Yamazaki T, Selkoe D J, Koo E H
Department of Neurology, Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
J Cell Biol. 1995 Apr;129(2):431-42. doi: 10.1083/jcb.129.2.431.
Amyloid beta-protein (A beta), the principal constituent of senile plaques seen in Alzheimer's disease (AD), is derived by proteolysis from the beta-amyloid precursor protein (beta PP). The mechanism of A beta production in neurons, which are hypothesized to be a rich source of A beta in brain, remains to be defined. In this study, we describe a detailed localization of cell surface beta PP and its subsequent trafficking in primary cultured neurons. Full-length cell surface beta PP was present primarily on perikarya and axons, the latter with a characteristic discontinuous pattern. At growth cones, cell surface beta PP was inconsistently detected. By visualizing the distribution of beta PP monoclonal antibodies added to intact cultures, beta PP was shown to be internalized from distal axons or terminals and retrogradely transported back to perikarya in organelles which colocalized with fluid-phase endocytic markers. Retrograde transport of beta PP was shown in both hippocampal and peripheral sympathetic neurons, the latter using a compartment culture system that isolated cell bodies from distal axons and terminals. In addition, we demonstrated that beta PP from distal axons was transcytotically transported to the surface of perikarya from distal axons in sympathetic neurons. Indirect evidence of this transcytotic pathway was obtained in hippocampal neurons using antisense oligonucleotide to the kinesin heavy chain to inhibit anterograde beta PP transport. Taken together, these results demonstrate novel aspects of beta PP trafficking in neurons, including retrograde axonal transport and transcytosis. Moreover, the axonal predominance of cell surface beta PP is unexpected in view of the recent report of polarized sorting of beta PP to the basolateral domain of MDCK cells.
β-淀粉样蛋白（Aβ）是阿尔茨海默病（AD）中可见的老年斑的主要成分，它是由β-淀粉样前体蛋白（βPP）经蛋白水解产生的。据推测，神经元是大脑中Aβ的丰富来源，但其产生Aβ的机制仍有待确定。在本研究中，我们描述了细胞表面βPP在原代培养神经元中的详细定位及其随后的运输过程。全长细胞表面βPP主要存在于胞体和轴突上，轴突上呈现出特征性的间断模式。在生长锥处，细胞表面βPP的检测结果不一致。通过观察添加到完整培养物中的βPP单克隆抗体的分布，发现βPP从远端轴突或终末内化，并通过与液相内吞标记物共定位的细胞器逆行运输回胞体。在海马神经元和外周交感神经元中均显示出βPP的逆行运输，后者使用了一种将细胞体与远端轴突和终末分离的分隔培养系统。此外，我们还证明，交感神经元中来自远端轴突的βPP通过转胞吞作用运输到胞体表面。在海马神经元中，使用针对驱动蛋白重链的反义寡核苷酸抑制βPP的顺行运输，从而获得了这种转胞吞途径的间接证据。综上所述，这些结果揭示了βPP在神经元中运输的新方面，包括轴突逆行运输和转胞吞作用。此外，鉴于最近有报道称βPP在MDCK细胞的基底外侧结构域进行极化分选，细胞表面βPP在轴突上占优势是出乎意料的。
