Hansson Camilla A, Popescu Bogdan O, Laudon Hanna, Cedazo-Minguez Angel, Popescu Laurentiu M, Winblad Bengt, Ankarcrona Maria
Karolinska Institutet, Neurotec, Section for Experimental Geriatrics, Huddinge, Sweden.
J Neurochem. 2006 Apr;97(2):356-64. doi: 10.1111/j.1471-4159.2006.03735.x. Epub 2006 Mar 15.
gamma-Secretase is a key enzyme involved in the processing of the beta-amyloid precursor protein into amyloid beta-peptides (Abeta). Abeta accumulates and forms plaques in Alzheimer's disease (AD) brains. A progressive neurodegeneration and cognitive decline occurs during the course of the disease, and Abeta is believed to be central for the molecular pathogenesis of AD. Apoptosis has been implicated as one of the mechanisms behind the neuronal cell loss seen in AD. We have studied preservation and activity of the gamma-secretase complex during apoptosis in neuroblastoma cells (SH-SY5Y) exposed to staurosporine (STS). We report that the known components (presenilin, Nicastrin, Aph-1 and Pen-2) interact and form active gamma-secretase complexes in apoptotic cells. In addition, the fragments corresponding to the PS1 N-terminal fragment and the caspase-cleaved PS1 C-terminal fragment (PS1-caspCTF) were found to form active gamma-secretase complexes when co-expressed in presenilin (PS) knockout cells. Interestingly, PS1-caspCTF replaced the normal PS1 C-terminal fragment and was co-immunoprecipitated with the gamma-secretase complex in SH-SY5Y cells exposed to STS. In addition, Abeta was detected in medium from apoptotic HEK APP(swe) cells. Together, the data show that gamma-secretase complexes containing PS1-caspCTF are active, and suggest that this proteolytic activity is also important in dying cells and may affect the progression of AD.
γ-分泌酶是一种关键酶，参与将β-淀粉样前体蛋白加工成淀粉样β肽（Aβ）。在阿尔茨海默病（AD）患者的大脑中，Aβ会积聚并形成斑块。在疾病过程中会发生进行性神经退行性变和认知衰退，Aβ被认为是AD分子发病机制的核心。细胞凋亡被认为是AD中神经元细胞丢失背后的机制之一。我们研究了暴露于星形孢菌素（STS）的神经母细胞瘤细胞（SH-SY5Y）在凋亡过程中γ-分泌酶复合物的保存和活性。我们报告称，已知成分（早老素、尼卡斯特林、Aph-1和Pen-2）在凋亡细胞中相互作用并形成活性γ-分泌酶复合物。此外，当在早老素（PS）基因敲除细胞中共表达时，发现与PS1 N端片段和半胱天冬酶切割的PS1 C端片段（PS1-caspCTF）相对应的片段形成活性γ-分泌酶复合物。有趣的是，在暴露于STS的SH-SY5Y细胞中，PS1-caspCTF取代了正常的PS1 C端片段，并与γ-分泌酶复合物共免疫沉淀。此外，在凋亡的HEK APP（swe）细胞的培养基中检测到了Aβ。总之，数据表明含有PS1-caspCTF的γ-分泌酶复合物具有活性，并表明这种蛋白水解活性在垂死细胞中也很重要，可能会影响AD的进展。
