Changes in cellular prion protein expression, processing and localisation during differentiation of the neuronal cell line CAD 5

Background information Cellular prion protein (PrP C ) is infamous for its role in prion diseases. The physiological function of PrP C remains enigmatic, but several studies point to its involvement in cell differentiation processes. To test this possibility, we monitored PrP C changes during the differentiation of prion‐susceptible CAD 5 cells, and then we analysed the effect of PrP C ablation on the differentiation process. Results Neuronal CAD 5 cells differentiate within 5 days of serum withdrawal, with the majority of the cells developing long neurites. This process is accompanied by an up to sixfold increase in PrP C expression and enhanced N‐terminal β‐cleavage of the protein, which suggests a role for the PrP C in the differentiation process. Moreover, the majority of PrP C in differentiated cells is inside the cell, and a large proportion of the protein does not associate with membrane lipid rafts. In contrast, PrP C in proliferating cells is found mostly on the cytoplasmic membrane and is predominantly associated with lipid rafts. To determine the importance of PrP C in cell differentiation, a CAD 5 PrP −/− cell line with ablated PrP C expression was created using the CRISPR/Cas9 system. We observed no considerable difference in morphology, proliferation rate or expression of molecular markers between CAD 5 and CAD 5 PrP −/− cells during the differentiation initiated by serum withdrawal. Conclusions PrP C characteristics, such as cell localisation, level of expression and posttranslational modifications, change during CAD 5 cell differentiation, but PrP C ablation does not change the course of the differentiation process. Significance Ablation of PrP C expression does not affect CAD 5 cell differentiation, although we observed many intriguing changes in PrP C features during the process. Our study does not support the concept that PrP C is important for neuronal cell differentiation, at least in simple in vitro conditions.