Gap junction gamma-3, also known as connexin-29 (Cx29) or gap junction epsilon-1 (GJE1), is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the ''GJC3''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
GJC3 is a
conexin
Connexins (Cx)TC# 1.A.24, or gap junction proteins, are structurally related transmembrane proteins that assemble to form vertebrate gap junctions. An entirely different family of proteins, the innexins, forms gap junctions in invertebrates. Each ...
.
Function
This gene encodes a
gap junction
Gap junctions are membrane channels between adjacent cells that allow the direct exchange of cytoplasmic substances, such small molecules, substrates, and metabolites.
Gap junctions were first described as ''close appositions'' alongside tight ...
protein. The encoded protein is known as a
connexin
Connexins (Cx)TC# 1.A.24, or gap junction proteins, are structurally related transmembrane proteins that assemble to form vertebrate gap junctions. An entirely different family of proteins, the innexins, forms gap junctions in invertebrates. Eac ...
, most of which form gap junctions that provide direct connections between neighboring cells.
However, Cx29, which is highly expressed in myelin-forming glial cells of the CNS and PNS, has not been documented to form gap junctions in any cell type. In both PNS and CNS myelinated axons, Cx29 is precisely colocalized with Kv1.2 voltage-gated K+ channels, where both proteins are concentrated in the juxtaparanode and along the inner mesaxon.
By freeze-fracture immunogold labeling electron microscopy, Cx29 is identified in abundant "rosettes" of transmembrane protein particles in the innermost layer of myelin, directly apposed to equally abundant immunogold-labeled Kv1.1 potassium channels, both in the juxtaparanodal axolemma and along the inner mesaxon.
A role in K
+ handling during saltatory conduction is implied but not yet demonstrated.
Clinical significance
Mutations in this gene have been reported to be associated with
nonsyndromic hearing loss.
References
Further reading
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Connexins
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