Primary cilia of inv/inv mouse renal epithelial cells sense physiological fluid flow: bending of primary cilia and Ca2+ influx.
Primary cilia are hypothesized to act as a mechanical sensor to detect renal tubular fluid flow. Anomalous structure of primary cilia and/or impairment of increases in intracellular Ca2+ concentration in response to fluid flow are thought to result in renal cyst formation in conditional kif3a knockout, Tg737 and pkd1/pkd2 mutant mice. The mutant inv/inv mouse develops multiple renal cysts like kif3a, Tg737 and pkd1/pkd2 mutants. Inv proteins have been shown to be localized in the renal primary cilia, but response of inv/inv cilia to fluid stress has not been examined. In the present study, we examined the mechanical response of primary cilia to physiological fluid flow using a video microscope, as well as intracellular Ca2+ increases in renal epithelial cells from normal and inv/inv mice in response to flow stress. Percentages of ciliated cells and the length of primary cilia were not significantly different between primary renal cell cultures from normal and inv/inv mutant mice. Localization of inv protein was restricted to the base of primary cilia even under flow stress. Inv/inv mutant cells had similar bending mechanics of primary cilia in response to physiological fluid flow compared to normal cells. Furthermore, no difference was found in intracellular Ca2+ increases in response to physiological fluid flow between normal and inv/inv mutant cells. Our present study suggests that the function of the inv protein is distinct from polaris (the Tg737 gene product), polycystins (pkd1 and pkd2 gene products).
Shiba
Dai
D
Department of Anatomy and Developmental Biology, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Takamatsu
Tetsuro
T
Yokoyama
Takahiko
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002923:Cilia / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D045604:Extracellular Fluid / Q000378:metabolism*; D007668:Kidney / Q000737:chemistry / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D052177:Kidney Diseases, Cystic / Q000378:metabolism / Q000503:physiopathology; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology; D051379:Mice; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D018715:Microscopy, Video; D011506:Proteins / Q000235:genetics / Q000502:physiology; D050396:TRPP Cation Channels; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000502:physiology
D002118:Calcium; D008565:Membrane Proteins; D011506:Proteins; D050396:TRPP Cation Channels; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C491947:Invs protein, mouse; C490898:Tg737Rpw protein, mouse