Saito Shigeru, Tominaga Makoto
Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institute of Natural Sciences, Okazaki, Japan.
Department of Physiological Sciences, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan.
Temperature (Austin). 2017 Apr 7;4(2):141-152. doi: 10.1080/23328940.2017.1315478. eCollection 2017.
Thermal perception is an essential sensory system for survival since temperature fluctuations affect various biologic processes. Therefore, evolutionary changes in thermosensory systems may have played important roles in adaptation processes. Comparative analyses of sensory receptors among different species can provide us with important clues to understand the molecular basis for adaptation. Several ion channels belonging to the transient receptor potential (TRP) superfamily serve as thermal sensors in a wide variety of animal species. These TRP proteins are multimodal receptors that are activated by temperature as well as other sensory stimuli. Among them TRPV1 and TRPA1 are activated by noxious ranges of thermal stimuli and irritating chemicals, and are mainly expressed in nociceptive sensory neurons. Comparative analyses of TRPV1 and TRPA1 among various vertebrate species revealed evolutionary changes that likely contributed to diversification of sensory perception. Whereas heat-induced TRPV1 responses have been conserved across many vertebrates, TRPA1 varied among species. Mutagenesis experiments using these two channels from various species also helped characterize the molecular basis for their activation and inhibition. Meanwhile, recent detailed comparative analyses using closely related species showed shifts in TRPV1 and TRPA1 thermal sensitivity that allowed adaptation to different thermal environments. Changes in TRPV1 heat responses appear to arise from just a few amino acid differences among species. These observations suggest that evolutionary changes in peripheral sensors are likely driving force for shifting thermal perception in adaptation processes.
热感知是一种对于生存至关重要的感觉系统，因为温度波动会影响各种生物过程。因此，热感觉系统的进化变化可能在适应过程中发挥了重要作用。对不同物种间感觉受体的比较分析能够为我们理解适应的分子基础提供重要线索。属于瞬时受体电位（TRP）超家族的几种离子通道在多种动物物种中充当热传感器。这些TRP蛋白是多模态受体，可被温度以及其他感觉刺激激活。其中，TRPV1和TRPA1被有害范围的热刺激和刺激性化学物质激活，且主要表达于伤害性感觉神经元中。对各种脊椎动物物种中的TRPV1和TRPA1进行比较分析，揭示了可能促成感觉感知多样化的进化变化。虽然热诱导的TRPV1反应在许多脊椎动物中得以保留，但TRPA1在不同物种间存在差异。使用来自不同物种的这两种通道进行的诱变实验，也有助于阐明它们激活和抑制的分子基础。与此同时，最近使用近缘物种进行的详细比较分析显示，TRPV1和TRPA1的热敏感性发生了变化，从而使其能够适应不同的热环境。TRPV1热反应的变化似乎仅源于物种间少数几个氨基酸的差异。这些观察结果表明，外周传感器的进化变化可能是适应过程中热感知转变的驱动力。
