title: Identification of secreted beta-amyloid precursor protein binding sites on intact human fibroblasts.
abstract: Based upon recent evidence that the secreted form of APP can cause the release of cytokines and elicit other biological activities, we sought to identify whether a receptor could be identified on the surface of cells. The secreted amyloid precursor protein containing the Kunitz domain (scAPP751) is identical to protease nexin II, a protease inhibitor which has been shown to form complexes with labeled EGF binding protein that subsequently binds to cells. Results of [125I]scAPP751-trypsin complex incubated with intact fibroblast cells show that the complex appears to bind in a saturable time-dependent and reversible manner. The kinetic constants from the binding studies demonstrate a k1 = 2.5 x 10(7) M-1 s-1 and k2 = 4.7 x 10(-4) s-1 and thus a KD (= k2/k1) = 20 pM. Furthermore, the complex formation of [125I]scAPP751 with a protease appears to be a requirement for optimal binding. The binding affinity of secreted APP demonstrated in this study is consistent with its potency in eliminating a range of biological efforts that have been documented.
authors.affiliation: Athena Neurosciences, Inc., South San Francisco, CA 94080.
authors.forename: K L
authors.initials: KL
authors.lastname: Johnson-Wood
authors.forename: T
authors.initials: T
authors.lastname: Henriksson
authors.forename: P
authors.initials: P
authors.lastname: Seubert
authors.forename: T
authors.initials: T
authors.lastname: Oltersdorf
authors.forename: I
authors.initials: I
authors.lastname: Lieberburg
authors.forename: D B
authors.initials: DB
authors.lastname: Schenk
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D011994:Recombinant Proteins; D012995:Solubility
chemical_list: D016564:Amyloid beta-Protein Precursor; D011994:Recombinant Proteins