Oishee Mumtarin J, McDermott Jeffrey P, Sánchez Gladis, Blanco Gustavo
Reproduction. 2025 Aug 5;170(3). doi: 10.1530/REP-25-0114. Print 2025 Sep 1.
This manuscript shows that the Na+ and K+ transporter Na+,K+-ATPase α4, specific to sperm, is expressed on the surface of the sperm head and flagellum in a very structured manner. This is also true for Na+,K+-ATPase α1, the other Na+,K+-ATPase isoform present in sperm and also in all cells. However, Na+,K+-ATPase α4 distribution changes when the cells are capacitated, an event necessary for fertilization. This dynamic remodeling, along with the distinct functional properties of Na+,K+-ATPase α4 and α1, provides evidence for the refined level of specialization that sperm have developed to achieve the amazing goal of fertilizing the oocyte.
Na+,K+-ATPase α4 is a unique Na+ and K+ transporter of the plasma membrane of spermatozoa, which is essential for male fertility. While previous studies have found Na+,K+-ATPase α4 to be mainly expressed in the sperm flagellum, less is known about its localization in the sperm head. Moreover, the spatial arrangement of Na+,K+-ATPase α4 at the subcellular level and its relationship to the functional state of the cells are unclear. We studied this using stimulated emission depletion (STED) super-resolution microscopy. We show that, under non-capacitated conditions, Na+,K+-ATPase α4 is distributed in a trilinear pattern along the midpiece and as a scattered single line along the principal piece of the sperm flagellum. Under capacitated conditions, Na+,K+-ATPase α4 pattern undergoes remodeling and its distribution shifts to a single line along the flagellum. On the other hand, Na+,K+-ATPase α1, the somatic isoform of Na+,K+-ATPase also present in sperm, exhibits a similar trilaminar localization at the flagellar midpiece but a bilinear pattern in the principal piece. This distribution, unlike that of Na+,K+-ATPase α4, does not change during sperm capacitation. We also found Na+,K+-ATPase α1 and α4 in the sperm head, where they present a complex distribution under both non-capacitated and capacitated conditions. These differences in the localization pattern and spatial dynamics of Na+,K+-ATPase isoform expression, along with their different functional properties, highlight the distinct roles that both isoforms play to support sperm function.
本手稿表明，精子特有的钠钾转运体钠钾ATP酶α4以非常有组织的方式表达于精子头部和鞭毛表面。精子以及所有细胞中存在的另一种钠钾ATP酶亚型钠钾ATP酶α1也是如此。然而，当细胞获能时，钠钾ATP酶α4的分布会发生变化，而获能是受精所必需的过程。这种动态重塑，连同钠钾ATP酶α4和α1不同的功能特性，为精子为实现使卵母细胞受精这一惊人目标而发展出的精细特化水平提供了证据。
钠钾ATP酶α4是精子质膜独特的钠钾转运体，对雄性生育能力至关重要。虽然先前的研究发现钠钾ATP酶α4主要在精子鞭毛中表达，但对其在精子头部的定位了解较少。此外，钠钾ATP酶α4在亚细胞水平的空间排列及其与细胞功能状态的关系尚不清楚。我们使用受激发射损耗（STED）超分辨率显微镜对此进行了研究。我们发现，在未获能条件下，钠钾ATP酶α4沿线粒体鞘呈三线分布模式，沿精子鞭毛主段呈分散的单线分布。在获能条件下，钠钾ATP酶α4的模式发生重塑，其分布沿鞭毛转移为单线。另一方面，精子中也存在的钠钾ATP酶的体细胞亚型钠钾ATP酶α1，在线粒体鞘处呈现类似的三层定位，但在主段呈双线模式。这种分布与钠钾ATP酶α4不同，在精子获能过程中不会改变。我们还在精子头部发现了钠钾ATP酶α1和α4，它们在未获能和获能条件下均呈现复杂的分布。钠钾ATP酶亚型表达的定位模式和空间动态的这些差异，连同它们不同的功能特性，突出了两种亚型在支持精子功能方面所起的不同作用。
