Okochi Masayasu, Steiner Harald, Fukumori Akio, Tanii Hisashi, Tomita Taisuke, Tanaka Toshihisa, Iwatsubo Takeshi, Kudo Takashi, Takeda Masatoshi, Haass Christian
Department of Post-Genomics and Diseases, Division of Psychiatry and Behavioral Proteomics, Osaka University Graduate School of Medicine, 565-0871 Osaka, Japan.
EMBO J. 2002 Oct 15;21(20):5408-16. doi: 10.1093/emboj/cdf541.
Following ectodomain shedding, Notch-1 undergoes presenilin (PS)-dependent constitutive intramembranous endoproteolysis at site-3. This cleavage is similar to the PS-dependent gamma-secretase cleavage of the beta-amyloid precursor protein (betaAPP). However, topological differences in cleavage resulting in amyloid beta-peptide (Abeta) or the Notch-1 intracellular domain (NICD) indicated independent mechanisms of proteolytic cleavage. We now demonstrate the secretion of an N-terminal Notch-1 Abeta-like fragment (Nbeta). Analysis of Nbeta by MALDI-TOF MS revealed that Nbeta is cleaved at a novel site (site-4, S4) near the middle of the transmembrane domain. Like the corresponding cleavage of betaAPP at position 40 and 42 of the Abeta domain, S4 cleavage is PS dependent. The precision of this cleavage is affected by familial Alzheimer's disease-associated PS1 mutations similar to the pathological endoproteolysis of betaAPP. Considering these similarities between intramembranous processing of Notch and betaAPP, we conclude that these proteins are cleaved by a common mechanism utilizing the same protease, i.e. PS/gamma-secretase.
在胞外结构域脱落之后，Notch-1在3位点经历早老素（PS）依赖的组成型膜内蛋白水解。这种切割类似于β-淀粉样前体蛋白（βAPP）的PS依赖的γ-分泌酶切割。然而，导致淀粉样β肽（Aβ）或Notch-1细胞内结构域（NICD）的切割在拓扑结构上的差异表明蛋白水解切割的机制是独立的。我们现在证明了一种N端Notch-1 Aβ样片段（Nβ）的分泌。通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）对Nβ进行分析显示，Nβ在跨膜结构域中部附近的一个新位点（4位点，S4）被切割。与βAPP在Aβ结构域40和42位的相应切割一样，S4切割是PS依赖的。这种切割的精确性受到与家族性阿尔茨海默病相关的PS1突变的影响，类似于βAPP的病理性蛋白水解。考虑到Notch和βAPP膜内加工之间的这些相似性，我们得出结论，这些蛋白质是通过利用相同蛋白酶即PS/γ-分泌酶的共同机制进行切割的。
