Intra- or intercomplex binding to the γ-secretase enzyme
Intra- or intercomplex binding to the γ-secretase enzyme
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DOI：
10.1074/jbc.m605051200
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发表时间：
2006-10-20
影响因子：
4.8
通讯作者：
Beher, Dirk
中科院分区：
文献类型：
--
作者：
Clarke, Earl E.;Churcher, Ian;Beher, Dirk
γ-分泌酶是从β-淀粉样前体蛋白产生淀粉样β肽所需的关键酶之一。由于淀粉样β肽被普遍认为在阿尔茨海默病中起关键作用，因此γ-分泌酶抑制剂有望成为这种神经退行性疾病的疾病修饰疗法。虽然最近的进展已经加强了对γ-分泌酶复合物的生物学和组成的理解，但关于各种抑制剂与酶的实际相互作用的信息较少。在这里，我们表明，在科学和专利文献中描述的两个主要类别的抑制剂，乙酰基蛋白酶过渡态类似物和小分子非过渡态抑制剂，显示它们与酶相互作用的方式的根本差异。利用γ-分泌酶过表达的细胞系统和不同的放射性标记的γ-分泌酶抑制剂，我们观察到，非过渡态γ-分泌酶抑制剂的最大结合仅占重组酶复合物催化位点数量的一半。这种特征化学计量可以最好地适应于非过渡态抑制剂结合到二聚酶界面处的独特位点的模型。随后的竞争研究证实，该位点似乎是主要类别的小分子γ-分泌酶抑制剂的靶向位点。相比之下，非甾体抗炎药γ-分泌酶调节剂舒林酸硫化物对所有类型的抑制剂都表现出非竞争性拮抗作用。这一发现表明，非甾体抗炎药型γ-分泌酶调节剂靶向酶上的替代位点，从而改变γ-分泌酶抑制剂结合位点的构象。
gamma-Secretase is one of the critical enzymes required for the generation of amyloid-beta peptides from the beta-amyloid precursor protein. Because amyloid-beta peptides are generally accepted to play a key role in Alzheimer disease, gamma-secretase inhibition holds the promise for a disease-modifying therapy for this neurodegenerative condition. Although recent progress has enhanced the understanding of the biology and composition of the gamma-secretase enzyme complex, less information is available on the actual interaction of various inhibitor classes with the enzyme. Here we show that the two principal classes of inhibitor described in the scientific and patent literature, aspartyl protease transition state analogue and small molecule non-transition state inhibitors, display fundamental differences in the way they interact with the enzyme. Taking advantage of a gamma-secretase enzyme overexpressing cellular system and different radiolabeled gamma-secretase inhibitors, we observed that the maximal binding of nontransition state gamma-secretase inhibitors accounts only for half the number of catalytic sites of the recombinant enzyme complex. This characteristic stoichiometry can be best accommodated with a model whereby the non-transition state inhibitors bind to a unique site at the interface of a dimeric enzyme. Subsequent competition studies confirm that this site appears to be targeted by the main classes of small molecule gamma-secretase inhibitor. In contrast, the non-steroidal anti-inflammatory drug gamma-secretase modulator sulindac sulfide displayed noncompetitive antagonism for all types of inhibitor. This finding suggests that non-steroidal anti-inflammatory drug-type gamma-secretase modulators target an alternative site on the enzyme, thereby changing the conformation of the binding sites for gamma-secretase inhibitors.