A role for inwardly rectifying K+ channels in differentiation of NG108-15 neuroblastoma � glioma cells
✍ Scribed by Pancrazio, Joseph J. ;Ma, Wu ;Grant, Geraldine M. ;Shaffer, Kara M. ;Kao, Winfred Y. ;Liu, Qi-Ying ;Manos, Patricia ;Barker, Jeffery L. ;Stenger, David A.
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 170 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0022-3034
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✦ Synopsis
The whole-cell patch-clamp technique was used to assess the current carried by inwardly rectifying K ؉ channels (K ir ) and the resting membrane potential (RMP) during long-term culture of NG108-15 cells. Culture of this cell line in serum-free medium triggers differentiation of a type I, neuron-like cell type followed by an eventual predominance of a type II, proliferative cell type. NG108-15 K ir currents, which strongly resemble currents carried by human ether-ago-go related gene (HERG) K ؉ channels, exhibited significantly smaller current density for the more depolarized undifferentiated cells in growth media (GM) and type II cells compared to the neuron-like type I cells. Detailed examination of the transition from undifferentiated GM cells to type I cells revealed a shift in the voltage dependence of K ir activation which paralleled the more hyperpolarized RMP, neurite outgrowth, and biochemical differentiation characteristic of type I cells. Reverse-transcription polymerase chain reaction experiments using primers for the rat variant of HERG, RERG, revealed a a nearly twofold increase in RERG mRNA as cells differentiate from GM to type I, a finding entirely consistent with the increased K ir current density derived from patch-clamp recordings. Administration of CsCl (5 mM) blocked K ir currents and depolarized the RMP of type I cells. Furthermore, culture of NG108-15 cells in serum-free medium but with CsCl added significantly prevented neurite extension, an effect which was entirely reversible upon subsequent removal of CsCl. In contrast, other K ؉ channel inhibitors (4-aminopyridine and tetraethylammonium), at concentrations without marked effects on K ir , failed to affect neurite extension. These results suggest an important role of the K ir channels in determining the RMP and triggering morphological differentiation of the cell line.