Gladstone Institute of Neurological Disease, University of California, San Francisco, California 94158, USA.
J Biol Chem. 2011 May 13;286(19):17217-26. doi: 10.1074/jbc.M110.217380. Epub 2011 Mar 18.
Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer disease (AD) and likely contributes to neuropathology through various pathways. Here we report that the intracellular trafficking of apoE4 is impaired in Neuro-2a cells and primary neurons, as shown by measuring fluorescence recovery after photobleaching. In Neuro-2a cells, more apoE4 than apoE3 molecules remained immobilized in the endoplasmic reticulum (ER) and the Golgi apparatus, and the lateral motility of apoE4 was significantly lower in the Golgi apparatus (but not in the ER) than that of apoE3. Likewise, the immobile fraction was larger, and the lateral motility was lower for apoE4 than apoE3 in mouse primary hippocampal neurons. ApoE4 with the R61T mutation, which abolishes apoE4 domain interaction, was less immobilized, and its lateral motility was comparable with that of apoE3. The trafficking impairment of apoE4 was also rescued by disrupting domain interaction with the small-molecule structure correctors GIND25 and PH002. PH002 also rescued apoE4-induced impairments of neurite outgrowth in Neuro-2a cells and dendritic spine development in primary neurons. ApoE4 did not affect trafficking of amyloid precursor protein, another AD-related protein, through the secretory pathway. Thus, domain interaction renders more newly synthesized apoE4 molecules immobile and slows their trafficking along the secretory pathway. Correcting the pathological structure of apoE4 by disrupting domain interaction is a potential therapeutic approach to treat or prevent AD related to apoE4.
载脂蛋白 E4（apoE4）是阿尔茨海默病（AD）的主要遗传风险因素，可能通过多种途径促进神经病理学。在这里，我们报告在 Neuro-2a 细胞和原代神经元中，apoE4 的细胞内转运受损，如光漂白后荧光恢复测量所示。在 Neuro-2a 细胞中，与 apoE3 分子相比，更多的 apoE4 分子固定在内质网（ER）和高尔基体中，并且 apoE4 在高尔基体中的侧向运动明显低于 apoE3（但在 ER 中没有）。同样，apoE4 的固定分数更大，其侧向运动速度也低于 apoE3 在小鼠原代海马神经元中。具有 R61T 突变的 apoE4 消除了 apoE4 结构域的相互作用，因此固定化程度较低，其侧向运动与 apoE3 相当。用小分子结构校正剂 GIND25 和 PH002 破坏结构域相互作用也可以挽救 apoE4 的转运缺陷。PH002 还挽救了 apoE4 诱导的 Neuro-2a 细胞中神经突生长和原代神经元树突棘发育受损。apoE4 不影响通过分泌途径的另一种 AD 相关蛋白淀粉样前体蛋白的转运。因此，结构域相互作用使更多新合成的 apoE4 分子固定不动，并减缓其沿分泌途径的转运。通过破坏结构域相互作用纠正 apoE4 的病理结构是治疗或预防与 apoE4 相关的 AD 的一种潜在治疗方法。
