1Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550 Sant Joan d'Alacant, Spain.
FASEB J. 2014 Apr;28(4):1543-54. doi: 10.1096/fj.13-239350. Epub 2013 Dec 16.
The reelin signaling protein and its downstream components have been associated with synaptic plasticity and neurotransmission. The reelin signaling pathway begins with the binding of reelin to the transmembrane lipoprotein receptor apolipoprotein E receptor 2 (ApoER2), which in turns induces the sequential cleavage of ApoER2 by the sequential action of α- and γ-secretases. Using conditional-knockout mice of the catalytic component of the γ-secretase complex, presenilin 1 (PS1), we demonstrated increased brain ApoER2 and reelin protein and transcript levels, with no changes in the number of reelin-positive cells. Using the human SH-SY5Y neuroblastoma cell line, we showed that ApoER2 processing occurs in the presence of PS1, producing an intracellular ApoER2 C-terminal fragment. In addition, the pharmacologic inhibition of γ-secretase in SH-SY5Y cells led to increased reelin levels. Overexpression of ApoER2 decreased reelin mRNA levels in these cells. A luciferase reporter gene assay and nuclear fractionation confirmed that increased amounts of intracellular fragment of ApoER2 suppressed reelin expression at a transcriptional level. Chromatin immunoprecipitation experiments corroborated that the intracellular fragment of ApoER2 bound to the RELN promoter region. Our study suggests that PS1/γ-secretase-dependent processing of the reelin receptor ApoER2 inhibits reelin expression and may regulate its signaling.
Reelin 信号蛋白及其下游成分与突触可塑性和神经递质传递有关。Reelin 信号通路始于 Reelin 与跨膜脂蛋白受体载脂蛋白 E 受体 2（ApoER2）结合，ApoER2 依次被 α-和 γ-分泌酶的顺序作用切割。我们使用 γ-分泌酶复合物催化成分早老素 1（PS1）的条件性敲除小鼠，证明了大脑 ApoER2 和 Reelin 蛋白和转录本水平增加，而 Reelin 阳性细胞数量没有变化。使用人 SH-SY5Y 神经母细胞瘤细胞系，我们表明 ApoER2 加工发生在 PS1 的存在下，产生 ApoER2 胞内 C 端片段。此外，在 SH-SY5Y 细胞中用药物抑制 γ-分泌酶会导致 Reelin 水平升高。ApoER2 的过表达降低了这些细胞中的 Reelin mRNA 水平。荧光素酶报告基因测定和核分馏证实，增加的 ApoER2 胞内片段在转录水平上抑制 Reelin 表达。染色质免疫沉淀实验证实 ApoER2 的胞内片段与 RELN 启动子区域结合。我们的研究表明，PS1/γ-分泌酶依赖性处理 Reelin 受体 ApoER2 抑制 Reelin 表达并可能调节其信号转导。
