Amyloid β-protein precursor juxtamembrane domain regulates specificity of γ-secretase-dependent cleavages
Amyloid β-protein precursor juxtamembrane domain regulates specificity of γ-secretase-dependent cleavages
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DOI：
10.1074/jbc.m702739200
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发表时间：
2007-11-30
影响因子：
4.8
通讯作者：
Shapiro, I. Paul
中科院分区：
文献类型：
--
作者：
Ren, Zhao;Schenk, Dale;Shapiro, I. Paul
淀粉样β蛋白(Aβ)是阿尔茨海默病(AD)相关脑斑块的主要成分，由淀粉样β蛋白前体(APP)经β-和γ-分泌酶参与的蛋白水解酶降解而来。APP的膜内被伽马分泌酶切割发生在两个主要位置，即伽马和epsilon，尽管这些切割之间的时间和/或机制关系尚不清楚。在我们试图解决这个问题的过程中，我们发现了APP管腔近膜结构域的一个重要调节作用。我们在基于细胞的分析中证明，该区域的结构域替换可以极大地减少伽马切割产生的分泌Aβ，而不影响epsilon切割产物。这种Aβ的减少可能是由于伽马裂解部位的蛋白分解受损所致。进一步的定点突变分析发现，两个膜旁残基Lys-28和Ser-26(Aβ编号)是伽马部位有效的膜内蛋白分解的关键决定因素。越来越多的证据表明，APP的epsilon裂解先于伽马处理，这与越来越多的证据一致，细胞内检测到来自伽马裂解缺陷底物的更长的Aβ物种。这些结果表明，APP的管腔膜旁区域是一个重要的调节域，它调节依赖于γ-分泌酶的膜内蛋白分解，特别是在区分β-和γ-裂解过程中。
Amyloid beta-protein (A beta), the major component of cerebral plaques associated with Alzheimer disease, is derived from amyloid beta-protein precursor (APP) through sequential proteolytic cleavage involving beta- and gamma-secretase. The intramembrane cleavage of APP by gamma-secretase occurs at two major sites, gamma and epsilon, although the temporal and/or mechanistic relationships between these cleavages remain unknown. In our attempt to address this issue, we uncovered an important regulatory role for the APP luminal juxtamembrane domain. We demonstrated in cell-based assays that domain replacements in this region can greatly reduce secreted A beta resulting from gamma-cleavage without affecting the epsilon-cleavage product. This A beta reduction is likely due to impaired proteolysis at the gamma-cleavage site. Further analyses with site-directed mutagenesis identified two juxtamembrane residues, Lys-28 and Ser-26 ( A beta numbering), as the critical determinants for efficient intramembrane proteolysis at the gamma-site. Consistent with the growing evidence that epsilon-cleavage of APP precedes gamma- processing, longer A beta species derived from the gamma-cleavage-deficient substrates were detected intra-cellularly. These results indicate that the luminal juxtamembrane region of APP is an important regulatory domain that modulates gamma-secretase-dependent intramembrane proteolysis, particularly in differentiating beta- and gamma- cleavages.