Optical Control of TRPM8 Channels with Photoswitchable Menthol

Abstract

Transient receptor potential melastatin 8 (TRPM8) channels are well known as sensors for cold temperatures and cooling agents such as menthol and icilin and these channels are tightly regulated by the membrane lipid phosphoinositol-4,5-bisphosphate (PIP₂). Since TRPM8 channels emerged as promising drug targets for treating pain, itching, obesity, cancer, dry eye disease, and inflammation, we aimed at developing a high-precision TRPM8 channel activator, to achieve spatiotemporal control of TRPM8 activity with light. In this study, we designed, synthesized and characterized the first photoswitchable TRPM8 activator azo-menthol (AzoM). AzoM enables optical control of endogenously and heterologously expressed TRPM8 channels with UV and blue light which is demonstrated by performing patch-clamp experiments. Moreover, AzoM facilitates the reliable determination of activation, inactivation, and deactivation kinetics thereby providing further insights into the channel gating. Using AzoM, the specific roles of individual amino acids for AzoM or PIP₂ binding and for sensitization by PIP₂ can be elucidated. Altogether, AzoM represents as a high-precision pharmaceutical tool for reversible control of TRPM8 channel function that enhances our biophysical understanding of TRPM8 channels and holds the potential to support the development of novel pharmaceuticals.

Keywords: TRPM8; current kinetics; ion channels; photopharmacology; photoswitchable menthol.