Walter J, Fluhrer R, Hartung B, Willem M, Kaether C, Capell A, Lammich S, Multhaup G, Haass C
Adolf Butenandt-Institute, Department of Biochemistry, Laboratory for Alzheimer's and Parkinson's Disease Research, Ludwig-Maximilians-University, 44 Schillerstrasse, 80336 Munich, Germany.
J Biol Chem. 2001 May 4;276(18):14634-41. doi: 10.1074/jbc.M011116200. Epub 2001 Jan 29.
beta-Secretase (BACE) is a transmembrane aspartyl protease, which generates the N terminus of Alzheimer's disease amyloid beta-peptide. Here, we report that BACE can be phosphorylated within its cytoplasmic domain at serine residue 498 by casein kinase 1. Phosphorylation exclusively occurs after full maturation of BACE by propeptide cleavage and complex N-glycosylation. Phosphorylation/dephosphorylation affects the subcellular localization of BACE. BACE wild type and an S498D mutant that mimics phosphorylated BACE are predominantly located within juxtanuclear Golgi compartments and endosomes, whereas nonphosphorylatable BACE S498A accumulates in peripheral EEA1-positive endosomes. Antibody uptake assays revealed that reinternalization of BACE from the cell surface is independent of its phosphorylation state. After reinternalization, BACE wild type as well as BACE S498D are efficiently retrieved from early endosomal compartments and further targeted to later endosomal compartments and/or the trans-Golgi network. In contrast, nonphosphorylatable BACE S498A is retained within early endosomes. Our results therefore demonstrate regulated trafficking of BACE within the secretory and endocytic pathway.
β-分泌酶（BACE）是一种跨膜天冬氨酸蛋白酶，可生成阿尔茨海默病淀粉样β肽的N端。在此，我们报告BACE可在其胞质结构域内的丝氨酸残基498处被酪蛋白激酶1磷酸化。磷酸化仅在BACE通过前肽切割和复杂的N-糖基化完全成熟后发生。磷酸化/去磷酸化影响BACE的亚细胞定位。野生型BACE和模拟磷酸化BACE的S498D突变体主要位于核周高尔基体区室和内体中，而不可磷酸化的BACE S498A则积聚在周围EEA1阳性内体中。抗体摄取试验表明，BACE从细胞表面的再内化与其磷酸化状态无关。再内化后，野生型BACE以及BACE S498D可从早期内体区室有效回收，并进一步靶向晚期内体区室和/或反式高尔基体网络。相比之下，不可磷酸化的BACE S498A则保留在早期内体中。因此，我们的结果证明了BACE在分泌和内吞途径中的运输受到调控。
