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Updated: Aug 20, 2026
Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
Published on: December 13, 2024
Voltage-dependent changes of TRPV6-mediated Ca2+ currents
1Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, D-66421 Homburg, Germany. matthias.boedding@uniklinik-saarland.de
Abstract:
The physiological role and activation mechanism for most proteins of the transient receptor potential (TRP) family are unknown. This is also the case for the highly Ca(2+) selective transient receptor potential vanilloid type 6 (TRPV6) channel. Patch clamp experiments were performed on transiently transfected human embryonic kidney (HEK) cells to address this issue. Currents were recorded under various conditions of intracellular Ca(2+) buffering and monitored at the same voltage throughout. No TRPV6-mediated Ca(2+) entry was detected under in vivo Ca(2+) buffering conditions at a slightly negative holding potential; however, moderate depolarization resulted in current activation. Very similar results were obtained with different Ca(2+) chelators, either EGTA or BAPTA dialyzing the cell. TRPV6 channel activity showed a negative correlation with the intracellular free Ca(2+) concentration ([Ca(2+)](i)) and was modulated by the membrane potential: Hyperpolarization decreases and depolarization increases TRPV6-mediated currents. Monovalent ions permeated TRPV6 channels in the absence of extracellular divalent cations. These currents were resistant to changes in the holding potential while the negative correlation to the [Ca(2+)](i) was conserved, indicating that the voltage-dependent current changes depend on blocking and unblocking the charge carrier Ca(2+) within the pore. In summary, these results suggest that the voltage dependence of TRPV6-mediated Ca(2+) influx is of physiological importance since it occurs at cytosolic Ca(2+) buffering and takes place within a physiologically relevant membrane potential range.
Insights
The transient receptor potential vanilloid type 6 (TRPV6) channel
Area of Science:
- Ion channel physiology
- Calcium signaling
- Cell membrane electrophysiology
Background:
- The physiological roles and activation mechanisms of most Transient Receptor Potential (TRP) channels remain largely uncharacterized.
- Specifically, the highly calcium-selective Transient Receptor Potential Vanilloid type 6 (TRPV6) channel's function and activation are not fully understood.
Purpose of the Study:
- To investigate the physiological role and activation mechanism of the TRPV6 channel.
- To elucidate the impact of intracellular calcium buffering and membrane potential on TRPV6 channel activity.
Main Methods:
- Patch clamp electrophysiology was employed on human embryonic kidney (HEK) cells transiently expressing TRPV6.
- Experiments were conducted under varying intracellular calcium buffering conditions using EGTA and BAPTA.
- TRPV6-mediated currents were monitored across a range of membrane potentials.
Main Results:
- TRPV6-mediated calcium entry was undetectable under physiological intracellular calcium buffering at negative potentials but activated upon moderate depolarization.
- TRPV6 channel activity exhibited a negative correlation with intracellular free calcium concentration ([Ca2+]i) and was modulated by membrane potential.
- Monovalent ion permeation through TRPV6 was observed in the absence of extracellular divalent cations and was independent of holding potential, while the negative correlation to [Ca2+]i persisted.
Conclusions:
- The voltage dependence of TRPV6-mediated calcium influx is physiologically significant.
- TRPV6 activation occurs within physiological ranges of cytosolic calcium buffering and membrane potential.
- These findings suggest that membrane potential plays a crucial role in regulating TRPV6 channel function in vivo.
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