Prion proteins cellular

Saborio GP, Soto C, Kascsak RJ, Levy E, Kascsak R, Harris DA, Frangione B. Cell-lysate conversion of prion protein into its protease-resistant isoform suggests the participation of a cellular chaperone. Biochem Biophys Res Commun 1999 258 470-475. 

All fungal prion proteins have a so-called prion domain and a functional domain. The prion domain is a region of the polypeptide chain that is necessary and sufficient for prion formation and maintenance (Fig. 1 Wickner et al., 2002). For Ure2p and Sup35p, the functional domain is responsible for the cellular activity of the normal form of the protein. 

The prion protein, implicated in diseases such as mad cow and Creutzfeldt-Jakob, is another that has been proposed to undergo extensive refolding to form fibrils. In its native, cellular conformation (PrPc), residues 23-124 are... 

The normal cellular form of prion protein (PrPc) can exist as a Cu-metalloprotein in vivo (492). This PrPc is a precursor of the pathogenic protease-resistant form PrPsc, which is thought to cause scrapie, bovine spongiform encephalopathy (BSE), and Creutzfeldt—Jakob disease. Two octa-repeats of PHGGGWGQ have been proposed as Cu(II) binding sites centered on histidine (493). They lack secondary and tertiary structure in the absence of Cu(II). Neurons may therefore have special mechanisms to regulate the distribution of copper. 

With the background of the mad cow crisis in Europe, questions relating to the prion diseases have attracted intensive interest. It is now widely accepted that prion diseases, such as Creutzfeldt-Jakob disease (CJd) in humans and bovine spongiform encephalopathy (BSE) are caused by a conformational change of the prion protein (PrP) from a normally folded cellular form, PrP ", to an alternate, aggregation-prone, pathogenic scrapie form,... 

SL Shyng, S Lehmann, KL Moulder, DA Harris. Sulfated glycans stimulate endocytosis of the cellular isoform of the prion protein, PrP, in cultured cells. J Biol Chem 270 30221-30229, 1995. 

The abnormal deposits found in the brains of CJD victims consist of an abnormal isoform of PrP. Prion protein is normally found in cells. Detailed structural studies show that normal cellular PrP (PrP ) is a soluble protein whose conformation is rich in a-helices with very little P-sheet. The PrP protein extracted from the brains of CJD victims (i.e., PrP ) is identical in primary amino acid sequence to the normal PrP (PrP ). However, PrP has a much greater content of P-sheet conformation with little a-helical structure. Thus PrP is neurotoxic because of its three-dimensional structure. When the prion protein is predominantly in an a-helical conformation it is nontoxic when the prion protein is predominantly in a P-sheet conformation, it kills neurons. The prion protein is thus made neurotoxic not by its amino acid composition but by its conformation. This concept is both fascinating and terrifying. Prion diseases are transmissible thus prions are infectious agents. However, prions are not like bacteria or viruses, or other infectious microbes—they are simply protein molecules. Prions are not microbes with cell membranes and nucleic acids they are not living things. Indeed, prions are not even infectious molecules, they are infectious molecular shapes. 

Vogtherr M., Grimme S., Elshorst B., Jacobs D. M., Fiebig K., Griesinger C., and Zahn R. (2003). Antimalarial drug quinacrine binds to C-terminal helix of cellular prion protein. J. Med. Chem. 

Simak J, Holada K, D Agnillo F, Janota J, Vostal JG. Cellular prion protein is expressed on endothelial cells and is released during apoptosis on membrane microparticles found in human plasma. Transfusion 2002 42 334-342. 

The cellular form of the prion protein, called PrP, is synthesized as a 253 amino acid precursor protein in humans (Figure 29. IB) (Prusiner, 1991). The N-terminal 22 amino acid residues serve as the signal peptide that allows insertion of the nascent PrP peptide into the secretory pathway during biosynthesis. The C-terminal 22 amino acid residues are involved in the covalent addition of the glycosylphosphatidylino-sitol (GPI) moiety to serine at amino acid 231 (i.e., Ser 9-The GPI anchor tethers PrP to the exhacellular side of the plasma membrane. PrP has two N-hnked glycosylation sites (Asn and Asn ) that are the sites of attachment of complex... 

Solforosi L, Criado JR, McGavem DB, Wirz S, Sanchez-Alavez M, Sugama S, DeGiorgio LA, Volpe BT, Wiseman E, Abalos G, Mashah E, Gilden D, Oldstone MB, Conti B, Williamson RA (2004) Cross linking cellular prion protein triggers neuronal apoptosis in vivo. Science 303 1514—1516. 

Fig. 5.11 Dehydron pattern of the cellular prion protein (PDB.1QM0). Reprinted with permission from [19] copyright 2007 American Chemical Society...

Ermonval M, Baudry A, Baychelier F et al (2009) The cellular prion protein interacts with the tissue non-specific alkaline phosphatase in membrane microdomains of bioami-nergic neuronal cells. PLoS One 4 e6497... 

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