Mutations in the transmembrane domain of APP altering gamma-secretase specificity
Mutations in the transmembrane domain of APP altering gamma-secretase specificity
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DOI：
10.1021/bi971071m
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发表时间：
1997-12-09
期刊：
影响因子：
2.9
通讯作者：
Beyreuther, K
中科院分区：
文献类型：
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作者：
Lichtenthaler, SF;Ida, N;Beyreuther, K
阿尔茨海默病 (AD) β-淀粉样肽（Aβ 和 βA4）是通过迄今为止尚未鉴定的 β 和 γ 分泌酶的后续作用衍生自淀粉样前体蛋白 (APP)。 γ-分泌酶产生 A beta 的 C 末端，在 APP 的跨膜结构域内裂解，优先在 A beta 残基 40 (A beta 40) 之后，也在残基 42 (A beta 42) 之后裂解。该 A beta 42 代表 AD 斑块的主要亚基，由于 γ 分泌酶裂解的位置对于理解致病途径至关重要，因此我们研究了 Thr43 的不同点突变对表达 SPA4CT (SPC99) 的 COS7 细胞中 γ 分泌酶特异性的影响。这些构建体仅需要 γ 裂解即可释放 A beta。我们观察到所有 Thr43 突变都会改变 γ 分泌酶的特异性。小的疏水性残基有利于Aβ42的产生，导致Aβ的42/40比率增加（1.6-2.8倍），当与家族突变Val46Phe结合时，这种增加甚至更强（5.6-5.8倍）。因此，这些构建体对于 AD 动物模型的生成可能非常有价值。全长 APP 或 SPA4CT 的处理产生了相同的 42/40 比率的 A beta (4.7%)。两种带有家族性 AD 突变 Val46Phe 的构建体均导致 42/40 比率类似的增加（3.3 倍与 3.6 倍）。由 α 和 γ 分泌酶产生的 p3 片段，当源自野生型和突变蛋白时，显示出与 A β 相似的 42/40 比率。这些结果表明，不同的 A β 和 p3 物种是由具有类似酶促机制的 γ 裂解活性产生的。
Alzheimer's disease (AD) beta-amyloid peptide (A beta and beta A4) is derived from the amyloid precursor protein (APP) by the subsequent action of the so-far unidentified beta- and gamma-secretases. gamma-secretase, which generates the C-terminus of A beta, cleaves within the transmembrane domain of APP, preferentially after A beta-residue 40 (A beta 40) but also after residue 42 (A beta 42). This A beta 42 represents the major subunit of the plaques in AD, Since the position of gamma-secretase cleavage is crucial for understanding the pathogenic pathway, we investigated the effect of different point mutations at Thr43 on gamma-secretase specificity in SPA4CT (SPC99)-expressing COS7 cells. These constructs only require gamma-cleavage for A beta release. We observed that all Thr43 mutations altered the specificity of gamma-secretase. Small hydrophobic residues favored the generation of A beta 42, leading to an increase in the 42/40 ratio of A beta (1.6-2.8-fold), The increase was even stronger (5.6-5.8-fold) when combined with the familial mutation Val46Phe. Thus, these constructs might be highly valuable for the generation of animal models for AD. Processing of full-length APP or SPA4CT yielded the same 42/40 ratio of A beta (4.7%). Both constructs, bearing the familial AD mutation Val46Phe, led to a similar increase in the 42/40 ratio (3.3- versus 3.6-fold). The p3 fragment, produced by alpha- and gamma-secretase, showed 42/40 ratios similar to A beta when derived from wild-type and mutant proteins, These results suggest that the different A beta- and p3-species are generated by gamma-cleavage activities with a similar enzymatic mechanism.