title: Cloning and functional characterization of inward-rectifying potassium (Kir) channels from Malpighian tubules of the mosquito Aedes aegypti.
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(+) > 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(+).
authors.affiliation: Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, 1680 Madison Avenue, 224 Thorne Hall, Wooster, OH 44691, USA. piermarini.1@osu.edu
authors.forename: Peter M
authors.initials: PM
authors.lastname: Piermarini
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Rouhier
authors.forename: Matthew
authors.initials: M
authors.lastname: Schepel
authors.forename: Christin
authors.initials: C
authors.lastname: Kosse
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Beyenbach
mesh_terms: D000330:Aedes / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005260:Female; D017344:Genes, Insect; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007552:Isotonic Solutions; D008317:Malpighian Tubules / Q000378:metabolism*; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D000077331:Ringer's Solution; D012964:Sodium / Q000378:metabolism; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D019476:Insect Proteins; D007552:Isotonic Solutions; D024661:Potassium Channels, Inwardly Rectifying; D001464:Barium; D000077331:Ringer's Solution; D012964:Sodium; D011188:Potassium