BPS2026 – Converging pathways of chemical and thermal activation in nociceptor TRPM3

Sensing noxious heat is crucial for survival, as it triggers pain responses that help prevent tissue damage. The TRPM3 ion channel plays a key role in detecting noxious heat and is an emerging target for treating pain and neurological conditions like epilepsy. In this study, we combined functional and structural analyses to investigate TRPM3 activation by various stimuli, including heat, the synthetic superagonist CIM0216, and the anticonvulsant antagonist primidone. Our results demonstrate that TRPM3 is inherently dynamic, with its intracellular domain (ICD) sampling both resting and activated conformations, though it prefers the resting state under unstimulated conditions. The superagonist CIM0216 binds to the S1-S4 transmembrane region, causing conformational changes in the ICD that shifts the equilibrium toward channel activation. Notably, heat triggers similar ICD rearrangements, pointing to a shared activation mechanism between thermal and chemical stimuli. Functional data further support this mechanism, showing that mutations enhancing ICD mobility significantly increase TRPM3’s responsiveness to both heat and chemical agonists. These findings highlight the ICD as a critical regulator of thermal sensitivity in TRPM3 and suggest this mechanism may be conserved across other TRPM channels. Additionally, we show that primidone competes with CIM0216 at the same binding site but produces an opposite effect and acts as an inhibitor, blocking channel activation. Together, these insights reveal how distinct chemical and thermal stimuli converge on a common activation pathway in TRPM3 and lay the groundwork for designing targeted therapies. This study not only advances our understanding of temperature sensing in ion channels but also provides a structural basis for the development of TRPM3-specific treatments for pain and neurological disorders.