Isolated liver gap junctions: gating of transjunctional currents is similar to that in intact pairs of rat hepatocytes.

Spray, David C.; Sáez, Juan C.; Brosius, D. C.; Bennett, Michael V. L.; Hertzberg, Elliot L.

doi:10.1073/pnas.83.15.5494

Cited by 77 publications

(35 citation statements)

References 17 publications

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“…Channels composed of pGF5 have a measured unitary conductance value of 160 pS. This is of interest because the length of the pGF5 cytoplasmic tail domain approximates that of the wild-type connexin32 protein, whose channels have a similar unitary conductance, as determined in several cell types and expression systems, including acinar cells (20), isolated liver junctional membranes incorporated into lipid bilayers (21,22), and SKHepl cells transfected with connexin32 cDNA (10).…”

Section: Discussionmentioning

confidence: 99%

Functional analysis of human cardiac gap junction channel mutants.

Fishman

Moreno

Spray

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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149

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The connexins form a family of membrane spanning proteins that assemble into gap junction channels. The biophysical properties of these channels are dependent upon the constituent connexin isoform. To begin identifying the molecular basis for gap junction channel behavior in the human heart, a tissue that expresses connexin43, we used site-directed mutagenesis to generate mutant cDNAs of human connexin43 with shortened cytoplasmic tail domains. Premature stop codons were inserted, resulting in proteins corresponding in length to the mammalian isoforms connexin32 and connexin26, which are expressed primarily in liver. AU constructs restore intercellular coupling when they are transfected into SKHep1 cells, a human hepatoma line that is communication deficient. Whereas wild-type connexin43 transfectants display two distinct unitary conductance values of about 60 and 100 pS, transfectants expressing the mutant proteins, from which 80 and 138 amino acids have been deleted, exhibit markedly different single-channel properties, with unitary conductance values of about 160 and 50 pS, respectively.Junctional conductance of channels composed of wild-type connexin43 is less voltage-sensitive compared with transfectants expressing wild-type connexin32. However, neither of the connexin43 truncation mutants alters this relative voltage insensitivity. These results suggest that the cytoplasmic tail domain is an important determinant ofthe unitary conductance event of gap junction channels but not their voltage dependence. Furthermore, since the mutant connexins are missing several consensus phosphorylation sites, modification of these particular sites may not be required for membrane insertion or assembly of human connexin43 into functional channels.Gap junctions are specialized regions of adjoining cell membranes typically composed of numerous intercellular low resistance channels. Each channel is thought to consist of 12 connexin monomers, which assemble as coaxially aligned pairs of hexameric hemichannels. By permitting the passage of ions and chemical mediators from cell to cell, gap junction channels are likely to play a major role in a wide variety of cellular processes, including embryogenesis, cellular differentiation and development, and electrotonic coupling (for reviews see refs. 1 and 2). The connexins constitute a family of proteins whose expression is tissue specific and developmentally regulated (3-7). This diversity presumably reflects the temporal and/or spatial requirement of different tissues for the unique biophysical properties associated with channels assembled from particular connexin isoforms. These properties include the unitary conductance value, as well as channel gating characteristics in response to transjunctional potential, intracellular pH or Ca2+ concentration, and second messenger molecules.There is considerable speculation about the structural domains of connexins that determine their unique functional characteristics (8). Theoretical modeling based on sequence analysis, as well as c...

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Section: Discussionmentioning

confidence: 99%

Functional analysis of human cardiac gap junction channel mutants.

Fishman

Moreno

Spray

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

149

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“…voltage (Bennett and Verselis, 1992;Spray et al, 1986), growth factors (Lau et aI., 1992;Madhukar et aI., 1989;Maldonado et aI., 1988), and transforming oncogene activity (Atkinson and Sheridan, 1985;Azarnia et al, 1988). The mechanisms which mediate changes in gap junctional permeability are at present incompletely understood.…”

Section: 1)mentioning

confidence: 99%

pp60 -mediated Phosphorylation of Connexin 43, a Gap Junction Protein

Loo

Berestecky

Kanemitsu

et al. 1995

Journal of Biological Chemistry

138

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“…Functional demonstration that a given polypeptide is capable of forming an intercellular channel should be obtained by showing that dye and/or electrical coupling between two adjacent cells is/are blocked after intracellular micro-injection of specific antibodies against the candidate protein [40,41]. In addition, reconstitution of the purified protein into lipid bilayers should allow for a direct functional assessment of the electrophysiological properties of the putative channel the protein may form [42,43]. Another elegant approach, which has already been applied successfully, involves the introduction of the specific mRNA coding for a gap junctional protein into cells, followed by the measurement of the ability of these cells to communicate [44].…”

Section: Molecular Structure Of the Gap Junctional Channelmentioning

confidence: 99%

“…The presence of extensive coupling within an acinus raises the obvious question of its role under resting conditions and makes it likely that relevant information could be gathered by modulating the extent of cell-to-cell communication. As a first approach to this modulation, we have used alcohols such as heptanol, octanol and nonanol, which have been shown to block synaptic transmission and cell coupling [63,64] by a still undetermined mechanism that may involve their direct interaction with gap junctions [42]. We found that heptanol causes a marked reduction of the dye [I 1,121 and electrical [65] coupling within intact pancreatic acini, and abolishes, within seconds, the conductance of junctional channels between pairs of acinar cells [65].…”

Section: The Exocrine Pancreasmentioning

confidence: 99%

The gap junction: a channel for multiple functions?

Bruzzone

Meda

1988

Eur J Clin Investigation

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Abstract. Gap junctions are specialized membrane structures that enable the intercytoplasmic exchange of small molecules and ions between contacting cells. During the past decade, biophysical and structural analyses of the junctional channel have considerably increased our understanding of the pharmacological properties and gating mechanisms of gap junctions. Despite this impressive amount of work, until recently the physiological role of these ubiquitous intercellular pathways has remained speculative in most tissues. This review summarizes the most recent information obtained on the structure of the gap junction by molecular cloning of the major protein components and emphasizes the growing evidence for their functional role in adult tissues formed by highly differentiated secretory cells. The relevance of cell-to-cell coupling for the co-ordinated function of the exocrine and endocrine pancreas is discussed.

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Isolated liver gap junctions: gating of transjunctional currents is similar to that in intact pairs of rat hepatocytes.

Abstract: We have shown previously that conductance of rat liver gap junctions is blocked by an affinity-purifiled

Cited by 77 publications

References 17 publications

Functional analysis of human cardiac gap junction channel mutants.

Functional analysis of human cardiac gap junction channel mutants.

pp60 -mediated Phosphorylation of Connexin 43, a Gap Junction Protein

The gap junction: a channel for multiple functions?

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