Voltage-dependent changes of TRPV6-mediated Ca2+ currents

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.