Sun Xiao-Long, Chen Bei-Yu, Duan Li, Xia Yi, Luo Zhuo-Jing, Wang Jing-Jie, Rao Zhi-Ren, Chen Liang-Wei
Institute of Neurosciences, Fourth Military Medical University, Xi'an, 710032, People's Republic of China.
Mol Neurobiol. 2014 Feb;49(1):234-50. doi: 10.1007/s12035-013-8515-6. Epub 2013 Aug 10.
Growing evidences have revealed that the proforms of several neurotrophins including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3), by binding to p75 neurotrophin receptor and sortilin, could induce neuronal apoptosis and are implicated in the pathogenesis of various neurodegenerative diseases. The glial cell line-derived neurotrophic factor (GDNF), one of the most potent useful neurotrophic factors for the treatment of Parkinson's disease (PD), is firstly synthesized as the proform (proGDNF) like other neurotrophin NGF, BDNF, and NT3. However, little is known about proGDNF expression and secretion under physiological as well as pathological states in vivo or in vitro. In this study, we investigated the expression profile and dynamic changes of proGDNF in brains of aging and PD animal models, with the interesting finding that proGDNF was a predominant form of GDNF with molecular weight of about 36 kDa by reducing and nonreducing immunoblots in adult brains and was unregulated in the aging, lipopolysaccharide (LPS), and 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) insult. We further provided direct evidence that accompanied activation of primary astrocytes as well as C6 cell line induced by LPS stimulation, proGDNF was increasingly synthesized and released as the uncleaved form in cell culture. Taken together, our results strongly suggest that proGDNF may be a biologically active protein and has specific effects on the cells close to its secreting site, and a potentially important role of proGDNF signaling in the brains, in the glia-neuronal interaction or in the pathogenesis of PD, should merit further investigation.
越来越多的证据表明，包括神经生长因子（NGF）、脑源性神经营养因子（BDNF）和神经营养因子-3（NT3）在内的几种神经营养因子的前体形式，通过与p75神经营养因子受体和sortilin结合，可诱导神经元凋亡，并与各种神经退行性疾病的发病机制有关。胶质细胞系源性神经营养因子（GDNF）是治疗帕金森病（PD）最有效的神经营养因子之一，它最初像其他神经营养因子NGF、BDNF和NT3一样以前体形式（proGDNF）合成。然而，关于proGDNF在体内或体外生理及病理状态下的表达和分泌情况知之甚少。在本研究中，我们调查了衰老和PD动物模型大脑中proGDNF的表达谱和动态变化，有趣的是，通过还原和非还原免疫印迹法发现，proGDNF是GDNF在成年大脑中的主要形式，分子量约为36 kDa，并且在衰老、脂多糖（LPS）和1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）损伤中表达上调。我们进一步提供了直接证据，即伴随LPS刺激诱导的原代星形胶质细胞以及C6细胞系的激活，proGDNF在细胞培养中以未切割形式越来越多地合成和释放。综上所述，我们的结果强烈表明，proGDNF可能是一种生物活性蛋白，对其分泌位点附近的细胞有特定作用，proGDNF信号在大脑、神经胶质-神经元相互作用或PD发病机制中的潜在重要作用值得进一步研究。
