Department of Physiology and Biophysical Sciences, State University of New York, Buffalo, New York, USA.
Biophys J. 2010 Sep 22;99(6):1743-53. doi: 10.1016/j.bpj.2010.07.022.
Thermal TRP channels are important for thermal sensation and nociception, but their gating mechanisms have remained elusive. With optically generated submillisecond temperature steps from 22°C to >60°C, we have directly measured the activation and deactivation kinetics of TRPV1 channels, and from the measurements we determined the energetics of thermal gating. We show that activation by temperature follows single exponential time courses. It occurs in a few milliseconds and is significantly faster than activation by agonists. The gating has characteristics of a melting process involving large compensatory enthalpy (>100 kcal/mol) and entropy changes with little free energy change. The reaction path is asymmetrical with temperature mainly driving the opening while the closing has nominal but negative temperature dependence (i.e., sensitivity to cold). Both voltage and agonists alter the slope of the temperature-dependent gating curve as well as shifting the midpoint. However, compared to the energetic effect of temperature on gating, the effect of voltage is small. Our data on the interdependence between voltage and direct temperature responses are not fit to a model involving independent stimuli but instead support a temperature-sensing mechanism that is coupled to charge movement or agonist binding.
热温度敏感型 TRP 通道对于热感觉和痛觉很重要，但它们的门控机制仍然难以捉摸。我们使用从 22°C 到 >60°C 的光产生的亚毫秒级温度阶跃，直接测量 TRPV1 通道的激活和失活动力学，并从测量结果中确定热门控的能量学。我们表明，温度的激活遵循单指数时间过程。它在几毫秒内发生，明显快于激动剂的激活。门控具有涉及大补偿焓（>100 千卡/摩尔）和熵变化的熔融过程的特征，自由能变化很小。反应路径是不对称的，温度主要驱动打开，而关闭具有名义但负的温度依赖性（即对冷的敏感性）。电压和激动剂都会改变温度依赖性门控曲线的斜率，并改变中点。然而，与温度对门控的能量效应相比，电压的影响较小。我们关于电压和直接温度响应之间相互依赖性的数据不适用于涉及独立刺激的模型，而是支持一种与电荷移动或激动剂结合耦联的温度感应机制。
