Two Drosophila innexins are expressed in overlapping domains and cooperate to form gap-junction channels

Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes, Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notabl...

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Bibliographic Details
Published in:Molecular biology of the cell 2000-07, Vol.11 (7), p.2459-2470
Main Authors: Stebbings, L A, Todman, M G, Phelan, P, Bacon, J P, Davies, J A
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Connexins - genetics
Connexins - metabolism
DNA, Complementary
Drosophila - embryology
Drosophila - genetics
Drosophila - metabolism
Drosophila Proteins
Gap Junctions - metabolism
Gene Expression
Genes, Insect
Genes, Overlapping
Insect Proteins - genetics
Insect Proteins - metabolism
Molecular Sequence Data
Oocytes
Protein Biosynthesis
Protein Structure, Tertiary
Xenopus
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Summary:Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes, Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notably in epidermal cells bordering each segment. We also explore the gap-junction-forming capabilities of the encoded proteins. In paired Xenopus oocytes, the injection of Dm-inx2 mRNA results in the formation of voltage-sensitive channels in only approximately 40% of cell pairs. In contrast, Dm-Inx3 never forms channels. Crucially, when both mRNAs are coexpressed, functional channels are formed reliably, and the electrophysiological properties of these channels distinguish them from those formed by Dm-Inx2 alone. We relate these in vitro data to in vivo studies. Ectopic expression of Dm-inx2 in vivo has limited effects on the viability of Drosophila, and animals ectopically expressing Dm-inx3 are unaffected. However, ectopic expression of both transcripts together severely reduces viability, presumably because of the formation of inappropriate gap junctions. We conclude that Dm-Inx2 and Dm-Inx3, which are expressed in overlapping domains during embryogenesis, can form oligomeric gap-junction channels.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.11.7.2459