocyte maturation and fertilization methods in mice." PeerJ 4 (March 3, 2016): e1761. http://dx.doi.org/10.7717/peerj.1761.
Full textAbstract:
Cumulus cells are a group of closely associated granulosa cells that surround and nourish oocytes. Previous studies have shown that cumulus cells contribute to oocyte maturation and fertilization through gap junction communication. However, it is not known how this gap junction signaling affectsin vivoversusin vitromaturation of oocytes, and their subsequent fertilization and embryonic development following insemination. Therefore, in our study, we performed mouse oocyte maturation and insemination usingin vivo- orin vitro-matured oocyte-cumulus complexes (OCCs, which retain gap junctions between the cumulus cells and the oocytes),in vitro-matured, denuded oocytes co-cultured with cumulus cells (DCs, which lack gap junctions between the cumulus cells and the oocytes), andin vitro-matured, denuded oocytes without cumulus cells (DOs). Using these models, we were able to analyze the effects of gap junction signaling on oocyte maturation, fertilization, and early embryo development. We found that gap junctions were necessary for bothin vivoandin vitrooocyte maturation. In addition, for oocytes maturedin vivo, the presence of cumulus cells during insemination improved fertilization and blastocyst formation, and this improvement was strengthened by gap junctions. Moreover, for oocytes maturedin vitro, the presence of cumulus cells during insemination improved fertilization, but not blastocyst formation, and this improvement was independent of gap junctions. Our results demonstrate, for the first time, that the beneficial effect of gap junction signaling from cumulus cells depends on oocyte maturation and fertilization methods.
40
Sun, Jianjun, Shoab Ahmad, Shanping Chen, Wenxue Tang, Yanping Zhang, Ping Chen, and Xi Lin. "Cochlear gap junctions coassembled from Cx26 and 30 show faster intercellular Ca2+ signaling than homomeric counterparts." American Journal of Physiology-Cell Physiology 288, no. 3 (March 2005): C613—C623. http://dx.doi.org/10.1152/ajpcell.00341.2004.
Full textAbstract:
The importance of connexins (Cxs) in cochlear functions has been demonstrated by the finding that mutations in Cx genes cause a large proportion of sensorineural hearing loss cases. However, it is still unclear how Cxs contribute to the cochlear function. Recent data ( 33 ) obtained from Cx30 knockout mice showing that a reduction of Cx diversity in assembling gap junctions is sufficient to cause deafness suggest that functional interactions of different subtypes of Cxs may be essential in normal hearing. In this work we show that the two major forms of Cxs (Cx26 and Cx30) in the cochlea have overlapping expression patterns beginning at early embryonic stages. Cx26 and Cx30 were colocalized in most gap junction plaques in the cochlea, and their coassembly was tested by coimmunoprecipitation. To compare functional differences of gap junctions with different molecular configurations, homo- and heteromeric gap junctions composed of Cx26 and/or Cx30 were reconstituted by transfections in human embryonic kidney-293 cells. The ratio imaging technique and fluorescent tracer diffusion assays were used to assess the function of reconstituted gap junctions. Our results revealed that gap junctions with different molecular configurations show differences in biochemical coupling, and that intercellular Ca2+ signaling across heteromeric gap junctions consisting of Cx26 and Cx30 was at least twice as fast as their homomerically assembled counterparts. Our data suggest that biochemical permeability and the dynamics of intercellular signaling through gap junction channels, in addition to gap junction-mediated intercellular ionic coupling, may be important factors to consider for studying functional roles of gap junctions in the cochlea.
41
Agrawal, R., and E. E. Daniel. "Control of gap junction formation in canine trachea by arachidonic acid metabolites." American Journal of Physiology-Cell Physiology 250, no. 3 (March 1, 1986): C495—C505. http://dx.doi.org/10.1152/ajpcell.1986.250.3.c495.
Full textAbstract:
This study examined whether the synthesis of the metabolites of arachidonic acid (AA) was involved in gap junction formation by 4-aminopyridine (4-AP) treatment in vitro in canine trachealis. Studies were made of the effects on gap junction formation of putative inhibitors of the cyclooxygenase and of both this and the lipoxygenase pathway of AA metabolism and the direct effects of prostaglandins (PG) E2 and I2. The number of gap junctions of similar size was increased after brief exposure to 4-AP. After indomethacin (IDM), 4-AP treatment decreased the number of gap junctions but did not affect their size. Pretreatment with 5,8,11,14-eicosatetraynoic acid or nordihydroguiaretic acid, putative inhibitors of cyclooxygenase and lipoxygenase enzymes, inhibited both the 4-AP-induced increase and decrease in the number of gap junctions. FPL 55712, a putative antagonist of leukotriene C4, did not alter either the number or the size of gap junctions when added alone or in combination with IDM. AA alone increased the number of gap junctions, but after IDM, AA decreased the number of gap junctions compared with the controls. Incubation of trachealis strips in vitro for 30 min with PGE2 increased the number of gap junctions by about threefold along with an increase in the size of the gap junctions. Similar incubation with PGI2, however, increased the number of gap junctions by approximately 60% without any change in the size. In the course of some control experiments, an interaction between carbachol and alcohol was observed such that alcohol caused an IDM-sensitive relaxation of carbachol-induced contractions, which was not observed when serotonin was the contractile agent. These results strongly suggest that PGE2 and PGI2 increase the formation of gap junctions in canine trachealis and that these prostanoids are released by 4-AP treatment. Leukotrienes may also be inhibitory in the formation of gap junctions, but FPL 55712 did not affect either the increase or the decrease in gap junctions after 4-AP.
42
Shibata, Y., C. K. Manjunath, and E. Page. "Differences between cytoplasmic surfaces of deep-etched heart and liver gap junctions." American Journal of Physiology-Heart and Circulatory Physiology 249, no. 3 (September 1, 1985): H690—H693. http://dx.doi.org/10.1152/ajpheart.1985.249.3.h690.
Full textAbstract:
We have compared the ultrastructures of the cytoplasmic surfaces (CS) of isolated, glutaraldehyde-fixed gap junctional pellets from rat ventricles and liver by rapid freezing on a liquid helium-cooled surface, freeze fracture, deep etching, and double-axis rotary replication (J. Microsc. Oxford 137: 121-123, 1984). Deep-etched unproteolyzed cardiac junctions [protein subunit relative molecular wt (Mr) 44,000-47,000], isolated with phenylmethylsulfonylfluoride (PMSF) [Am. J. Physiol. 246 (Heart Circ. Physiol. 15): H865-H875, 1984; C.K. Manjunath, G.E. Goings, and E. Page. Proteolysis of cardiac gap junctions during their isolation from rat hearts. J. Membr. Biol. In press.] had particulate CS, while proteolyzed cardiac junctions (subunit Mr 29,500) made without PMSF and liver junctions (Mr 28,000) made with or without PMSF had nonparticulate CS. Taken together with our previous findings that electron micrographs of thin-sectioned isolated unproteolyzed cardiac junctions have urea-resistant fuzzy CS coatings [Am. J. Physiol. 246 (Heart Circ. Physiol. 15): H865-H875, 1984], that proteolyzed cardiac junctions and isolated liver junctions lack this fuzzy layer, and that the CS of in situ cardiac junctions is fuzzy [J. Membr. Biol. 78: 147-155, 1984; Am. J. Physiol. 246 (Heart Circ. Physiol 15): H865-H875, 1984], and published data that in situ freeze-etched liver gap junctions are nonparticulate (Cell 30: 395-406, 1982), these new observations strongly indicate that CS components of heart and liver gap junction proteins are structurally different.
43
Eugenín, Eliseo A., Hernan González, Claudia G. Sáez, and Juan C. Sáez. "Gap junctional communication coordinates vasopressin-induced glycogenolysis in rat hepatocytes." American Journal of Physiology-Gastrointestinal and Liver Physiology 274, no. 6 (June 1, 1998): G1109—G1116. http://dx.doi.org/10.1152/ajpgi.1998.274.6.g1109.
Full textAbstract:
Because hepatocytes communicate via gap junctions, it has been proposed that Ca2+waves propagate through this pathway and in the process activate Ca2+-dependent cellular responses. We tested this hypothesis by measuring vasopressin-induced glycogenolysis in short-term cultures of rat hepatocytes. A 15-min vasopressin (10−8 M) stimulation induced a reduction of glycogen content that reached a maximum 1–3 h later. Gap junction blockers, octanol or 18α-glycyrrhetinic acid, reduced the effect by 70%. The glycogenolytic response induced by Ca2+ ionophore 8-bromo-A-21387, which acts on each hepatocyte, was not affected by gap junction blockers. Moreover, the vasopressin-induced glycogenolysis was lower (70%) in dispersed than in reaggregated hepatocytes and in dispersed hepatocytes was not affected by gap junction blockers. In hepatocytes reaggregated in the presence of a synthetic peptide homologous to a domain of the extracellular loop 1 of the main hepatocyte gap junctional protein, vasopressin-induced glycogenolysis and incidence of dye coupling were drastically reduced. Moreover, gap junctional communication was detected between reaggregated cells, suggesting that hepatocytes with different vasopressin receptor densities become coupled to each other. The vasopressin-induced effect was not affected by suramin, ruling out ATP as a paracrine mediator. We propose that gap junctions allow for a coordinated vasopressin-induced glycogenolytic response despite the heterogeneity among hepatocytes.
44
Goodenough, D. A., D. L. Paul, and L. Jesaitis. "Topological distribution of two connexin32 antigenic sites in intact and split rodent hepatocyte gap junctions." Journal of Cell Biology 107, no. 5 (November 1, 1988): 1817–24. http://dx.doi.org/10.1083/jcb.107.5.1817.
Full textAbstract:
The membrane topology of connexin32, a principal polypeptide of gap junctions in diverse cell types, has been studied in rat and mouse hepatocyte gap junctions using site-specific antisera raised against synthetic oligopeptides corresponding to amino acid sequences deduced from cDNA clones. Based on published hydropathicity maps and identified protease-sensitive cleavage sites, oligopeptides were synthesized corresponding to two hydrophilic domains of connexin32, one predicted to face the cytoplasm, the other predicted to be directed extracellularly. Antisera were raised to keyhole limpet hemocyanin conjugates of the oligopeptides and used to map the distribution of their antigens using indirect immunocytochemistry on isolated gap junctions. The results directly demonstrated the cytoplasmic orientation of an antigen contained within amino acids 98-124 of the connexin32 sequence. The extracellular space in intact, isolated gap junctions is too small to permit binding of antibody molecules, necessitating the experimental separation of the junctional membranes to expose their extracellular surfaces using a urea/alkali procedure. While an antigen contained within amino acids 164-189 was visualized on the extracellular surfaces of some of the separated junctional membranes, variability in the observations and in the splitting procedure left ambiguities concerning the biological relevance of the observations after the denaturing conditions necessary to separate the junctional membranes. Using a different approach, however, the antigen could be exposed in intact liver using a hypertonic disaccharide junction-splitting procedure. The period of time of antigen exposure at the cell surface appears to peak at 30 s and disappear by 2-4 min. Taken together, these data demonstrate the extracellular orientation of an antigen contained within amino acids 164-189, which may be involved in cell-cell interaction within the gap junction.
45
Wolf, Klaus V. "Light and Electron Microscopic Studies Regarding Cell Contractility and Cell Coupling in Light Sensitive Smooth Muscle Cells from the Isolated Frog Iris Sphincter." Zeitschrift für Naturforschung C 42, no. 7-8 (August 1, 1987): 977–85. http://dx.doi.org/10.1515/znc-1987-7-842.
Full textAbstract:
(1) In light microscopical studies of living isolated frog irises, it was found that the maximal areas of experimentally light induced contractions in the m. sphincter pupillae were located beneath small illuminated regions. There were no visible contractions of muscle cells outside the illuminated areas. It was shown that exposure to light could directly cause contractions of isolated single sphincter muscle cells. (2) Junctional structures of the iris sphincter cells were studied by means of thin sections and freeze fracture electron microscopy. Intermediate junctions, a few focal tight junctions and occasional small gap junctions were identified. Pit containing intramembranous particles which resemble gap junction connexons were found in large numbers, dispersed over the plasmalemmas of sphincter muscle cells. From these physiological and morphological observations, it is concluded that sphincter muscle cells of the frog iris may be coupled via gap junctions, but that the cell coupling is not sufficiently extensive to form the basis for a functional syncytium.
46
Jeong, S.-H., M.-H. Cho, and J.-H. Cho. "Effects of cadmium on gap junctional intercellular communication in WB-F344 rat liver epithelial cells." Human & Experimental Toxicology 20, no. 11 (November 2001): 577–83. http://dx.doi.org/10.1191/096032701718620855.
Full textAbstract:
Cadmium has been associated with a number of tumors but its role in tumor promotion has not been elucidated clearly or the results obtained from various studies have been conflicting. This study was designed to investigate the effects of cadmium on the gap junctional intercellular communication (GJIC), number of gap junctions per cell, and cell proliferation in WB-F344 rat liver epithelial cells from the viewpoint of tumor promotion. GJIC was monitored by counting the cells stained with Lucifer yellow CH dye, using the scrape-loading and dye-transfer method. The numbers of gap junctions per cell were visually quantitated after an indirect immunostaining for gap junction protein using an antibody to connexin 43. Cell proliferation was assayed by direct counting of the living cells using the trypan blue dye exclusion method. In the time course study, cells treated with 200 μM CdCl2 showed rapid and nearly complete inhibition of GJIC (approximately 14% of the control) and a decrease in the number of gap junctions per cell (approximately 21% of the control) at 30 min, and the decrease continued up to 4 h without any changes in the cell viability. Treatment with CdCl2 7.4-200 μM) for 4 h resulted in the decrease of GJIC and gap junction numbers per cell in a dose-response pattern without changes in the cell viability. In the long-term (14 days) exposure studies at doses of 0.01-7.4 μM CdCl2, an increase in cell proliferation was observed at low doses of 0.03-2.5 μM CdCl2, with GJIC also decreasing. These data demonstrate that cadmium inhibits GJIC, reduces the number of gap junctions per cell, and induces cell proliferation while decreasing the function of the gap junction.
47
de Rivero Vaccari, Juan Carlos, Roderick A. Corriveau, and Andrei B. Belousov. "Gap Junctions Are Required for NMDA Receptor–Dependent Cell Death in Developing Neurons." Journal of Neurophysiology 98, no. 5 (November 2007): 2878–86. http://dx.doi.org/10.1152/jn.00362.2007.
Full textAbstract:
A number of studies have indicated an important role for N-methyl-d-aspartate (NMDA) receptors in cell survival versus cell death decisions during neuronal development, trauma, and ischemia. Coupling of neurons by electrical synapses (gap junctions) is high or increases in neuronal networks during all three of these conditions. However, whether neuronal gap junctions contribute to NMDA receptor–regulated cell death is not known. Here we address the role of neuronal gap junction coupling in NMDA receptor–regulated cell death in developing neurons. We report that inactivation or hyperactivation of NMDA receptors induces neuronal cell death in primary hypothalamic cultures, specifically during the peak of developmental gap junction coupling. In contrast, increasing or decreasing NMDA receptor function when gap junction coupling is low has no or greatly reduced impact on cell survival. Pharmacological inactivation of gap junctions or knockout of neuronal connexin 36 prevents the cell death caused by NMDA receptor hypofunction or hyperfunction. The results indicate the critical role of neuronal gap junctions in cell death caused by increased or decreased NMDA receptor function in developing neurons. Based on these data, we propose the novel hypothesis that NMDA receptors and gap junctions work in concert to regulate neuronal survival.
48
Gairhe, Salina, Natalie N. Bauer, Sarah A. Gebb, and Ivan F. McMurtry. "Serotonin passes through myoendothelial gap junctions to promote pulmonary arterial smooth muscle cell differentiation." American Journal of Physiology-Lung Cellular and Molecular Physiology 303, no. 9 (November 1, 2012): L767—L777. http://dx.doi.org/10.1152/ajplung.00183.2012.
Full textAbstract:
Myoendothelial gap junctional signaling mediates pulmonary arterial endothelial cell (PAEC)-induced activation of latent TGF-β and differentiation of cocultured pulmonary arterial smooth muscle cells (PASMCs), but the nature of the signal passing from PAECs to PASMCs through the gap junctions is unknown. Because PAECs but not PASMCs synthesize serotonin, and serotonin can pass through gap junctions, we hypothesized that the monoamine is the intercellular signal. We aimed to determine whether PAEC-derived serotonin mediates PAEC-induced myoendothelial gap junction-dependent activation of TGF-β signaling and differentiation of PASMCs. Rat PAECs and PASMCs were monocultured or cocultured with (touch) or without (no-touch) direct cell-cell contact. In all cases, tryptophan hydroxylase 1 (Tph1) transcripts were expressed predominantly in PAECs. Serotonin was detected by immunostaining in both PAECs and PASMCs in PAEC/PASMC touch coculture but was not found in PASMCs in either PAEC/PASMC no-touch coculture or in PASMC/PASMC touch coculture. Furthermore, inhibition of gap junctions but not of the serotonin transporter in PAEC/PASMC touch coculture prevented serotonin transfer from PAECs to PASMCs. Inhibition of serotonin synthesis pharmacologically or by small interfering RNAs to Tph1 in PAECs inhibited the PAEC-induced activation of TGF-β signaling and differentiation of PASMCs. We concluded that serotonin synthesized by PAECs is transferred through myoendothelial gap junctions into PASMCs, where it activates TGF-β signaling and induces a more differentiated phenotype. This finding suggests a novel role of gap junction-mediated intercellular serotonin signaling in regulation of PASMC phenotype.
49
Saunders, M. M., J. You, J. E. Trosko, H. Yamasaki, Z. Li, H. J. Donahue, and C. R. Jacobs. "Gap junctions and fluid flow response in MC3T3-E1 cells." American Journal of Physiology-Cell Physiology 281, no. 6 (December 1, 2001): C1917—C1925. http://dx.doi.org/10.1152/ajpcell.2001.281.6.c1917.
Full textAbstract:
In the current study, we examined the role of gap junctions in oscillatory fluid flow-induced changes in intracellular Ca2+concentration and prostaglandin release in osteoblastic cells. This work was completed in MC3T3-E1 cells with intact gap junctional communication as well as in MC3T3-E1 cells rendered communication deficient through expression of a dominant-negative connexin. Our results demonstrate that MC3T3-E1 cells with intact gap junctions respond to oscillatory fluid flow with significant increases in prostaglandin E2 (PGE2) release, whereas cells with diminished gap junctional communication do not. Furthermore, we found that cytosolic Ca2+ (Ca[Formula: see text]) response was unaltered by the disruption in gap junctional communication and was not significantly different among the cell lines. Thus our results suggest that gap junctions contribute to the PGE2 but not to the Ca[Formula: see text] response to oscillatory fluid flow. These findings implicate gap junctional intercellular communication (GJIC) in bone cell ensemble responsiveness to oscillatory fluid flow and suggest that gap junctions and GJIC play a pivotal role in mechanotransduction mechanisms in bone.
50
Jordan, K., R. Chodock, A. R. Hand, and D. W. Laird. "The origin of annular junctions: a mechanism of gap junction internalization." Journal of Cell Science 114, no. 4 (February 15, 2001): 763–73. http://dx.doi.org/10.1242/jcs.114.4.763.
Full textAbstract:
Gap junctional intercellular communication is established when connexin proteins oligomerize into connexon hemichannels, which then pair at the cell surface with connexons from neighboring cells to form functional gap junction channels. Gap junction channels routinely cluster into gap junction plaques, which can exhibit dynamic characteristics while under the frequent processes of formation and removal from the cell surface. We have three lines of evidence to suggest that one mechanism of gap junction removal occurs when one of two contacting cells internalizes the gap junction contribution from both cells. First, in coculture experiments, green fluorescent protein-tagged connexin43 (Cx43-GFP) expressed in normal rat kidney (NRK) cells can be internalized into contacting cells that do not express Cx43-GFP, and the incidences of identifying these internalized structures increase in the presence of lysosomal inhibitors. Secondly, time-lapse imaging of live NRK cells revealed that large areas of gap junction plaques containing Cx43-GFP were internalized as vesicular-like structures into one of two adjacent cells. Finally, when live NRK cells that express endogenous Cx43 were microinjected with anti-Cx43 antibodies, antibody-tagged gap junctions were visualized in cells that contacted the microinjected cell within 3–6.5 hours. Together our results strongly suggest that one mechanism of gap junction removal from the cell surface involves a unique process in which the entire gap junction or a fragment of it is internalized into one of the two contacting cells as an annular junction.