Activation of phospholipase A 2 (PLA 2) and the subsequent metabolism of arachidonic acid (AA) to prostaglandins have been shown to play an important role in neuronal death in neurodegenerative disease. Here we report the effects of the prion peptide fragment HuPrP106-126 on the PLA 2 cascade in primary cortical neurons and translocation of cPLA 2 to neurites.
Exposure of primary cortical neurons to HuPrP106-126 increased the levels of phosphorylated cPLA 2 and caused phosphorylated cPLA 2 to relocate from the cell body to the cellular neurite in a PrP-dependent manner, a previously unreported observation. HuPrP106-126 also induced significant AA release, an indicator of cPLA 2 activation; this preceded synapse damage and subsequent cellular death. The novel translocation of p-cPLA 2 postulated the potential for exposure to HuPrP106-126 to result in a re-arrangement of the cellular cytoskeleton. However p-cPLA 2 did not colocalise significantly with F-actin, intermediate filaments, or microtubule-associated proteins. Conversely, p-cPLA 2 did significantly colocalise with the cytoskeletal protein beta III tubulin. Pre-treatment with the PLA 2 inhibitor, palmitoyl trifluoromethyl ketone (PACOCF 3) reduced cPLA 2 activation, AA release and damage to the neuronal synapse. Furthermore, PACOCF 3 reduced expression of p-cPLA 2 in neurites and inhibited colocalisation with beta III tubulin, resulting in protection against PrP-induced cell death.
Collectively, these findings suggest that cPLA 2 plays a vital role in the action of HuPrP106-126 and that the colocalisation of p-cPLA 2 with beta III tubulin could be central to the progress of neurodegeneration caused by prion peptides. Further work is needed to define exactly how PLA 2 inhibitors protect neurons from peptide-induced toxicity and how this relates to intracellular structural changes occurring in neurodegeneration.