So-called annular gap junctions in bone cells of normal mice

1977 ◽  
Vol 33 (2) ◽  
pp. 270-272 ◽  
Author(s):  
K. -H. Marquart
Keyword(s):  
Gap Junctions ◽  
Bone Cells ◽  
Annular Gap

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 Intercellular calcium wave propagation in linear and circuit-like bone cell networks

2010 ◽  
Vol 368 (1912) ◽  
pp. 617-633 ◽  
Author(s):  
Bo Huo ◽  
Xin L. Lu ◽  
X. Edward Guo
Keyword(s):  
Wave Propagation ◽  
Gap Junctions ◽  
Calcium Release ◽  
Bone Cells ◽  
Molecular Transport ◽  
Bone Cell ◽  
Calcium Wave ◽  
Contact Printing ◽  
Inhibition Studies ◽  
Cell Networks

In the present study, the mechanism of intercellular calcium wave propagation in bone cell networks was identified. By using micro-contact printing and self-assembled monolayer technologies, two types of in vitro bone cell networks were constructed: open-ended linear chains and looped hexagonal networks with precisely controlled intercellular distances. Intracellular calcium responses of the cells were recorded and analysed when a single cell in the network was mechanically stimulated by nano-indentation. The looped cell network was shown to be more efficient than the linear pattern in transferring calcium signals from cell to cell. This phenomenon was further examined by pathway-inhibition studies. Intercellular calcium wave propagation was significantly impeded when extracellular adenosine triphosphate (ATP) in the medium was hydrolysed. Chemical uncoupling of gap junctions, however, did not significantly decrease the transferred distance of the calcium wave in the cell networks. Thus, it is extracellular ATP diffusion, rather than molecular transport through gap junctions, that dominantly mediates the transmission of mechanically elicited intercellular calcium waves in bone cells. The inhibition studies also demonstrated that the mechanical stimulation-induced calcium responses required extracellular calcium influx, whereas the ATP-elicited calcium wave relied on calcium release from the calcium store of the endoplasmic reticulum.

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

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

Gap Junctions and Osteoblast-like Cell Gene Expression in Response to Fluid Flow

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Michael G. Jekir ◽  
Henry J. Donahue
Keyword(s):  
Fluid Flow ◽  
Gap Junctions ◽  
Gap Junction ◽  
Bone Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mrna Levels ◽  
Mechanical Stimuli ◽  
Junctional Communication ◽  
Osteogenic Response

Bone formation occurs in vivo in response to mechanical stimuli, but the signaling pathways involved remain unclear. The ability of bone cells to communicate with each other in the presence of an applied load may influence the overall osteogenic response. The goal of this research was to determine whether inhibiting cell-to-cell gap junctional communication between bone-forming cells would affect the ensemble cell response to an applied mechanical stimulus in vitro. In this study, we investigated the effects of controlled oscillatory fluid flow (OFF) on osteoblastic cells in the presence and the absence of a gap-junction blocker. MC3T3-E1 Clone 14 cells in a monolayer were exposed to 2h of OFF at a rate sufficient to create a shear stress of 20dynes∕cm2 at the cell surface, and changes in steady-state mRNA levels for a number of key proteins known to be involved in osteogenesis were measured. Of the five proteins investigated, mRNA levels for osteopontin (OPN) and osteocalcin were found to be significantly increased 24h postflow. These experiments were repeated in the presence of 18β-glycyrrhetinic acid (BGA), a known gap-junction blocker, to determine whether gap-junction intercellular communication is necessary for this response. We found that the increase in OPN mRNA levels is not observed in the presence of BGA, suggesting that gap junctions are involved in the signaling process. Interestingly, enzyme linked immunosorbent assay data showed that levels of secreted OPN protein increased 48h postflow and that this increase was unaffected by the presence of intact gap junctions.

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.

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