Jin Lu, Hu Xinhua, Feng Linyin
Institute of Neuroscience, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Shonghai, China.
J Neurochem. 2005 Jun;93(5):1251-61. doi: 10.1111/j.1471-4159.2005.03118.x.
Neurotrophin 3 (NT3), a member of the neurotrophin family, antagonizes the proliferative effect of fibroblast growth factor 2 (FGF2) on cortical precursors. However, the mechanism by which NT3 inhibits FGF2-induced neural progenitor (NP) cell proliferation is unclear. Here, using an FGF2-dependent rat neurosphere culture system, we found that NT3 inhibits both FGF2-induced neurosphere growth and bromodeoxyuridine (BrdU) incorporation in a dose-dependent manner. U0126, a mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor, and LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, both inhibited FGF2-induced BrdU incorporation, suggesting that the extracellular signal-regulated kinase1/2 (ERK1/2) and PI3K pathways are required for FGF2-induced NP cell proliferation. NT3 significantly inhibited FGF2-induced phosphorylation of Akt and glycogen synthase kinase 3beta (GSK3beta), a downstream kinase of Akt, whereas phosphorylation of ERK1/2 was unaffected. The inhibitory effect of NT3 on FGF2-induced NP cell proliferation was abolished by LY294002, and treatment with SB216763, a specific GSK3 inhibitor, antagonized the NT3 effect, rescuing both neurosphere growth and BrdU incorporation. Moreover, experiments with anti-NT3 antibody revealed that endogenous NT3 also plays a role in inhibiting FGF2-induced NP cell proliferation, and that anti-NT3 antibody enhanced phospho-Akt and phospho-GSK3beta levels in the presence of FGF2. These findings indicate that FGF2-induced NP cell proliferation is inhibited by NT3 via the PI3K/GSK3 pathway.
神经营养因子3（NT3）是神经营养因子家族的成员之一，它可拮抗成纤维细胞生长因子2（FGF2）对皮质前体细胞的增殖作用。然而，NT3抑制FGF2诱导的神经祖细胞（NP）增殖的机制尚不清楚。在此，我们使用依赖FGF2的大鼠神经球培养系统，发现NT3以剂量依赖的方式抑制FGF2诱导的神经球生长和溴脱氧尿苷（BrdU）掺入。丝裂原活化蛋白激酶激酶1/2（MEK1/2）抑制剂U0126和磷脂酰肌醇3激酶（PI3K）抑制剂LY294002均抑制FGF2诱导的BrdU掺入，这表明细胞外信号调节激酶1/2（ERK1/2）和PI3K信号通路是FGF2诱导的NP细胞增殖所必需的。NT3显著抑制FGF2诱导的Akt和糖原合酶激酶3β（GSK3β，Akt的下游激酶）的磷酸化，而ERK1/2的磷酸化未受影响。LY294002消除了NT3对FGF2诱导的NP细胞增殖的抑制作用，并且用特异性GSK3抑制剂SB216763处理可拮抗NT3的作用，挽救神经球生长和BrdU掺入。此外，抗NT3抗体实验表明内源性NT3在抑制FGF2诱导的NP细胞增殖中也发挥作用，并表明在存在FGF2的情况下抗NT3抗体可提高磷酸化Akt和磷酸化GSK3β的水平。这些发现表明，NT3通过PI3K/GSK3信号通路抑制FGF2诱导的NP细胞增殖。
