scholarly journals ERp29 Restricts Connexin43 Oligomerization in the Endoplasmic Reticulum

2009 ◽  
Vol 20 (10) ◽  
pp. 2593-2604 ◽  
Author(s):  
Shamie Das ◽  
Tekla D. Smith ◽  
Jayasri Das Sarma ◽  
Jeffrey D. Ritzenthaler ◽  
Jose Maza ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Protein Complexes ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Family Protein ◽  
Junction Protein ◽  
Specific Complex ◽  
And Function ◽  
Gap Junctional

Connexin43 (Cx43) is a gap junction protein that forms multimeric channels that enable intercellular communication through the direct transfer of signals and metabolites. Although most multimeric protein complexes form in the endoplasmic reticulum (ER), Cx43 seems to exit from the ER as monomers and subsequently oligomerizes in the Golgi complex. This suggests that one or more protein chaperones inhibit premature Cx43 oligomerization in the ER. Here, we provide evidence that an ER-localized, 29-kDa thioredoxin-family protein (ERp29) regulates Cx43 trafficking and function. Interfering with ERp29 function destabilized monomeric Cx43 oligomerization in the ER, caused increased Cx43 accumulation in the Golgi apparatus, reduced transport of Cx43 to the plasma membrane, and inhibited gap junctional communication. ERp29 also formed a specific complex with monomeric Cx43. Together, this supports a new role for ERp29 as a chaperone that helps stabilize monomeric Cx43 to enable oligomerization to occur in the Golgi apparatus.

Phosphorylation of connexin43 gap junction protein in uninfected and Rous sarcoma virus-transformed mammalian fibroblasts

1990 ◽  
Vol 10 (4) ◽  
pp. 1754-1763
Author(s):  
D S Crow ◽  
E C Beyer ◽  
D L Paul ◽  
S S Kobe ◽  
A F Lau
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Rous Sarcoma Virus ◽  
Gap Junctional Communication ◽  
Rous Sarcoma ◽  
Junctional Communication ◽  
Junction Protein ◽  
Sarcoma Virus ◽  
Gap Junction Protein ◽  
Gap Junctional

Gap junctions are membrane channels that permit the interchange of ions and other low-molecular-weight molecules between adjacent cells. Rous sarcoma virus (RSV)-induced transformation is marked by an early and profound disruption of gap-junctional communication, suggesting that these membrane structures may serve as sites of pp60v-src action. We have begun an investigation of this possibility by identifying and characterizing putative proteins involved in junctional communication in fibroblasts, the major cell type currently used to study RSV-induced transformation. We found that uninfected mammalian fibroblasts do not appear to contain RNA or protein related to connexin32, the major rat liver gap junction protein. In contrast, vole and mouse fibroblasts contained a homologous 3.0-kilobase RNA similar in size to the heart tissue RNA encoding the gap junction protein, connexin43. Anti-connexin43 peptide antisera specifically reacted with three proteins of approximately 43, 45 and 47 kilodaltons (kDa) from communicating fibroblasts. Gap junctions of heart cells contained predominantly 45- and 47-kDa species similar to those found in fibroblasts. Uninfected fibroblast 45- and 47-kDa proteins were phosphorylated on serine residues. Phosphatase digestions of 45- and 47-kDa proteins and pulse-chase labeling studies indicated that these proteins represented phosphorylated forms of the 43-kDa protein. Phosphorylation of connexin protein appeared to occur shortly after synthesis, followed by an equally rapid dephosphorylation. In comparison with these results, connexin43 protein in RSV-transformed fibroblasts contained both phosphotyrosine and phosphoserine. Thus, the presence of phosphotyrosine in connexin43 correlates with the loss of gap-junctional communication observed in RSV-transformed fibroblasts.

Mechanisms for the coordination of intercellular calcium signaling in insulin-secreting cells

1997 ◽  
Vol 110 (4) ◽  
pp. 497-504 ◽  
Author(s):  
D. Cao ◽  
G. Lin ◽  
E.M. Westphale ◽  
E.C. Beyer ◽  
T.H. Steinberg
Keyword(s):  
Gap Junction ◽  
Islet Cells ◽  
Cytosolic Calcium ◽  
Calcium Waves ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Junction Protein ◽  
Insulin Secreting Cells ◽  
Gap Junction Protein ◽  
Gap Junctional

Insulin-mediated increases in cytosolic calcium are synchronized among the cells in a pancreatic islet, and result in pulsatile secretion of insulin. Pancreatic beta cells express the gap junction protein connexin43 and are functionally coupled, making gap junctional communication a likely mechanism for the synchronization of calcium transients among islet cells. To define the mechanism by which pancreatic islet cells coordinate calcium responses, we studied mechanically-induced intercellular calcium waves in the communication-deficient rat insulinoma cell line RINm5f, and in RINm5f cells transfected with the gap junction protein connexin43. Both RINm5f and RINm5f cells transfected with connexin43 propagated calcium waves that required release of calcium from intracellular stores, did not involve gap junctional communication, and appeared to be mediated by autocrine activity of secreted ATP acting on P2U purinergic receptors. Connexin43 transfectants also propagated calcium waves that required gap junctional communication and influx of extracellular calcium through voltage-gated calcium channels. Gap junction-dependent intercellular calcium waves were inhibited by preventing plasma membrane depolarization. These studies demonstrate two distinct pathways by which insulin-secreting cells can coordinate cytosolic calcium rises, and show that it is by ionic traffic that gap junctions synchronize calcium-dependent events in these cells.

Phenotypic control of gap junctional communication by cultured alveolar epithelial cells

1999 ◽  
Vol 276 (5) ◽  
pp. L825-L834 ◽  
Author(s):  
Valsamma Abraham ◽  
Michael L. Chou ◽  
Kristine M. DeBolt ◽  
Michael Koval
Keyword(s):  
Lamellar Body ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Junction Protein ◽  
Gap Junctional ◽  
Cells Cultured

We examined phenotype-specific changes in gap junction protein [connexin (Cx)] expression and function by cultured rat alveolar type II cells. Type II cells cultured on extracellular matrix in medium containing keratinocyte growth factor (KGF) and 2% fetal bovine serum (FBS; KGF/2) retained expression of surfactant protein C and the 180-kDa lamellar body membrane protein (lbm180). These markers were lost when cells were cultured in medium containing 10% FBS (MEM/10). With RT-PCR, cells cultured in MEM/10 showed transient increases in Cx43 and Cx46 mRNA expression, whereas Cx32 and Cx26 decreased and Cx30.3 and Cx37 were unchanged. Transient changes in Cx32, Cx43, and Cx46 protein expression were confirmed by immunoblot. In contrast, cells cultured in KGF/2 retained expression of Cx32 and showed increased expression of Cx30.3 and Cx46 mRNAs, compared with that in day 0 cells. With immunofluorescence microscopy, Cx32 and Cx43 were at the plasma membrane of cells grown in KGF/2, whereas Cx46 was exclusively intracellular. Type II cells cultured in MEM/10 showed ∼3- to 4-fold more intercellular transfer of microinjected lucifer yellow through gap junctions than cells grown in 2% FBS. Thus type II cells dynamically alter gap junctional communication, and distinct alveolar epithelial cell phenotypes express different connexins.

Shapes of astrocyte networks in the juvenile brain

2006 ◽  
Vol 2 (1) ◽  
pp. 3-14 ◽  
Author(s):  
VANESSA HOUADES ◽  
NATHALIE ROUACH ◽  
PASCAL EZAN ◽  
FRANK KIRCHHOFF ◽  
ANNETTE KOULAKOFF ◽  
...  
Keyword(s):  
Gap Junction ◽  
Brain Function ◽  
Connexin 43 ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Junction Protein ◽  
Gap Junction Protein ◽  
High Level ◽  
Gap Junctional ◽  
Neuronal Compartments

The high level of intercellular communication mediated by gap junctions between astrocytes indicates that, besides individual astrocytic domains, a second level of organization might exist for these glial cells as they form communicating networks. Therefore, the contribution of astrocytes to brain function should also be considered to result from coordinated groups of cells. To evaluate the shape and extent of these networks we have studied the expression of connexin 43, a major gap junction protein in astrocytes, and the intercellular diffusion of gap junction tracers in two structures of the developing brain, the hippocampus and the cerebral cortex. We report that the shape of astrocytic networks depends on their location within neuronal compartments in a defined brain structure. Interestingly, not all astrocytes are coupled, which indicates that connections within these networks are restricted. As gap junctional communication in astrocytes is reported to contribute to several glial functions, differences in the shape of astrocytic networks might have consequences on neuronal activity and survival.

scholarly journals Phosphorylation of connexin43 gap junction protein in uninfected and Rous sarcoma virus-transformed mammalian fibroblasts.

1990 ◽  
Vol 10 (4) ◽  
pp. 1754-1763 ◽  
Author(s):  
D S Crow ◽  
E C Beyer ◽  
D L Paul ◽  
S S Kobe ◽  
A F Lau
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Rous Sarcoma Virus ◽  
Gap Junctional Communication ◽  
Rous Sarcoma ◽  
Junctional Communication ◽  
Junction Protein ◽  
Sarcoma Virus ◽  
Gap Junction Protein ◽  
Gap Junctional

Gap junctions are membrane channels that permit the interchange of ions and other low-molecular-weight molecules between adjacent cells. Rous sarcoma virus (RSV)-induced transformation is marked by an early and profound disruption of gap-junctional communication, suggesting that these membrane structures may serve as sites of pp60v-src action. We have begun an investigation of this possibility by identifying and characterizing putative proteins involved in junctional communication in fibroblasts, the major cell type currently used to study RSV-induced transformation. We found that uninfected mammalian fibroblasts do not appear to contain RNA or protein related to connexin32, the major rat liver gap junction protein. In contrast, vole and mouse fibroblasts contained a homologous 3.0-kilobase RNA similar in size to the heart tissue RNA encoding the gap junction protein, connexin43. Anti-connexin43 peptide antisera specifically reacted with three proteins of approximately 43, 45 and 47 kilodaltons (kDa) from communicating fibroblasts. Gap junctions of heart cells contained predominantly 45- and 47-kDa species similar to those found in fibroblasts. Uninfected fibroblast 45- and 47-kDa proteins were phosphorylated on serine residues. Phosphatase digestions of 45- and 47-kDa proteins and pulse-chase labeling studies indicated that these proteins represented phosphorylated forms of the 43-kDa protein. Phosphorylation of connexin protein appeared to occur shortly after synthesis, followed by an equally rapid dephosphorylation. In comparison with these results, connexin43 protein in RSV-transformed fibroblasts contained both phosphotyrosine and phosphoserine. Thus, the presence of phosphotyrosine in connexin43 correlates with the loss of gap-junctional communication observed in RSV-transformed fibroblasts.

scholarly journals Connexin43 phosphorylation: structural changes and biological effects

2009 ◽  
Vol 419 (2) ◽  
pp. 261-272 ◽  
Author(s):  
Joell L. Solan ◽  
Paul D. Lampe
Keyword(s):  
Gap Junction ◽  
Structural Changes ◽  
Biological Effects ◽  
Gap Junctional Communication ◽  
Connexin Gene ◽  
Gap Junction Channel ◽  
Junctional Communication ◽  
Cell Growth And Differentiation ◽  
And Function ◽  
Gap Junctional

Vertebrate gap junctions, composed of proteins from the connexin gene family, play critical roles in embryonic development, co-ordinated contraction of excitable cells, tissue homoeostasis, normal cell growth and differentiation. Phosphorylation of connexin43, the most abundant and ubiquitously expressed connexin, has been implicated in the regulation of gap junctional communication at several stages of the connexin ‘life cycle’, including hemichannel oligomerization, export of the protein to the plasma membrane, hemichannel activity, gap junction assembly, gap junction channel gating and connexin degradation. Consistent with a short (1–5 h) protein half-life, connexin43 phosphorylation is dynamic and changes in response to activation of many different kinases. The present review assesses our current understanding of the effects of phosphorylation on connexin43 structure and function that in turn regulate gap junction biology, with an emphasis on events occurring in heart and skin.

scholarly journals Epidermal growth factor disrupts gap-junctional communication and induces phosphorylation of connexin43 on serine.

1992 ◽  
Vol 3 (8) ◽  
pp. 865-874 ◽  
Author(s):  
A F Lau ◽  
M Y Kanemitsu ◽  
W E Kurata ◽  
S Danesh ◽  
A L Boynton
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Tyrosine Kinase ◽  
Gap Junction ◽  
Intracellular Signaling ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Junction Protein ◽  
Epidermal Growth ◽  
Gap Junctional

Growth factors regulate cellular proliferation and differentiation by activating plasma membrane tyrosine kinase receptors and triggering a cascade of events mediated by intracellular signaling proteins. The mechanism underlying growth factor modification of cellular functions, such as gap-junctional communication (gjc), has not been established clearly. Addition of epidermal growth factor (EGF) to T51B rat liver epithelial cells resulted in the rapid activation of EGF receptor tyrosine kinase activity followed by a transient dose-dependent disruption of gjc. This change did not result from the gross disturbance of membrane gap junction plaques as measured by immunofluorescence microscopy, but instead correlated with markedly elevated phosphorylation of the connexin43 (cx43) gap junction protein, a profound shift to predominantly phosphorylated forms of cx43, and the appearance of a novel phosphorylated cx43 protein. These changes in cx43 phosphorylation involved only serine residues. On restoration of gjc, these alterations in cx43 phosphorylation reverted to the pre-EGF treatment state. Both events were inhibited by the serine/threonine protein phosphatase inhibitor, okadaic acid. Therefore, unlike the case for pp60v-src, EGF-induced disruption of gjc is not associated with tyrosine phosphorylation of cx43, but instead may result from phosphorylation of cx43 by activated intracellular signaling serine protein kinase(s).

The relationship of gap junctions and compaction in the preimplantation mouse embryo

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. 113-118
Author(s):  
David L. Becker ◽  
Catherine Leclerc-David ◽  
Anne Warner
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Mouse Embryo ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Gap Junctional Communication ◽  
Stage Of Development ◽  
Junctional Communication ◽  
Junction Protein ◽  
Gap Junctional

In the mouse embryo, gap junctions first appear at the 8-cell stage as compaction is about to take place. Compaction of the embryo is important for the differentiation of the first two cell types; the inner cell mass and the trophectoderm. Our studies examine the contribution of gap junctional communication at this stage of development We have characterised the normal sequence of appearance of gap junction protein and its distribution. The extent of communication as shown by the passage of dye between cells has been recorded in both normal embryos and embryos treated with drugs that influence gap junctional communication. Comparisons have been made with embryos that express a lethal gap junction defect and attempts were made to rescue such embryos by increasing their gap junction communication.

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