Cobellis Gilda, Meccariello Rosaria, Fienga Giulia, Pierantoni Riccardo, Fasano Silvia
Dipartimento di Medicina Sperimentale, Sez. F. Bottazzi, II Università di Napoli, Via Constantinopoli 16, 80138 Naples, Italy.
Endocrinology. 2002 Jan;143(1):163-70. doi: 10.1210/endo.143.1.8567.
The role of Fos proteins in the regulation of germ cell progression during spermatogenesis has been studied in the frog, Rana esculenta. A peculiarity of this animal model is the finding of Fos in cytoplasmic compartment of primary spermatogonia during the resting period of the annual reproductive cycle. Interestingly, Fos is localized in the nuclear compartment when spermatogenesis resumes. Using Western blot analysis, we show that a 52-kDa Fos protein occurs in testicular cytosolic preparations, whereas two different Fos signals of 43 and 68 kDa are typical of the nuclear compartment. The 68-kDa Fos immunoreactive protein increases in nuclear extracts in concomitance with spermatogonia (SPG) proliferation either during the annual sexual cycle or in experimental animal groups where SPG proliferation was induced by thermal stimulus (24 C). Indeed, an increase in proliferating cell nuclear antigen was detectable after thermal induction of mitotic activity. A decrease in the 52-kDa signal and a concomitant increase in the 68-kDa signal is observed in testes of 24 C treated groups. The use of alkaline phosphatase and alkaline phosphatase inhibitors indicates that the 68-kDa protein is a phosphorylated form. Estrogens, which are able to induce SPG proliferation, are responsible for the appearance of the 43-kDa Fos form in nuclear testicular extracts. In conclusion, our results show, for the first time in a vertebrate species, that storage in the cytoplasm, on the one hand, and appearance as well as phosphorylation of Fos proteins in the nucleus of germ cells, on the other hand, regulate spermatogenesis progression during the seasonal breeding. Moreover, the phosphorylated 68-kDa Fos form may be involved in mechanisms underlying SPG proliferation.
在食用蛙中研究了Fos蛋白在精子发生过程中对生殖细胞进程的调控作用。该动物模型的一个特点是，在年度生殖周期的静止期，在初级精原细胞的细胞质区室中发现了Fos。有趣的是，当精子发生恢复时，Fos定位于细胞核区室。通过蛋白质免疫印迹分析，我们发现睾丸胞质制剂中存在一种52 kDa的Fos蛋白，而43 kDa和68 kDa的两种不同Fos信号是细胞核区室的典型特征。在年度性周期期间或在通过热刺激（24℃）诱导精原细胞（SPG）增殖的实验动物组中，68 kDa的Fos免疫反应性蛋白在核提取物中的含量随着精原细胞增殖而增加。实际上，在有丝分裂活性的热诱导后可检测到增殖细胞核抗原增加。在24℃处理组的睾丸中观察到52 kDa信号减少，同时68 kDa信号增加。使用碱性磷酸酶和碱性磷酸酶抑制剂表明68 kDa蛋白是一种磷酸化形式。能够诱导SPG增殖的雌激素导致睾丸核提取物中出现43 kDa的Fos形式。总之，我们的结果首次在脊椎动物物种中表明，一方面，Fos蛋白在细胞质中的储存，另一方面，其在生殖细胞核中的出现以及磷酸化，调节季节性繁殖期间的精子发生进程。此外，磷酸化的68 kDa Fos形式可能参与了SPG增殖的潜在机制。
