Identification of interaction domains of the prion protein with its 37-kDa/67-kDa laminin receptor

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Abstract
Cell‐binding and internalization studies on neuronal and non‐neuronal cells have demonstrated that the 37‐kDa/67‐kDa laminin receptor (LRP/LR) acts as the receptor for the cellular prion protein (PrP). Here we identify direct and heparan sulfate proteoglycan (HSPG)‐dependent interaction sites mediating the binding of the cellular PrP to its receptor, which we demonstrated in vitro on recombinant proteins. Mapping analyses in the yeast two‐hybrid system and cell‐binding assays identified PrPLRPbd1 [amino acids (aa) 144–179] as a direct and PrPLRPbd2 (aa 53–93) as an indirect HSPG‐dependent laminin receptor precursor (LRP)‐binding site on PrP. The yeast two‐hybrid system localized the direct PrP‐binding domain on LRP between aa 161 and 179. Expression of an LRP mutant lacking the direct PrP‐binding domain in wild‐type and mutant HSPG‐deficient Chinese hamster ovary cells by the Semliki Forest virus system demonstrates a second HSPG‐dependent PrP‐binding site on LRP. Considering the absence of LRP homodimerization and the direct and indirect LRP–PrP interaction sites, we propose a comprehensive model for the LRP–PrP–HSPG complex.