Chloride Potassium Symporter 5 - Location

Location

KCC2 is a neuron-specific membrane protein expressed throughout the central nervous system, including the hippocampus, hypothalamus, brainstem, and motoneurons of the ventral spinal cord.

At the subcellular level, KCC2 has been found in membranes of the somata and dendrites of neurons, with no evidence of expression on axons. KCC2 has also been shown to colocalize with GABA_A receptors, which serve as ligand-gated ion channels to allow chloride ion movement across the cell membrane. Under normal conditions, the opening of GABA_A receptors permits the hyperpolarizing influx of chloride ions to inhibit postsynaptic neurons from firing.

Counterintuitively, KCC2 has also been shown to colocalize at excitatory synapses. One suggested explanation for such colocalization is a potential protective role of KCC2 against excitotoxicity. Ion influx due to the excitatory synaptic stimulation of ion channels in the neuronal membrane causes osmotic swelling of cells as water is drawn in alongside the ions. KCC2 may help to eliminate excess ions from the cell in order to re-establish osmotic homeostasis.