title: A SLC4-like anion exchanger from renal tubules of the mosquito (Aedes aegypti): evidence for a novel role of stellate cells in diuretic fluid secretion.
abstract: Transepithelial fluid secretion across the renal (Malpighian) tubule epithelium of the mosquito (Aedes aegypti) is energized by the vacuolar-type (V-type) H(+)-ATPase and not the Na(+)-K(+)-ATPase. Located at the apical membrane of principal cells, the V-type H(+)-ATPase translocates protons from the cytoplasm to the tubule lumen. Secreted protons are likely to derive from metabolic H(2)CO(3), which raises questions about the handling of HCO(3)(-) by principal cells. Accordingly, we tested the hypothesis that a Cl/HCO(3) anion exchanger (AE) related to the solute-linked carrier 4 (SLC4) superfamily mediates the extrusion of HCO(3)(-) across the basal membrane of principal cells. We began by cloning from Aedes Malpighian tubules a full-length cDNA encoding an SLC4-like AE, termed AeAE. When expressed heterologously in Xenopus oocytes, AeAE is both N- and O-glycosylated and mediates Na(+)-independent intracellular pH changes that are sensitive to extracellular Cl(-) concentration and to DIDS. In Aedes Malpighian tubules, AeAE is expressed as two distinct forms: one is O-glycosylated, and the other is N-glycosylated. Significantly, AeAE immunoreactivity localizes to the basal regions of stellate cells but not principal cells. Concentrations of DIDS that inhibit AeAE activity in Xenopus oocytes have no effects on the unstimulated rates of fluid secretion mediated by Malpighian tubules as measured by the Ramsay assay. However, in Malpighian tubules stimulated with kinin or calcitonin-like diuretic peptides, DIDS reduces the diuretic rates of fluid secretion to basal levels. In conclusion, Aedes Malpighian tubules express AeAE in the basal region of stellate cells, where this transporter may participate in producing diuretic rates of transepithelial fluid secretion.
authors.affiliation: Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA. pmp26@cornell.edu
authors.forename: Peter M
authors.initials: PM
authors.lastname: Piermarini
authors.forename: Laura F
authors.initials: LF
authors.lastname: Grogan
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lau
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Beyenbach
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000378:metabolism; D000330:Aedes / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics; D017920:Antiporters / Q000235:genetics; D001665:Binding Sites / Q000502:physiology; D015153:Blotting, Western; D027963:Chloride-Bicarbonate Antiporters / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004231:Diuresis / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism; D005091:Exons / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006031:Glycosylation; D008317:Malpighian Tubules / Q000166:cytology / Q000502:physiology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010802:Phylogeny; D064606:SLC4A Proteins; D014882:Water-Electrolyte Balance / Q000502:physiology*; D014981:Xenopus
chemical_list: D027321:Anion Transport Proteins; D017920:Antiporters; D027963:Chloride-Bicarbonate Antiporters; D064606:SLC4A Proteins; C489237:SLC4A3 protein, human; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid