Alterations in the cytoplasmic domain of CLCN2 result in altered gating kinetics.
Mutations in the human ClC-2 Cl(-) channel have been described to influence its function dramatically. To test for naturally occurring gene variants in a human population and their functionality, all 24 CLCN2 exons from a Central African population were sequenced. Six single amino acid exchanges in the intracellular N-terminus (P48R, R68H), in the pore domain (G199A), or in the intracellular C-terminus (R646Q, R725W, R747H) were identified at low frequency. Heterologous expression of these polymorphisms in Xenopus laevis oocytes demonstrated their functional significance as determined by two-electrode voltage-clamp. The polymorphisms R68H, R725W, and R747H exhibited faster voltage-stimulated gating as compared to the wild type channel, resulting in higher steady state currents of R725W. Probably due to decreased surface expression P48R, R68H, and R646Q mutants generated lower currents than the wild type channels. The inward currents of the mutated channels R725W, R747H, and G199A failed to increase during hypotonic swelling, a defect paralleled by impaired swelling-accelerated voltage-gating in one mutant (G199A). In conclusion, the Africans' gene pool comprises CLCN2 gene variants in the N-terminus, the C-terminus or the pore domain that affect surface expression and voltage- or cell-swelling-stimulated channel gating.
Paul
Jochen
J
Department of Physiology, University of Tübingen, Germany.
Jeyaraj
Sankarganesh
S
Huber
Stephan M
SM
Seebohm
Guiscard
G
Böhmer
Christoph
C
Lang
Florian
F
Kremsner
Peter G
PG
Kun
Jürgen F J
JF
D000349:Africa; D000595:Amino Acid Sequence; D000818:Animals; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D004566:Electrodes; D004594:Electrophysiology; D005091:Exons / Q000235:genetics; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009865:Oocytes; D009997:Osmotic Pressure; D018408:Patch-Clamp Techniques; D011110:Polymorphism, Genetic / Q000235:genetics; D017434:Protein Structure, Tertiary; D012680:Sensitivity and Specificity; D016415:Sequence Alignment; D014982:Xenopus laevis; D017967:Zinc Compounds / Q000494:pharmacology
D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D002712:Chlorides; D017967:Zinc Compounds; C016837:zinc chloride; D004247:DNA