Variable loss of Kir4.1 channel function in SeSAME syndrome mutations

• Published in: Biochemical and biophysical research communications 2010-09, Vol.399 (4), p.537-541
• Main Authors: Tang, Xiaofang, Hang, Darwin, Sand, Andrea, Kofuji, Paulo
• Format: Article
• Language: English
• Subjects: Animals; Ataxia; Ataxia - genetics; Ataxia - metabolism; Biotinylation; Cell Line; EAST syndrome; Glia; Hearing Loss, Sensorineural - genetics; Hearing Loss, Sensorineural - metabolism; Humans; Intellectual Disability - genetics; Intellectual Disability - metabolism; KCNJ10; Kir4.1; Mutation; Potassium Channels, Inwardly Rectifying - genetics; Potassium Channels, Inwardly Rectifying - metabolism; Rats; Seizures - genetics; Seizures - metabolism; SeSAME syndrome; Syndrome; Water-Electrolyte Imbalance - genetics; Water-Electrolyte Imbalance - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2010.07.105

► SeSAME syndrome channelopathy is caused by loss of Kir4.1 channel function. ► Magnitude of loss of function depends on the mutated residue. ► SeSAME syndrome channel mutants are rescued with the wild-type Kir4.1 channel. ► Non-sense mutant R199X impairs expression to plasma membrane. SeSAME syndrome is a complex disease characterized by seizures, sensorineural deafness, ataxia, mental retardation and electrolyte imbalance. Mutations in the inwardly rectifying potassium channel Kir4.1 ( KCNJ10 gene) have been linked to this condition. Kir4.1 channels are weakly rectifying channels expressed in glia, kidney, cochlea and possibly other tissues. We determined the electrophysiological properties of SeSAME mutant channels after expression in transfected mammalian cells. We found that a majority of mutations (R297C, C140R, R199X, T164I) resulted in complete loss of Kir4.1 channel function while two mutations (R65P and A167V) produced partial loss of function. All mutant channels were rescued upon co-transfection of wild-type Kir4.1 but not Kir5.1 channels. Cell-surface biotinylation assays indicate significant plasma membrane expression of all mutant channels with exception of the non-sense mutant R199X. These results indicate the differential loss of Kir channel function among SeSAME syndrome mutations.