Cloning and functional characterization of inward-rectifying potassium (Kir) channels from Malpighian tubules of the mosquito Aedes aegypti |
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| Authors: | Peter M Piermarini Matthew F Rouhier Matthew Schepel Christin Kosse Klaus W Beyenbach |
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| Institution: | 1. Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, 1680 Madison Avenue, 224 Thorne Hall, Wooster, OH 44691, USA;2. Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA;1. Areawide Pest Management Research, Southern Plains Agricultural Research Center, USDA, 2881 F/B Road, College Station, TX 77845, USA;2. Department of Chemistry, MC 0212, Virginia Tech, Blacksburg, VA 24061, USA;3. Institute of Organic Chemistry, Technical University of Lodz, 90-924 Lodz, Poland;4. Peptaderm, Inc., 00-071 Warsaw, Poland;5. School of Biological and Chemical Sciences, Birkbeck (University of London), Malet Street, London WC1E 7HX, UK;1. Department of Entomology, Texas A&M University, College Station, TX, 77843, USA;2. Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, U.S. Department of Agriculture, 2881 F/B Road, College Station, TX, 77845, USA;1. Instituto Tecnologico de Conkal, Km. 16.3, Ex-Carretera Merida-Motul, Conkal , Yucatan C.P. 97345, Mexico;2. Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada |
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| Abstract: | 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+ > NH4+) 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+. |
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