Degradation of Annular Gap Junctions of the Equine Hoof Wall

1984 ◽  
Vol 120 (4) ◽  
pp. 214-219 ◽  
Author(s):  
D.H. Leach ◽  
L.W. Oliphant
Keyword(s):  
Gap Junctions ◽  
Annular Gap ◽  
Equine Hoof

Annular Gap Junctions of the Equine Hoof Wall

1983 ◽  
Vol 116 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Doug Leach ◽  
Lynn Oliphant
Keyword(s):  
Gap Junctions ◽  
Annular Gap ◽  
Equine Hoof

scholarly journals Gap junction internalization and processing in vivo: a 3D immuno-electron microscopy study

2020 ◽  
pp. jcs.252726
Author(s):  
Rachael P. Norris ◽  
Mark Terasaki
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
New Technology ◽  
Cell Communication ◽  
Membrane Vesicles ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Annular Gap

Gap junctions have well-established roles in cell-cell communication by way of forming permeable intercellular channels. Less is understood about their internalization, which forms double membrane vesicles containing cytosol and membranes from another cell, called connexosomes or annular gap junctions. Here, we systematically investigated the fate of connexosomes in intact ovarian follicles. High pressure frozen, serial sectioned tissue was immunogold labeled for Connexin 43. Within a volume corresponding to ∼35 cells, every labeled structure was categorized and its surface area was measured. Measurements support the concept that multiple connexosomes form from larger invaginated gap junctions. Subsequently, the inner and outer membranes separate, Cx43 immunogenicity is lost from the outer membrane, and the inner membrane appears to undergo fission. One pathway for processing involves lysosomes, based on localization of Cathespin B to some processed connexosomes. In summary, this study demonstrates new technology for high-resolution analyses of gap junction processing.

scholarly journals Molecular mechanisms regulating formation, trafficking and processing of annular gap junctions

2016 ◽  
Vol 17 (S1) ◽  
Author(s):  
Matthias M. Falk ◽  
Cheryl L. Bell ◽  
Rachael M. Kells Andrews ◽  
Sandra A. Murray
Keyword(s):  
Gap Junctions ◽  
Molecular Mechanisms ◽  
Annular Gap

scholarly journals Connexin 43 K63-polyubiquitination on lysines 264 and 303 regulates gap junction internalization

2017 ◽  
Author(s):  
Rachael M. Kells-Andrews ◽  
Rachel A. Margraf ◽  
Charles G. Fisher ◽  
Matthias M. Falk
Keyword(s):  
Plasma Membrane ◽  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Room Temperature ◽  
Cell Communication ◽  
Mapk Phosphorylation ◽  
Annular Gap ◽  
Summary Statement ◽  
Triton X

ABSTRACTGap junctions (GJs) assembled from connexin (Cx) proteins play a pivotal role in cell-to-cell communication by forming channels that connect the cytosols of adjacent cells. Connexin 43, the best-studied Cx, is ubiquitously expressed in vertebrates. While phosphorylation is known to regulate multiple aspects of GJ function, much less is known about the role ubiquitination plays in these processes. Here we show by using ubiquitination-type specific antibodies and Cx43 lysine (K) to arginine (R) mutants that a portion of Cx43 in GJs can become K63-polyubiquitinated on K264 and K303. Relevant Cx43 K/R mutants assembled significantly larger GJ plaques, exhibited much longer protein half-lives and were internalization impaired. Interestingly, ubiquitin-deficient Cx43 mutants accumulated as hyper-phosphorylated polypeptides in the plasma membrane, suggesting that K63-polyubiquitination may be triggered by phosphorylation. Phospho-specific Cx43 antibodies revealed that upregulated phosphorylation affected serines 368, 279/282, and 255, well-known regulatory PKC and MAPK phosphorylation sites. Together, these novel findings suggest that upon internalization, some Cx43 in GJs becomes K63-polyubiquitinated, ubiquitination is critical for GJ internalization, and that K63-polyubiquitination may be induced by Cx phosphorylation.Summary StatementHere we show that connexin 43 in gap junctions becomes K63-poly ubiquitinated on lysines 264 and 303 and its requirement for gap junction endocytosis. These novel findings significantly contribute to our understanding of GJ turnover and patho-/physiology.Abbreviations usedAGJannular gap junctionAMSHassociated molecule with the SH3 domain of STAMCMEclathrin-mediated endocytosisCxConnexinCx43Connexin 43DUBdeubiquitinaseGJgap junctionMonoUbmonoubiquitinNedd4-1neural precursor cell expressed developmentally down-regulated protein 4-1PMplasma membranePolyUbpolyubiquitinTPA12-O-Tetradecanoylphorbol 13-AcetateTX-100Triton X-100RTroom temperatureUbubiquitin

scholarly journals Structure of rapidly frozen gap junctions.

1980 ◽  
Vol 87 (1) ◽  
pp. 273-279 ◽  
Author(s):  
E Raviola ◽  
D A Goodenough ◽  
G Raviola
Keyword(s):  
Gap Junctions ◽  
Corneal Endothelium ◽  
Time Course ◽  
Morphological Changes ◽  
Low Ph ◽  
Ciliary Epithelium ◽  
Rapid Freezing ◽  
Annular Gap ◽  
Living State ◽  
Smooth Membrane

The structure of gap junctions in the rabbit ciliary epithelium, corneal endothelium, and mouse stomach and liver was studied with the freeze-fracturing technique after rapid freezing to near 4 degrees K from the living state. In the ciliary epithelium, the connexons were randomly distributed, separated by smooth membrane matrix. In the corneal endothelium, both random and crystalline arrangements of the connexons were observed. In the stomach and liver, the connexons were packed but not crystalline. Experimental anoxia or lowered pH caused crystallization of the connexons within 20-30 min. In the ciliary epithelium, the effects of prolonged anoxia or low pH could not be reversed . In addition, invaginated or annular gap junctions increased in number, but their connexons were usually distributed at random. Rapid freezing thus demonstrates that gap junctions of different tissues are highly pleiomorphic in the living state, and this may explain their variations in structure after chemical fixation. The slow time-course and irreversibility of the morphological changes induced by prolonged anoxia or low pH suggest that connexon crystallization may be a long-term consequence rather than the morphological correlate of the switch to high resistance.

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 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 Gap junction internalization and processing in vivo: a 3D immuno-electron microscopy study

2020 ◽  
Author(s):  
Rachael P. Norris ◽  
Mark Terasaki
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Cell Communication ◽  
Membrane Vesicles ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Annular Gap ◽  
Cell Cell

AbstractGap junctions have well-established roles in cell-cell communication by way of forming permeable intercellular channels. Less is understood about their internalization, which forms double membrane vesicles containing cytosol and membranes from another cell, called connexosomes or annular gap junctions. Here, we systematically studied the fate of connexosomes in intact ovarian follicles. High pressure frozen, serial sectioned tissue was immunogold labeled for Connexin 43. Within a volume of electron micrographs, every labeled structure was categorized and counted. Surface area measurements indicate that large connexosomes undergo fission. Subsequent modifications are separation of inner and outer membranes, loss of Cx43 from the outer membrane, and outward budding of the modified membranes. We also documented several clear examples of organelle transfer from one cell to another by gap junction internalization. We discuss how connexosome formation and processing may be a novel means for gap junctions to mediate cell-cell communication.

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