The isolated polycystin-1 cytoplasmic COOH terminus prolongs ATP-stimulated Cl- conductance through increased Ca2+ entry.
The precise steps leading from mutation of the polycystic kidney disease (PKD1) gene to the autosomal dominant polycystic kidney disease (ADPKD) phenotype remain to be established. Fluid accumulation is a requirement for cyst expansion in ADPKD, suggesting that abnormal fluid secretion into the cyst lumen might play a role in disease. In this study, we sought to establish a link between polycystin-1 (the PKD1 gene product) and ATP-stimulated Cl- secretion in renal tubule cells. To do this, we performed a whole cell patch-clamp analysis of the effects of expression of the isolated cytoplasmic COOH-terminus of polycystin-1 in stably transfected mouse cortical collecting duct cells. The truncated polycystin-1 fusion protein prolonged the duration of ATP-stimulated Cl- conductance and intracellular Ca2+ responses. Both effects were dependent on extracellular Ca2+. It was determined that expression of the truncated polycystin-1 fusion protein introduced, or activated, an ATP-induced Ca2+ entry pathway that was undetectable in transfection control cell lines. Our findings are concordant with increasing evidence for a role of polycystin-1 in cell Ca2+ homeostasis and indicate that dysregulated Ca2+ entry might promote Cl- secretion and cyst expansion in ADPKD.
Wildman
Scott S
SS
Laboratory of Cardiological Sciences, Gerontology Research Center, Division of Renal Medicine, Johns Hopkins Bayview Medical Center, 4940 Eastern Avenue, Baltimore, MD 21224, USA.
Hooper
Kimberly M
KM
Turner
Clare M
CM
Sham
James S K
JS
Lakatta
Edward G
EG
King
Brian F
BF
Unwin
Robert J
RJ
Sutters
Michael
M
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009154:Mutation; D018408:Patch-Clamp Techniques; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050396:TRPP Cation Channels; D014162:Transfection
D000255:Adenosine Triphosphate; D002118:Calcium; D002712:Chlorides; D011506:Proteins; D050396:TRPP Cation Channels