A unique alkaline pH-regulated and fatty acid-activated tandem pore domain potassium channel (K-2P) from a marine sponge

作者：Wells Gregory D; Tang Qiong Yao; Heler Robert; Tompkins MacDonald Gabrielle J; Pritchard Erica N; Leys Sally P; Logothetis Diomedes E; Boland Linda M^*

来源：Journal of Experimental Biology, 2012, 215(14): 2435-2444.

DOI：10.1242/jeb.066233

• sponge
• Porifera
• K-2P
• tandem-pore K+ channel
• arachidonic acid
• pH

A cDNA encoding a potassium channel of the two-pore domain family (K-2P, KCNK) of leak channels was cloned from the marine sponge Amphimedon queenslandica. Phylogenetic analysis indicated that AquK(2P) cannot be placed into any of the established functional groups of mammalian K-2P channels. We used the Xenopus oocyte expression system, a two-electrode voltage clamp and inside-out patch clamp electrophysiology to determine the physiological properties of AquK(2P). In whole cells, non-inactivating, voltage-independent, outwardly rectifying K+ currents were generated by external application of micromolar concentrations of arachidonic acid (AA; EC50 similar to 30 mu mol l(-1)), when applied in an alkaline solution (%26gt;= pH8.0). Prior activation of channels facilitated the pH-regulated, AA-dependent activation of AquK(2P) but external pH changes alone did not activate the channels. Unlike certain mammalian fatty-acid-activated K-2P channels, the sponge K-2P channel was not activated by temperature and was insensitive to osmotically induced membrane distortion. In inside-out patch recordings, alkalinization of the internal pH (pK(a)8.18) activated the AquK(2P) channels independently of AA and also facilitated activation by internally applied AA. The gating of the sponge K-2P channel suggests that voltage-independent outward rectification and sensitivity to pH and AA are ancient and fundamental properties of animal K-2P channels. In addition, the membrane potential of some poriferan cells may be dynamically regulated by pH and AA.

• 出版日期2012-7