Williamson T G, Mok S S, Henry A, Cappai R, Lander A D, Nurcombe V, Beyreuther K, Masters C L, Small D H
Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
J Biol Chem. 1996 Dec 6;271(49):31215-21. doi: 10.1074/jbc.271.49.31215.
The amyloid precursor protein (APP) of Alzheimer's disease has been shown to stimulate neurite outgrowth in vitro. The effect of APP on neurite outgrowth can be enhanced if APP is presented to neurons in substrate-bound form, in the presence of heparan sulfate proteoglycans. To identify specific heparan sulfate proteoglycans that bind to APP, conditioned medium from neonatal mouse brain cells was subjected to affinity chromatography with recombinant APP695 as a ligand. Glypican bound strongly to the APP affinity column. Purified glypican bound to APP with an equilibrium dissociation constant of 2.8 nM and inhibited APP-induced neurite outgrowth from chick sympathetic neurons. The effect of glypican was specific for APP, as glypican did not inhibit laminin-induced neurite outgrowth. Furthermore, treatment of cultures with 4-methylumbelliferyl-beta-D-xyloside, a competitive inhibitor of proteoglycan glycanation, inhibited APP-induced neurite outgrowth but did not inhibit laminin-induced neurite outgrowth. This result suggests that endogenous proteoglycans are required for substrate-bound APP to stimulate neurite outgrowth. Secreted glypican may act to inhibit APP-induced neurite outgrowth in vivo by competing with endogenous proteoglycans for binding to APP.
阿尔茨海默病的淀粉样前体蛋白（APP）已被证明在体外可刺激神经突生长。如果APP以与底物结合的形式，在硫酸乙酰肝素蛋白聚糖存在的情况下作用于神经元，其对神经突生长的影响会增强。为了鉴定与APP结合的特定硫酸乙酰肝素蛋白聚糖，将新生小鼠脑细胞的条件培养基用重组APP695作为配体进行亲和层析。磷脂酰肌醇蛋白聚糖强烈结合到APP亲和柱上。纯化的磷脂酰肌醇蛋白聚糖以2.8 nM的平衡解离常数与APP结合，并抑制APP诱导的鸡交感神经元神经突生长。磷脂酰肌醇蛋白聚糖对APP的作用具有特异性，因为它不抑制层粘连蛋白诱导的神经突生长。此外，用4-甲基伞形酮基-β-D-木糖苷（一种蛋白聚糖糖基化竞争性抑制剂）处理培养物，可抑制APP诱导的神经突生长，但不抑制层粘连蛋白诱导的神经突生长。这一结果表明，底物结合的APP刺激神经突生长需要内源性蛋白聚糖。分泌的磷脂酰肌醇蛋白聚糖可能通过与内源性蛋白聚糖竞争结合APP，在体内抑制APP诱导的神经突生长。
