Trapping Prion Protein in the Endoplasmic Reticulum Impairs PrPC Maturation and Prevents PrPSc Accumulation

Department of Neuroscience, University of Tor Vergata, Via Montpellier 1, 00133 Roma, Italy.
Journal of Biological Chemistry (Impact Factor: 4.57). 01/2005; 280(1):685-94. DOI: 10.1074/jbc.M407360200
Source: PubMed


The conversion of the normal cellular prion protein (PrPC) into the abnormal scrapie isoform (PrPSc) is a key feature of prion diseases. The pathogenic mechanisms and the subcellular sites of the conversion are complex and
not completely understood. In particular, little is known on the role of the early compartment of the secretory pathway in
the processing of PrPC and in the pathogenesis of prion diseases. In order to interfere with the intracellular traffic of endogenous PrPC we have generated two anti-prion single chain antibody fragments (scFv) directed against different epitopes, each fragment
tagged either with a secretory leader or with the ER retention signal KDEL. The stable expression of these constructs in PC12
cells allowed us to study their specific effects on the synthesis, maturation, and processing of endogenous PrPC and on PrPSc formation. We found that ER-targeted anti-prion scFvs retain PrPC in the ER and inhibit its translocation to the cell surface. Retention in the ER strongly affects the maturation and glycosylation
state of PrPC, with the appearance of a new aberrant endo-H sensitive glycosylated species. Interestingly, ER-trapped PrPC acquires detergent insolubility and proteinase K resistance. Furthermore, we show that ER-targeted anti-prion antibodies
prevent PrPSc accumulation in nerve growth factor-differentiated PC12 cells, providing a new tool to study the molecular pathology of prion

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    • "Therefore, blocking PrPC/PrPSc interaction is a major therapeutic target. Intrabodies can be used to halt this pathological interaction by different modes of action: (a) direct binding to one of the two molecular species [38, 39], (b) trapping PrPC in the ER [14], and (c) rerouting PrPC to the proteasome degradation pathway [40]. In particular, rerouting native proteins in precise intracellular locations is a unique property of intrabodies. "
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    • "Initially, the constant region genes (C␥, C␧ and C␣) were expressed as transfectomas to produce bovine × mouse chimeric antibodies [5]. Now recombinant scFvs of bovine origin have been developed against foot-and-mouth disease [20] and prion protein [21] [22] [23]. Earlier we constructed functional scFv [24] against bovine herpes virus type-1 (BoHV-1) expressed in secretory form in Pichia pastoris [25] [26] [27] under the influence of methanol regulated promoters . "
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