A characterization of permolybdate and its effect on cellular tyrosine phosphorylation, gap junctional intercellular communication and phosphorylation status of the gap junction protein, connexin43

Germ cells require intimate associations and signals from the surrounding somatic cells throughout gametogenesis. The zero population growth (zpg) locus of Drosophila encodes a germline-specific gap junction protein, Innexin 4, that is required for survival of differentiating early germ cells during gametogenesis in both sexes. Animals with a null mutation in zpg are viable but sterile and have tiny gonads. Adult zpg-null gonads contain small numbers of early germ cells, resembling stem cells or early spermatogonia or oogonia, but lack later stages of germ cell differentiation. In the male, Zpg protein localizes to the surface of spermatogonia, primarily on the sides adjacent to the somatic cyst cells. In the female, Zpg protein localizes to germ cell surfaces, both those adjacent to surrounding somatic cells and those adjacent to other germ cells. We propose that Zpg-containing gap junctional hemichannels in the germ cell plasma membrane may connect with hemichannels made of other innexin isoforms on adjacent somatic cells. Gap junctional intercellular communication via these channels may mediate passage of crucial small molecules or signals between germline and somatic support cells required for survival and differentiation of early germ cells in both sexes.

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Low pH enhances connexin32 degradation in the pancreatic acinar cell

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00010.2014 ◽

2014 ◽

Vol 307 (1) ◽

pp. G24-G32 ◽

Cited By ~ 7

Author(s):

Anamika M. Reed ◽

Thomas Kolodecik ◽

Sohail Z. Husain ◽

Fred S. Gorelick

Keyword(s):

Gap Junctions ◽

Acinar Cell ◽

Intercellular Communication ◽

Pancreatic Acinar Cell ◽

Low Ph ◽

Extracellular Ph ◽

Gap Junctional Intercellular Communication ◽

Junction Protein ◽

Clinical Conditions ◽

Gap Junctional

Decreased extracellular pH is observed in a number of clinical conditions and can sensitize to the development and worsen the severity of acute pancreatitis. Because intercellular communication through gap junctions is pH-sensitive and modulates pancreatitis responses, we evaluated the effects of low pH on gap junctions in the rat pancreatic acinar cell. Decreasing extracellular pH from 7.4 to 7.0 significantly inhibited gap junctional intracellular communication. Acidic pH also significantly reduced levels of connexin32, the predominant gap junction protein in acinar cells, and altered its localization. Increased degradation through the proteasomal, lysosomal, and autophagic pathways mediated the decrease in connexin32 under low-pH conditions. These findings provide the first evidence that low extracellular pH can regulate gap junctional intercellular communication by enhancing connexin degradation.

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Characterization of a variant of gap junction protein α8 identified in a family with hereditary cataract

PLoS ONE ◽

10.1371/journal.pone.0183438 ◽

2017 ◽

Vol 12 (8) ◽

pp. e0183438 ◽

Cited By ~ 1

Author(s):

Debbie S. Kuo ◽

Jared T. Sokol ◽

Peter J. Minogue ◽

Viviana M. Berthoud ◽

Anne M. Slavotinek ◽

...

Keyword(s):

Gap Junction ◽

Junction Protein ◽

Gap Junction Protein

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

Molecular and Cellular Biology ◽

10.1128/mcb.10.4.1754-1763.1990 ◽

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.

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