Longer forms of amyloid beta protein: implications for the mechanism of intramembrane cleavage by gamma-secretase.
Longer forms of amyloid beta protein: implications for the mechanism of intramembrane cleavage by gamma-secretase.
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2005
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通讯作者：
Yue Qi-Takahara;M. Morishima-kawashima;Y. Tanimura;G. Dolios;Naoko Hirotani;Y. Horikoshi;F. Kametani;M. Maeda;T. Saido;Rong Wang;Y. Ihara
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作者：
Yue Qi-Takahara;M. Morishima-kawashima;Y. Tanimura;G. Dolios;Naoko Hirotani;Y. Horikoshi;F. Kametani;M. Maeda;T. Saido;Rong Wang;Y. Ihara
β-淀粉样前体蛋白（APP）在细胞膜中部的γ-裂解产生淀粉样β蛋白（Abeta），γ-裂解位点下游约10个残基的ε-裂解释放APP胞内结构域（AICD）。Abeta和AICD的产生与未能检测到AICD 41 -99之间的重要联系使我们假设ε-切割产生更长的Abeta，然后加工成Abeta 40/42。使用新开发的凝胶系统和N端特异性单克隆抗体，我们已经确定了细胞和脑组织中较长的Abeta（Abeta 1 -43，Abeta 1 -45，Abeta 1 -46和Abeta 1 -48）。这些较长的Abeta以及Abeta 40/42的产生是早老素依赖性的，并且被{1 S-苄基-4R-[1 S-氨基甲酰基-2-苯基乙基氨基甲酰基-1S-3-甲基丁基氨基甲酰基]-2R-羟基-5-苯基戊基}氨基甲酸叔丁酯（一种乙酰基蛋白酶的过渡态类似物抑制剂）抑制。相比之下，N-[N-（3，5-二氟苯乙酰基）-L-丙氨酰]-S-苯基甘氨酸叔丁酯，一种有效的二肽γ-分泌酶抑制剂，在细胞内积累A β 1 -43和A β 1 -46，这也通过质谱法证实。值得注意的是，抑制A β 40似乎导致A β 43增加，这反过来又以剂量依赖性方式导致A β 46增加。因此，我们提出了一个α-螺旋模型，其中ε-裂解产生的较长的Abeta物种在其羧基部分的每三个残基被裂解。
Gamma-cleavage of beta-amyloid precursor protein (APP) in the middle of the cell membrane generates amyloid beta protein (Abeta), and epsilon-cleavage, approximately 10 residues downstream of the gamma-cleavage site, releases the APP intracellular domain (AICD). A significant link between generation of Abeta and AICD and failure to detect AICD41-99 led us to hypothesize that epsilon-cleavage generates longer Abetas, which are then processed to Abeta40/42. Using newly developed gel systems and an N-end-specific monoclonal antibody, we have identified the longer Abetas (Abeta1-43, Abeta1-45, Abeta1-46, and Abeta1-48) within the cells and in brain tissues. The production of these longer Abetas as well as Abeta40/42 is presenilin dependent and is suppressed by {1S-benzyl-4R-[1S-carbamoyl-2-phenylethylcarbamoyl-1S-3-methylbutylcarbamoyl]-2R-hydroxy-5-phenylpentyl}carbamic acid tert-butyl ester, a transition state analog inhibitor for aspartyl protease. In contrast, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, a potent dipeptide gamma-secretase inhibitor, builds up Abeta1-43 and Abeta1-46 intracellularly, which was also confirmed by mass spectrometry. Notably, suppression of Abeta40 appeared to lead to an increase in Abeta43, which in turn brings an increase in Abeta46, in a dose-dependent manner. We therefore propose an alpha-helical model in which longer Abeta species generated by epsilon-cleavage is cleaved at every three residues in its carboxyl portion.