Temperature-Dependent Menthol Binding across TRPM8 Conformational States

Cold sensation is mediated by TRPM8, a polymodal ion channel activated by temperature, pH, voltage, and cooling compounds such as menthol. Despite its central role in thermosensation and pharmacology, the molecular basis of menthol-mediated activation remains unclear, particularly how temperature influences ligand binding and channel activation. Polymodal ion channels further challenge site-centric views of ligand binding, as function emerges from coupled conformational equilibria and environment-dependent membrane partitioning. Here, we investigate temperature-dependent menthol distribution in TRPM8 using flooding molecular dynamics simulations of open and closed channel conformations across a physiological temperature range. This approach reveals distributed, low-affinity interactions that are not captured by discrete binding-site models. Below the TRPM8 activation threshold (<300 K), menthol preferentially accumulates in intracellular and interfacial regions, whereas above this threshold it redistributes toward transmembrane regions, indicating that temperature-dependent activation regimes reshape ligand partitioning at the protein-membrane interface. Across all conditions, menthol behaves as a low-affinity multisite ligand sampling a continuum of metastable interaction regions, consistent with experimentally identified interaction regions spanning the N-terminal domain, pore domain, voltage sensor-like domain (VSLD), and C-terminal region. A two-state allosteric model indicates that these temperature-dependent occupancy patterns shift the open-closed equilibrium of TRPM8. Together, these results suggest that temperature regulates function not only through channel energetics but also by modulating ligand interactions at the protein-membrane interface. This work identifies temperature-dependent ligand partitioning as a key physicochemical determinant of ligand efficacy in polymodal ion channels and provides molecular-level insight into menthol modulation of TRPM8.