Tompkins-Macdonald Gabrielle J, Gallin Warren J, Sakarya Onur, Degnan Bernard, Leys Sally P, Boland Linda M
University of Alberta, Department of Biological Sciences, Edmonton, AB, Canada T6G 2E9.
J Exp Biol. 2009 Mar;212(Pt 6):761-7. doi: 10.1242/jeb.026971.
Ion channels establish and regulate membrane potentials in excitable and non-excitable cells. How functional diversification of ion channels contributed to the evolution of nervous systems may be understood by studying organisms at key positions in the evolution of animal multicellularity. We have carried out the first analysis of ion channels cloned from a marine sponge, Amphimedon queenslandica. Phylogenetic comparison of sequences encoding for poriferan inward-rectifier K(+) (Kir) channels suggests that Kir channels from sponges, cnidarians and triploblastic metazoans each arose from a single channel and that duplications arose independently in the different groups. In Xenopus oocytes, AmqKirA and AmqKirB produced K(+) currents with strong inward rectification, as seen in the mammalian Kir2 channels, which are found in excitable cells. The pore properties of AmqKir channels demonstrated strong K(+) selectivity and block by Cs(+) and Ba(2+). We present an original analysis of sponge ion channel physiology and an examination of the phylogenetic relationships of this channel with other cloned Kir channels.
离子通道在可兴奋细胞和非可兴奋细胞中建立并调节膜电位。通过研究处于动物多细胞进化关键位置的生物，或许可以了解离子通道的功能多样化是如何促进神经系统进化的。我们首次对从一种海洋海绵——昆士兰扁海绵（Amphimedon queenslandica）中克隆出的离子通道进行了分析。对编码海绵动物内向整流钾（Kir）通道的序列进行系统发育比较表明，海绵动物、刺胞动物和三胚层后生动物的Kir通道均起源于单一通道，且不同类群中的复制是独立发生的。在非洲爪蟾卵母细胞中，AmqKirA和AmqKirB产生了具有强烈内向整流的钾电流，这与在可兴奋细胞中发现的哺乳动物Kir2通道类似。AmqKir通道的孔特性表现出对钾离子的强选择性以及被铯离子（Cs(+)）和钡离子（Ba(2+)）阻断的特性。我们展示了对海绵离子通道生理学的原创性分析以及该通道与其他克隆的Kir通道之间系统发育关系的研究。
