The potassium chloride cotransporter KCC-2 coordinates development of inhibitory neurotransmission and synapse structure in Caenorhabditis elegans.
Chloride influx through GABA-gated chloride channels, the primary mechanism by which neural activity is inhibited in the adult mammalian brain, depends on chloride gradients established by the potassium chloride cotransporter KCC2. We used a genetic screen to identify genes important for inhibition of the hermaphrodite-specific motor neurons (HSNs) that stimulate Caenorhabditis elegans egg-laying behavior and discovered mutations in a potassium chloride cotransporter, kcc-2. Functional analysis indicates that, like mammalian KCCs, C. elegans KCC-2 transports chloride, is activated by hypotonic conditions, and is inhibited by the loop diuretic furosemide. KCC-2 appears to establish chloride gradients required for the inhibitory effects of GABA-gated and serotonin-gated chloride channels on C. elegans behavior. In the absence of KCC-2, chloride gradients appear to be altered in neurons and muscles such that normally inhibitory signals become excitatory. kcc-2 is transcriptionally upregulated in the HSN neurons during synapse development. Loss of KCC-2 produces a decrease in the synaptic vesicle population within mature HSN synapses, which apparently compensates for a lack of HSN inhibition, resulting in normal egg-laying behavior. Thus, KCC-2 coordinates the development of inhibitory neurotransmission with synapse maturation to produce mature neural circuits with appropriate activity levels.
Tanis
Jessica E
JE
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Bellemer
Andrew
A
Moresco
James J
JJ
Forbush
Biff
B
Koelle
Michael R
MR
D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005665:Furosemide / Q000494:pharmacology; D007038:Hypotonic Solutions; D009046:Motor Neurons / Q000502:physiology; D009132:Muscles / Q000502:physiology; D009154:Mutation; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D017385:Sequence Homology; D012726:Sexual Behavior, Animal / Q000502:physiology; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D027981:Symporters / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000502:physiology; D015854:Up-Regulation; D000096922:K Cl- Cotransporters
D029742:Caenorhabditis elegans Proteins; D002712:Chlorides; D005665:Furosemide; D007038:Hypotonic Solutions; D043562:Receptors, G-Protein-Coupled; D049994:Sodium Potassium Chloride Symporter Inhibitors; D027981:Symporters; D000096922:K Cl- Cotransporters; C499425:EGL-47 protein, C elegans
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