Preferential allosteric modulation of Otop1 channels by small molecule compounds

Area of Science:

• Ion channel biophysics
• Molecular pharmacology
• Sensory neuroscience

Background:

• Otopetrin (Otop) proteins, including Otop1, are proton-gated proton channels involved in crucial biological functions.
• Otop1 functions as a receptor for sour and ammonium salt tastes in mammals.
• The gating mechanisms and pharmacology of Otop1 remain incompletely understood.

Purpose of the Study:

• To functionally characterize small molecule positive allosteric modulators of Otop1.
• To investigate the pH-dependent effects of these modulators on Otop1 activity.
• To identify structural elements and residues critical for Otop1 gating and modulation.

Main Methods:

• Functional characterization of Otop1 using three novel small molecule modulators: MFaN, HIMOP, and B2FAMP.
• Assessment of proton and alkali gating under varying pH conditions.
• Investigation of modulator specificity for Otop1 over Otop2 and Otop3.
• Site-directed mutagenesis to identify key residues involved in Otop1 modulation.

Main Results:

• MFaN, HIMOP, and B2FAMP were identified as positive allosteric modulators of Otop1.
• These modulators enhance proton gating in a pH-dependent manner, potentiating Otop1 activity under weak acidic conditions.
• HIMOP uniquely enhances Otop1's alkali gating, and modulators show preferential targeting of Otop1.
• MFaN associates with residues on Otop1's S5-6 and S11-12 loops, including R554, crucial for Zn2+ and alkali activation.

Conclusions:

• Novel small molecule modulators of Otop1 have been identified.
• Key structural elements, including R554, and their role in Otop1 gating have been elucidated.
• These findings provide valuable tools and insights for further research into Otop1 function and pharmacology.