alpha-Synuclein aggregation in neurodegenerative diseases and its inhibition as a potential therapeutic strategy

There is strong evidence for the involvement of alpha-synuclein in the pathologies of several neurodegenerative disorders, including PD (Parkinson's disease). Development of disease appears to be linked to processes that increase the rate at which alpha-synuclein forms aggregates. These processes include increased protein concentration (via either increased rate of synthesis or decreased rate of degradation), and altered forms of alpha-synuclein (such as truncations, missense mutations, or chemical modifications by oxidative reactions). Aggregated forms of the protein are toxic to cells and one therapeutic strategy would be to reduce the rate at which aggregation occurs. To this end we have designed several peptides that reduce alpha-synuclein aggregation. A cell-permeable version of one such peptide was able to inhibit the DNA damage induced by Fe(II) in neuronal cells transfected with alpha-synuclein (A53T), a familial PD-associated mutation.

alpha-Synuclein aggregation

Alpha-synuclein is a major component of Lewy bodies in Parkinson's disease and is found associated with several other forms of dementia. As with other neurodegenerative diseases, the ability of alpha-synuclein to aggregate and form fibrillar deposits seems central to its pathology. We have defined a sequence within the NAC region of alpha-synuclein that is necessary for aggregation. Exploitation of chemically modified analogues of this peptide may produce inhibitors of aggregation.

Aggregation and neurotoxicity of alpha-synuclein and related peptides

Fibrillar deposits of alpha-synuclein occur in several neurodegenerative diseases. Two mutant forms of alpha-synuclein have been associated with early-onset Parkinson's disease, and a fragment has been identified as the non-amyloid-beta peptide component of Alzheimer's disease amyloid (NAC). Upon aging, solutions of alpha-synuclein and NAC change conformation to beta-sheet, detectable by CD spectroscopy, and form oligomers that deposit as amyloid-like fibrils, detectable by electron microscopy. These aged peptides are also neurotoxic. Experiments on fragments of NAC have enabled the region of NAC responsible for its aggregation and toxicity to be identified. NAC(8-18) is the smallest fragment that aggregates, as indicated by the concentration of peptide remaining in solution after 3 days, and forms fibrils, as determined by electron microscopy. Fragments NAC(8-18) and NAC(8-16) are toxic, whereas NAC(12-18), NAC(9-16) and NAC(8-15) are not. Hence residues 8-16 of NAC comprise the region crucial for toxicity. Toxicity induced by alpha-synuclein, NAC and NAC(1-18) oligomers occurs via an apoptotic mechanism, possibly initiated by oxidative damage, since these peptides liberate hydroxyl radicals in the presence of iron. Molecules with anti-aggregational and/or antioxidant properties may therefore be potential therapeutic agents.

Identification of the region of non-A beta component (NAC) of alzheimer's disease amyloid responsible for its aggregation and toxicity

The non-beta-amyloid (Aß) component of Alzheimer's disease amyloid (NAC) and its precursor a-synuclein have been linked to amyloidogenesis in several neurodegenerative diseases. NAC and a-synuclein both form ß-sheet structures upon ageing, aggregate to form fibrils, and are neurotoxic. We recently established that a peptide comprising residues 3±18 of NAC retains these properties. To pinpoint the exact region responsible we have carried out assays of toxicity and physicochemical properties on smaller fragments of NAC. Toxicity was measured by the ability of fresh and aged peptides to inhibit the reduction of the redox dye 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) by rat pheochromocytoma PC12 cells and human neuroblastoma SHSY-5Y cells. On immediate dissolution, or after ageing, the fragments NAC(8±18) and NAC(8±16) are toxic, whereas NAC(12±18), NAC(9±16) and NAC(8±15) are not. Circular dichroism indicates that none of the peptides displays ß-sheet structure; rather all remain random coil throughout 24 h. However, in acetonitrile, an organic solvent known to induce ß sheet, fragments NAC(8±18) and NAC(8±16) both form ß-sheet structure. Only NAC(8±18) aggregates, as indicated by concentration of peptide remaining in solution after 3 days, and forms fibrils, as determined by electron microscopy. These findings indicate that residues 8±16 of NAC, equivalent to residues 68±76 in a-synuclein, comprise the region crucial for toxicity.

A strategy for designing inhibitors of alpha-synuclein aggregation and toxicity as a novel treatment for Parkinson's disease and related disorders.

Convergent biochemical and genetic evidence suggests that the formation of alpha-synuclein (alpha-syn) protein deposits is an important and, probably, seminal step in the development of Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). It has been reported that transgenic animals overexpressing human alpha-syn develop lesions similar to those found in the brain in PD, together with a progressive loss of dopaminergic cells and associated abnormalities of motor function. Inhibiting and/or reversing alpha-syn self-aggregation could, therefore, provide a novel approach to treating the underlying cause of these diseases. We synthesized a library of overlapping 7-mer peptides spanning the entire alpha-syn sequence, and identified amino acid residues 64-100 of alpha-syn as the binding region responsible for its self-association. Modified short peptides containing alpha-syn amino acid sequences from part of this binding region (residues 69-72), named alpha-syn inhibitors (ASI), were found to interact with full-length alpha-syn and block its assembly into both early oligomers and mature amyloid-like fibrils. We also developed a cell-permeable inhibitor of alpha-syn aggregation (ASID), using the polyarginine peptide delivery system. This ASID peptide was able to inhibit the DNA damage induced by Fe(II) in neuronal cells transfected with alpha-syn(A53T), a familial PD-associated mutation. ASI peptides without this delivery system did not reverse levels of Fe(II)-induced DNA damage. Furthermore, the ASID peptide increased (P

A Be star with a low nitrogen abundance in the SMC cluster NGC330

High- resolution UVES/ VLT spectra of B 12, an extreme pole- on Be star in the SMC cluster NGC 330, have been analysed using non-LTE model atmospheres to obtain its chemical composition relative to the SMC standard star AV304. We find a general underabundance of metals which can be understood in terms of an extra contribution to the stellar continuum due to emission from a disk which we estimate to be at the similar to 25% level. When this is corrected for, the nitrogen abundance for B12 shows no evidence of enhancement by rotational mixing as has been found in other non-Be B-type stars in NGC 330, and is inconsistent with evolutionary models which include the effects of rotational mixing. A second Be star, NGC330-B 17, is also shown to have no detectable nitrogen lines. Possible explanations for the lack of rotational mixing in these rapidly rotating stars are discussed, one promising solution being the possibility that magnetic fields might inhibit rotational mixing.

High-resolution spectroscopy of globular cluster post-Asymptotic Giant Branch stars

We present model atmosphere analyses of high resolution Keck and VLT optical spectra for three evolved stars in globular clusters, viz. ZNG-1 in M 10, ZNG-1 in M 15 and ZNG-1 in NGC 6712. The derived atmospheric parameters and chemical compositions confirm the programme stars to be in the post- Asymptotic Giant Branch (post-AGB) evolutionary phase. Differential abundance analyses reveal CNO abundance patterns in M 10 ZNG-1, and possibly M 15 ZNG-1, which Suggest that both objects may have evolved off the AGB before the third dredge-up occurred. The abundance pattern of these stars is similar to the third class of optically, bright post-AGB objects discussed by van Winckel (1997). Furthermore, M 10 ZNG-1 exhibits a large C underabundance (with Delta[C/O] similar to -1.6 dex), typical of other hot post-AGB objects. Differential Delta[alpha/Fe] abundance ratios in both M 10 ZNG-1 and NGC 6712 ZNG-1 are found to be approximately 0.0 dex, with the Fe abundance of the former being in disagreement with the cluster metallicity of M 10. Given that the Fe absorption features in both M 10 ZNG-1 and NGC6712 ZNG-1 are well observed and reliably modelled, we believe that these differential Fe abundance estimates to be secure. However, our Fe abundance is difficult to explain in terms of previous evolutionary processes that Occur oil both the Horizontal Branch and the AGB.

Hybrid cluster state proposal for a quantum game

We propose an experimental implementation of a quantum game algorithm in a hybrid scheme combining the quantum circuit approach and the cluster state model. An economical cluster configuration is suggested to embody a quantum version of the Prisoners' Dilemma. Our proposal is shown to be within the experimental state of the art and can be realized with existing technology. The effects of relevant experimental imperfections are also carefully examined.