title: Temperature and voltage coupling to channel opening in transient receptor potential melastatin 8 (TRPM8).
abstract: Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca(2+)-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening reaction is voltage-independent. Voltage is a partial activator of TRPM8 channels, because absolute open probability values measured with fully activated voltage sensors are less than 1, and they decrease as temperature rises. By unveiling the fast temperature-dependent deactivation process, we show that TRPM8 channel deactivation is well described by a double exponential time course. The fast and slow deactivation processes are temperature-dependent with enthalpy changes of 27.2 and 30.8 kcal mol(-1). The overall Q10 for the closing reaction is about 33. A three-tiered allosteric model containing four voltage sensors and four temperature sensors can account for the complex deactivation kinetics and coupling between voltage and temperature sensor activation and channel opening.
authors.affiliation: From the Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103 and.
authors.forename: Natalia
authors.initials: N
authors.lastname: Raddatz
authors.affiliation: From the Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103 and.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Castillo
authors.affiliation: From the Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103 and.
authors.forename: Carlos
authors.initials: C
authors.lastname: Gonzalez
authors.affiliation: From the Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103 and the Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800003, Chile oalvarez@uchile.cl.
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Alvarez
authors.affiliation: From the Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103 and ramon.latorre@uv.cl.
authors.forename: Ramon
authors.initials: R
authors.lastname: Latorre
mesh_terms: D000465:Algorithms; D000818:Animals; D003080:Cold Temperature; D004558:Electric Stimulation; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008610:Menthol / Q000494:pharmacology; D008954:Models, Biological; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology; D051381:Rats; D050053:TRPM Cation Channels / Q000235:genetics / Q000502:physiology*; D013696:Temperature; D014982:Xenopus laevis
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D050053:TRPM Cation Channels; C498947:Trpm8 protein, rat; D008610:Menthol
keywords: Allosteric Model; Allosteric Regulation; Calcium Channel; Deactivation Processes; Gating; Ion Channel; TRPM8; Temperature Coefficient; Thermodynamics