title: Affinity purification of proteoglycans that bind to the amyloid protein precursor of Alzheimer's disease.
abstract: 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.
authors.affiliation: Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: T G
authors.initials: TG
authors.lastname: Williamson
authors.forename: V
authors.initials: V
authors.lastname: Nurcombe
authors.forename: K
authors.initials: K
authors.lastname: Beyreuther
authors.forename: C L
authors.initials: CL
authors.lastname: Masters
authors.forename: D H
authors.initials: DH
authors.lastname: Small
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002846:Chromatography, Affinity; D051379:Mice; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D011509:Proteoglycans / Q000302:isolation & purification* / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D016564:Amyloid beta-Protein Precursor; D011509:Proteoglycans