Amyloid precursor protein is enriched in axolemma and periaxolemmal-myelin and associated clathrin-coated vesicles.
Amyloid precursor protein is enriched in axolemma and periaxolemmal-myelin and associated clathrin-coated vesicles.
复制标题
淀粉样前体蛋白富含轴膜和轴膜周围髓磷脂以及相关的网格蛋白包被的囊泡。
DOI：
10.1002/jnr.490370307
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发表时间：
1994
影响因子：
4.2
通讯作者：
Marks,N
中科院分区：
文献类型：
--
作者：
Sapirstein,VS;Durrie,R;Berg,MJ;Marks,N
淀粉样前体蛋白（APP）广泛分布于中枢神经系统内，在神经元和神经胶质细胞中表达。我们从大鼠大脑中分离出轴膜和轴膜周围髓磷脂，并通过蛋白质印迹确定 APPs（Mr 100-110 kDa）是这些膜的主要成分。轴膜、轴膜周围髓磷脂和致密髓磷脂的分离表明，虽然 APP 代表这些膜的蛋白质的 1% 和 0.6%，但致密髓磷脂中不存在 APP。这些结果表明，沿着轴突运输的 APP 沉积在轴突和突触的位点，并且在髓鞘复合体中，APP 靶向轴突周围区域。轴膜和轴膜周髓磷脂均含有 10.5 kDa APP 肽，根据与抗 C 端 APP 抗体的反应性，但不与抗 N 端抗体的反应性，该肽似乎是膜相关的 C 端片段。阿尔茨海默前体样蛋白 (APLP) 抗体的蛋白质印迹表明 APP 免疫反应性不是与 APLP 交叉反应的结果。从人体尸检材料中分离轴膜显示出几乎相同的结果，相对于匀浆，APP Mr 100-100 和 10.5 kDa C 末端肽明显富集。 APP 在轴膜和轴膜周围髓磷脂中的表现在从牛脑分离的膜中得到了复制。牛研究扩展到白质网格蛋白包被的囊泡的分析；这些数据表明，在先前的研究表明主要是内吞性囊泡的条件下，从白质中分离出的包被囊泡含有与轴膜和轴膜周髓磷脂中发现的相当的 APP 水平。此外，这些囊泡含有半胱氨酸和天冬氨酰蛋白酶。当用 APP672-695 的抗体进行分析时，轴膜与组织蛋白酶 B 在 pH 6.0 下孵育会导致 APP Mr 100-110 和 Mr 10.5 的免疫反应性迅速丧失。这似乎是表位内水解的结果，而不是 APP 或 C 末端肽的蛋白水解的结果，因为当用抗体对 C 末端更远端的位点进行分析时，没有观察到反应性损失。因此，组织蛋白酶 B 可以水解靠近 C 末端的膜结合 APP，并且可能是改变 C 末端 APP 功能的有用工具。 © 1994 Wiley-Liss, Inc.
The amyloid precursor protein (APP) is widely distributed within the CNS, where it is expressed in both neurons and glia. We have isolated axolemma and periaxolemmal‐myelin from rat brain and have determined by Western blot that APPs, Mr 100–110 kDa, are major constituents of these membrane. Isolation of axolemma, periaxolemmal‐myelin, and compact myelin show that while APP represents 1 and 0.6% of the proteins of these respective membranes, it is absent from compact myelin. These results indicate that APP transported down the axon is deposited at sites in the axolemma as well as the synapse, and that within the myelin complex, APP is targeted to the periaxolemmal domain. Both axolemma and periaxolemmal‐myelin contained a 10.5 kDa APP peptide which, based on reactivity with anti‐C‐terminal APP antibodies but not with anti‐N‐terminal antibody, appears to be a membrane‐associated C‐terminal fragment. Western blots with antibodies to Alzheimer precursor‐like proteins (APLP) indicate that APP immune reactivity is not a result of cross reactivity with APLPs. Isolation of axolemma from human autopsy material showed nearly identical results with a clear enrichment, relative to homogenate, of APP Mr 100–100 and the 10.5 kDa C‐terminal peptide. The demonstration of APP in axolemma and periaxolemmal‐myelin was replicated in membrane isolated from bovine brain. Bovine studies were extended to analysis of white matter clathrin‐coated vesicles; these data show that coated vesicles isolated from white matter, under conditions that previous studies indicate are largely endocytic vesicles, contain levels of APP comparable to that found in axolemma and periaxolemmal‐myelin. In addition, these vesicles contain cysteinly and aspartyl proteases. Incubation of axolemma with cathepsin B at pH 6.0 caused a rapid loss in the immune reactivity of APP Mr 100–110 and Mr 10.5 when analyzed with antibodies to APP672–695. This appears to be the result of hydrolysis within the epitope and not proteolysis of APP or the C‐terminal peptide, since no loss of reactivity was observed when analyzed with antibodies to sites more distal to the C‐terminus. Thus, cathepsin B hydrolyses membrane bound APP close to the C‐terminus and may be a useful tool for altering C‐terminal APP function. © 1994 Wiley‐Liss, Inc.