American Journal of Physiology. Renal Physiology vol:298 issue:3 pages:F692-F701
The bladder urothelium is currently believed to be a sensory structure, contributing to mechano- and chemosensation in the bladder. Transient receptor potential (TRP) cation channels act as polymodal sensors, and may underlie some of the receptive properties of urothelial cells. However, the exact TRP channel expression profile of urothelial cells is unclear. Here, we have performed a systematic analysis of the molecular and functional expression of various TRP channels in mouse urothelium. Urothelial cells from control and trpv4(-/-) mice were isolated, cultured (12-48h) and used for quantitative Real Time (RT)-PCR, immunocytochemistry, calcium imaging and whole-cell patch-clamp experiments. At the mRNA level, TRPV4, TRPV2 and TRPM7 were the most abundantly expressed TRP genes. Immunohistochemistry showed a clear expression of TRPV4 in the plasma membrane, whereas TRPV2 was more prominent in the cytoplasm. TRPM7 was detected in the plasma membrane as well as cytoplasmatic vesicles. Calcium-imaging and patch-clamp experiments using TRP channel agonists and antagonists provided evidence for the functional expression of TRPV4, TRPV2 and TRPM7, but not of TRPA1, TRPV1 and TRPM8. In conclusion, we have demonstrated functional expression of TRPV4, TRPV2 and TRPM7 in mouse urothelial cells. These channels may contribute to the (mechano)-sensory function of the urothelial layer and represent potential targets for the treatment of bladder dysfunction.