Rossner S, Ueberham U, Schliebs R, Perez-Polo J R, Bigl V
Department of Neurochemistry, Paul Flechsig Institute for Brain Research, Leipzig, Germany.
J Neurochem. 1998 Aug;71(2):757-66. doi: 10.1046/j.1471-4159.1998.71020757.x.
The pheochromocytoma PC12 cell line was used as a model system to characterize the role of the p75 neurotrophin receptor (p75NTR) and tyrosine kinase (Trk) A nerve growth factor (NGF) receptors on amyloid precursor protein (APP) expression and processing. NGF increased in a dose-dependent fashion neurite outgrowth, APP mRNA expression, and APP secretion with maximal effects at concentrations known to saturate TrkA receptor binding. Displacement of NGF binding to p75NTR by addition of an excess of brain-derived neurotrophic factor abolished NGF's effects on neurite outgrowth and APP metabolism, whereas addition of brain-derived neurotrophic factor alone did not induce neurite outgrowth or affect APP mRNA or protein processing. However, treatment of PC12 cells with C2-ceramide, an analogue of ceramide, the endogenous product produced by the activity of p75NTR-activated sphingomyelinase, mimicked the effects of NGF on cell morphology and stimulation of both APP mRNA levels and APP secretion. Specific stimulation of TrkA receptors by receptor cross-linking, on the other hand, selectively stimulated neurite outgrowth and APP secretion but not APP mRNA levels, which were decreased. These findings demonstrate that in PC12 cells expressing p75NTR and TrkA receptors, binding of NGF to the p75NTR is required to mediate NGF effects on cell morphology and APP metabolism. Furthermore, our data are consistent with NGF having specific effects on p75NTR not shared with other neurotrophins. Lastly, we have shown that specific activation of TrkA receptors--in contrast to p75NTR-associated signaling--stimulates neurite outgrowth and increases nonamyloidogenic secretory APP processing without increases in APP mRNA levels.
嗜铬细胞瘤PC12细胞系被用作一个模型系统，以表征p75神经营养因子受体（p75NTR）和酪氨酸激酶（Trk）A神经生长因子（NGF）受体在淀粉样前体蛋白（APP）表达及加工过程中的作用。NGF以剂量依赖的方式增加神经突生长、APP mRNA表达和APP分泌，在已知能使TrkA受体结合饱和的浓度下具有最大效应。通过添加过量的脑源性神经营养因子来取代NGF与p75NTR的结合，消除了NGF对神经突生长和APP代谢的影响，而单独添加脑源性神经营养因子并不会诱导神经突生长或影响APP mRNA或蛋白质加工。然而，用C2-神经酰胺（一种神经酰胺类似物，由p75NTR激活的鞘磷脂酶活性产生的内源性产物）处理PC12细胞，模拟了NGF对细胞形态以及APP mRNA水平和APP分泌的刺激作用。另一方面，通过受体交联对TrkA受体进行特异性刺激，选择性地刺激了神经突生长和APP分泌，但并未刺激APP mRNA水平，反而使其降低。这些发现表明，在表达p75NTR和TrkA受体的PC12细胞中，NGF与p75NTR的结合是介导NGF对细胞形态和APP代谢影响所必需的。此外，我们的数据与NGF对p75NTR具有其他神经营养因子所不具备的特异性作用一致。最后，我们已经表明，与p75NTR相关信号传导相反，TrkA受体的特异性激活刺激神经突生长并增加非淀粉样生成性分泌型APP的加工，而不会增加APP mRNA水平。
