Analysis of distribution patterns of gap junctions during development of embryonic chick facial primordia and brain

Gap junction distribution in the facial primordia of chick embryos at the time of primary palate formation was studied employing indirect immunofluorescence localization with antibodies to gap junction proteins initially identified in rat liver (27 × 10(3) Mr, connexin 32) and heart (43 × 10(3) Mr, connexin 43). Immunolocalization with antibodies to the rat liver gap junction protein (27 × 10(3) Mr) demonstrated a ubiquitous and uniform distribution in all regions of the epithelium and mesenchyme except the nasal placode. In the placodal epithelium, a unique non-random distribution was found characterized by two zones: a very heavy concentration of signal in the superficial layer of cells adjacent to the exterior surface and a region devoid of detectable signal in the interior cell layer adjacent to the mesenchyme. This pattern was seen during all stages of placode invagination that were examined. The separation of gap junctions in distinct cell layers was unique to the nasal placode, and was not found in any other region of the developing primary palate. One other tissue was found that exhibited this pattern-the developing neural epithelium of the brain and retina. These observations suggest the presence of region-specific signaling mechanisms and, possibly, an impedance of cell communication among subpopulations of cells in these structures at critical stages of development. Immunolocalization with antibodies to the ‘heart’ 43 × 10(3) Mr gap junction protein also revealed the presence of gap junction protein in facial primordia and neural epithelium. A non-uniform distribution of immunoreactivity was also observed for connexin 43.

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Amyloid-β regulates gap junction protein connexin 43 trafficking in cultured primary astrocytes

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.013705 ◽

2020 ◽

Vol 295 (44) ◽

pp. 15097-15111

Author(s):

Mahua Maulik ◽

Lakshmy Vasan ◽

Abhishek Bose ◽

Saikat Dutta Chowdhury ◽

Neelanjana Sengupta ◽

...

Keyword(s):

Gap Junctions ◽

Gap Junction ◽

Connexin 43 ◽

Cx43 Expression ◽

Chemical Chaperone ◽

Junction Protein ◽

Gap Junction Coupling ◽

Gap Junction Protein ◽

Junction Coupling ◽

And Function

Altered expression and function of astroglial gap junction protein connexin 43 (Cx43) has increasingly been associated to neurotoxicity in Alzheimer disease (AD). Although earlier studies have examined the effect of increased β-amyloid (Aβ) on Cx43 expression and function leading to neuronal damage, underlying mechanisms by which Aβ modulates Cx43 in astrocytes remain elusive. Here, using mouse primary astrocyte cultures, we have examined the cellular processes by which Aβ can alter Cx43 gap junctions. We show that Aβ25-35 impairs functional gap junction coupling yet increases hemichannel activity. Interestingly, Aβ25-35 increased the intracellular pool of Cx43 with a parallel decrease in gap junction assembly at the surface. Intracellular Cx43 was found to be partly retained in the endoplasmic reticulum-associated cell compartments. However, forward trafficking of the newly synthesized Cx43 that already reached the Golgi was not affected in Aβ25-35-exposed astrocytes. Supporting this, treatment with 4-phenylbutyrate, a well-known chemical chaperone that improves trafficking of several transmembrane proteins, restored Aβ-induced impaired gap junction coupling between astrocytes. We further show that interruption of Cx43 endocytosis in Aβ25-35-exposed astrocytes resulted in their retention at the cell surface in the form of functional gap junctions indicating that Aβ25-35 causes rapid internalization of Cx43 gap junctions. Additionally, in silico molecular docking suggests that Aβ can bind favorably to Cx43. Our study thus provides novel insights into the cellular mechanisms by which Aβ modulates Cx43 function in astrocytes, the basic understanding of which is vital for the development of alternative therapeutic strategy targeting connexin channels in AD.

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Localization and function of the connexin 43 gap-junction protein in normal and various oncogene-expressing rat liver epithelial cells

Molecular Carcinogenesis ◽

10.1002/(sici)1098-2744(199608)16:4<203::aid-mc4>3.0.co;2-g ◽

1996 ◽

Vol 16 (4) ◽

pp. 203-212 ◽

Cited By ~ 52

Author(s):

Adriaan W. de Feijter ◽

Diane F. Matesic ◽

Randall J. Ruch ◽

Xiaojun Guan ◽

Chia-Cheng Chang ◽

...

Keyword(s):

Epithelial Cells ◽

Gap Junction ◽

Rat Liver ◽

Connexin 43 ◽

Liver Epithelial Cells ◽

Junction Protein ◽

Gap Junction Protein ◽

Rat Liver Epithelial Cells ◽

And Function

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Bimodal inhibition of connexin 43 gap junctions decreases ACTH-induced steroidogenesis and increases bovine adrenal cell population growth

Journal of Endocrinology ◽

10.1677/joe.0.1710199 ◽

2001 ◽

Vol 171 (1) ◽

pp. 199-208 ◽

Cited By ~ 20

Author(s):

US Shah ◽

SA Murray

Keyword(s):

Gap Junctions ◽

Gap Junction ◽

Growth Rates ◽

Connexin 43 ◽

Cell Populations ◽

Adrenal Cell ◽

Junction Protein ◽

Acth Treatment ◽

Cell Population Growth ◽

Gap Junction Protein

In order to elucidate the role of gap junctions in adrenal cell responses, we measured the effect of inhibiting gap junctions with 18-alpha glycerrhetinic acid (GA; a potent inhibitor of cell-cell communication) and connexin antisense transfection on cell proliferation and adrenocorticotropin (ACTH)-stimulated steroidogenesis. In these experiments we utilized a bovine adrenocortical cell (SBAC) population, which responds to ACTH treatment with a dose-dependent increase in steroid production, an increase in connexin 43 (alpha(1)-Cx43) gap junction protein concentrations, and a decrease in cell population growth. SBAC cell populations treated with GA had increased growth rates, decreased ACTH-stimulated steroidogenesis, but no reduction in alpha(1)-Cx43 gap junction protein contents. In contrast, when SBAC cells were transfected with alpha(1)-Cx43 antisense cDNA, gap junction protein concentration was dramatically reduced as expected, unlike the GA-treated cell populations. Cell populations transfected with alpha(1)-Cx43-antisense also exhibited increased growth rates and a decreased steroidogenic response to ACTH treatment as compared with control or vector-only transfected cell populations. The decreased responsiveness and increased number of cells in the population after gap junction function was decreased by either GA treatment or antisense transfection, suggests that gap junctions may be necessary factors in ACTH-stimulated responsiveness and growth control in the adrenal gland.

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