Scholefield Zoe, Yates Edwin A, Wayne Gareth, Amour Augustin, McDowell William, Turnbull Jeremy E
School of Biosciences, University of Birmingham, Birmingham, UK.
J Cell Biol. 2003 Oct 13;163(1):97-107. doi: 10.1083/jcb.200303059. Epub 2003 Oct 6.
Cleavage of amyloid precursor protein (APP) by the Alzheimer's beta-secretase (BACE1) is a key step in generating amyloid beta-peptide, the main component of amyloid plaques. Here we report evidence that heparan sulfate (HS) interacts with beta-site APP-cleaving enzyme (BACE) 1 and regulates its cleavage of APP. We show that HS and heparin interact directly with BACE1 and inhibit in vitro processing of peptide and APP substrates. Inhibitory activity is dependent on saccharide size and specific structural characteristics, and the mechanism of action involves blocking access of substrate to the active site. In cellular assays, HS specifically inhibits BACE1 cleavage of APP but not alternative cleavage by alpha-secretase. Endogenous HS immunoprecipitates with BACE1 and colocalizes with BACE1 in the Golgi complex and at the cell surface, two of its putative sites of action. Furthermore, inhibition of cellular HS synthesis results in enhanced BACE1 activity. Our findings identify HS as a natural regulator of BACE1 and suggest a novel mechanism for control of APP processing.
阿尔茨海默病β-分泌酶（BACE1）切割淀粉样前体蛋白（APP）是生成淀粉样β肽的关键步骤，淀粉样β肽是淀粉样斑块的主要成分。在此我们报告证据表明，硫酸乙酰肝素（HS）与β位点APP切割酶（BACE）1相互作用并调节其对APP的切割。我们发现HS和肝素直接与BACE1相互作用，并抑制肽和APP底物的体外加工。抑制活性取决于糖的大小和特定结构特征，作用机制涉及阻止底物进入活性位点。在细胞试验中，HS特异性抑制BACE1对APP的切割，但不抑制α-分泌酶的替代性切割。内源性HS与BACE1免疫共沉淀，并在高尔基体复合体和细胞表面与BACE1共定位，这是其两个假定的作用位点。此外，抑制细胞HS合成会导致BACE1活性增强。我们的研究结果确定HS是BACE1的天然调节剂，并提示了一种控制APP加工的新机制。
