The Second Affiliated Hospital and Yuying Children's Hospital, Department of Anesthesiology, Wenzhou Medical University, Wenzhou, Zhejiang, China.
The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, NY, USA.
Endocrinology. 2021 Apr 1;162(4). doi: 10.1210/endocr/bqab010.
Throughout spermatogenesis, cellular cargoes including haploid spermatids are required to be transported across the seminiferous epithelium, either toward the microtubule (MT) plus (+) end near the basement membrane at stage V, or to the MT minus (-) end near the tubule lumen at stages VI to VIII of the epithelial cycle. Furthermore, preleptotene spermatocytes, differentiated from type B spermatogonia, are transported across the Sertoli cell blood-testis barrier (BTB) to enter the adluminal compartment. Few studies, however, have been conducted to explore the function of MT-dependent motor proteins to support spermatid transport during spermiogenesis. Herein, we examined the role of MT-dependent and microtubule plus (+) end-directed motor protein kinesin 15 (KIF15) in the testis. KIF15 displayed a stage-specific expression across the seminiferous epithelium, associated with MTs, and appeared as aggregates on the MT tracks that aligned perpendicular to the basement membrane and laid across the entire epithelium. KIF15 also tightly associated with apical ectoplasmic specialization, displaying strict stage-specific distribution, apparently to support spermatid transport across the epithelium. We used a loss-of-function approach by RNAi to examine the role of KIF15 in Sertoli cell epithelium in vitro to examine its role in cytoskeletal-dependent Sertoli cell function. It was noted that KIF15 knockdown by RNAi that reduced KIF15 expression by ~70% in Sertoli cells with an established functional tight junction barrier impeded the barrier function. This effect was mediated through remarkable changes in the cytoskeletal organization of MTs, but also actin-, vimentin-, and septin-based cytoskeletons, illustrating that KIF15 exerts its regulatory effects well beyond microtubules.
在整个精子发生过程中，包括单倍体精子在内的细胞货物需要穿过生精上皮进行运输，要么朝着靠近基底膜的微管（MT）正（+）端运输，要么朝着上皮周期的第 VI 至第 VIII 阶段靠近管腔的 MT 负（-）端运输。此外，从 B 型精原细胞分化而来的早粗线期精母细胞穿过支持细胞血睾屏障（BTB）进入管腔。然而，很少有研究探讨 MT 依赖性马达蛋白在精子发生过程中支持精子运输的功能。在此，我们研究了 MT 依赖性和微管正（+）端导向的马达蛋白 kinesin 15（KIF15）在睾丸中的作用。KIF15 在生精上皮中呈阶段特异性表达，与 MT 相关，并且在与基底膜垂直且横跨整个上皮的 MT 轨道上呈现为聚集物。KIF15 还与顶外侧细胞外特化紧密相关，表现出严格的阶段特异性分布，显然是为了支持精子穿过上皮的运输。我们使用 RNAi 敲低的方法研究了 KIF15 在体外支持细胞上皮中的作用，以研究其在细胞骨架依赖性支持细胞功能中的作用。研究发现，用 RNAi 敲低 KIF15，可使支持细胞中 KIF15 的表达减少约 70%，从而阻碍了紧密连接屏障的功能。这种效应是通过 MT 细胞骨架的显著变化介导的，但也与肌动蛋白、中间丝和 septin 细胞骨架有关，表明 KIF15 的调节作用远远超出了微管。
