Bhamra, SK; (2014) Systematic mutagenesis of the mouse prion protein to identify critical regions for the efficient propagation of prions. Doctoral thesis , UCL (University College London).

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Abstract

The aim of this study was to systematically investigate the contributions of various amino acids within the prion protein, on prion propagation. To test this in a cellular system, we used a sub-cloned population of N2a cells (PK1) that are highly susceptible to RML mouse prions. A library of stable PK1 cells was generated, which expressed the full length mouse prion protein (moPrP) bearing either point, double, or triple alanine replacements. The effects these changes in the prion protein sequence had on the ability of PK1 cells to propagate RML was tested using a previously established cell based assay. We found that: (i) in the unstructured region of the protein, alanine replacements in CC2 region 90-111 of the prion protein severely diminish, but do not abrogate the ability of cells to propagate prions whilst substitutions K23A.K24A.R25A and Q41A exerted a moderate inhibitory effect on propagation; (ii) alanine replacements in CC2 displayed a dominant negative effect by imposing their propagation inhibition phenotype in the presence of the wild-type protein; (iii) the diminished propagation abilities of cells expressing CC2 alanine mutants were a result of these cells being less susceptible to infection than their wild-type counterparts (iv) all alanine replacements tested in the structured region of the protein appeared to hamper prion propagation, regardless of their positioning within this globular domain. Taken together, these results suggest that integrity of the structured region is vital for successful prion propagation, and that although the flexible region of the prion protein alone (residues 23-111), does not exclusively confer infectivity and/or propagative capacity, charge interactions in this region govern the efficacy with which propagation ensues.

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