Family Planning Research Institute and Centre for Reproductive Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China.
Theriogenology. 2010 May;73(8):1096-103. doi: 10.1016/j.theriogenology.2010.01.009. Epub 2010 Feb 19.
Brain-derived neurotrophic factor (BDNF) can promote developmental competence in mammalian oocytes during in vitro maturation, but the signal transduction pathways are not clear. In this study, we investigated (using western blots) the effects of BDNF on the phosphorylation of protein kinase B (PKB) and mitogen-activated protein kinase (MAPK) in mouse oocytes and cumulus cells cultured in vitro. Treatment with BDNF enhanced phosphorylation of PKB in oocytes at 2h (P=0.0006) and 3h (P<0.0001) of in vitro maturation, compared with control oocytes. However, the pan-specific tyrosine kinase (Trk) inhibitor K252a together with BDNF completely inhibited phosphorylation of PKB in the oocytes. Furthermore, BDNF increased phosphorylation of MAPK in oocytes at 16h of in vitro maturation (P=0.0041), but K252a together with BDNF did not reduce phosphorylation of MAPK in the oocytes. For cumulus cells, BDNF significantly prolonged the phosphorylation of PKB and MAPK and increased the total amounts of PKB and MAPK proteins after 16h of in vitro maturation. However, BDNF did not affect apoptosis of the cumulus cells during oocyte maturation in vitro. In conclusion, the PKB pathway is likely to be one signaling cascade activated by BDNF in combination with the TrkB receptor, whereas the MAPK pathway is not involved. These findings may have relevance for BDNF-induced promotion of developmental capacity of in vitro-matured oocytes.
脑源性神经营养因子（BDNF）可以在体外成熟过程中提高哺乳动物卵母细胞的发育能力，但信号转导途径尚不清楚。本研究通过 Western blot 法研究了 BDNF 对体外培养的小鼠卵母细胞和卵丘细胞中蛋白激酶 B（PKB）和丝裂原活化蛋白激酶（MAPK）磷酸化的影响。与对照组卵母细胞相比，BDNF 处理可增强卵母细胞在体外成熟 2h（P=0.0006）和 3h（P<0.0001）时 PKB 的磷酸化。然而，泛特异性酪氨酸激酶（Trk）抑制剂 K252a 与 BDNF 一起完全抑制了卵母细胞中 PKB 的磷酸化。此外，BDNF 增加了体外成熟 16h 时卵母细胞中 MAPK 的磷酸化（P=0.0041），但 K252a 与 BDNF 一起并未降低卵母细胞中 MAPK 的磷酸化。对于卵丘细胞，BDNF 可显著延长 PKB 和 MAPK 的磷酸化时间，并增加体外成熟 16h 后 PKB 和 MAPK 蛋白的总量。然而，BDNF 并未影响体外成熟过程中卵丘细胞的凋亡。总之，PKB 途径可能是 BDNF 与 TrkB 受体结合激活的信号级联之一，而 MAPK 途径不参与其中。这些发现可能与 BDNF 诱导体外成熟卵母细胞发育能力的提高有关。
