Correlation of cellular factors and differential scrapie prion permissiveness in ovine microglia

Authors: DINKEL, KELCEY - Washington State University; Schneider, David; MUÑOZ-GUTIÉRREZ, JUAN - University Of Wyoming; MCELLIOTT, VALERIE - University Of Georgia; STANTON, JAMES - University Of Georgia

Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2017
Publication Date: 7/25/2017
Citation: Dinkel, K.D., Schneider, D.A., Muñoz-Gutiérrez, J.F., Mcelliott, V.R., Stanton, J.B. 2017. Correlation of cellular factors and differential scrapie prion permissiveness in ovine microglia. Virus Research. 240:69-80.

Interpretive Summary: Prion diseases, including scrapie in sheep and goats, are fatal brain disorders for which the mechanisms of cellular infection are poorly understood. Working with cultures of sheep microglia, a type of brain cell important to scrapie disease, we previously showed that infection by scrapie prions was associated with the altered expression of multiple genes, potentially linking the process of infection to multiple cellular processes. In the present study, we studied several highly related clones of the microglial cell line in order to determine if specific pathways explained why some clones were poorly permissive to scrapie infection while the permissiveness of other clones was intermediate or high. Permissiveness to infection was correlated with gene pathways known to affect cell growth, intracellular protein degradation, and extracellular antioxidant activity. Surprisingly, permissiveness was not correlated with the activity of certain extracellular matrix metalloproteinases nor with the different rates of cell proliferation between clones. The results help clarify the role of these genes and cellular processes in microglia during scrapie infection. The genes and pathways identified represent potential targets for therapeutic investigation but are also useful toward development a robust cell culture system that is highly permissive to detecting scrapie infected tissues.

Technical Abstract: Prion diseases are fatal neurodegenerative disorders by which the native cellular prion protein (PrP-C) is misfolded into an accumulating, disease-associated isoform (PrP-D). To improve the understanding of prion pathogenesis and develop effective treatments, it is essential to elucidate factors contributing to cellular permissiveness. We previously isolated five clones from an immortalized subline of ovine microglia, two of which had demonstrated differential permissiveness to a natural isolate of sheep scrapie and distinct transcriptomic profiles. To more robustly identify factors contributing to this activity, relative permissiveness, cell proliferation, selected gene transcript level, and matrix metalloproteinase 2 (MMP2) activity were compared amongst all five clones. Differences in cell proliferation were not detected between clones; however, significant correlations were identified between relative permissiveness and genes associated with cell growth (i.e., RARRES1 and PTN), protein degradation (i.e., CTSB and SQSTM1), and heparin binding (i.e., SEPP1). MMP2 activity varied amongst clones, but did not correlate with permissiveness. These associations support the contribution of cell division and protein degradation on the permissiveness of cultured ovine microglia to PrP-D.