Zakrzewski Przemysław, Lenartowski Robert, Rędowicz Maria Jolanta, Miller Kathryn G, Lenartowska Marta
Laboratory of Developmental Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University in Toruń, Toruń, Poland.
Laboratory of Isotope and Instrumental Analysis, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University in Toruń, Toruń, Poland.
Histochem Cell Biol. 2017 Oct;148(4):445-462. doi: 10.1007/s00418-017-1579-z. Epub 2017 May 12.
Myosin VI (MVI) is a versatile actin-based motor protein that has been implicated in a variety of different cellular processes, including endo- and exocytic vesicle trafficking, Golgi morphology, and actin structure stabilization. A role for MVI in crucial actin-based processes involved in sperm maturation was demonstrated in Drosophila. Because of the prominence and importance of actin structures in mammalian spermiogenesis, we investigated whether MVI was associated with actin-mediated maturation events in mammals. Both immunofluorescence and ultrastructural analyses using immunogold labeling showed that MVI was strongly linked with key structures involved in sperm development and maturation. During the early stage of spermiogenesis, MVI is associated with the Golgi and with coated and uncoated vesicles, which fuse to form the acrosome. Later, as the acrosome spreads to form a cap covering the sperm nucleus, MVI is localized to the acroplaxome, an actin-rich structure that anchors the acrosome to the nucleus. Finally, during the elongation/maturation phase, MVI is associated with the actin-rich structures involved in nuclear shaping: the acroplaxome, manchette, and Sertoli cell actin hoops. Since this is the first report of MVI expression and localization during mouse spermiogenesis and MVI partners in developing sperm have not yet been identified, we discuss some probable roles for MVI in this process. During early stages, MVI is hypothesized to play a role in Golgi morphology and function as well as in actin dynamics regulation important for attachment of developing acrosome to the nuclear envelope. Next, the protein might also play anchoring roles to help generate forces needed for spermatid head elongation. Moreover, association of MVI with actin that accumulates in the Sertoli cell ectoplasmic specialization and other actin structures in surrounding cells suggests additional MVI functions in spermatid movement across the seminiferous epithelium and in sperm release.
肌球蛋白VI（MVI）是一种多功能的基于肌动蛋白的运动蛋白，它参与了多种不同的细胞过程，包括内吞和外排小泡运输、高尔基体形态以及肌动蛋白结构稳定。在果蝇中证明了MVI在精子成熟所涉及的关键肌动蛋白相关过程中发挥作用。由于肌动蛋白结构在哺乳动物精子发生中十分突出且重要，我们研究了MVI是否与哺乳动物中肌动蛋白介导的成熟事件相关。使用免疫金标记的免疫荧光和超微结构分析均表明，MVI与精子发育和成熟所涉及的关键结构紧密相连。在精子发生的早期阶段，MVI与高尔基体以及有被小泡和无被小泡相关，这些小泡融合形成顶体。后来，随着顶体扩展形成覆盖精子细胞核的帽状结构，MVI定位于顶体下板，这是一种富含肌动蛋白的结构，将顶体锚定到细胞核上。最后，在伸长/成熟阶段，MVI与参与细胞核塑形的富含肌动蛋白的结构相关：顶体下板、袖套和支持细胞肌动蛋白环。由于这是关于小鼠精子发生过程中MVI表达和定位的首次报道，且尚未确定发育中精子里MVI的相互作用蛋白，我们讨论了MVI在此过程中的一些可能作用。在早期阶段，推测MVI在高尔基体形态和功能中发挥作用，以及在调节肌动蛋白动力学方面发挥作用，这对于发育中的顶体附着到核膜很重要。接下来，该蛋白可能还起到锚定作用，以帮助产生精子细胞头部伸长所需的力。此外，MVI与在支持细胞外质特化中积累的肌动蛋白以及周围细胞中的其他肌动蛋白结构相关，这表明MVI在精子细胞穿过生精上皮的运动以及精子释放中具有其他功能。
