Harvard Medical School, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America.
PLoS One. 2011 Jan 31;6(1):e14586. doi: 10.1371/journal.pone.0014586.
We applied a novel application of FLIM-FRET to in situ measurement and quantification of protein interactions to explore isoform specific differences in Aβ-ApoE interaction and ApoE tertiary conformation in senile plaques in human Alzheimer brain. ApoE3 interacts more closely with Aβ than ApoE4, but a greater proportion of Aβ molecules within plaques are decorated with ApoE4 than ApoE3, lending strong support to the hypothesis that isoform specific differences in ApoE are linked with Aβ deposition. We found an increased number of ApoE N-terminal fragments in ApoE4 plaques, consistent with the observation that ApoE4 is more easily cleaved than ApoE3. In addition, we measured a small but significant isoform specific difference in ApoE domain interaction. Based on our in situ data, supported by traditional biochemical data, we propose a pathway by which isoform specific conformational differences increase the level of cleavage at the hinge region of ApoE4, leading to a loss of ApoE function to mediate clearance of Aβ and thereby increase the risk of AD for carriers of the APOEε4 allele.
我们应用 FLIM-FRET 的新应用于原位测量和定量蛋白质相互作用，以探索 Aβ-ApoE 相互作用和 ApoE 三级构象在人类阿尔茨海默病大脑中的异构体特异性差异。与 ApoE4 相比，ApoE3 与 Aβ 相互作用更紧密，但斑块内 Aβ 分子与 ApoE4 修饰的比例大于 ApoE3，这有力地支持了 ApoE 异构体特异性差异与 Aβ 沉积相关的假设。我们发现 ApoE4 斑块中 ApoE N 端片段数量增加，这与 ApoE4 比 ApoE3 更容易被切割的观察结果一致。此外，我们还测量了 ApoE 结构域相互作用的微小但显著的异构体特异性差异。基于我们的原位数据，并得到传统生化数据的支持，我们提出了一种途径，通过该途径，异构体特异性构象差异增加了 ApoE4 铰链区域切割的水平，导致 ApoE 功能丧失，从而无法清除 Aβ，从而增加了 APOEε4 等位基因携带者患 AD 的风险。
