The Structure and Function of JPH3 and Its Encoded Protein

JPH3 contains at least six exons (Fig. 6). The HDL2 repeat is located in a previously unidentified alternative 3' exon of the gene. Surprisingly, the repeat is oriented in the CTG direction, and various splice acceptor sites place the repeat in-frame to encode polyalanine or polyleucine, or in 3' UTR. JPH3 is one of a four-member gene family encoding proteins thought to be involved in physically bridging the gap between plasma membrane and sarcoplasmic reticulum (SR, muscle) or endoplasmic reticulum (ER, neurons) [16, 22]. Each protein in the family has a terminal region that serves to anchor the protein into plasma membrane, and a C-terminal domain that functions to attach the protein to the SR or ER. Myocytes of mice in which junctophilin-1 is not expressed show abnormal ultrastructure of the junctions between SR and plasma membrane, and the muscle develops an abnormally low contractile force after low frequency electrical stimulation [8].

Knock out of JP3 (the mouse orthologue of JPH3) resulted in only a mild motor phenotype and no clear electrophysiological or pathological abnormalities, though

JPH3 genomic structure full length transcript 1

JPH3 genomic structure

exon 1

exon 2A

exon 2B

transcripts with repeat 1

exon 3

exon 4

exon 5





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