Primary cilia sense environmental conditions including osmolality, but whether cilia participate in osmotic response in renal epithelial cells is not known. Transient receptor potential (TRP) channels TRPV4 and TRPM3 are osmoresponsive. TRPV4 localizes to cilia in certain cell types, while renal subcellular localization of TRPM3 is not known. We hypothesized that primary cilia are required for maximal activation of the osmotic response of renal epithelial cells, and that ciliary TRPM3 and TRPV4 mediate that response. Ciliated (mIMCD-3 and 176-5) and non-ciliated (176-5∆) renal cells expressed Trpv4 and Trpm3. Ciliary expression of TRPM3 was observed in mIMCD-3 and 176-5 cells and in wildtype mouse kidney tissue. TRPV4 was identified in cilia and apical membrane of mIMCD-3 cells by electrophysiology, and in the cell body by immunofluorescence. Hyperosmolal stress at 500 mOsm/kg (via NaCl addition) induced the osmotic response genes Bgt1 and Akr1b3 in all ciliated cell lines. This induction was attenuated in non-ciliated cells. A TRPV4 agonist abrogated Bgt1 and Akr1b3 induction in ciliated and non-ciliated cells. A TRPM3 agonist attenuated Bgt1 and Akr1b3 induction in ciliated cells only. Knocking out TRPM3 attenuated Akr1b3 induction. Ciliated cells had greater viability under osmotic stress compared to non-ciliated cells. Akr1b3 induction was also less in non-ciliated than in ciliated cells when mannitol was used to induce hyperosmolal stress. These findings suggest that primary cilia are required for the maximal osmotic response in renal epithelial cells and that TRPM3 is involved in this mechanism. TRPV4 appears to modulate the osmotic response independent of cilia.
- primary cilium
- Copyright © 2015, American Journal of Physiology-Renal Physiology