Prion protein expression in bovine podocytes and extraglomerular mesangial cells

The cellular form of the prion protein (PrPc) is thought to be a substrate for an abnormal isoform of the prion protein (PrPsc). One emerging hypothesis is that the proposed conversion phenomenon takes place at the site at which the infectious agent meets PrPc. PrPc is abundant in the central nervous system, but little is known about the cell-type-specific distribution of PrPc in non-neuronal tissues of cattle. We have studied whether PrPc, a protein found predominantly in neurons, also exists in bovine podocytes, since neurons and podocytes share a large number of similarities. We have therefore examined the expression of PrPc by immunohistochemistry, reverse transcription/polymerase chain reaction and enzyme-linked immunosorbent analysis. Immunostained serial sections and specific antibodies against PrPc have revealed that PrPc is selectively localized in podocytes and is particularly strongly expressed in extraglomerular mesangial cells but not in endothelial or intraglomerular mesangial cells. The selective expression of PrPc in podocytes is of special importance, as it suggests that these cells represent possible targets for peripheral infection with prions and demonstrates that PrPc can be added to the list of neuronal factors expressed in mammalian podocytes.