Alternative splicing of N- and C-termini of a C. elegans CIC channel alters gating and sensitivity to external Cl- and H+

被引:20
作者
Denton, J
Nehrke, K
Rutledge, E
Morrison, R
Strange, K
机构
[1] Vanderbilt Univ, Ctr Med, Dept Anaesthesiol, Nashville, TN 37232 USA
[2] Vanderbilt Univ, Ctr Med, Dept Pharmacol, Nashville, TN 37232 USA
[3] Vanderbilt Univ, Ctr Med, Dept Physiol & Mol Biophys, Nashville, TN 37232 USA
[4] Univ Rochester, Ctr Med, Dept Med, Nephrol Unit, Rochester, NY 14642 USA
来源
JOURNAL OF PHYSIOLOGY-LONDON | 2004年 / 555卷 / 01期
关键词
D O I
10.1113/jphysiol.2003.053165
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
CLH-3 is a meiotic cell cycle-regulated ClC Cl- channel that is functionally expressed in oocytes of the nematode Caenorhabditis elegans. CLH-3a and CLH-3b are alternatively spliced variants that have identical intramembrane regions, but which exhibit striking differences in their N- and C-termini. Structural and functional studies indicate that N- and C-terminal domains modulate ClC channel activity. We therefore postulated that alternative splicing of CLH-3 would alter channel gating and physiological functions. To begin testing this hypothesis, we characterized the biophysical properties of CLH-3a and CLH-3b expressed heterologously in HEK293 cells. CLH-3a activates more slowly and requires stronger hyperpolarization for activation than CLH-3b. Depolarizing conditioning voltages dramatically increase CLH-3a current amplitude and induce a slow inactivation process at hyperpolarized voltages, but have no significant effect on CLH-3b activity. CLH-3a also differs significantly in its extracellular Cl- and pH sensitivity compared to CLH-3b. Immunofluorescence microscopy demonstrated that CLH3b is translationally expressed during all stages of oocyte development, and furthermore, the biophysical properties of the native oocyte Cl- current are indistinguishable from those of heterologously expressed CLH-3b. We conclude that CLH-3b carries the oocyte Cl- current and that the channel probably functions in nonexcitable cells to depolarize membrane potential and/or mediate net Cl- transport. The unique voltage-dependent properties of CLH-3a suggest that the channel may function in muscle cells and neurones to regulate membrane excitability. We suggest that alternative splicing of CLH-3 N- and C-termini modifies the functional properties of the channel by altering the accessibility and/or function of pore-associated ion-binding sites.
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收藏
页码:97 / 114
页数:18
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