Cyclin-dependent Kinase 5 Phosphorylation of Familial Prion Protein Mutants Exacerbates Conversion into Amyloid Structure

• DOI: 10.1074/jbc.m114.630699
• Publication Date: 2015-01-09T05:32:53Z
• Authors: Raphaël Rouget; Gyanesh Sharma; Andréa C. LeBlanc
• Keywords: Thioflavin; Dephosphorylation

Familial prion protein (PrP) mutants undergo conversion from soluble and protease-sensitive to insoluble partially protease-resistant proteins. Cyclin-dependent kinase 5 (Cdk5) phosphorylation of wild type PrP (pPrP) at serine 43 induces a into aggregates fibrils. Here, we investigated whether familial are predisposed Cdk5 increases conversion. representing three major diseases different structural domains were studied. We developed novel in vitro reaction coupled with Thioflavin T binding amyloid structure assay monitor phosphorylation-dependent Although non-phosphorylated full-length or did not convert amyloid, rapidly converted these T-positive structures following first order kinetics. Dephosphorylation reversed Phosphorylation-dependent α-helical β-sheet was confirmed by circular dichroism. Relative pPrP, most showed increased rate constants In contrast, truncated Y145X (where X represents stop codon) Q160X spontaneously fibrils after lag phase over 20 h, indicating nucleation-dependent polymerization. Phosphorylation reduced the 50% thus accelerated formation nucleating event. Consistently, phosphorylated exacerbated homologous seeding reaction, whereas WT pPrP could seed PrP. These results demonstrate an influence both N terminus C on conclude that post-translational modifications flexible can cause exacerbate mutant