Functional implications of the presenilin dimerization -: Reconstitution of γ-secretase activity by assembly of a catalytic site at the dimer interface of two catalytically inactive presenilins
Functional implications of the presenilin dimerization -: Reconstitution of γ-secretase activity by assembly of a catalytic site at the dimer interface of two catalytically inactive presenilins
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DOI：
10.1074/jbc.m404832200
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发表时间：
2004-08-27
影响因子：
4.8
通讯作者：
Marfany, G
中科院分区：
文献类型：
--
作者：
Cervantes, S;Saura, CA;Marfany, G
早老素是γ -分泌酶的催化成分，γ -分泌酶是一种膜内切割蛋白酶，其底物包括β -淀粉样前体蛋白（betaAPP）和Notch受体。这些I型跨膜蛋白在跨膜区域经历两种不同的早老素依赖的裂解，导致细胞内域（由betaAPP）产生Abeta和APP以及细胞内域Notch信号肽。大多数家族性阿尔茨海默病是由早老素突变引起的，这些突变分散在整个编码序列中。虽然潜在的分子机制尚不清楚，但家族性阿尔茨海默病突变会导致γ分泌酶产生的长和短形式的β肽的比例发生变化。我们和其他人之前已经证明早老素同二聚体，并表明早老素二聚体是γ -分泌酶的催化核心。在这里，我们证明早老素跨膜结构域有助于二聚体的形成。位于跨膜I和II之间的亲水性环1的框架内取代，调节n端片段/ n端片段二聚体内的相互作用，消除早老素酶和γ -分泌酶的活性。此外，通过重建两个催化失活的早老素天冬氨酸突变体的γ -分泌酶活性，我们提供了在两个早老素单体之间的界面上组装有活性的天门冬氨酸基团的证据。在我们的实验条件下，该催化基团介导了APP胞内结构域和Abeta的生成，但不介导Notch胞内结构域的生成，这表明在γ -分泌酶的早老素催化核心内的特定diaspartyl基团介导了不同底物的裂解。
Presenilins are the catalytic components of gamma-secretase, an intramembrane-cleaving protease whose substrates include beta-amyloid precursor protein (betaAPP) and the Notch receptors. These type I transmembrane proteins undergo two distinct presenilin-dependent cleavages within the transmembrane region, which result in the production of Abeta and APP intracellular domain (from betaAPP) and the Notch intracellular domain signaling peptide. Most cases of familial Alzheimer's disease are caused by presenilin mutations, which are scattered throughout the coding sequence. Although the underlying molecular mechanism is not yet known, the familial Alzheimer's disease mutations produce a shift in the ratio of the long and short forms of the Abeta peptide generated by the gamma-secretase. We and others have previously shown that presenilin homodimerizes and suggested that a presenilin dimer is at the catalytic core of gamma-secretase. Here, we demonstrate that presenilin transmembrane domains contribute to the formation of the dimer. In-frame substitution of the hydrophilic loop 1, located between transmembranes I and II, which modulates the interactions within the N-terminal fragment/N-terminal fragment dimer, abolishes both presenilinase and gamma-secretase activities. In addition, by reconstituting gamma-secretase activity from two catalytically inactive presenilin aspartic mutants, we provide evidence of an active diaspartyl group assembled at the interface between two presenilin monomers. Under our conditions, this catalytic group mediates the generation of APP intracellular domain and Abeta but not Notch intracellular domain, therefore suggesting that specific diaspartyl groups within the presenilin catalytic core of gamma-secretase mediate the cleavage of different substrates.