Cellular isoform of the prion protein PrPc in human intestinal cell lines: Genetic polymorphism at codon 129, mRNA quantification and protein detection in lipid rafts

The cellular isoform of the normal prion protein PrPc, encoded by the PRNP gene, is expressed in human intestinal epithelial cells where it may represent a potential target for infectious prions. We have sequenced the PRNP gene in Caco-2 and HT-29 parental and clonal cell lines, and found that these cells have a distinct polymorphism at codon 129. HT-29 cells are homozygous Met/Met, whereas Caco-2 cells are heterozygous Met/Val. The 129Val variant was also detected in Caco-2 mRNAs. Real-time PCR quantifications revealed that PrPc mRNAs were more expressed in HT-29 cells than in Caco-2 cells. These data were confirmed by studying the expression of PrPc in plasma membranes and lipid rafts prepared from these cells. Overall, these results may be important in view of using human intestinal cell lines Caco-2 and HT-29 as cellular in vitro models to study the initial steps of prion propagation after oral inoculation.