Nonomura T, Kubo T, Oka T, Shimoke K, Yamada M, Enokido Y, Hatanaka H
Division of Protein Biosynthesis, Osaka University, Japan.
Brain Res Dev Brain Res. 1996 Nov 22;97(1):42-50. doi: 10.1016/s0165-3806(96)00130-7.
We investigated the signaling pathways exerted by brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in relation to their survival-promoting effects on dissociated cultures of cerebellar granule cells prepared from postnatal 9-day-old rats. Granule neuron survival in culture was supported by BDNF, but not significantly by either nerve growth factor (NGF) or NT-3. BDNF and NT-3 resulted in not only the respective autophosphorylation of the Trk receptors, TrkB or TrkC, but also tyrosine phosphorylation of SHC, a protein involved in controlling p21ras activity, and phosphatidylinositol-3' (PI-3') kinase. NGF does not result in TrkA phosphorylation. In parallel, c-fos was induced within 30 min, in response to BDNF and NT-3. NT-3 induced the phosphorylation of these proteins to a lesser extent than BDNF. BDNF also induced the tyrosine phosphorylation of phospholipase C gamma (PLC gamma), but the NT-3-induced one was not detected. We postulate that no survival promotion by NT-3 is due to lesser level of trkC expression and of the NT-3-induced signaling in the cultured cerebellar granule neurons. Wortmannin, a specific inhibitor of PI-3' inhibited the BDNF effect on neuronal survival. PI-3' kinase-dependent pathways might be involved in the promotion of cerebellar granule cell survival by BDNF.
我们研究了脑源性神经营养因子（BDNF）和神经营养素-3（NT-3）发挥的信号通路，及其对出生后9日龄大鼠解离培养的小脑颗粒细胞的促存活作用。培养中的颗粒神经元存活受BDNF支持，但神经生长因子（NGF）或NT-3均无明显作用。BDNF和NT-3不仅分别导致Trk受体TrkB或TrkC的自身磷酸化，还导致参与控制p21ras活性的蛋白SHC以及磷脂酰肌醇-3'（PI-3'）激酶的酪氨酸磷酸化。NGF不会导致TrkA磷酸化。同时，BDNF和NT-3作用后30分钟内可诱导c-fos表达。NT-3诱导这些蛋白磷酸化的程度低于BDNF。BDNF还可诱导磷脂酶Cγ（PLCγ）的酪氨酸磷酸化，但未检测到NT-3诱导的这种磷酸化。我们推测，NT-3不能促进存活是由于培养的小脑颗粒神经元中trkC表达水平较低以及NT-3诱导的信号传导较弱。渥曼青霉素，一种PI-3'的特异性抑制剂，可抑制BDNF对神经元存活的作用。PI-3'激酶依赖性通路可能参与BDNF对小脑颗粒细胞存活的促进作用。
