Heterologeous expression of a glial Kir channel (KCNJ10) in a neuroblastoma spinal cord (NSC-34) cell line.

Heterologeous expression of Kir channels offers a tool to modulate excitability of neurons which provide insight into Kir channel functions in general. Inwardly-rectifying K(+) channels (Kir channels) are potential candidate proteins to hyperpolarise neuronal cell membranes. However, heterologeous expression of inwardly-rectifying K(+) channels has previously proven to be difficult. This was mainly due to a high toxicity of the respective Kir channel expression. We investigated the putative role of a predominantly glial-expressed, weakly rectifying Kir channel (Kir4.1 channel subunit; KCNJ10) in modulating electrophysiological properties of a motoneuron-like cell culture (NSC34). Transfection procedures using an EGFP-tagged Kir4.1 protein in this study proved to have no toxic effects on NSC34 cells. Using whole cell-voltage clamp, a substantial increase of inward rectifying K(+) currents as well as hyperpolarisation of the cell membrane was observed in Kir4.1-transfected cells. Na(+) inward currents, observed in NSC34 controls, were absent in Kir4.1-EGFP motoneuronal cells. The Kir4.1-transfection did not influence the NaV1.6 sodium channel expression. This study demonstrates the general feasibility of a heterologeous expression of a weakly inward-rectifying K(+) channel (Kir4.1 subunit) and shows that in vitro overexpression of Kir4.1 shifts electrophysiological properties of neuronal cells to a more glial-like phenotype and may therefore be a candidate tool to dampen excitability of neurons in experimental paradigms.