A proton current associated with sour taste: distribution and functional properties

Area of Science:

• Taste receptor cell physiology
• Molecular mechanisms of taste transduction
• Ion channel function in sensory systems

Background:

• Sour taste perception involves taste receptor cells responding to acids via poorly understood mechanisms.
• PKD2L1 protein marks sour taste cells but is not the primary sour receptor.
• Previous studies indicated a proton current in sour cells of the circumvallate papillae.

Purpose of the Study:

• To establish a correlation between the proton current and sour taste transduction.
• To determine the distribution of the proton current in different taste cell populations.
• To characterize the biophysical properties of the identified proton current.

Main Methods:

• Utilizing mice engineered to express yellow fluorescent protein under the PKD2L1 promoter.
• Employing patch-clamp recording techniques to examine ion currents in taste cells.
• Analyzing the current's properties in response to varying pH and ion concentrations.

Main Results:

• The proton current was detected in PKD2L1-expressing taste cells from circumvallate, foliate, and fungiform papillae.
• The current was absent in other cell types, including spinal cord neurons expressing PKD2L1.
• Biophysical characterization revealed pH-dependent Zn(2+) inhibition, lack of voltage-dependent gating, and activation at pH 6.5.

Conclusions:

• The study defines a functional signature for the taste cell proton current.
• The proton current's expression is largely restricted to the subset of taste cells responsible for sour taste detection.
• These findings provide critical insights into the molecular mechanisms underlying sour taste transduction.