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XB-ART-45918
J Neurosci 2012 Jun 20;3225:8746-51. doi: 10.1523/JNEUROSCI.6089-11.2012.
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Hyperpolarizing GABAergic transmission requires the KCC2 C-terminal ISO domain.

Acton BA , Mahadevan V , Mercado A , Uvarov P , Ding Y , Pressey J , Airaksinen MS , Mount DB , Woodin MA .


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KCC2 is the neuron-specific member of the of K(+)-Cl(-) cotransporter gene family. It is also the only member of its family that is active under physiologically normal conditions, in the absence of osmotic stress. By extruding Cl(-) from the neuron under isotonic conditions, this transporter maintains a low concentration of neuronal Cl(-), which is essential for fast inhibitory synaptic transmission by GABA and glycine in the mature nervous system. The other members of this K(+)-Cl(-) cotransporter gene family are exclusively swelling-activated. Here we demonstrate that a 15 aa region near the end of the C terminus, unique to KCC2 (termed the ISO domain), is required for KCC2 to cotransport K(+) and Cl(-) out of the neuron under isotonic conditions. We made this discovery by overexpressing chimeric KCC2-KCC4 cDNA constructs in cultured hippocampal neurons prepared from Sprague Dawley rat embryos and assaying neuronal Cl(-) through gramicidin perforated patch-clamp recordings. We found that when neurons had been transfected with a chimeric KCC2 that lacked the unique ISO domain, hyperpolarizing responses to GABA were abolished. This finding indicates that the ISO domain is required for neuronal Cl(-) regulation. Furthermore, we discovered that when KCC2 lacks the ISO domain, it still retains swelling-activated transport, which demonstrates that there are exclusive molecular determinants of isotonic and swelling-induced K(+)-Cl(-) cotransport in neurons.

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Species referenced: Xenopus
Genes referenced: slc12a5

References [+] :
Balena, GABAergic synaptic transmission regulates calcium influx during spike-timing dependent plasticity. 2010, Pubmed