Berg M M, Krafft G A, Klein W L
Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA.
J Neurosci Res. 1997 Dec 15;50(6):979-89. doi: 10.1002/(SICI)1097-4547(19971215)50:6<979::AID-JNR8>3.0.CO;2-A.
Beta-amyloid1-42 (Abeta) is a naturally occuring peptide whose accumulation in the brain is putatively coupled to Alzheimer's disease pathogenesis. Deleterious effects of Abeta on neurons have been linked to the inappropriate activation of signaling pathways within the cell (reviewed in Yankner, 1996), including tyrosine phosphorylation of focal adhesion kinase (FAK) (Zhang et al., 1994, 1996a,b). Here we have investigated the effects of Abeta on paxillin in a neural cell line. Paxillin, a substrate for FAK, is thought to act as a signal "integrator," functioning to link other proteins into multi-molecular signaling complexes (reviewed in Turner, 1994). Treatment of the rat central nervous system B103 cell line with aggregates of Abeta was found to induce the tyrosine phosphorylation of paxillin within 30 min, nearly 24 hr prior to significant cell death. Particularly striking was a subsequent "mobilization" of paxillin to the cytoskeleton in Abeta-treated cells. The amount of paxillin associated with the cytoskeleton in Abeta-treated cells was increased 10-fold over controls. The Abeta-induced paxillin accumulation could be visualized immunocytochemically, with an increase in number and size of paxillin-labeled focal contacts upon treatment with Abeta. This effect was specific, in that vinculin, another focal contact protein, was unaffected by Abeta. Disruption of f-actin, which inhibits both Abeta-induced neurotoxicity (Furukawa and Mattson, 1995) and focal contact signaling in B103 cells (Zhang et al., 1996b) was found to block the cytoskeletal paxillin accumulation. The rapid tyrosine phosphorylation and cytoskeletal mobilization of paxillin links Abeta to the activation of focal contact signaling events that may influence neuronal cytoskeletal architecture, gene expression, synaptic plasticity and cell viability.
β-淀粉样蛋白1-42（Aβ）是一种天然存在的肽，其在大脑中的积累被认为与阿尔茨海默病的发病机制相关。Aβ对神经元的有害作用与细胞内信号通路的不适当激活有关（见Yankner，1996年综述），包括粘着斑激酶（FAK）的酪氨酸磷酸化（Zhang等人，1994年、1996a、b）。在此，我们研究了Aβ对神经细胞系中桩蛋白的影响。桩蛋白是FAK的底物，被认为起到信号“整合器”的作用，其功能是将其他蛋白质连接成多分子信号复合物（见Turner，1994年综述）。发现用Aβ聚集体处理大鼠中枢神经系统B103细胞系会在30分钟内诱导桩蛋白的酪氨酸磷酸化，这比明显的细胞死亡提前近24小时。特别显著的是，在Aβ处理的细胞中，随后桩蛋白会“转移”到细胞骨架上。与对照组相比，Aβ处理的细胞中与细胞骨架相关的桩蛋白量增加了10倍。Aβ诱导的桩蛋白积累可以通过免疫细胞化学方法观察到，用Aβ处理后，桩蛋白标记的粘着斑的数量和大小会增加。这种效应是特异性的，因为另一种粘着斑蛋白纽蛋白不受Aβ影响。发现破坏丝状肌动蛋白会阻断细胞骨架桩蛋白的积累，而丝状肌动蛋白的破坏既抑制Aβ诱导的神经毒性（Furukawa和Mattson，1995年），也抑制B103细胞中的粘着斑信号传导（Zhang等人，1996b）。桩蛋白的快速酪氨酸磷酸化和细胞骨架转移将Aβ与粘着斑信号传导事件的激活联系起来，这些事件可能影响神经元细胞骨架结构、基因表达、突触可塑性和细胞活力。
