A proton current drives action potentials in genetically identified sour taste cells

Area of Science:

• * Taste receptor cell physiology
• * Molecular mechanisms of sensory transduction
• * Acid sensing pathways

Background:

• * Five basic tastes are recognized, with sour taste (acid stimuli) being the least understood.
• * Sour taste is detected by taste cells expressing the TRP channel PKD2L1, but the exact detection mechanism remains unclear.
• * Previous research was limited by the small number of sour cells and non-specific acid-sensitive ion channels.

Purpose of the Study:

• * To identify unique acid-sensitive conductances in sour taste cells.
• * To elucidate the molecular mechanisms underlying sour taste transduction.
• * To differentiate sour cell responses from other pH-sensitive cells.

Main Methods:

• * Generation of genetically modified mice with YFP-marked PKD2L1-expressing sour cells.
• * Development of a novel method combining suction electrode recording with UV photolysis of caged protons.
• * Analysis of acid-induced responses in identified sour taste cells.

Main Results:

• * Sour taste transduction is mediated by a proton conductance, not Na(+) permeable channels.
• * This proton conductance is specific to PKD2L1-expressing taste cells.
• * The conductance directly depolarizes taste cells and drives action potentials, independent of PKD1L3.

Conclusions:

• * Protons enter sour taste cells via an apical proton conductance.
• * This influx directly depolarizes the taste cell membrane, initiating the sour taste signal.
• * The findings reveal a novel mechanism for sour taste transduction.