PDF(Pubmed)
Abstract：
In recent years it became apparent that, in mammals, rhodopsin and other opsins, known to act as photosensors in the visual system, are also present in spermatozoa, where they function as highly sensitive thermosensors for thermotaxis. The intriguing question how a well-conserved protein functions as a photosensor in one type of cells and as a thermosensor in another type of cells is unresolved. Since the moiety that confers photosensitivity on opsins is the chromophore retinal, we examined whether retinal is substituted in spermatozoa with a thermosensitive molecule. We found by both functional assays and mass spectrometry that retinal is present in spermatozoa and required for thermotaxis. Thus, starvation of mice for vitamin A (a precursor of retinal) resulted in loss of sperm thermotaxis, without affecting motility and the physiological state of the spermatozoa. Thermotaxis was restored after replenishment of vitamin A. Using reversed-phase ultra-performance liquid chromatography mass spectrometry, we detected the presence of retinal in extracts of mouse and human spermatozoa. By employing UltraPerformance convergence chromatography, we identified a unique retinal isomer in the sperm extracts-tri-cis retinal, different from the photosensitive 11-cis isomer in the visual system. The facts (a) that opsins are thermosensors for sperm thermotaxis, (b) that retinal is essential for thermotaxis, and (c) that tri-cis retinal isomer uniquely resides in spermatozoa and is relatively thermally unstable, suggest that tri-cis retinal is involved in the thermosensing activity of spermatozoa.
摘要：
近年来，很明显，在哺乳动物中，视紫红质和其他视蛋白，已知作为视觉系统中的光电传感器，也存在于精子中，它们的功能是作为热轴的高灵敏度热传感器。一个有趣的问题是，一个保守的蛋白质如何在一种类型的细胞中充当光传感器，而在另一种类型的细胞中充当热传感器。由于赋予视蛋白光敏性的部分是发色团视网膜，我们检查了精子中的视黄醛是否被热敏分子取代。我们通过功能测定和质谱发现，视黄醛存在于精子中，并且是热轴所必需的。因此，小鼠对维生素A（视网膜的前体）的饥饿导致精子热迁移的丧失，不影响精子的运动性和生理状态。补充维生素A后热轴性恢复。使用反相超高效液相色谱质谱，我们在小鼠和人类精子的提取物中检测到视网膜的存在。通过使用UltraPerformance收敛色谱法，我们在精子提取物中发现了一种独特的视网膜异构体-三顺式视网膜,不同于视觉系统中的光敏11-顺式异构体。事实（a）视蛋白是精子热迁移的温度传感器，(b)视黄醛对于热轴至关重要，和（c）三-顺式视网膜异构体独特地存在于精子中，并且相对热不稳定，提示三顺式视网膜参与精子的热感应活动。
