Departments of Physiology and Pharmacology, Obstetrics and Gynecology, and Pediatrics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada.
Biol Reprod. 2010 May;82(5):865-75. doi: 10.1095/biolreprod.109.080903. Epub 2010 Jan 27.
WNTs are secreted extracellular signaling molecules that transduce their signals by binding to G protein-coupled receptors of the frizzled (FZD) family. They control diverse developmental processes, such as cell fate specification, cell proliferation, cell differentiation, and apoptosis. Although WNT signaling has been shown to be essential for development of the ovary, its mechanistic role in folliculogenesis within the adult ovary has not been studied extensively. Therefore, the objective of this study was to investigate the regulation and function of WNT2 signaling in mouse granulosa cells. Immunostaining identified WNT2 as being expressed in granulosa cells throughout folliculogenesis, but with varying signal strength: in sequential sections, WNT2 immunoreactivity was strongest in healthy antral follicles but weak in atretic follicles. Knockdown of WNT2 expression using transfected short interfering RNA decreased DNA synthesis in granulosa cells, whereas WNT2 overexpression using a recombinant viral vector enhanced it. WNT2 knockdown led to accumulation of glycogen synthase kinase-3beta (GSK3B) in the cytoplasm but reduced the expression of beta-catenin. Conversely, WNT2 overexpression reduced the expression of GSK3B in the cytoplasm and induced beta-catenin translocation from the membrane into the nucleus. Beta-catenin knockdown also inhibited DNA synthesis in granulosa cells and neutralized the effect of WNT2 overexpression. WNT2/beta-catenin signaling had a slight effect on the apoptosis of granulosa cells. Taken together, the data indicate that WNT2 regulates beta-catenin localization in granulosa cells, and WNT2/beta-catenin signaling contributes to regulating their proliferation.
WNTs 是分泌型细胞外信号分子，通过与卷曲（FZD）家族的 G 蛋白偶联受体结合来传递信号。它们控制着多种发育过程，如细胞命运特化、细胞增殖、细胞分化和细胞凋亡。尽管已经表明 WNT 信号对于卵巢的发育至关重要，但它在成年卵巢中卵泡发生过程中的机制作用尚未得到广泛研究。因此，本研究的目的是研究 WNT2 信号在小鼠颗粒细胞中的调节和功能。免疫染色鉴定出 WNT2 在卵泡发生过程中在颗粒细胞中表达，但信号强度不同：在连续切片中，WNT2 免疫反应性在健康的窦卵泡中最强，但在闭锁卵泡中较弱。使用转染的短干扰 RNA 敲低 WNT2 表达会降低颗粒细胞中的 DNA 合成，而使用重组病毒载体过表达 WNT2 则会增强其表达。WNT2 敲低导致细胞质中糖原合酶激酶-3β（GSK3B）积累，但降低了β-连环蛋白的表达。相反，WNT2 过表达减少了细胞质中 GSK3B 的表达，并诱导β-连环蛋白从膜转移到核内。β-连环蛋白敲低也抑制了颗粒细胞中的 DNA 合成，并中和了 WNT2 过表达的作用。WNT2/β-连环蛋白信号对颗粒细胞的凋亡有轻微影响。总之，数据表明 WNT2 调节颗粒细胞中β-连环蛋白的定位，WNT2/β-连环蛋白信号有助于调节其增殖。
