Hansson Emil M, Strömberg Kia, Bergstedt Susanne, Yu Gang, Näslund Jan, Lundkvist Johan, Lendahl Urban
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, Stockholm, Sweden.
J Neurochem. 2005 Mar;92(5):1010-20. doi: 10.1111/j.1471-4159.2004.02926.x.
The activity of the gamma-secretase complex is critical for the processing of a number of transmembrane proteins, including Notch. Functional gamma-secretase activity can be reconstituted from four proteins--presenilin, nicastrin, Pen-2 and Aph-1--but the role of the individual proteins remains unclear. In this report we describe the cellular localization and protein interactions of Aph-1, with particular regard to Notch receptor processing. We found that Aph-1 is present at the cell surface, where it interacts with Pen-2, the mature forms of presenilin and nicastrin, and full-length Notch. Aph-1 also interacts with a truncated form of Notch, which is a direct substrate for gamma-secretase, but not with the Notch intracellular domain. Immunoprecipitation data for Notch and Aph-1 showed that the Notch-containing gamma-secretase complexes most likely form a small subset of the total number of gamma-secretase complexes. In conclusion, these data demonstrate that Aph-1 is present at the cell surface, presumably in active gamma-secretase complexes, and interacts with the Notch receptor, both before and after ligand activation.
γ-分泌酶复合物的活性对于包括Notch在内的多种跨膜蛋白的加工至关重要。功能性γ-分泌酶活性可由四种蛋白质——早老素、尼卡斯特林、Pen-2和Aph-1重组而成，但单个蛋白质的作用仍不清楚。在本报告中，我们描述了Aph-1的细胞定位和蛋白质相互作用，特别是关于Notch受体加工方面。我们发现Aph-1存在于细胞表面，在那里它与Pen-2、早老素和尼卡斯特林的成熟形式以及全长Notch相互作用。Aph-1还与Notch的截短形式相互作用，后者是γ-分泌酶的直接底物，但不与Notch细胞内结构域相互作用。Notch和Aph-1的免疫沉淀数据表明，含Notch的γ-分泌酶复合物很可能仅占γ-分泌酶复合物总数的一小部分。总之，这些数据表明Aph-1存在于细胞表面，可能存在于活性γ-分泌酶复合物中，并在配体激活前后与Notch受体相互作用。
