F413C and A531V but not R894X myotonia congenita mutations cause defective endoplasmic reticulum export of the muscle-specific chloride channel CLC-1

• Published in: Muscle & nerve Vol. 37; no. 3; pp. 317 - 325
• Main Authors: Papponen, Hinni, Nissinen, Marja, Kaisto, Tuula, Myllylä, Vilho V., Myllylä, Raili, Metsikkö, Kalervo
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-03-2008; Wiley
• Subjects: Alanine - genetics; Amino Acids - genetics; Animals; Arginine - genetics; Biological and medical sciences; Cells, Cultured; chloride channel; Chloride Channels - genetics; Chloride Channels - metabolism; ClC-1; CLCN1; Coatomer Protein - metabolism; Cysteine - genetics; Diseases of striated muscles. Neuromuscular diseases; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - physiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Immunoprecipitation - methods; Medical sciences; Muscle Cells - ultrastructure; muscle fiber; Muscle Proteins - metabolism; Mutation; myotonia congenita; Neurology; Oligonucleotides, Antisense - pharmacology; Phenylalanine - genetics; Protein Transport - drug effects; Protein Transport - genetics; Rats; Rats, Sprague-Dawley; Semliki Forest virus; Striated muscle. Tendons; Transfection - methods; Valine - genetics; Vertebrates: osteoarticular system, musculoskeletal system; Nervous system diseases; Neuromuscular diseases; Stability; Rat; Myotonia; Biological transport; muscle fiber; Rodentia; Ionic channel; Muscular fiber; Protein; CLCN1; Vertebrata; Mammalia; CIC-1; chloride channel; myotonia congenita; Muscle; Mutation
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.20922

In northern Finland myotonia congenita is caused by three main mutations in the ClC‐1 chloride channel. We studied the molecular basis of these mutations (1238T>G/F413C, 1592C>T/A531V, and 2680C>T/R894X). The mutated cDNAs were expressed either in L6 myotubes or in isolated rat myofibers using recombinant Semliki Forest virus. Experiments in L6 cells indicated that A531V and R894X proteins suffered from stability problems in these cells. Analysis in myofibers indicated that the A531V protein was totally retained in the endoplasmic reticulum (ER), whereas the export of the F413C protein was severely reduced. The C‐terminal nonsense mutant (R894X), however, was normally transported to the Golgi elements in the myofibers. Defective export or reduced stability of the mutated proteins may thus be reasons for the myotonic symptoms. Muscle Nerve, 2007