NRSF/REST impairs brain spatial K+ buffering and glutamate uptake via downregulation of inwardly rectifying K+ channel Kir4.1 and GLT-1 transporter in cultured cortical astrocytes

Neuron-restrictive silencer factor/repressor element 1 (RE1)-silencing transcription factor (NRSF/REST) regulates many genes and signaling pathways involved in neuronal differentiation, synaptic homeostasis and maintenance of normal glial cell functions. REST activity is progressively downregulated in neurons during development, while it is normally expressed in glial cells. Astrocytes are the most abundant glial cells and play an important role in maintaining the functional integrity of neuronal networks by forming tripartite synapses. In this study, we have explored the in vitro role of REST in astrocyte functions using REST conditional knockout mice (REST-KO). We studied the electrophysiological properties of primary cultures of REST-KO cortical astrocytes by the patch-clamp method. We provided biophysical and pharmacological evidence of a reduced plasma membrane density of the inward rectifying K+ channel subtypes 4.1 (Kir4.1). Loss of Kir4.1 causes reduction of the expression and activity of glutamate transporter-1 (GLT-1), accompanied by a decrease in the astroglial glutamate uptake. Because a reduced activity of astrocyte Kir4.1 has been observed in a number of neurological diseases including temporal lobe epilepsy, we have studied the firing properties of neurons co-cultured with REST-KO astrocytes. Loss of Kir4.1 impairs the astrocyte ability to buffer extracellular K+ concentration that, increased by neuronal activity, indirectly enhances the action potential firing of neurons co-cultured with REST-KO astrocytes. This study adds a new piece to the discovery of REST-regulated mechanisms in astrocytes and contributes to our understanding of the involvement of Kir4.1 and GLT-1 in a variety of neurological disorders.