Sodhi Chhinder P, Perez Ruth G, Gottardi-Littell Numa R
Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
Brain Res. 2008 Mar 10;1198:204-12. doi: 10.1016/j.brainres.2008.01.031. Epub 2008 Jan 26.
Secretion and progressive cerebral accumulation of beta-amyloid peptides (Abeta) derived by endoproteolytic ("amyloidogenic") processing of beta-amyloid precursor protein (APP) represent collectively an early and necessary event in the pathogenesis of Alzheimer's disease. We previously demonstrated that secretion of the neurotoxic species Abeta42 increases during staurosporine-induced apoptosis in undifferentiated PC12 cells, in an endocytosis-dependent manner. In the present study, we tested whether phosphorylation of the APP cytoplasmic-tail is contributory to this apoptosis-related increased Abeta-secretory response. We demonstrate that cytoplasmic-tail phosphorylation specifically at amino-acid residue T668 (APP-695 numbering) increases during staurosporine-induced apoptosis, in parallel with activation of the mitogen-activated, proline-directed serine/threonine protein kinase ERK1. We demonstrate additionally that specific ERK inhibition during staurosporine induction, with serum-free conditions, results in down-regulation of APP phosphorylation at T668, together with attenuation of the increased Abeta-secretory response. These results are consistent with APP cytoplasmic-tail phosphorylation at T668 during apoptosis as contributory to increased Abeta42 secretion originating from the endocytotic pathway, likely with cell-line restriction.
由β-淀粉样前体蛋白（APP）经内蛋白水解（“淀粉样生成”）加工产生的β-淀粉样肽（Aβ）的分泌及在大脑中的渐进性蓄积，共同构成了阿尔茨海默病发病机制中的一个早期且必要的事件。我们先前证明，在未分化的PC12细胞中，神经毒性物质Aβ42的分泌在星形孢菌素诱导的细胞凋亡过程中以内吞作用依赖的方式增加。在本研究中，我们测试了APP胞质尾的磷酸化是否促成这种与细胞凋亡相关的Aβ分泌增加反应。我们证明，在星形孢菌素诱导的细胞凋亡过程中，特别是在氨基酸残基T668（APP-695编号）处的胞质尾磷酸化增加，这与丝裂原活化的、脯氨酸定向的丝氨酸/苏氨酸蛋白激酶ERK1的激活同时发生。我们还证明，在无血清条件下，在星形孢菌素诱导期间特异性抑制ERK，会导致T668处APP磷酸化的下调，同时减弱Aβ分泌增加反应。这些结果与细胞凋亡期间T668处APP胞质尾磷酸化促成源自内吞途径的Aβ42分泌增加一致，可能存在细胞系限制。
