A novel epitope for the specific detection of exogenous prion proteins in transgenic mice and transfected murine cell lines

Prion diseases are closely linked to the conversion of host-encoded cellula r prion protein (PrPC) into its pathological isoform (PrPSc). PrP conversio n experiments in scrapie infected tissue culture cells, transgenic mice, an d cell-free systems usually require unique epitopes and corresponding monoc lonal antibodies (MAbs) for the immunological discrimination of exogenously introduced and endogenous PrP compounds (e.g., MAb 3F4, which is directed to an epitope on hamster and human but not on murine PrP). In the current w ork, we characterize a novel MAb designated L42 that reacts to PrP of a var iety of species, including cattle, sheep, goat, dog, human, cat, mink, rabb it, and guinea pig, but does not bind to mouse, hamster, and rat PrP. There fore, MAb L42 may allow future in vitro conversion and transgenic studies o n PrPs of the former species. The MAb L42 epitope on PrPC includes a tyrosi ne residue at position 144, whereas mouse, rat, and hamster PrPs incorporat e tryptophane at this site. To verify this observation, we generated PrP ex pression vectors coding for authentic or mutated murine PrP(C)s (i.e., codo n 144 encoding tyrosine instead of tryptophan). After transfection into neu roblastoma cells, MAb L42 did not react with immunoblotted wild-type murine PrPC, whereas L42 epitope-tagged murine PrPC was strongly recognized. Immu noblot and fluorescence-activated cell sorting data revealed that tagged Pr PC was correctly posttranslationally processed and translocated to the cell surface; (C) 1999 Academic Press.