Identification of a gene regulatory network associated with prion replication

Abstract

Prions consist of aggregates of abnormal conformers of the cellular prion protein (PrP C ). They propagate by recruiting host‐encoded Pr P C although the critical interacting proteins and the reasons for the differences in susceptibility of distinct cell lines and populations are unknown. We derived a lineage of cell lines with markedly differing susceptibilities, unexplained by Pr P C expression differences, to identify such factors. Transcriptome analysis of prion‐resistant revertants, isolated from highly susceptible cells, revealed a gene expression signature associated with susceptibility and modulated by differentiation. Several of these genes encode proteins with a role in extracellular matrix ( ECM ) remodelling, a compartment in which disease‐related PrP is deposited. Silencing nine of these genes significantly increased susceptibility. Silencing of Papss2 led to undersulphated heparan sulphate and increased Pr P C deposition at the ECM , concomitantly with increased prion propagation. Moreover, inhibition of fibronectin 1 binding to integrin α8 by RGD peptide inhibited metalloproteinases ( MMP )‐2/9 whilst increasing prion propagation. In summary, we have identified a gene regulatory network associated with prion propagation at the ECM and governed by the cellular differentiation state. image The rate of prion replication in cells is controlled by a gene regulatory network that is associated with glycosaminoglycan sulphation and activation of metalloproteinases. Retinoic acid differentiation of prion‐resistant revertants, isolated from highly susceptible neuroblastoma cells, leads to a gain of susceptibility and is associated with downregulation of an inhibitory gene signature. Silencing of 3′‐phosphoadenosine 5′‐phosphosulphate synthase 2 (Papss2) leads to undersulphation of heparan sulphate proteoglycans and increases susceptibility to prion propagation. Disruption of integrin α8 signalling inhibits fibronectin1‐mediated metalloproteinase activation and augments the rate of prion replication. Fn1 and Papss2 silencing is associated with increased deposition of PrP C at the extracellular matrix.