Abstract
The soluble Nterminal ectodomain of amyloid precursor protein (sAPP), resulting from secretasemediated proteolytic processing, has been shown to function as a growth factor for epithelial cells, including keratinocytes and thyrocytes. Extracellularly applied sAPP binds to a cell surface receptor and exhibits a patchy binding pattern reminiscent of that observed for raft proteins. Here we show that (i) the receptorbound sAPP resides in a detergentinsoluble membrane microdomain which cofractionates in density gradients with cholesterolrich membrane rafts and caveolae; (ii) the sAPPbinding microdomains are different from caveolae; and (iii) sAPP is capable of binding to isolated rafts and inducing tyrosine phosphorylation of some raft proteins. These observations suggest that a novel type of membrane raft is involved in sAPP signaling.
Copyright © 2002 by Walter de Gruyter GmbH & Co. KG
