Wu Siwen, Li Huitao, Wang Lingling, Mak Nathan, Wu Xiaolong, Ge Renshan, Sun Fei, Cheng C Yan
The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Zhejiang, China.
The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, NY, USA.
Adv Exp Med Biol. 2021;1288:131-159. doi: 10.1007/978-3-030-77779-1_7.
Unlike the intermediate filament- and septin-based cytoskeletons which are apolar structures, the microtubule (MT) and actin cytoskeletons are polarized structures in mammalian cells and tissues including the testis, most notable in Sertoli cells. In the testis, these cytoskeletons that stretch across the epithelium of seminiferous tubules and lay perpendicular to the basement membrane of tunica propria serve as tracks for corresponding motor proteins to support cellular cargo transport. These cargoes include residual bodies, phagosomes, endocytic vesicles and most notably developing spermatocytes and haploid spermatids which lack the ultrastructures of motile cells (e.g., lamellipodia, filopodia). As such, these developing germ cells require the corresponding motor proteins to facilitate their transport across the seminiferous epithelium during the epithelial cycle of spermatogenesis. Due to the polarized natures of these cytoskeletons with distinctive plus (+) and minus (-) end, directional cargo transport can take place based on the use of corresponding actin- or MT-based motor proteins. These include the MT-based minus (-) end directed motor proteins: dyneins, and the plus (+) end directed motor proteins: kinesins, as well as the actin-based motor proteins: myosins, many of which are plus (+) end directed but a few are also minus (-) end directed motor proteins. Recent studies have shown that these motor proteins are essential to support spermatogenesis. In this review, we briefly summarize and evaluate these recent findings so that this information will serve as a helpful guide for future studies and for planning functional experiments to better understand their role mechanistically in supporting spermatogenesis.
与中间丝和基于septin的细胞骨架(它们是无极性结构)不同,微管(MT)和肌动蛋白细胞骨架在包括睾丸在内的哺乳动物细胞和组织中是极性结构,在支持细胞中最为显著。在睾丸中,这些横跨生精小管上皮并垂直于固有膜基底膜排列的细胞骨架,作为相应运动蛋白的轨道,以支持细胞货物运输。这些货物包括残余小体、吞噬体、内吞小泡,最显著的是缺乏运动细胞超微结构(如片状伪足、丝状伪足)的发育中的精母细胞和单倍体精子细胞。因此,这些发育中的生殖细胞需要相应的运动蛋白,以促进它们在精子发生上皮周期中穿过生精上皮的运输。由于这些细胞骨架具有独特的正(+)端和负(-)端的极性性质,基于相应的肌动蛋白或MT的运动蛋白的使用,可以进行定向货物运输。这些包括基于MT的负(-)端定向运动蛋白:动力蛋白,以及正(+)端定向运动蛋白:驱动蛋白,以及基于肌动蛋白的运动蛋白:肌球蛋白,其中许多是正(+)端定向,但也有一些是负(-)端定向运动蛋白。最近的研究表明,这些运动蛋白对于支持精子发生至关重要。在这篇综述中,我们简要总结和评估这些最新发现,以便这些信息将作为未来研究的有用指南,并用于规划功能实验,以更好地从机制上理解它们在支持精子发生中的作用。