Cellular prion protein is expressed in a subset of neuroendocrine cells of the rat gastrointestinal tract.
Prion diseases are believed to develop from the conformational change of normal cellular prion protein (PrPc) to a pathogenic isoform (PrPsc). PrPc is present in both the central nervous system and many peripheral tissues, although protein concentration is significantly lower in non-neuronal tissues. PrPc expression is essential for internalization and replication of the infectious agent. Several works have pointed to the gastrointestinal (GI) tract as the principal site of entry of PrPsc, but how passage through the GI mucosa occurs is not yet known. Here we studied PrPc expression using Western blot, RT-PCR, and immunohistochemistry in rat GI tract. PrPc mRNA and protein were detected in corpus, antrum, duodenum, and colon. Immunoreactivity was found in scattered cells of the GI epithelium. With double immunofluorescence, these cells have been identified as neuroendocrine cells. PrPc immunostaining was found in subsets of histamine, somatostatin (Som), ghrelin, gastrin (G), and serotonin (5HT) cells in stomach. In small and large bowel, PrPc cells co-localized with subpopulations of 5HT-, Som-, G-, and peptide YY-immunolabeled cells. Our results provide evidence for a possible and important role of endocrine cells in the internalization of PrPsc from gut lumen.