Julien J P, Mushynski W E
Centre for Research in Neuroscience, McGill University, Montreal, Canada.
Prog Nucleic Acid Res Mol Biol. 1998;61:1-23. doi: 10.1016/s0079-6603(08)60823-5.
This article reviews current knowledge of neurofilament structure, phosphorylation, and function and neurofilament involvement in disease. Neurofilaments are obligate heteropolymers requiring the NF-L subunit together with either the NF-M or the NF-H subunit for polymer formation. Neurofilaments are very dynamic structures; they contain phosphorylation sites for a large number of protein kinases, including protein kinase A (PKA), protein kinase C (PKC), cyclin-dependent kinase 5 (Cdk5), extracellular signal regulated kinase (ERK), glycogen synthase kinase-3 (GSK-3), and stress-activated protein kinase gamma (SAPK gamma). Most of the neurofilament phosphorylation sites, located in tail regions of NF-M and NF-H, consist of the repeat sequence motif, Lys-Ser-Pro (KSP). In addition to the well-established role of neurofilaments in the control of axon caliber, there is growing evidence based on transgenic mouse studies that neurofilaments can affect the dynamics and perhaps the function of other cytoskeletal elements, such as microtubules and actin filaments. Perturbations in phosphorylation or in metabolism of neurofilaments are frequently observed in neurodegenerative diseases. A down-regulation of mRNA encoding neurofilament proteins and the presence of neurofilament deposits are common features of human neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Parkinson's disease, and Alzheimer's disease. Although the extent to which neurofilament abnormalities contribute to pathogenesis in these human diseases remains unknown, emerging evidence, based primarily on transgenic mouse studies and on the discovery of deletion mutations in the NF-H gene of some ALS eases, suggests that disorganized neurofilaments can provoke selective degeneration and death of neurons. An interference of axonal transport by disorganized neurofilaments has been proposed as one possible mechanism of neurofilament-induced pathology. Other factors that can potentially lead to the accumulation of neurofilaments will be discussed as well as the emerging evidence for neurofilaments as being possible targets of oxidative damage by mutations in the superoxide dismutase enzyme (SOD1); such mutations are responsible for approximately 20% of familial ALS cases.
本文综述了目前关于神经丝结构、磷酸化、功能以及神经丝与疾病关系的知识。神经丝是专性异源聚合物，形成聚合物需要NF-L亚基与NF-M或NF-H亚基共同参与。神经丝是非常动态的结构；它们含有大量蛋白激酶的磷酸化位点，包括蛋白激酶A（PKA）、蛋白激酶C（PKC）、细胞周期蛋白依赖性激酶5（Cdk5）、细胞外信号调节激酶（ERK）、糖原合酶激酶-3（GSK-3）和应激激活蛋白激酶γ（SAPKγ）。大多数位于NF-M和NF-H尾部区域的神经丝磷酸化位点由重复序列基序赖氨酸-丝氨酸-脯氨酸（KSP）组成。除了神经丝在控制轴突管径方面已确定的作用外，基于转基因小鼠研究的证据越来越多，表明神经丝可以影响其他细胞骨架成分（如微管和肌动蛋白丝）的动力学，甚至可能影响其功能。在神经退行性疾病中经常观察到神经丝磷酸化或代谢的紊乱。编码神经丝蛋白的mRNA下调以及神经丝沉积物的存在是人类神经退行性疾病（包括肌萎缩侧索硬化症（ALS）、帕金森病和阿尔茨海默病）的常见特征。尽管神经丝异常在这些人类疾病发病机制中的作用程度尚不清楚，但主要基于转基因小鼠研究以及在一些ALS病例的NF-H基因中发现缺失突变的新证据表明，紊乱的神经丝可引发神经元的选择性变性和死亡。有人提出紊乱的神经丝对轴突运输的干扰是神经丝诱导病理的一种可能机制。还将讨论可能导致神经丝积累的其他因素，以及神经丝作为超氧化物歧化酶（SOD1）突变导致氧化损伤的可能靶点的新证据；此类突变约占家族性ALS病例的20%。
