Biosynthesis of Prion Protein Nucleocytoplasmic Isoforms by Alternative Initiation of Translation

María E. Juanes, Gema Elvira, Aranzazu García-Grande, Miguel Calero, María Gasset
2008 Journal of Biological Chemistry  
The cellular prion protein PrP C is synthesized as a family of four distinct forms. Of these, Cyt PrP is a minor member that segregates outside of the secretory route and can generate cytotoxic forms. Using signal sequence mutants, we found that Cyt PrP is translated from a downstream AUG (coding for Met-8 in human PrP or Met-15 in Syrian hamster PrP). Shortening of the signal sequence dictated the spillage of this isoform into the cytosol, from where it accessed the nucleus or formed insoluble
more » ... cytosolic aggregates if the proteasome is inhibited. The PrP isoform isolated from the nuclear fractions of cell and brain homogenates was partially SUMO-1-conjugated. Expression of HaPrP(M15) in cells caused an antiproliferative phenotype due to a cell cycle arrest at the G 0 /G 1 phase. The identification of this PrP isoform and its properties provides novel insight into PrP C physiological and pathological functions. . 2 The abbreviations used are: PrP, prion protein; PrP C , cellular prion protein; PrP(M15), isoform produced by translation starting at Met-15; PrP(M8), isoform produced by translation starting at Met-8; PIPLC, phosphatidylinositol-specific phospholipase C; PBS, phosphate-buffered saline; YFP, yellow fluorescent protein; SUMO, small ubiquitin-like modifier; WT, wild type; PNGase F, peptide N-glycosidase F; PDI, protein disulfide isomerase; CHO, Chinese hamster ovary; Tricine, N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine; Ha, Syrian hamster; Hu, human.
doi:10.1074/jbc.m804051200 pmid:19059915 fatcat:ag4eg6aqmrehbbuohntemomvq4