Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
Biophys J. 2010 Apr 21;98(8):1582-8. doi: 10.1016/j.bpj.2009.12.4314.
In sea urchin spermatozoa, the energy source powering flagellar motion is provided as ATP produced by mitochondria located at the proximal ends of flagella. However, the bottleneck structure between the sperm head and the flagellar tail seems to restrict the free entry of ATP from mitochondria into the tail region. To test this possibility, we investigated the diffusion properties in sperm cells using fluorescence recovery after photobleaching. We found that the rate of fluorescence recovery in the head region was approximately 10% of that observed in the flagellar tail regions. We also found that, even within the tail region, rates varied depending on location, i.e., rates were slower at the more distal regions. Using computational analysis, the rate heterogeneity was shown to be caused mainly by the geometry of the sperm structure, even if little or no difference in diffusion rates through the neck region was assumed. Therefore, we concluded that materials such as ATP would generally diffuse freely between the heads and the flagella of sperm cells. We believe these findings regarding the diffusion properties inside spermatozoa provide further insights into material transportation and chemical signaling inside eukaryotic cilia and flagella.
在海胆精子中，为鞭毛运动提供动力的能量来源是由位于鞭毛近端的线粒体产生的 ATP。然而，精子头部和鞭毛尾部之间的瓶颈结构似乎限制了 ATP 从线粒体自由进入尾部区域。为了验证这一可能性，我们使用光漂白后荧光恢复法研究了精子细胞中的扩散特性。我们发现头部区域的荧光恢复速率约为鞭毛尾部观察到的速率的 10%。我们还发现，即使在尾部区域，速率也因位置而异，即尾部更远的区域速率较慢。通过计算分析，表明这种速率异质性主要是由精子结构的几何形状引起的，即使假设颈部区域的扩散速率几乎没有差异或没有差异。因此，我们得出结论，ATP 等物质通常可以在精子的头部和鞭毛之间自由扩散。我们认为这些关于精子内部扩散特性的发现为真核纤毛和鞭毛内的物质运输和化学信号传递提供了进一步的见解。
