Prion protein as a target for therapeutic interventions

Abstract

Abstract Transmissible spongiform encephalopathies (TSEs), currently known as prion diseases, are neurodegenerative disorders of the central nervous system (CNS) caused by an elusive infectious agent called “prion” (proteinaceous infectious particle). These dis orders include: kuru, Creutzfeldt –Jakob disease (CJD) and its variant (vCJD), Gerstmann–Sträussler–Scheinker (GSS) disease and fatal familial insomnia (FFI) in humans, scrapie in sheep and goats, bovine spongiform encephalopathy (BSE) or mad cow disease, and chronic wasting disease (CWD) in cervids. According to the widely accepted “prion hypothesis”, prion is an aggregate of the abnormal isoform of prion protein (PrPSc). Prion protein is a cell-derived glycoprotein (this normal isoform is called PrPc) encoded by a gene on chromosome 20 in humans (PRNP). In familial forms of TSEs, mutations within the ORF of PRNP are linked to the phenotypic expression of the disease. TSEs are important from public health perspective, and “mad cow disease has created the greatest threat to the safety of human food supply in modern times. vCJD threatens the safety of the blood supply worldwide”. Thus, to search for effective therapy is more than an urgent task. In TSEs, aggregates of PrPSc accumulate in the brain in a form of plaques, or synaptic deposits. The conversion of PrPc into PrPSc and subsequent deposits of PrPSc are targets for therapeutic interventions. These include: tricyclic compounds—acridine and phenothiazine derivatives; quinacrine; anti-PrPSc antibodies; dendrimers; polyethylene antibiotics (amphotericin B, MS-8209); pentosan polysulfate; and dextran sulfate. All these compounds are active in many in vitro and in vivo assays, but not proved definitely active in humans. Thus, albeit interesting and promising, the chemotherapy of TSEs is still in the infant phase.