Effects of tamoxifen citrate and cycloheximide on estradiol induction of rat myometrial gap junctions

1986 ◽  
Vol 64 (6) ◽  
pp. 703-706 ◽  
Author(s):  
L. W. MacKenzie ◽  
R. E. Garfield
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Hormone Treatment ◽  
Control Groups ◽  
Estradiol Treatment ◽  
Myometrial Cells ◽  
Tamoxifen Citrate ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Junction Proteins

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.

scholarly journals Comparative analysis of the major polypeptides from liver gap junctions and lens fiber junctions.

1982 ◽  
Vol 92 (1) ◽  
pp. 53-59 ◽  
Author(s):  
E L Hertzberg ◽  
D J Anderson ◽  
M Friedlander ◽  
N B Gilula
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Peptide Mapping ◽  
Freeze Fracture ◽  
Apparent Molecular Weight ◽  
Lens Fiber ◽  
Physiological Properties ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

Gap junctions from rat liver and fiber junctions from bovine lens have similar septilaminar profiles when examined by thin-section electron microscopy and differ only slightly with respect to the packing of intramembrane particles in freeze-fracture images. These similarities have often led to lens fiber junctions being referred to as gap junctions. Junctions from both sources were isolated as enriched subcellular fractions and their major polypeptide components compared biochemically and immunochemically. The major liver gap junction polypeptide has an apparent molecular weight of 27,000, while a 25,000-dalton polypeptide is the major component of lens fiber junctions. The two polypeptides are not homologous when compared by partial peptide mapping in SDS. In addition, there is not detectable antigenic similarity between the two polypeptides by immunochemical criteria using antibodies to the 25,000-dalton lens fiber junction polypeptide. Thus, in spite of the ultrastructural similarities, the gap junction and the lens fiber junction are comprised of distinctly different polypeptides, suggesting that the lens fiber junction contains a unique gene product and potentially different physiological properties.

Dissociation of lens fibre gap junctions releases MP70

1988 ◽  
Vol 91 (3) ◽  
pp. 415-421 ◽  
Author(s):  
J. Kistler ◽  
S. Bullivant
Keyword(s):  
Electron Microscope ◽  
Gap Junctions ◽  
Gap Junction ◽  
Plasma Membranes ◽  
Gradient Centrifugation ◽  
Membrane Structures ◽  
Treatment Results ◽  
Double Membrane ◽  
Lens Fibre ◽  
Junction Proteins

MIP and MP70 are putative gap junction components in the plasma membranes of the mammalian lens fibre cells. We show now that MP70 can be solubilized separately from MIP in mild detergent solutions, and that this treatment results in the dissociation of the fibre gap junctions. Solubilized MP70 was isolated as 16.9 S particles by velocity gradient centrifugation and in the electron microscope had the appearance of short double-membrane structures consistent with connexon-pairs. These observations open a new experimental avenue in which to characterize separately the two putative lens gap junction proteins structurally and functionally.

scholarly journals Visualization of Annular Gap Junction Vesicle Processing: The Interplay between Annular Gap Junctions and Mitochondria

2018 ◽  
Author(s):  
Cheryl L. Bell ◽  
Teresa I. Shakespeare ◽  
Sandra A. Murray
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Cell Communication ◽  
Super Resolution ◽  
Protective Role ◽  
Annular Gap ◽  
Transmission Electron ◽  
Junction Proteins

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 unknown. In this study, immunocytochemical, super-resolution and transmission electron microscopy were used to detect cytoplasmic Cx43-containing structure 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 that the contact between annular gap junction vesicles and mitochondria facilitates Cx43 deliver to the mitochondria. Furthermore, it points to the need for investigating trafficking of Cx43 to cytoplasmic compartments and annular gap junction as more than only a vesicle destined for degradation.

scholarly journals βPS-Integrin acts downstream of Innexin 2 in modulating stretched cell morphogenesis in the Drosophila ovary

2021 ◽  
Author(s):  
Yi-Chia Huang ◽  
Kuan-Han Chen ◽  
Yu-Yang Chen ◽  
Liang-Hsuan Tsao ◽  
Tsung-Han Yeh ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Adaptor Proteins ◽  
Follicle Cells ◽  
Cell Morphogenesis ◽  
Independent Manner ◽  
Gap Junction Proteins ◽  
Intercellular Exchange ◽  
Drosophila Ovary ◽  
Junction Proteins

Abstract During oogenesis, a group of specialized follicle cells, known as stretched cells, flatten drastically from cuboidal to squamous shape. While morphogenesis of epithelia is critical for organogenesis, genes and signaling pathways involved in this process remain to be revealed. In addition to formation of gap junctions for intercellular exchange of small molecules, gap junction proteins form channels or act as adaptor proteins to regulate various cellular behaviors. In invertebrates, gap junction proteins are Innexins. Knockdown of Innexin 2 but not other Innexins expressed in follicle cells attenuates stretched cell morphogenesis. Interestingly, blocking of gap junctions with an inhibitor carbenoxolone does not affect stretched cell morphogenesis, suggesting that Innexin 2 might control stretched cell flattening in a gap-junction-independent manner. An excessive level of βPS-Integrin encoded by myospheroid is detected in Innexin 2 mutant cells specifically during stretched cell morphogenesis. Simultaneous knockdown of Innexin 2 and myospheroid partially rescues the morphogenetic defect resulted from Innexin 2 knockdown. Furthermore, reduction of βPS-Integrin is sufficient to induce early stretched cell flattening. Taken together, our data suggest that βPS-Integrin acts downstream of Innexin 2 in modulating stretched cell morphogenesis.

scholarly journals Visualization of Annular Gap Junction Vesicle Processing: The Interplay Between Annular Gap Junctions and Mitochondria

2018 ◽  
Vol 20 (1) ◽  
pp. 44 ◽  
Author(s):  
Cheryl Bell ◽  
Teresa Shakespeare ◽  
Amber Smith ◽  
Sandra Murray
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Cell Communication ◽  
Super Resolution ◽  
Protective Role ◽  
Annular Gap ◽  
Transmission Electron ◽  
Junction Proteins

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.

scholarly journals Astroglial connexins and cognition: memory formation or deterioration?

2020 ◽  
Vol 40 (1) ◽  
Author(s):  
Jin-Ting He ◽  
Xiao-Yan LI ◽  
Le Yang ◽  
Xin Zhao
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Memory Formation ◽  
Gap Junction Communication ◽  
Different Types ◽  
Excessive Activation ◽  
High Conductance ◽  
Junction Proteins

Abstract Connexins are the membrane proteins that form high-conductance plasma membrane channels and are the important constituents of gap junctions and hemichannels. Among different types of connexins, connexin 43 is the most widely expressed and studied gap junction proteins in astrocytes. Due to the key involvement of astrocytes in memory impairment and abundant expression of connexins in astrocytes, astroglial connexins have been projected as key therapeutic targets for Alzheimer’s disease. On the other hand, the role of connexin gap junctions and hemichannels in memory formation and consolidation has also been reported. Moreover, deletion of these proteins and loss of gap junction communication result in loss of short-term spatial memory. Accordingly, both memory formation and memory deteriorating functions of astrocytes-located connexins have been documented. Physiologically expressed connexins may be involved in the memory formation, while pathologically increased expression of connexins with consequent excessive activation of astrocytes may induce neuronal injury and cognitive decline. The present review describes the memory formation as well as memory deteriorating functions of astroglial connexins in memory disorders of different etiology with possible mechanisms.

Effect of gap junction number and permeability on intercellular coupling in rat myometrium

1991 ◽  
Vol 261 (6) ◽  
pp. C1001-C1009 ◽  
Author(s):  
M. G. Blennerhassett ◽  
R. E. Garfield
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Lucifer Yellow ◽  
Input Resistance ◽  
Cell Coupling ◽  
Intercellular Coupling ◽  
Myometrial Cells ◽  
Intercellular Spread

Gap junctions (GJ) increase between myometrial cells immediately before labor. To provide evidence of their role in cell-to-cell coupling, we evaluated input resistance (Ro) and intercellular spread of Lucifer yellow (LY) in intact preparations of rat longitudinal myometrium of preterm, term, and antiprogesterone-treated preterm delivering animals. LY injected into cells from either term or preterm delivering rats (many GJ) spread rapidly to neighboring cells by 60 s, but in preparations from nondelivering controls required 4-6 min to become detectable in adjacent cells. Ro of cells in preterm nondelivering preparations was 24.1 +/- 0.8 (SE) M omega, but dropped to 12.0 +/- 0.4 M omega (P less than 0.05) at delivery, similar to preterm delivering tissues at 13.8 +/- 0.6 M omega. The putative GJ uncoupling agent octanol reversibly increased Ro of term- and preterm-delivering tissues fourfold (P less than 0.01) within 60 s, and Ro of preterm-nondelivering tissue was further increased so that Ro values were similar among the three classes. These increased Ro values are interpreted as decreased coupling. Both K+ depolarization and oxytocin (10(-8) to 10(-6) M) increased Ro of delivering tissues (P less than 0.05), suggesting that high levels of contractile agonists may lead to reduced cell-to-cell coupling. Therefore, myometrial coupling can be modulated over seconds via GJ permeability as well as over hours by GJ number.

scholarly journals Hormonal regulation of gap junction differentiation.

1976 ◽  
Vol 69 (3) ◽  
pp. 669-685 ◽  
Author(s):  
R S Decker
Keyword(s):  
Plasma Membrane ◽  
Gap Junctions ◽  
Gap Junction ◽  
Hormonal Regulation ◽  
Large Particle ◽  
Rana Pipiens ◽  
Hormone Treatment ◽  
Junction Area ◽  
Plaque Area ◽  
New Protein

Thin-section, tracer, and freeze-cleave experiments on hypophysectomized Rana pipiens larvae reveal that gap junctions form between differentiating ependymoglial cells in response to thyroid hormone. These junctions assemble in large particle-free areas of the plasma membrane known as formation plaques. Between 20 and 40 h after hormone application, formation plaque area increases approximately 26-fold while gap junction area rises about 20-fold. The differentiation of these junctions requires the synthesis of new protein and probably RNA as well. On the basis of inhibitor experiments, it can be reported that formation plaques develop at about 16-20 h after hormone treatment and stages in the construction of gap junctions appear 4-8 h later. These studies suggest that gap junction subunits are synthesized and inserted into formation plaque membrane during the differentiation of the anuran ependymoglial cells.

scholarly journals Facets of Communication: Gap Junction Ultrastructure and Function in Cancer Stem Cells and Tumor Cells

Cancers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 288 ◽  
Author(s):  
Anja Beckmann ◽  
Nadine Hainz ◽  
Thomas Tschernig ◽  
Carola Meier
Keyword(s):  
Stem Cells ◽  
Cancer Stem Cells ◽  
Gap Junctions ◽  
Gap Junction ◽  
Cancer Cells ◽  
Freeze Fracture ◽  
Plaque Morphology ◽  
Junctional Communication ◽  
Gap Junction Proteins ◽  
Junction Proteins

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.

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