A novel N-terminal isoform of the neuron-specific K-Cl cotransporter KCC2

被引:108
作者
Uvarov, Pavel
Ludwig, Anastasia
Markkanen, Marika
Pruunsild, Priit
Kaila, Kai
Delpire, Eric
Timmusk, Tonis
Rivera, Claudio
Airaksinen, Matti S.
机构
[1] Univ Helsinki, Ctr Neurosci, FIN-00014 Helsinki, Finland
[2] Univ Helsinki, Inst Biotechnol, FIN-00014 Helsinki, Finland
[3] Univ Helsinki, Dept Biol & Environm Sci, FIN-00014 Helsinki, Finland
[4] Tallinn Univ Technol, Dept Gene Technol, EE-19086 Tallinn, Estonia
[5] Vanderbilt Univ, Med Ctr, Dept Anesthesiol, Nashville, TN 37232 USA
基金
英国惠康基金;
关键词
D O I
10.1074/jbc.M705095200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The neuronal K-Cl cotransporter KCC2 maintains the low intracellular chloride concentration required for the hyperpolarizing actions of inhibitory neurotransmitters gamma-aminobutyric acid and glycine in the central nervous system. This study shows that the mammalian KCC2 gene ( alias Slc12a5) generates two neuron-specific isoforms by using alternative promoters and first exons. The novel KCC2a isoform differs from the only previously known KCC2 isoform (now termed KCC2b) by 40 unique N-terminal amino acid residues, including a putative Ste20-related proline alanine-rich kinase-binding site. Ribonuclease protection and quantitative PCR assays indicated that KCC2a contributes 20-50% of total KCC2 mRNA expression in the neonatal mouse brain stem and spinal cord. In contrast to the marked increase in KCC2b mRNA levels in the cortex during postnatal development, the overall expression of KCC2a remains relatively constant and makes up only 5-10% of total KCC2 mRNA in the mature cortex. A rubidium uptake assay in human embryonic kidney 293 cells showed that the KCC2a isoform mediates furosemide-sensitive ion transport activity comparable with that of KCC2b. Mice that lack both KCC2 isoforms die at birth due to severe motor defects, including disrupted respiratory rhythm, whereas mice with a targeted disruption of the first exon of KCC2b survive for up to 2 weeks but eventually die due to spontaneous seizures. We show that these mice lack KCC2b but retain KCC2a mRNA. Thus, distinct populations of neurons show a differential dependence on the expression of the two isoforms: KCC2a expression in the absence of KCC2b is presumably sufficient to support vital neuronal functions in the brain stem and spinal cord but not in the cortex.
引用
收藏
页码:30570 / 30576
页数:7
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