title: Plasminogen stimulates propagation of protease-resistant prion protein in vitro.
abstract: To clarify the role of plasminogen as a cofactor for prion propagation, we conducted functional assays using a cell-free prion protein (PrP) conversion assay termed protein misfolding cyclic amplification (PMCA) and prion-infected cell lines. Here, we report that plasminogen stimulates propagation of the protease-resistant scrapie PrP (PrP(Sc)). Compared to control PMCA conducted without plasminogen, addition of plasminogen in PMCA using wild-type brain material significantly increased PrP conversion, with an EC(50) = ∼56 nM. PrP conversion in PMCA was substantially less efficient with plasminogen-deficient brain material than with wild-type material. The activity stimulating PrP conversion was specific for plasminogen and conserved in its kringle domains. Such activity was abrogated by modification of plasminogen structure and interference of PrP-plasminogen interaction. Kinetic analysis of PrP(Sc) generation demonstrated that the presence of plasminogen in PMCA enhanced the PrP(Sc) production rate to ∼0.97 U/μl/h and reduced turnover time to ∼1 h compared to those (∼0.4 U/μl/h and ∼2.5 h) obtained without supplementation. Furthermore, as observed in PMCA, plasminogen and kringles promoted PrP(Sc) propagation in ScN2a and Elk 21(+) cells. Our results demonstrate that plasminogen functions in stimulating conversion processes and represents the first cellular protein cofactor that enhances the hypothetical mechanism of prion propagation.
authors: Sanders-Brown Center on Aging and Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
authors: Charles E
authors: CE
authors: Mays
authors: Chongsuk
authors: C
authors: Ryou
mesh_terms: D000818:Animals; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D010958:Plasminogen / Q000737:chemistry* / Q000378:metabolism*; D018620:PrPSc Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017510:Protein Folding
chemical_list: D018620:PrPSc Proteins; D010958:Plasminogen