Domain-specific Quantification of Prion Protein in Cerebrospinal Fluid by Targeted Mass Spectrometry

Minikel, E.V.; Kuhn, E.; Cocco, A.R.; et al.

Accurate and reliable quantitation of prion protein (PrP) is necessary in prion disease therapeutics. Considering the potential challenges of current quantitative methods (e.g., inability to capture protein fragments), Carr and colleagues developed an alternative approach. This involved the quantitation of PrP in cerebrospinal fluid (CSF) by bottom-up LC-MRM-MS using uniform ¹⁵N-labeled PrP (expressed using CGM-1000-N) as an internal standard for human sample analysis and ¹³C/¹⁵N PrP tryptic peptides (synthesized using protected amino acids) for human and other species sample analyses. The metrics of the validated assay enable the selective and precise quantitation of CSF PrP and provides a basis for its clinical translation in support of on-going PrP-lowering drug studies.