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BSE (TSE) researchers closing in on 'Factor X'

Kathy

Well-known member
These two leading prion researchers both appear to be heading to the same finish line; at least their on the same track!!

Very interesting abstracts, considering that Dr. David Brown and Dr. BS Wong, et al. "found a decrease of up to 50% of copper and an increase in manganese of approximately 10-fold in the brain tissues from sCJD subjects." "Aberrant metal binding by prion protein in human prion disease. (2001)

J Neurochem. 2006 Jun 19; [Epub ahead of print]

Prion protein reduces both oxidative and non-oxidative copper toxicity

Haigh CL, Brown DR.

Department of Biology and Biochemistry, University of Bath, Bath, UK.

The prion protein is a membrane tethered glycoprotein that binds copper. Conversion to an abnormal isoform is associated with neurodegenerative diseases known as prion diseases. Expression of the prion protein has been suggested to prevent cell death caused by oxidative stress. Using cell based models we investigated the potential of the prion protein to protect against copper toxicity. Although prion protein expression effectively protected neurones from copper toxicity, this protection was not necessarily associated with reduction in oxidative damage. We also showed that glycine and the prion protein could both protect neuronal cells from oxidative stress. Only the prion protein could protect these cells from the toxicity of copper. In contrast glycine increased copper toxicity without any apparent oxidative stress or lipid peroxidation. Mutational analysis showed that protection by the prion protein was dependent upon the copper binding octameric repeat region. Our findings demonstrate that copper toxicity can be independent of measured oxidative stress and that prion protein expression primarily protects against copper toxicity independently of the mechanism of cell death.

PMID: 16787422



Arch Virol. 2006 Jun 22; [Epub ahead of print]

Copper induces conformational changes in the N-terminal part of cell-surface PrP(C).

Leclerc E, Serban H, Prusiner SB, Burton DR, Williamson RA.

Department of Immunology, The Scripps Research Institute, La Jolla, CA, U.S.A..

Prion diseases are caused by misfolding of the cellular prion protein, PrP(C). In vitro studies have shown that PrP binds copper via the octarepeat region lying within the unstructured N-terminal segment of the protein, but the significance of copper in PrP metabolism remains unclear. Here, six specific antibodies recognizing different epitope regions of PrP were used to measure the effect of copper on the conformation of the molecule at the cell surface. Binding of an antibody, E149, to an epitope within the octarepeat domain of PrP is halved in the presence of copper, whereas binding of antibodies recognizing epitope motifs C-terminal to residue 90 of PrP remain relatively unaltered under equivalent conditions. These experiments strongly suggest that copper induces localized conformational change within the N-terminal portion of cell-surface PrP(C).

PMID: 16791441

kind of makes me feel all fuzzy and warm.
 

Kathy

Well-known member
Keep in mind what Dr. DL Cox is stating here; that with copper in the back-bone of the PrPC protein, its doesn't fit with the models of the so-called "infectious" prion.

(Free on-line at www.biophysj.org)

Biophys J. 2006 May 12; [Epub ahead of print]

A mechanism for copper inhibition of infectious prion conversion.

Cox DL, Pan J, Singh RR.

UC Davis.

We employ ab initio electronic structure calculations to obtain two structural models for copper bound in the strongest binding site of the noninfectious form of the prion protein. The models are compatible with available experimental constraints from electron spin resonance data. The bending of the peptide backbone attendant with the copper binding is not compatible with the requisite straight beta-strand backbone structure for the same sequence contained in two recently proposed models of the prion protein structure in its infectious form. We hypothesize that copper binding at this site is protective against conversion to the infectious form, discuss experimental data which appear to support and conflict with our hypothesis, and propose tests using recombinant prion protein, genetically modified cultured neurons, and transgenic mice.

PMID: 16698781
 

Kathy

Well-known member
Dr. CL Haigh and Dr. DR Brown have collaberated on an earlier paper, which documents that when the PrPC protein binds with extracellular copper, it is internalized into the cell. Other metals did not permit this biological function.

So what happens when copper isn't bioavailable to the PrPC protein?

Mol Cell Neurosci. 2005 Oct;30(2):186-96.

Copper binding is the governing determinant of prion protein turnover.

Haigh CL, Edwards K, Brown DR.

Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK.

The cellular isoform of the prion protein (PrP(c)) is located at the cell membrane, anchored externally by a glycosylphosphatidylinositol (GPI) anchor. It is a copper (Cu) binding glycoprotein with a rapid basal turnover. Previous studies have shown that exposure of cells to Cu causes internalisation of PrP(c) in vitro. In this study, we show that physiological levels of Cu promote internalisation of PrP(c). Interaction between PrP(c) and Cu was found to be the overriding factor in stimulating the internalisation response with other metals showing no effect. Deletion mutation studies have shown that two domains are essential for copper-induced internalisation to occur. These two domains are the octameric repeat region, encompassing amino acids 51-89, and the palindromic region, amino acids 112-119 with the sequence AGAAAAGA. The decrease in detectable levels of PrP(c) at the cell surface following Cu treatment was found to be the result of rapid internalisation rather than loss into the surrounding environment. These results have implications for both normal metabolism of PrP(c) and the possible mechanism of conversion of PrP(c) to PrP(sc).

PMID: 16084105
 

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