Loss of Prion Protein Leads to Age-Dependent Behavioral Abnormalities and Changes in Cytoskeletal Protein Expression

The cellular prion protein (PrPC) is a highly conserved protein whose exact physiological role remains elusive. In the present study, we investigated age-dependent behavioral abnormalities in PrPC-knockout (Prnp0/0) mice and wildtype (WT) controls. Prnp0/0 mice showed age-dependent behavioral deficits in memory performance, associative learning, basal anxiety, and nest building behavior. Using a hypothesis-free quantitative proteomic investigation, we found that loss of PrPC affected the levels of neurofilament proteins in an age-dependent manner. In order to understand the biochemical basis of these observations, we analyzed the phosphorylation status of neurofilament heavy chain (NF-H). We found a reduction in NF-H phosphorylation in both Prnp0/0 mice and in PrPC-deficient cells. The expression of Fyn and phospho-Fyn, a potential regulator for NF phosphorylation, was associated with PrPC ablation. The number of beta-tubulin III-positive neurons in the hippocampus was diminished in Prnp0/0 mice relative to WT mice. These data indicate that PrPC plays an important role in cytoskeletal organization, brain function, and age-related neuroprotection. Our work represents the first direct biochemical link between these proteins and the observed behavioral phenotypes.