Kawarabayashi T, Shoji M, Sato M, Sasaki A, Ho L, Eckman C B, Prada C M, Younkin S G, Kobayashi T, Tada N, Matsubara E, Iizuka T, Harigaya Y, Kasai K, Hirai S
Department of Neurology, Gunma University School of Medicine, Japan.
Neurobiol Aging. 1996 Mar-Apr;17(2):215-22. doi: 10.1016/0197-4580(95)02061-6.
Some forms of familial Alzheimer's disease are caused by mutations in the amyloid beta protein precursor (beta APP), and there is excellent evidence that these mutations foster amyloid deposition by increasing secretion of total amyloid beta protein (A beta) or the highly amyloidogenic A beta 1-42 form. These observations provide a powerful rationale for developing an animal model of AD by generating transgenic mice in which cerebral amyloid deposition is induced by A beta overproduction. To produce substantial A beta in vivo, we generated mice expressing the transgene of signal peptide and 99 residues of carboxyl-terminal fragment (CTF) of beta APP under control of the cytomegalovirus enhancer/chicken beta-actin promoter. The transgenic mRNA was detected in many tissues of these mice, but the levels of transgenic mRNA, CTF, and A beta did not correlate well indicating that tissue-specific posttranslational processing may play an important role in determining the amount of A beta that accumulates in various tissues. A beta was detected biochemically in brain, kidney, and pancreas with the largest amount present in pancreas. In transgenic plasma, there was a marked accumulation of human A beta 1-40 and A beta 1-42(43) to levels over 30-times those observed in normal human plasma. Thus, the transgenic mice produce and secrete considerable A beta. Despite this increase in A beta secretion and the elevated A beta in brain, immunohistochemistry revealed no consistent cerebral A beta deposition. In pancreas, however, intracellular A beta deposits were detected immunohistochemically in acinar cells and interstitial macrophages, some of which showed severe degeneration. In addition, examination of these cells by immunoelectron microscopy revealed many putative amyloid fibrils (7-12 nm) that were stained by anti-A beta antibodies. Overall, our findings indicate that tissue-specific posttranslational processing may play a pivotal role in A beta production and amyloid fibril formation in vivo. By carefully analyzing the changes that occur in the transgenic mice described here as compared to the transgenic line that has recently been shown to form extracellular amyloid plaques in brain, it may be possible to gain considerable insight into the factors that determine the location and amount of A beta that accumulates as amyloid.
某些形式的家族性阿尔茨海默病是由淀粉样β蛋白前体（β-APP）的突变引起的，并且有充分的证据表明这些突变通过增加总淀粉样β蛋白（Aβ）或高度淀粉样生成性的Aβ1-42形式的分泌来促进淀粉样沉积。这些观察结果为通过生成转基因小鼠来开发阿尔茨海默病动物模型提供了有力的理论依据，在转基因小鼠中，Aβ的过量产生会诱导脑淀粉样沉积。为了在体内产生大量的Aβ，我们构建了在巨细胞病毒增强子/鸡β-肌动蛋白启动子控制下表达信号肽和β-APP羧基末端片段（CTF）99个残基转基因的小鼠。在这些小鼠的许多组织中检测到了转基因mRNA，但转基因mRNA、CTF和Aβ的水平之间没有很好的相关性，这表明组织特异性的翻译后加工可能在决定不同组织中积累的Aβ量方面起重要作用。通过生化方法在脑、肾和胰腺中检测到了Aβ，其中胰腺中的含量最高。在转基因小鼠血浆中，人Aβ1-40和Aβ1-42（43）显著积累，水平超过正常人血浆中观察到的30倍以上。因此，转基因小鼠产生并分泌了大量的Aβ。尽管Aβ分泌增加且脑中Aβ水平升高，但免疫组织化学显示没有一致的脑Aβ沉积。然而，在胰腺中，通过免疫组织化学在腺泡细胞和间质巨噬细胞中检测到细胞内Aβ沉积，其中一些细胞显示出严重的变性。此外，通过免疫电子显微镜检查这些细胞发现了许多被抗Aβ抗体染色的假定淀粉样纤维（7-12纳米）。总体而言，我们的研究结果表明组织特异性的翻译后加工可能在体内Aβ产生和淀粉样纤维形成中起关键作用。通过仔细分析此处描述的转基因小鼠与最近已被证明在脑中形成细胞外淀粉样斑块的转基因品系相比所发生的变化，有可能深入了解决定作为淀粉样物质积累的Aβ的位置和量的因素。
