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).
Department of Anatomy and Developmental Biology, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Dai
D
Shiba
Tetsuro
T
Takamatsu
Takahiko
T
Yokoyama
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