Williamson T G, Nurcombe V, Beyreuther K, Masters C L, Small D H
Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
J Neurochem. 1995 Nov;65(5):2201-8. doi: 10.1046/j.1471-4159.1995.65052201.x.
The binding of the amyloid protein precursor (APP) to heparan sulfate proteoglycans has been shown to stimulate the neurite-promoting activity of APP. In this study, proteoglycans that bind with high affinity to APP were characterized. Conditioned medium from cultures of postnatal day 3 mouse brain cells was applied to an affinity column containing a peptide homologous to a heparin-binding domain of APP. A fraction 17-fold enriched in proteoglycans was recovered by elution with a salt gradient. APP bound saturably and with high affinity to the affinity-purified proteoglycan fraction. Scatchard analysis of the binding showed that APP bound to high- and low-affinity sites with equilibrium dissociation constants of 1.4 x 10(-11) and 6.5 x 10(-10) M, respectively. APP, in conjunction with the affinity-purified proteoglycan fraction, promoted neurite outgrowth. The affinity-purified proteoglycan fraction contained a heparan sulfate proteoglycan and a chondroitin sulfate proteoglycan. Digestion of the affinity-purified fraction with heparitinase I revealed a core protein of 63-69-kDa molecular mass, whereas digestion with chondroitinase ABC revealed a core protein of 100-110 kDa. The results suggest that expression of specific APP-binding proteoglycans may be an important step in the regulation of the neurite outgrowth-promoting activity of APP.
淀粉样蛋白前体（APP）与硫酸乙酰肝素蛋白聚糖的结合已被证明可刺激APP的神经突促进活性。在本研究中，对与APP具有高亲和力结合的蛋白聚糖进行了表征。将出生后第3天小鼠脑细胞培养物的条件培养基应用于含有与APP肝素结合域同源肽的亲和柱。通过盐梯度洗脱回收了富含蛋白聚糖17倍的级分。APP以饱和且高亲和力的方式结合到亲和纯化的蛋白聚糖级分上。结合的Scatchard分析表明，APP分别以1.4×10⁻¹¹和6.5×10⁻¹⁰ M的平衡解离常数结合到高亲和力和低亲和力位点。APP与亲和纯化的蛋白聚糖级分一起促进了神经突的生长。亲和纯化的蛋白聚糖级分包含一种硫酸乙酰肝素蛋白聚糖和一种硫酸软骨素蛋白聚糖。用肝素酶I消化亲和纯化的级分，揭示了分子量为63 - 69 kDa的核心蛋白，而用软骨素酶ABC消化则揭示了100 - 110 kDa的核心蛋白。结果表明，特定APP结合蛋白聚糖的表达可能是调节APP神经突生长促进活性的重要步骤。
