Proteomic analysis of host brain components that bind to infectious particles in Creutzfeldt‐Jakob disease

Abstract

Transmissible encephalopathies (TSEs), such as CJD and scrapie, are caused by infectious agents that provoke strain-specific patterns of disease. Misfolded host prion protein (PrP-res amyloid) is believed to be the causal infectious agent. However, particles that are stripped of PrP retain both high infectivity and viral proteins not detectable in uninfected mouse controls. We here detail host proteins bound with FU-CJD infectious brain particles by proteomic analysis. More than 98 proteins were differentially regulated, and 56 FU-CJD exclusive proteins were revealed after PrP, GFAP, C1q, ApoE and other late pathologic response proteins were removed. Stripped FU-CJD particles revealed HSC70 (144× the uninfected control), cyclophilin B, an FU-CJD exclusive protein required by many viruses, and early endosome-membrane pathways known to facilitate viral processing, replication, and spread. Synaptosomal elements including synapsin-2 (at 33×) and AP180 (a major FU-CJD exclusive protein) paralleled the known ultrastructural location of 25nm virus-like TSE particles and infectivity in synapses. Proteins without apparent viral or neurodegenerative links (copine-3), and others involved in viral-induced protein misfolding and aggregation, were also identified. Human sCJD brain particles contained 146 exclusive proteins, and heat shock, synaptic and viral pathways were again prominent, in addition to Alzheimer (AD), Parkinson, and Huntington aggregation proteins. Host proteins that bind TSE infectious particles can prevent host immune recognition and contribute to prolonged cross-species transmissions (the species barrier). Our infectious particle strategy, which reduces background sequences by >99%, emphasizes host targets for new therapeutic initiatives. Such therapies can simultaneously subvert common pathways of neurodegeneration.

CJD and Scrapie Require Agent‐Associated Nucleic Acids for Infection

“…We previously showed that isolated brain particles without detectable PrP maintain their high infectivity, a finding that excludes a prion protein agent [Kipkorir et al, ]. The above results demonstrate that particles from two different agent strains require protected nucleic acids for infection.…”

The prokaryotic SPHINX 1.8 REP protein is tissue-specific and expressed in human germline cells

“…Many viruses also possess amyloid domains with critical functions such as viral transcription and receptor-mediated attachment to the host cell (14); the latter interaction fits neatly with the concept that host PrP is an essential receptor for an environmental TSE virus (1). While proteomics has highlighted common cellular proteins in neurodegeneration e.g., (6,15), it may overlook past or covert causal infectious agents, especially those that collaborate with human endogenous viruses. The prion seeding model for amyloids and other fibrillar accumulations in late onset human neurodegenerative diseases has largely discounted causal environmental pathogens.…”

Prokaryotic SPHINX 1.8 REP protein is tissue‐specific and expressed in human germline cells

“…These "seeded" mice transmitted only the laboratory RML strain of scrapie on serial passages. 2 While proteomics has highlighted common cellular proteins in neurodegeneration for example, Kipkorir et al, 9,16 it may overlook past or covert causal infectious agents, especially those that collaborate with human endogenous viruses. In fact, amyloid has been shown to function as an innate immune trap that can clear TSE infectious agents, 2,13 and it may also ensnare specific cells and clearance molecules.…”