Internalization and signal transduction of PrP106−126 in neuronal cells

Invasion of the nervous system and neuronal spread of infection are critical, but poorly understood steps in the pathogenesis of prion diseases. We have thus analyzed the internalization and signal transduction of the neurotoxic fragment of the prion protein PrP106-126 in the rat neuroblastoma cell line B104 by fluorescence microscopy and quantification by ELISA and in primary neuronal cells from mice. Phospholipase D (PLD) is known to be an enzyme involved in the regulation of secretion, endocytosis and receptor signalling. We determined the PLD activity using a transphosphatidylation assay and could show that PLD is involved in PrP106-126 internalization. The determination of receptor activity via quantification of ERK1/2 phosphorylation and cAMP level measurement verified the PrP106-126-induced signal transduction in B104 cells and primary neuronal cells. PrP106−126-induced a decrease in cAMP level in neuronal cells. These studies indicate the involvement of PLD in PrP106-126-endocytosis and mediated cellular signalling by an unidentified inhibitory G-protein-coupled receptor and may allow the development of therapeutic agents interfering with prion uptake and/or PLD function using PLD as a possible pharmaceutical target.