Department of Life Sciences Core Facilities, The Weizmann Institute of Science, 7610001, Rehovot, Israel.
Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001, Rehovot, Israel.
Sci Rep. 2024 May 10;14(1):10699. doi: 10.1038/s41598-024-61488-3.
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.
近年来，人们逐渐意识到，在哺乳动物中，视紫红质和其他视蛋白不仅在视觉系统中作为光感受器发挥作用，还存在于精子中，在精子中作为高度敏感的热感受器发挥作用，以进行趋热性运动。一个有趣的问题是，一种保守的蛋白质如何在一种细胞类型中作为光感受器，而在另一种细胞类型中作为热感受器发挥作用，这个问题尚未得到解决。由于赋予视蛋白光敏感性的部分是视黄醛色素，我们研究了视黄醛是否被另一种热敏分子替代存在于精子中。我们通过功能测定和质谱分析发现，视黄醛存在于精子中，并且是趋热性运动所必需的。因此，用维生素 A（视黄醛的前体）对小鼠进行饥饿处理会导致精子趋热性丧失，而不会影响精子的运动能力和生理状态。补充维生素 A 后，趋热性得到恢复。使用反相超高效液相色谱-质谱联用技术，我们在小鼠和人精子提取物中检测到视黄醛的存在。通过使用超高效收敛色谱法，我们在精子提取物中鉴定出一种独特的视黄醛异构体——三顺式视黄醛，与视觉系统中光敏的 11-顺式异构体不同。以下事实表明三顺式视黄醛可能参与了精子的热感觉活动：（a）视蛋白是精子趋热性的热感受器；（b）视黄醛是趋热性运动所必需的；（c）三顺式视黄醛异构体仅存在于精子中，并且相对不稳定。
