Show Matthew D, Anway Matthew D, Folmer Janet S, Zirkin Barry R
Division of Reproductive Biology, Department of Biochemistry and Molecular Biology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 2120, USA.
Endocrinology. 2003 Dec;144(12):5530-6. doi: 10.1210/en.2003-0735. Epub 2003 Sep 11.
The Sertoli cell intermediate filament cytoskeleton is composed of the type III family member vimentin. The distribution of Sertoli cell vimentin varies with the stage of spermatogenesis, with shortening of the filaments at stages VII-VIII, the stages of spermiation. Experimental reduction in intratesticular testosterone (T) concentration also results in the sloughing of advanced spermatids from the Sertoli cells, as well as in the apoptotic death of spermatocytes. We hypothesized that alteration of the distribution of Sertoli cell vimentin might play a role in the loss of germ cells that occurs in response to reduced intratesticular T. To test this hypothesis, intratesticular T was reduced by implanting LH-suppressive SILASTIC brand capsules containing T and estradiol into adult rats for 8 wk. Immunohistochemical analyses revealed that, in response to the implants, the vimentin cytoskeleton collapsed around the Sertoli cell nuclei at all stages of the cycle, losing the extensive branching and structure normally seen at most stages of the cycle. Western blots of isolated Sertoli cells revealed that protein levels did not differ significantly between control and T- and estradiol-treated rats. However, Sertoli cell fractions containing the vimentin monomer revealed that vimentin was cleaved into four to five fragments in Sertoli cells in response to the implants, suggestive of proteolysis. These results indicate that, in response to reduced intratesticular T, the vimentin cytoskeleton of the Sertoli cell collapses to a perinuclear localization, and suggest that this collapse is associated with, and perhaps caused by, the degradation of the vimentin monomer rather than by loss of its expression.
支持细胞中间丝细胞骨架由III型家族成员波形蛋白组成。支持细胞波形蛋白的分布随精子发生阶段而变化，在精子释放阶段（VII - VIII期）细丝会缩短。实验性降低睾丸内睾酮（T）浓度也会导致晚期精子细胞从支持细胞脱落，以及精母细胞的凋亡死亡。我们假设支持细胞波形蛋白分布的改变可能在因睾丸内T减少而发生的生殖细胞丢失中起作用。为了验证这一假设，将含有T和雌二醇的LH抑制性硅橡胶胶囊植入成年大鼠体内8周，以降低睾丸内T的水平。免疫组织化学分析显示，作为对植入物的反应，波形蛋白细胞骨架在周期的所有阶段都在支持细胞核周围塌陷，失去了在周期大多数阶段通常可见的广泛分支和结构。对分离的支持细胞进行的蛋白质免疫印迹分析显示，对照大鼠与经T和雌二醇处理的大鼠之间蛋白质水平没有显著差异。然而，含有波形蛋白单体的支持细胞组分显示，作为对植入物的反应，波形蛋白在支持细胞中被切割成四到五个片段，提示存在蛋白水解作用。这些结果表明，作为对睾丸内T减少的反应，支持细胞的波形蛋白细胞骨架塌陷至核周定位，并表明这种塌陷与波形蛋白单体的降解相关，甚至可能是由其降解引起的，而不是由于其表达的丧失。
