Group I mGluR signaling in BSE-infected bovine-PrP transgenic mice

Abnormalities of synapses and impaired synaptic transmission appear to be crucial in the pathogenesis of prion diseases. Excitotoxic mechanisms have been postulated as a major cause of neurodegeneration in these conditions. In this line, previous studies have shown abnormal group 1 metabotropic glutamate receptor signaling in Creutzfeldt-Jakob disease (CJD). In the present study, we have examined this pathway by western blotting in the cerebral cortex of bovine-spongiform encephalopathy (BSE)-infected bovine-PrP transgenic mice at different days post-inoculation (dpi). Activation of post-synaptic metabotropic glutamate receptor 1 (mGluR1) promotes phospholipase Cβ1 (PLCβ1) activation which may activate, in turn, protein kinase C (PKC), which regulates gene expression. Densitometric analysis of the western blot bands revealed no differences in the protein levels of (mGluR1) through time, but demonstrated decreased levels of PLCβ1 and protein kinase C delta (nPKCδ) at 270 dpi, at the time when mice showed neurological deficits accompanied by neuropathological changes and PrPres deposition in the brain. The present results show, for the first time impairment of the mGluR1/PLCβ1/PKCδ pathway signaling with disease-progression in a murine model of BSE.