scholarly journals Regulation of connexin43 gap junctional communication by phosphatidylinositol 4,5-bisphosphate

2007 ◽  
Vol 177 (5) ◽  
pp. 881-891 ◽  
Author(s):  
Leonie van Zeijl ◽  
Bas Ponsioen ◽  
Ben N.G. Giepmans ◽  
Aafke Ariaens ◽  
Friso R. Postma ◽  
...  
Keyword(s):  
Second Messengers ◽  
Pdz Domain ◽  
Cell Communication ◽  
Receptor Activation ◽  
Gap Junctional Communication ◽  
Signaling Complex ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Zona Occludens ◽  
Cell Cell

Cell–cell communication through connexin43 (Cx43)-based gap junction channels is rapidly inhibited upon activation of various G protein–coupled receptors; however, the mechanism is unknown. We show that Cx43-based cell–cell communication is inhibited by depletion of phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P2) from the plasma membrane. Knockdown of phospholipase Cβ3 (PLCβ3) inhibits PtdIns(4,5)P2 hydrolysis and keeps Cx43 channels open after receptor activation. Using a translocatable 5-phosphatase, we show that PtdIns(4,5)P2 depletion is sufficient to close Cx43 channels. When PtdIns(4,5)P2 is overproduced by PtdIns(4)P 5-kinase, Cx43 channel closure is impaired. We find that the Cx43 binding partner zona occludens 1 (ZO-1) interacts with PLCβ3 via its third PDZ domain. ZO-1 is essential for PtdIns(4,5)P2-hydrolyzing receptors to inhibit cell–cell communication, but not for receptor–PLC coupling. Our results show that PtdIns(4,5)P2 is a key regulator of Cx43 channel function, with no role for other second messengers, and suggest that ZO-1 assembles PLCβ3 and Cx43 into a signaling complex to allow regulation of cell–cell communication by localized changes in PtdIns(4,5)P2.

Gap-junctional communication in a communication-defective and in a communication-competent teratocarcinoma cell line

1985 ◽  
Vol 76 (1) ◽  
pp. 85-95
Author(s):  
C.W. Lo ◽  
D. Fang ◽  
M.L. Hooper
Keyword(s):  
Cell Line ◽  
Coupling Coefficient ◽  
Dye Coupling ◽  
Cell Coupling ◽  
Teratocarcinoma Cell ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Ionic Coupling ◽  
Cell Cell

We examined the gap-junctional communication properties of a communication-defective cell line R5/3 and its communication-competent revertant H2T12. For these studies, we carried out microelectrode impalements to monitor ionic coupling and dye coupling. Our dye-injection experiments revealed that the H2T12 cells are much more efficient in dye coupling than the R5/3 cells. This latter observation is in agreement with the previous finding that the H2T12 cells are much better metabolically coupled than the R5/3 cells. With ionic coupling measurements, however, both cell lines exhibited similar levels of cell-cell coupling. The R5/3 cells demonstrated an ionic coupling coefficient of 0.19 +/− 0.011 (S.E.M.) and H2T12 a coupling coefficient of 0.25 +/− 0.009 (S.E.M.). These results in conjunction with observations from other studies indicate that the different experimental approaches for monitoring gap-junctional communication may have different levels of sensitivity for detecting as opposed to measuring the level of cell-cell coupling.

scholarly journals Differential phosphorylation of the gap junction protein connexin43 in junctional communication-competent and -deficient cell lines.

1990 ◽  
Vol 111 (5) ◽  
pp. 2077-2088 ◽  
Author(s):  
L S Musil ◽  
B A Cunningham ◽  
G M Edelman ◽  
D A Goodenough
Keyword(s):  
Cell Adhesion ◽  
Gap Junctions ◽  
Gap Junction ◽  
Cell Lines ◽  
Gap Junctional Communication ◽  
Competent Cells ◽  
Deficient Cell ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Cell Cell

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.

scholarly journals Myocardial gap junctions: targets for novel approaches in the prevention of life-threatening cardiac arrhythmias

2008 ◽  
pp. S1-S13
Author(s):  
N Tribulová ◽  
V Knezl ◽  
Ľ Okruhlicová ◽  
J Slezák
Keyword(s):  
Gap Junctions ◽  
Heart Function ◽  
Cell Communication ◽  
Persistent Atrial Fibrillation ◽  
Gap Junctional Communication ◽  
Novel Treatments ◽  
Junctional Communication ◽  
Life Threatening ◽  
Direct Cell ◽  
Gap Junctional

Direct cell-to-cell communication in the heart is maintained via gap junction channels composed of proteins termed connexins. Connexin channels ensure molecular and electrical signals propagation and hence are crucial in myocardial synchronization and heart function. Disease-induced gap junctions remodeling and/or an impairment or even block of intercellular communication due to acute pathological conditions results in derangements of myocardial conduction and synchronization. This is critical in the development of both ventricular fibrillation, which is a major cause of sudden cardiac death and persistent atrial fibrillation, most common arrhythmia in clinical practice often resulting in stroke. Many studies suggest that alterations in topology (remodeling), expression, phosphorylation and particularly function of connexin channels due to age or disease are implicated in the development of these life-threatening arrhythmias. It seems therefore challenging to examine whether compounds that could prevent or attenuate gap junctions remodeling and connexin channels dysfunction can protect the heart against arrhythmias that cause sudden death in humans. This assumption is supported by very recent findings showing that an increase of gap junctional conductance by specific peptides can prevents atrial conduction slowing or re-entrant ventricular tachycardia in ischemic heart. Suppression of ischemia-induced dephosphorylation of connexin seems to be one of the mechanisms involved. Another approach for identifying novel treatments is based on the hypothesis that even non-antiarrhythmic drugs with antiarrhythmic ability can modulate gap junctional communication and hence attenuate arrhythmogenic substrates.

VEGF transiently disrupts gap junctional communication in endothelial cells

2001 ◽  
Vol 114 (6) ◽  
pp. 1229-1235
Author(s):  
S. Suarez ◽  
K. Ballmer-Hofer
Keyword(s):  
Endothelial Cells ◽  
Growth Factor ◽  
Tyrosine Kinase ◽  
Map Kinases ◽  
Cell Junctions ◽  
Early Effect ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Cell Cell

Vascular endothelial growth factor, VEGF, stimulates angiogenesis by directly acting on endothelial cells. The effects of VEGF are mediated by two tyrosine kinase receptors, VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR) that are highly related to receptors of the platelet derived growth factor (PDGF) receptor family. We are interested in early signalling events downstream from VEGF receptors that affect blood vessel homeostasis. Endothelial cells form multiple types of cell-cell junctions that are required for cellular organization into complex networks. These junctions also regulate communication among adjacent cells. Stimulation by various growth factors such as epidermal growth factor (EGF) or PDGF has been shown to disrupt cell-cell junctions, consequently affecting cell-to-cell communication. We investigated gap junctional communication (GJC) by monitoring the transfer of a low molecular mass fluorescent tracer molecule between adjacent cells using immunofluorescence microscopy. VEGF maximally blocked GJC 15 minutes after growth factor administration. The cells resumed communication via gap junctions within 1–2 hours after treatment. This early effect of VEGF on communication correlated with changes in the phosphorylation state of one of the proteins involved in gap junction formation, connexin 43 (Cx43). The signalling mechanisms involved in this phenomenon depend on activation of VEGFR-2, impinge on a tyrosine kinase of the Src family and activate the Erk family of MAP kinases. The function of VEGF-mediated disruption of GJC might be to restrict an increase in endothelium permeability to the environment affected by local injury to blood vessels.

Cell-cell interactions in regulating lung function

2004 ◽  
Vol 287 (3) ◽  
pp. L455-L459 ◽  
Author(s):  
Scott Boitano ◽  
Zeenat Safdar ◽  
Donald G. Welsh ◽  
Jahar Bhattacharya ◽  
Michael Koval
Keyword(s):  
Barrier Function ◽  
Cell Contact ◽  
Permeability Barrier ◽  
Washington Dc ◽  
Gap Junctional Communication ◽  
Metabolic Coupling ◽  
Junctional Communication ◽  
Barrier Formation ◽  
Gap Junctional ◽  
Cell Cell

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.

An inhibition of gap-junctional communication by cadherins

1997 ◽  
Vol 110 (3) ◽  
pp. 301-309 ◽  
Author(s):  
Y. Wang ◽  
B. Rose
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecules ◽  
Cell Adhesion Molecules ◽  
Hepatoma Cells ◽  
Cell Type ◽  
Gap Junctional Communication ◽  
L Cells ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Cell Cell

The action of Ca(2+)-dependent cell-cell adhesion molecules (cadherins) on cell-to-cell channel-mediated intercellular communication was investigated in mouse L and rat Morris hepatoma cells. These cells fail to adhere to one another in aggregation assays and thus seem to lack cell adhesion molecules. Expression of exogenous cadherin induced strong cell-cell adhesion in both cell types, but had opposite effects of communication, causing inhibition in L cells and improvement in hepatoma cells. Both cells express the connexin43 cell-to-cell channel protein. By western blot we found no cadherin-specific changes in connexin43 protein in either cell type, but connexin43 gap junctional plaque staining, i.e. connexin43 localization to cell-cell junctions, was inhibited in L cells and facilitated in hepatoma cells. In addition we found that the inhibitory effect is largely abolished by blockers of glycosylation. Cadherin-cadherin interactions are known to trigger cell type-specific intracellular signal cascades resulting in diverse end effects, and gap junctional communication/plaque formation seems a further example of such cell type-specificity.

scholarly journals Expression of a connexin 43/beta-galactosidase fusion protein inhibits gap junctional communication in NIH3T3 cells.

1995 ◽  
Vol 130 (2) ◽  
pp. 419-429 ◽  
Author(s):  
R Sullivan ◽  
C W Lo
Keyword(s):  
Fusion Protein ◽  
Gap Junctions ◽  
Connexin 43 ◽  
Dominant Negative Effect ◽  
Cell Contact ◽  
Nih3t3 Cells ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Cell Cell

Gap junctions contain membrane channels that mediate the cell-to-cell movement of ions, metabolites and cell signaling molecules. As gap junctions are comprised of a hexameric array of connexin polypeptides, the expression of a mutant connexin polypeptide may exert a dominant negative effect on gap junctional communication. To examine this possibility, we constructed a connexin 43 (Cx43)/beta-galactosidase (beta-gal) expression vector in which the bacterial beta-gal protein is fused in frame to the carboxy terminus of Cx43. This vector was transfected into NIH3T3 cells, a cell line which is well coupled via gap junctions and expresses high levels of Cx43. Transfectant clones were shown to express the fusion protein by northern and western analysis. X-Gal staining further revealed that all of the fusion protein containing cells also expressed beta-gal enzymatic activity. Double immunostaining with a beta-gal and Cx43 antibody demonstrated that the fusion protein is immunolocalized to the perinuclear region of the cytoplasm and also as punctate spots at regions of cell-cell contact. This pattern is similar to that of Cx43 in the parental 3T3 cells, except that in the fusion protein expressing cells, Cx43 expression was reduced at regions of cell-cell contact. Examination of gap junctional communication (GJC) with dye injection studies further showed that dye coupling was inhibited in the fusion protein expressing cells, with the largest reduction in coupling found in a clone exhibiting little Cx43 localization at regions of cell-cell contact. When the fusion protein expression vector was transfected into the communication poor C6 cell line, abundant fusion protein expression was observed, but unlike the transfected NIH3T3 cells, no fusion protein was detected at the cell surface. Nevertheless, dye coupling was inhibited in these C6 cells. Based on these observations, we propose that the fusion protein may inhibit GJC by sequestering the Cx43 protein intracellularly. Overall, these results demonstrate that the Cx43/beta-gal fusion protein can exert a dominant negative effect on GJC in two different cell types, and suggests that it may serve as a useful approach for probing the biological function of gap junctions.

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