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Rapid effects of 17beta-estradiol on TRPV5 epithelial Ca2+ channels in rat renal cells
Mustapha Irnaten1, Nicolas Blanchard-Gutton, Jeppe Praetorius
1Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Beaumont Hospital, PO Box 9063, Dublin 9, Ireland. irnatenm@yahoo.fr
Abstract:
The renal distal tubules and collecting ducts play a key role in the control of electrolyte and fluid homeostasis. The discovery of highly calcium selective channels, Transient Receptor Potential Vanilloid 5 (TRPV5) of the TRP superfamily, has clarified the nature of the calcium entry channels. It has been proposed that this channel mediates the critical Ca(2+) entry step in transcellular Ca(2+) re-absorption in the kidney. The regulation of transmembrane Ca(2+) flux through TRPV5 is of particular importance for whole body calcium homeostasis.In this study, we provide evidence that the TRPV5 channel is present in rat cortical collecting duct (RCCD(2)) cells at mRNA and protein levels. We demonstrate that 17beta-estradiol (E(2)) is involved in the regulation of Ca(2+) influx in these cells via the epithelial Ca(2+) channels TRPV5. By combining whole-cell patch-clamp and Ca(2+)-imaging techniques, we have characterized the electrophysiological properties of the TRPV5 channel and showed that treatment with 20-50nM E(2) rapidly (<5min) induced a transient increase in inward whole-cell currents and intracellular Ca(2+) via TRPV5 channels. This rise was significantly prevented when cells were pre-treated with ruthenium red and completely abolished in cells treated with siRNA specifically targeting TRPV5.These data demonstrate for the first time, a novel rapid modulation of endogenously expressed TRPV5 channels by E(2) in kidney cells. Furthermore, the results suggest calcitropic effects of E(2). The results are discussed in relation to present concepts of non-genomic actions of E(2) in Ca(2+) homeostasis.
Insights
17beta-estradiol rapidly enhances calcium influx in kidney cells by modulating the Transient Receptor Potential Vanilloid 5 (TRPV5) channel. This finding reveals a novel non-genomic action of estradiol in calcium homeostasis.
Area of Science:
- Nephrology
- Endocrinology
- Molecular Biology
Background:
- Renal tubules and collecting ducts are crucial for electrolyte and fluid balance.
- Transient Receptor Potential Vanilloid 5 (TRPV5) channels mediate critical calcium re-absorption in the kidney.
- Regulation of TRPV5 activity is vital for systemic calcium homeostasis.
Purpose of the Study:
- To investigate the presence and function of TRPV5 channels in rat cortical collecting duct (RCCD(2)) cells.
- To determine if 17beta-estradiol (E(2)) regulates Ca(2+) influx through TRPV5 channels.
- To elucidate the rapid, non-genomic effects of E(2) on kidney calcium transport.
Main Methods:
- Quantitative real-time PCR and Western blotting to confirm TRPV5 expression at mRNA and protein levels.
- Whole-cell patch-clamp electrophysiology to measure ion currents.
- Calcium imaging techniques to assess intracellular Ca(2+) levels.
- Pharmacological inhibition (ruthenium red) and gene silencing (siRNA) to validate TRPV5 involvement.
Main Results:
- TRPV5 channels are expressed in RCCD(2) cells.
- 17beta-estradiol (20-50nM) rapidly (<5min) increased inward whole-cell currents and intracellular Ca(2+) via TRPV5.
- These effects were blocked by ruthenium red and abolished by TRPV5 siRNA.
- E(2) demonstrated a rapid, non-genomic modulation of TRPV5 activity.
Conclusions:
- This study provides the first evidence of rapid E(2) modulation of endogenous TRPV5 channels in kidney cells.
- The findings suggest novel calcitropic effects of E(2) mediated by non-genomic signaling pathways.
- E(2) plays a significant role in regulating kidney calcium re-absorption and systemic calcium homeostasis.
