Unnatural Amino Acid-Substituted (Hydroxyethyl)urea Peptidomimetics Inhibit γ-Secretase and Promote the Neuronal Differentiation of Neuroblastoma Cells
作者:Yung-Feng Liao、Bo-Jeng Wang、Wen-Ming Hsu、Hsinyu Lee、Chia-Yin Liao、Shin-Ying Wu、Hui-Ting Cheng、Ming-Kuan Hu
DOI:10.1124/mol.106.024299
日期:2007.2
γ-Secretase, exhibiting characteristics of aspartyl protease, mediates the intramembranous proteolysis of β-amyloid precursor protein (APP) and Notch, and it is considered to be a prime pharmacological target in the development of therapeutics for Alzheimer's disease (AD). To identify compounds that block γ-secretase-mediated proteolysis, we used a highly sensitive cell-based reporter gene assay for γ-secretase in which Gal4/VP16-tagged C99-APP was expressed as the immediate substrate of γ-secretase, and Gal4/VP16-tagged APP intracellular domain released by the γ-secretase cleavage then activated the expression of the Gal4-driven luciferase reporter gene. Using this reporter assay, we demonstrated that the newly synthesized (hydroxyethyl)urea peptidomimetics, which contain unnatural amino acid moieties at positions P1′ and/or P3′, can effectively inhibit γ-secretase activity and significantly reduce Aβ production. The γ-secretase-dependent S3 cleavage of Notch was also consistently blocked by these (hydroxyethyl)ureas as evidenced by the decreased generation of the Notch intracellular domain, a prerequisite for the activation of Notch signaling. The inhibition of Notch signaling by active Jia compounds efficiently promotes the neuronal differentiation of neuroblastoma cells, intervening in tumorigenesis and the malignancy of neuroblastomas. Our results suggest that (hydroxyethyl)urea peptidomimetics containing unnatural amino acid substitutions could represent a novel class of γ-secretase inhibitors with enhanced stability, providing the basis for the further development of effective therapeutics for AD and neuroblastomas.
γ-分泌酶作为一种天冬氨酸蛋白酶,介导β淀粉样蛋白前体蛋白(APP)和Notch的跨膜蛋白水解作用,被认为是阿尔茨海默病(AD)治疗药物开发的主要药理学靶点。为了鉴定阻断γ-分泌酶介导的蛋白水解作用的化合物,我们使用了一种高度灵敏的基于细胞的报告基因检测方法,其中表达Gal4/VP16标记的C99-APP作为γ-分泌酶的直接底物,经过γ-分泌酶切割释放的Gal4/VP16标记的APP胞内域激活Gal4驱动的荧光素酶报告基因的表达。利用这一报告检测方法,我们证明新合成的(羟乙基)脲类拟肽,在P1′和/或P3′位置含有非天然氨基酸基团,能有效抑制γ-分泌酶活性并显著减少Aβ产生。γ-分泌酶依赖的Notch S3切割也被这些(羟乙基)脲类持续阻断,通过减少Notch胞内域的生成来证实,这是Notch信号激活的前提。活性Jia化合物抑制Notch信号有效地促进神经母细胞瘤细胞的神经分化,干预神经母细胞瘤的形成和恶性。我们的结果表明,含有非天然氨基酸替代的(羟乙基)脲类拟肽可能代表一类新的具有增强稳定性的γ-分泌酶抑制剂,为进一步开发有效的AD和神经母细胞瘤治疗药物提供了基础。