Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, 1680 Madison Avenue, 224 Thorne Hall, Wooster, OH 44691, USA.
Insect Biochem Mol Biol. 2013 Jan;43(1):75-90. doi: 10.1016/j.ibmb.2012.09.009. Epub 2012 Oct 17.
Inward-rectifying K(+) (Kir) channels play critical physiological roles in a variety of vertebrate cells/tissues, including the regulation of membrane potential in nerve and muscle, and the transepithelial transport of ions in osmoregulatory epithelia, such as kidneys and gills. It remains to be determined whether Kir channels play similar physiological roles in insects. In the present study, we sought to 1) clone the cDNAs of Kir channel subunits expressed in the renal (Malpighian) tubules of the mosquito Aedes aegypti, and 2) characterize the electrophysiological properties of the cloned Kir subunits when expressed heterologously in oocytes of Xenopus laevis. Here, we reveal that three Kir subunits are expressed abundantly in Aedes Malpighian tubules (AeKir1, AeKir2B, and AeKir3); each of their full-length cDNAs was cloned. Heterologous expression of the AeKir1 or the AeKir2B subunits in Xenopus oocytes elicits inward-rectifying K(+) currents that are blocked by barium. Relative to the AeKir2B-expressing oocytes, the AeKir1-expressing oocytes 1) produce larger macroscopic currents, and 2) exhibit a modulation of their conductive properties by extracellular Na(+). Attempts to functionally characterize the AeKir3 subunit in Xenopus oocytes were unsuccessful. Lastly, we show that in isolated Aedes Malpighian tubules, the cation permeability sequence of the basolateral membrane of principal cells (Tl(+) > K(+) > Rb(+) > NH(4)(+)) is consistent with the presence of functional Kir channels. We conclude that in Aedes Malpighian tubules, Kir channels contribute to the majority of the barium-sensitive transepithelial transport of K(+).
内向整流钾 (Kir) 通道在各种脊椎动物细胞/组织中发挥着重要的生理作用，包括调节神经和肌肉的膜电位，以及在肾脏和鳃等渗透调节上皮细胞中的离子跨上皮转运。目前尚不清楚 Kir 通道是否在昆虫中发挥类似的生理作用。在本研究中，我们试图 1) 克隆在蚊子埃及伊蚊肾脏 (马氏管) 中表达的 Kir 通道亚基的 cDNA，2) 表征在非洲爪蟾卵母细胞中异源表达时克隆的 Kir 亚基的电生理特性。在这里，我们揭示了三个 Kir 亚基在埃及伊蚊马氏管中大量表达 (AeKir1、AeKir2B 和 AeKir3)；克隆了它们的全长 cDNA。AeKir1 或 AeKir2B 亚基在非洲爪蟾卵母细胞中的异源表达会引发内向整流钾电流，该电流被钡阻断。与 AeKir2B 表达的卵母细胞相比，AeKir1 表达的卵母细胞 1) 产生更大的宏观电流，2) 其传导特性受到细胞外 Na(+) 的调节。尝试在非洲爪蟾卵母细胞中对 AeKir3 亚基进行功能表征的尝试没有成功。最后，我们表明，在分离的埃及伊蚊马氏管中，主细胞基底外侧膜的阳离子通透性顺序 (Tl(+) > K(+) > Rb(+) > NH(4)(+)) 与功能性 Kir 通道的存在一致。我们得出结论，在埃及伊蚊马氏管中，Kir 通道有助于大多数钡敏感的跨上皮钾转运。
