Identification of RBK1 potassium channels in C6 astrocytoma cells

✍ Scribed by Dr. Sho-Ya Wang; Neil A. Castle; Ging Kuo Wang

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 782 KB
• Volume: 5
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.440050209

✦ Synopsis

Ionic currents in C6 astrocytoma cells were studied using the patch clamp technique under the whole cell configuration. A delayed rectifier K+ current with an amplitude of -1 n A at + 50 mV was observed in 86% (92/107) of the cells examined. This Kt current resembled the delayed rectifier present in type-1 and type-2 astrocytes in vitro and could be inhibited by a variety of K+ channel blockers, including TEA (IC50: 0.5 mM), 4-aminopyridine 0.2 mM), MCD peptide (ICs0: 52 nM), dendrotoxin I (IC50: 9 nM), and charybdotoxin (74% inhibition a t 50 nM). Northern blot analysis, cloning of cDNA and subsequent sequencing showed that the C6 cell delayed rectifier K+ channel is equivalent to the RBKl Kt channel derived from a rat brain cDNA library. The level of RBKl transcripts in C6 cells was comparable to that reported in rat brain. The C6 delayed rectifier K' channel is probably a homomeric RBKl K+ channel judging from its pharmacological properties which are similar to the RBKl channel expressed inXenopus oocytes. Some C6 cells also expressed a transiently activated outward K+ current (IA). This current was found in less than 50% of the cells and in general contributed no more than 8% of the total outward current. No voltage-dependent inward Na+ or Ca2+ currents or inwardly rectifying Kt currents were observed in over 100 C6 cells examined. The present results show that the dominant voltage gated ionic current in C6 cells is the RBKl delayed rectifier K+ channel. Since C6 cells express RBKl mRNA at a level comparable to its rat brain counterpart, these cells may be a valuable system to study the RBKl channel and its gene expression.