Junctophilin-3 is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
that in humans, is encoded by the ''JPH3''
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
. The gene is approximately 97 kilobases long and is located at position 16q24.2.
Junctophilin proteins are associated with the formation of
junctional membrane complexes linking the
plasma membrane with the
endoplasmic reticulum in excitable cells.
Junctophilin-3 is specific to the brain and has an active role in
neurons involved in motor coordination and memory.
The protein contains 748 amino acid residues and is composed of a C-terminal hydrophobic segment that spans the
endoplasmic/
sarcoplasmic reticulum
The sarcoplasmic reticulum (SR) is a membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other cells. The main function of the SR is to store calcium ions (Ca2+). Calcium ion levels are ke ...
membrane, and a remaining cytoplasmic domain that shows specific affinity for the plasma membrane. The protein contains several MORN (membrane occupation and recognition nexus) repeats, that contribute to plasma membrane binding through interactions with phospholipids.
Junctophilin-3 is primarily expressed within the brain, specifically the dorsolateral prefrontal cortex. Although the precise function of the protein has not been determined, it has been demonstrated to play a role in motor coordination and memory through efficient
calcium ion signaling, and the stabilization of neuronal cellular architecture.
The JPH3 gene contains a CAG/CTG trinucleotide repeat segment. The expansion of this segment is associated with a number of
polyglutamine diseases (polyQ), which include
spinocerebellar ataxia
Spinocerebellar ataxia (SCA) is a progressive, degenerative, genetic disease with multiple types, each of which could be considered a neurological condition in its own right. An estimated 150,000 people in the United States have a diagnosis of s ...
,
Huntington's disease
Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...
, and
Huntington's disease-like 2 (HDL2). The pathological expansion of the CAG repeat coding region leads to an expanded polyQ tract, which aggregate in degenerated neurons leading to the degeneration of specific neuronal subpopulations.
References
External links
GeneReviews/NCBI/NIH/UW entry on Huntington Disease-Like 2
Further reading
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