junctophilin-3; JP-3; junctophilin type 3; trinucleotide repeat-containing gene 22 protein (JPH3, JP3, TNRC22)

Function

• contributes to stabilization of junctional membrane complexes, common to excitable cells
• probably acts by anchoring the plasma membrane & endoplasmic reticulum
• may play an active role in certain neurons
• involved in motor coordination (putative)

Structure

• the MORN (membrane occupation & recognition nexus) repeats contribute to the plasma membrane binding, possibly by interacting with phospholipids (putative)
• belongs to the junctophilin family
• contains 8 MORN repeats

Compartment

• cell membrane; peripheral membrane protein (putative)
• single-pass type 4 membrane protein (putative)
• endoplasmic reticulum membrane
• localized predominantly on the plasma membrane
• the transmembrane domain is anchored in ER membrane
• the N-terminal part associates with the plasma membrane (putative)

Alternative splicing

• named isoforms=2
• additional isoforms seem to exist

Expression

• specifically expressed in brain

Pathology

• defects in JPH3 are the cause of Huntington disease-like type 2 (HDL2)

Polymorphism

• isoform 2 length of the poly-Ala region is variable (6 to 27 CTG/CAG triplets) in the normal population & may be expanded (41 to 58 CTG/CAG triplets) in patients suffering from Huntington disease-like type 2

More general terms

• junctophilin
• phosphoprotein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=57338
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:57338
• OMIM: https://mirror.omim.org/entry/605268
• OMIM: https://mirror.omim.org/entry/606438
• UniProt: http://www.uniprot.org/uniprot/Q8WXH2.html