title: Expression of the polycystin-1 C-terminal cytoplasmic tail increases Cl channel activity in Xenopus oocytes.
abstract: Expression of the polycystin-1 C-terminal cytoplasmic tail increases Cl(-) channel activity in Xenopus oocytes. Background. Cyst expansion in autosomal-dominant polycystic kidney disease (ADPKD) is characterized by active Cl(-) secretion in excess of solute reabsorption. However, the connections between elevated epithelial Cl(-) secretion and loss-of-function or dysregulation of either ADPKD gene polycystin-1 (PC1) or polycystin-2 (PC2) remain little understood. Methods. Cl(-) transport in Xenopus oocytes expressing the CD16.7-PKD1 (115-226) fusion protein containing the final 112 amino acid (aa) of the PC1 C-terminal cytoplasmic tail, or in oocytes expressing related PC1 fusion protein mutants, was studied by isotopic flux, two-electrode voltage clamp, and outside-out patch clamp recording. Results. Expression in oocytes of CD16.7-PKD1 (115-226) increased rates of both influx and efflux of (36)Cl(-), whereas CD16.7-PKD1 (1-92) containing the initial 92 aa of the PC1 C-terminal cytoplasmic tail was inactive. The increased Cl(-) transport resembled CD16.7-PKD1 (115-226)-stimulated cation current in its sensitivity to ADPKD-associated missense mutations, to mutations in phosphorylation sites, and to mutations within or encroaching upon the PC1 coiled-coil domain, as well as in its partial suppression by coexpressed PC2. The NS3623- and 4, 4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS)-sensitive (36)Cl(-) flux was not blocked by injected ethyleneglycol tetraacetate (EGTA) or by the cation channel inhibitor SKF96365, and was stimulated by the cation channel inhibitor La(3+), suggesting that CD16.7-PKD1 (115-226)-associated cation conductance was not required for (36)CI(-) flux activation. Outside-out patches from oocytes expressing CD16.7-PKD1 (115-226) also exhibited increased NS3623-sensitive Cl(-) current. Conclusion. These data show that CD16.7-PKD1 (115-226) activates Cl(-) channels in the Xenopus oocyte plasma membrane in parallel with, but not secondary to, activation of Ca(2+)-permeable cation channels.
authors: Molecular and Vascular Medicine Unit and Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
authors: Marina N
authors: MN
authors: Chernova
authors: David H
authors: DH
authors: Vandorpe
authors: Jeffrey S
authors: JS
authors: Clark
authors: Seth L
authors: SL
authors: Alper
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018075:RNA, Complementary; D011868:Radioisotopes; D012694:Serine / Q000378:metabolism; D050396:TRPP Cation Channels; D014443:Tyrosine / Q000378:metabolism; D014981:Xenopus
chemical_list: D002118:Calcium; D002412:Cations; D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D011506:Proteins; D018075:RNA, Complementary; D011868:Radioisotopes; D012694:Serine; D050396:TRPP Cation Channels; D014443:Tyrosine