Cellular Prion Protein in the Bovine Mammary Gland Is Selectively Expressed in Active Lactocytes

Abstract

The cellular prion protein (PrPc) is a highly conserved glycoprotein with a still enigmatic physiological function. It is mainly expressed in the central nervous system but accumulating data suggest that PrPc is also found in a broad spectrum of non-neuronal tissue. Here we investigated the cell-type-related PrPc expression in the bovine mammary gland by using immunohistochemistry (IHC), ELISA, Western blot, and real-time RT-PCR. Specific immunostaining of serial sections revealed that PrPc is selectively localized in mammary gland epithelial cells. Particularly strong expression was found at the basolateral surface of those cells showing active secretion. Results obtained by RT-PCR and ELISA complemented IHC findings. No correlation was found between the level of PrPc expression and other parameters such as age of the animals under study or stage of lactation.

Distribution of Peripheral PrPSc in Sheep with Naturally Acquired Scrapie

“…In some cases, the topographical location of the immunolabeling (on the basal side of the epithelium) suggests that this pattern could be associated with nerve endings. In the case of the mammary gland and sweat glands, this location could also suggest the immunolabeling of myoepithelial cells; however, previous reports have shown that these cells do not express PrP c in the ovine mammary gland [44], [45]. Although natural scrapie infections exhibiting an intracellular immunolabeling pattern associated with the epithelial cells of the salivary glands have been previously reported [46], we classified our samples as inconclusive by IHC.…”

Quantification of PrPC in bovine peripheral tissues: Analysis in wild-type and PrPC-deficient cattle

“…PrP c is the substrate for the formation of pathologyassociated conformer PrP Sc (36). However, studies on PrP c distribution in cattle are limited (37)(38)(39). although quantitative studies of PrP c expression at the protein level have been documented in sheep, none have been attempted in cattle.…”

Progress on Milk Safety in Relation to Prion Protein

“…If animals were under inflammatory conditions, the total number of immune cells would increase in milk, it might be possible that infectious PrP Sc was also passing through and reaches the milk. Recent studies showed that PrP C was selectively localized in mammary gland epithelial cells and expressed largely at the basolateral cell surface that had active secretion [31] . PrP Sc was shed into milk from clinically normal, scrapie exposed animals, and it could be detected using serial protein misfolding cyclic amplification (sPMCA) at least 20 months before clinical onset [29] .…”

“…The protein exocytotic secretion produced epithelial cells within mammary gland, and the secretion was associated with milk fat globules, the vesicular transcytosis of serum-and stromal cell-derived proteins as well as through a paracellular transport system that was responsible for the secretion of plasma components and leukocytes [27] . Onecase demonstrated that bovine PrP C was selectively localized in mammary gland epithelial cells and expressed largely at the basolateral cell surface that showed active secretion [31] . The existence of PrP C in mammary gland cells supported the hypothesis that the apocrine secretion mode of milk fat globules was a major transporting way into the milk [26] .…”