A conserved GXXXG motif in APH-1 is critical for assembly and activity of the γ-secretase complex
A conserved GXXXG motif in APH-1 is critical for assembly and activity of the γ-secretase complex
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DOI：
10.1074/jbc.m309745200
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发表时间：
2004-02-06
影响因子：
4.8
通讯作者：
Yu, G
中科院分区：
文献类型：
--
作者：
Lee, SF;Shah, S;Yu, G
多通道膜蛋白 APH-1 与早老素、尼卡斯特林和 PEN-2 一起存在于 γ-分泌酶复合物中，对于秀丽隐杆线虫胚胎中的 Notch 信号传导至关重要，并且是哺乳动物和果蝇细胞中 Notch 和 β-淀粉样前体蛋白的膜内蛋白水解所必需的。在秀丽隐杆线虫中，APH-1（突变体 or28）中保守的跨膜 Gly(123) 的突变导致 notch/glp-1 功能丧失表型。在这项研究中，我们发现哺乳动物 APH-1a(L) (G122D) 中的相应突变破坏了 APH-1a(L) 与低糖基化的未成熟尼卡斯特林和早老素全蛋白以及与成熟尼卡斯特林、早老素和 PEN-2 的物理相互作用。 G122D 突变还降低了膜束缚 Notch 的膜内蛋白水解中的 γ 分泌酶活性。此外，我们发现哺乳动物APH-1a(L)第四跨膜区中保守的跨膜Gly(122)、Gly(126)和Gly(130)是膜螺旋-螺旋相互作用GXXXG基序的一部分，对于APH-1a(L)与早老素、尼卡斯特林和PEN-2的稳定结合至关重要。这些发现表明，APH-1 在活性 γ-分泌酶复合物的初始组装以及随后的成熟和维持中发挥 GXXXG 依赖性支架作用。
The multipass membrane protein APH-1, found in the gamma-secretase complex together with presenilin, nicastrin, and PEN-2, is essential for Notch signaling in Caenorhabditis elegans embryos and is required for intramembrane proteolysis of Notch and beta-amyloid precursor protein in mammalian and Drosophila cells. In C. elegans, a mutation of the conserved transmembrane Gly(123) in APH-1 (mutant or28) leads to a notch/glp-1 loss-of-function phenotype. In this study, we show that the corresponding mutation in mammalian APH-1a(L) (G122D) disrupts the physical interaction of APH-1a(L) with hypoglycosylated immature nicastrin and the presenilin holoprotein as well as with mature nicastrin, presenilin, and PEN-2. The G122D mutation also reduced gamma-secretase activity in intramembrane proteolysis of membrane-tethered Notch. Moreover, we found that the conserved transmembrane Gly(122), Gly(126), and Gly(130) in the fourth transmembrane region of mammalian APH-1a(L) are part of the membrane helix-helix interaction GXXXG motif and are essential for the stable association of APH-1a(L) with presenilin, nicastrin, and PEN-2. These findings suggest that APH-1 plays a GXXXG-dependent scaffolding role in both the initial assembly and subsequent maturation and maintenance of the active gamma-secretase complex.