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There are numerous neurodegenerative diseases but Alzheimer's disease and Parkinson's disease are the most common. In contrast, prion diseases are very rare but have sparked vast interest and study because of their potential threat. All three diseases have a common basis as they are linked to proteins that either aggregate or have break down products that aggregate. Even more strikingly, the three central proteins are metal binding proteins. Copper binds to both the prion protein and the amyloid precursor protein. Recently, alpha-synuclein has also been shown to bind copper. While study of the amyloid precursor protein (APP) and copper has not flourished since its discovery in the early 1990s and alpha-synuclein has only recently been a target for metallochemical investigation, the prion protein has been the centre of extensive research for the last decade. Therefore, recent insights into the metallochemistry of the prion protein are relevant to investigating APP and alpha-synuclein. This review considers what is known of the metallochemistry of all three proteins.

Neurodegenerative diseases remain perplexing and problematic for modern research. Those associated with amyloidogenic proteins have often been lumped together simply because those proteins aggregate. However, research has identified a more logical reason to group some of these diseases together. The associated proteins not only aggregate, but also bind copper. The APP (amyloid precursor protein) binds copper in an N-terminal region. Binding of copper has been suggested to influence generation of beta-amyloid from the protein. PrP (prion protein) binds copper, and this appears to be necessary for its normal function and might also reduce its probability of conversion into an infectious prion. alpha-Synuclein, a protein associated with Parkinson's disease, also binds copper, but, in this case, it potentially increases the rate at which the protein aggregates. The similarities between these proteins, in terms of metal binding, has allowed us to investigate them using similar approaches. In the present review, we discuss some of these approaches.

α-Synuclein misfolding and aggregation is often accompanied by β-amyloid deposition in some neurodegenerative diseases. We hypothesised that α-synuclein promotes β-amyloid production from APP. β-Amyloid levels and APP amyloidogenic processing were investigated in neuronal cell lines stably overexpressing wildtype and mutant α-synuclein. γ-Secretase activity and β-secretase expression were also measured. We show that α-synuclein expression induces β-amyloid secretion and amyloidogenic processing of APP in neuronal cell lines. Certain mutations of α-synuclein potentiate APP amyloidogenic processing. γ-Secretase activity was not enhanced by wildtype α-synuclein expression, however β-secretase protein levels were induced. Furthermore, a correlation between α-synuclein and β-secretase protein was seen in rat brain striata. Iron chelation abolishes the effect of α-synuclein on neuronal cell β-amyloid secretion, whereas overexpression of the ferrireductase enzyme Steap3 is robustly pro-amyloidogenic. We propose that α-synuclein promotes β-amyloid formation by modulating β-cleavage of APP, and that this is potentially mediated by the levels of reduced iron and oxidative stress. [ABSTRACT FROM AUTHOR]

The progression of many human neurodegenerative disorders is associated with an accumulation of alpha-synuclein. Alphasynuclein belongs to the homologous synuclein family which includes beta-synuclein. It has been proposed that betasynuclein may be a natural regulator of alpha-synuclein. Therefore controlling beta-synuclein expression may control the accumulation of alpha-synuclein and ultimately prevent disease progression. The regulation of synucleins is poorly understood. We investigated the transcriptional regulation of beta-synuclein with the aim of identifying molecules that differentially control beta-synuclein expression levels. To investigate transcriptional regulation of beta-synuclein we used reporter gene assays and bioinformatics. We identified a region 21.1/20.6 kb upstream of the beta-synuclein translational start site to be a key regulatory region of beta-synuclein 59-promoter activity in human dopaminergic cells (SH-SY5Y). Within this key promoter region we identified a metal response element pertaining to a putative Metal Transcription Factor-1 (MTF- 1) binding site. We demonstrated that MTF-1 binds to this 59-promoter region using EMSA analysis. Moreover we showed that MTF-1 differentially regulates beta-synuclein promoter binding site as well as beta-synuclein mRNA and protein expression. This effect of MTF-1 on expression was found to be specific to beta-synuclein when compared to alphasynuclein. Understanding the regulation of synucleins and how they interact may point to molecular targets that could be manipulated for therapeutic benefit. In this study we showed that MTF-1 differentially controls the expression of betasynuclein when compared to its homolog alpha-synuclein. This could potentially provide a novel targets or pathways for therapeutic intervention and/or treatment of synucleinopathies. [ABSTRACT FROM AUTHOR]

α-synuclein (αS) is a cellular protein mostly known for the association of its aggregated forms with a variety of diseases that include Parkinson's disease and Dementia with Lewy Bodies. While the role of αS in disease is well documented there is currently no agreement on the physiological function of the normal isoform of the protein. Here we provide strong evidence that αS is a cellular ferrireductase, responsible for reducing iron (III) to bio available iron (II). The recombinant form of the protein has a VMax of 2.72 nmols/min/mg and Km 23 μM. This activity is also evident in lysates from neuronal cell lines overexpressing αS. This activity is dependent on copper bound to αS as a cofactor and NADH as an electron donor. Overexpression of α-synuclein by cells significantly increases the percentage of iron (II) in cells. The common disease mutations associated with increased susceptibility to PD show differences in activity or iron (II) levels. This discovery may well provide new therapeutic targets for PD and Lewy body dementias. [ABSTRACT FROM AUTHOR]

Expression of the prion protein is necessary for infection with prion diseases. Altered expression levels may play an important role in susceptibility to infection. Therefore, understanding the mechanisms that regulate prion protein expression is of great importance. It was previously shown that expression of the prion protein is to some degree regulated by an alternative promoter within intron 1. Studies using GFP and luciferase reporter systems were undertaken to determine key sites for the repression and activation of expression of the prion protein driven by intron 1. We identified a region within intron 1 sufficient to drive prion protein expression. Our findings highlight two potential repressor regions. Both regions have binding sites for the known repressor Hes-1. Hes-1 overexpression caused a dramatic decrease in PrP protein expression. Additionally, we have identified Atox-1 as a transcription factor that upregulates prion protein expression. These findings clearly indicate that intron 1 plays a key role in regulation of prion protein expression levels. [ABSTRACT FROM AUTHOR]

Insertional mutations leading to expansion of the octarepeat domain of the prion protein (PrP) are directly linked to prion disease. While normal PrP has four PHGGGWGQ octapeptide segments in its flexible N-terminal domain, expanded forms may have up to nine additional octapeptide inserts. The type of prion disease segregates with the degree of expansion. With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades. In wild-type PrP, the octarepeat domain takes up copper (Cu2+) and is considered essential for in vivo function. Work from our lab demonstrates that the copper coordination mode depends on the precise ratio of Cu2+ to protein. At low Cu2+ levels, coordination involves histidine side chains from adjacent octarepeats, whereas at high levels each repeat takes up a single copper ion through interactions with the histidine side chain and neighboring backbone amides. Here we use both octarepeat constructs and recombinant PrP to examine how copper coordination modes are influenced by octarepeat expansion. We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts). However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity. We next pooled all published cases of human prion disease resulting from octarepeat expansion and find remarkable agreement between the sudden length-dependent change in copper coordination and onset age. Together, these findings suggest that either loss of PrP copper-dependent function or loss of copper-mediated protection against PrP polymerization makes a significant contribution to early onset prion disease. [ABSTRACT FROM AUTHOR]

α-synuclein is one of a family of proteins whose function remains unknown. This protein has become linked to a number of neurodegenerative disease although its potential causative role in these diseases remains mysterious. In diseases such as Parkinson's disease and Lewy body dementias, α-synuclein becomes deposited in aggregates termed Lewy bodies. Also, some inherited forms of Parkinson's diseases are linked to mutations in the gene for α-synuclein. Studies have mostly focussed on what causes the aggregation of the protein but, like many amyloidogenic proteins associated with a neurodegenerative disorder, this protein has now been suggested to bind copper. This finding is currently controversial. This review examines the evidence that α-synuclein is a copper binding protein and discusses whether this has any significance in determining the function of the protein or whether copper binding is at all necessary for aggregation. [ABSTRACT FROM AUTHOR]

We show that human stefin B, a protease inhibitor from the family of cystatins, is a copper binding protein, unlike stefin A. We have used isothermal titration calorimetry to directly monitor the binding event at pH 7 and pH 5. At pH 7 stefin B shows a picomolar affinity for copper but at pH 5 the affinity is in the nanomolar range. There is no difference in the affinity of copper between the wildtype stefin B (E31 isoform) and a variant (Y31 isoform), whereas the mutant (P79S), which is tetrameric, does not bind copper. The conformation of stefin B remains unaltered by copper binding. It is known that below pH 5 stefin B undergoes a conformational change and amyloid fibril formation. We show that copper binding inhibits the amyloid fibril formation and, to a lesser degree, the initial aggregation. Similarities to and differences from other copper binding amyloidogenic proteins are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, we report the characterization of copper(II) complexes with two prion (PrP) protein peptide fragment analogues (VNITKQHTVTTTT), one with the N-terminus acetylated and the C-terminus amidated (PrP Ac180–193NH2) and the other with both the C- and N-termini free (PrP 180–193). Such peptide sequence almost entirely encompasses the PrPC’s helix 2 in the C-terminal region. The stoichiometry, the binding modes and the conformational features of the copper(II) complexes with the above mentioned two peptides were investigated by electrospray ionization-mass spectrometry (ESI-MS), UV–visible (UV–Vis) spectrometry and electron paramagnetic resonance (EPR) spectrometry as well as by circular dichroism (CD) measurements. The binding site location of copper(II) in the structured region of the protein can be here suggested on the basis of our findings that show the involvement of His 187 residue. The similarity of the EPR parameters suggests that the anchoring imidazole residue drives the copper(II) coordination environment towards a common binding motif in different regions of the prion protein. [Copyright &y& Elsevier]

Abstract The prion protein is a copper (Cu)-binding protein. The abnormal isoform of this protein is associated with the transmissible spongiform encephalopathies or prion diseases. In prion diseases, the prion protein loses its Cu binding capacity. The effect of prion protein expression on the Cu content of the brain was investigated. Transgenic mice, either overexpressing the prion protein or expressing a mutant form lacking the Cu-binding region of the protein, were compared with wild-type mice and mice in which expression of the protein was knocked out. Age-dependent differences in Cu content of the brain were detected. Also, synaptosomal fractions from the brains of the mice showed different Cu content depending on the expression of the prion protein. Mice expressing prion protein, but without the Cu-binding domain showed reduced Cu content. Mice overexpressing the prion protein showed little difference in Cu in the brain compared with wild type but also the prion protein expressed by the mice showed a reduction in the level of Cu bound. These results confirm that prion protein expression modulates the Cu level found at the synapse and this effect is dependent on its Cu binding capacity. Loss of normal Cu binding by the prion protein altered age-related increases in metals in the brain. This may explain why many forms of human prion disease do not develop until late in life. [ABSTRACT FROM AUTHOR]

The prion protein (PrP) binds copper and has antioxidant activity enhancing the survival of neurones in culture. The ability of the PrP to bind other cations was tested and it was found that only manganese could substitute for copper. Although initially manganese-loaded PrP exhibited similar structure and activity to copper-loaded PrP, after aging, manganese-loaded PrP became proteinase resistant and lost function. It was also found that manganese could be incorporated into PrP expressed by astrocytes and that this PrP was partially proteinase resistant. These results show that it is possible to generate proteinase­resistant PrP from cells and suggest a possible mechanism for the formation of the scrapie isoform of the PrP as generated in sporadic prion disease. [ABSTRACT FROM AUTHOR]

A peptide based on amino acids 106-126 of the sequence of human prion protein (PrP106-126) is neurotoxic in culture. A role for astrocytes mediating PrP106-126 toxicity was investigated. The toxicity of PrP106-126 to cerebellar cell cultures was reduced by aminoadipate, a gliotoxin. Normally, PrP106-126 is not toxic to cultures containing neurones deficient in the cellular isoform of prion protein (PrPc). However, PrP106-126 was toxic to cerebellar cells derived from Prnp0/0 mice (deficient in PrPc expression) when those cerebellar cells were cocultured with astrocytes. This toxicity was found to occur only in the presence of PrPc-positive astrocytes and to be mediated by glutamate. Furthermore, PrPc-positive astrocytes were shown to protect Prnp0/0 cerebellar cells from glutamate toxicity. This effect could be inhibited by PrP106-126. PrP106-126 did not enhance the toxicity of glutamate to neurones directly. When cerebellar cells were cocultured with astrocytes, the neurones became dependent on astrocytes for protection from glutamate toxicity and expressed an increased sensitivity to glutamate. In such a system, the protective effects of astrocytes against glutamate toxicity to neurones were inhibited by PrP106-126, resulting in a greater reduction in neuronal survival than would have been caused by PrP106-126 when astrocytes were not present. This new model provides a possible mechanism by which the gliosis in prion disease may accelerate the neurodegeneration seen in the later stages of the disease. [ABSTRACT FROM AUTHOR]

Abstract: Expression of the cellular prion protein is necessary for the transmission and propagation of prion diseases. Increasing the level of prion protein expression decreases the incubation period for these diseases. Therefore, understanding the regulation of prion protein expression could be critical for treating or preventing these diseases. We investigated the regulation of prion protein expression by the promoter and noncoding regions of the bovine and murine Prnp genes. We determined that expression is modulated by intron 1 and exon 1. In the absence of intron1, exon 1 inhibited activity of the promoter. However, intron 1 demonstrated promoter-like activity and possessed a TATA box. In addition, we identified an alternative transcript present in the brains of cattle and mice that lacks exon 1. Taken together, these results show that intron 1 and exon 1 play a critical role in the regulation of prion protein expression. Because switching off prion protein expression has been shown to arrest prion disease, these regions present novel targets for intervention in the disease process. [Copyright &y& Elsevier]

Abstract: The cellular isoform of endogenous, newly synthesized prion protein (PrPc) can be transported by axons in the anterograde direction. To determine whether a mechanism exists for secreted PrPc to be internalized and then axonally transported, we analyzed internalization and anterograde axonal transport of radiolabeled recombinant PrPc after its intraocular injection in chick embryos. Internalization and axonal transport of exogenous PrPc to the midbrain by retinal ganglion cells (RGCs) is efficient, saturable and likely receptor-mediated. Ultrastructural quantitative localization of radiolabeled PrPc within RGC soma showed significant labeling of vesicular/endosomal compartments and much less labeling present over the Golgi apparatus and lysosomes, which indicates slow degradation of exogenous PrPc in this system. These data show that a mechanism exists to internalize a secreted form of PrPc and then to axonally transport such PrPc in an anterograde direction. This may provide an additional, novel mechanism for prion protein to spread among neurons. [Copyright &y& Elsevier]

The prion protein (PrP) is a Cu2+ binding cell surface glycoprotein that can misfold into a β-sheet-rich conformation to cause prion diseases. The majority of copper binding studies have concentrated on the octarepeat region of PrP. However, using a range of spectroscopic techniques, we show that copper binds preferentially to an unstructured region of PrP between residues 90 and 115, outside of the octarepeat domain. Comparison of recombinant PrP with PrP-(91-115) indicates that this prion fragment is a good model for Cu2+ binding to the full-length protein. In contrast to previous reports we show that Cu2+ binds to this region of PrP with a nanomolar dissociation constant. NMR and EPR spectroscopy indicate a square-planar or square-pyramidal Cu2+ coordination utilizing histidine residues. Studies with PrP analogues show that the high affinity site requires both His96 and His111 as Cu2+ ligands, rather than a complex centered on His96 as has been previously suggested. Our circular dichroism studies indicate a loss of irregular structure on copper coordination with an increase in β-sheet conformation. It has been shown that this unstructured region, between residues 90 and 120, is vital for prion propagation and different strains of prion disease have been linked with copper binding. The role of Cu2+ in prion misfolding and disease must now be re-evaluated in the light of these findings. [ABSTRACT FROM AUTHOR]

By means of electron spin resonance spectroscopy, in conjunction with the spin trapping technique, we have shown previously that Aβ and α-synuclein (aggregating proteins that accumulate in the brain in Alzheimer's disease, Parkinson's disease, and related disorders) both induce the formation of hydroxyl radicals following incubation in solution, upon addition of Fe(II). These hydroxyl radicals are apparently formed from hydrogen peroxide, via Fenton's reaction. An N-terminally truncated fragment of the mouse prion protein (termed PrP121-231) is toxic to cerebellar cells in culture, and certain human mutations, responsible for inherited prion disease, enhance this toxicity. Here we report that PrP121-231 containing three such mutations (E200K, D178N, and F198S) also generated hydroxyl radicals, upon addition of Fe(II). The formation of these radicals was blocked by catalase, or by metal chelators, each of which also reduced the toxicity of the PrP121-231 fragments to cultured normal mouse cerebellar cells. Wild-type PrP121-231, full-length cellular PrP, and its homologue doppel did not generate any detectable hydroxyl radicals. We conclude that the additional cytotoxic effects of the mutant forms of PrP121-231 could be due to their ability to generate hydrogen peroxide, by a metal-dependent mechanism. Thus, one effect of these (and possibly other) prion mutations could be production of a particularly toxic form of the prion protein, with an enhanced capacity to induce oxidative damage, neurodegeneration, and cell loss. [ABSTRACT FROM AUTHOR]

The prion protein (PrP) is a cell-surface Cu2+ binding glycoprotein which can bind six copper ions. The role of Cu2+ in PrP function, misfolding, and prion disease has generated much interest; however, the field has been hampered by a lack of consensus with regard to the affinity of Cu2+ for PrPC. Here we build on our understanding of the appearance of visible CD spectra for full-length PrP and fragments to determine the affinity of Cu2+ for four different binding modes, with dissociation constants ranging between 13 and 66 nM at pH 7.4. [ABSTRACT FROM AUTHOR]

There is considerable evidence that the prion protein binds copper. However, there have also been suggestions that prion protein (PrP) binds manganese. We used isothermal titration calorimetry to identify the manganese binding sites in wild-type mouse PrP. The protein showed two manganese binding sites with affinities that would bind manganese at concentrations of 63 and 200 µM at pH 5.5. This indicates that PrP binds manganese with affinity similar to other known manganese-binding proteins. Further study indicated that the main manganese binding site is associated with His-95 in the so-called "fifth site" normally associated with copper binding. Additionally, it was shown that occupancy by copper does not prevent manganese binding. Under these conditions, manganese binding resulted in an altered conformation of PrP, displacement of copper, and altered redox chemistry of the metal-protein complex. Cyclic voltammetric measurements suggested a complex redox chemistry involving manganese bound to PrP, whereas copper-bound PrP was able to undergo fully reversible electron cycling. Additionally, manganese binding to PrP converted it to a form able to catalyze aggregation of metal-free PrP. These results further support the notion that manganese binding could cause a conformation change in PrP and trigger changes in the protein similar to those associated with prion disease. [ABSTRACT FROM AUTHOR]

The prion protein (PrP) is a cell-surface Cu2+-binding glycoprotein that when misfolded is responsible for a number of transmissible spongiform encephalopathies. Full-length PrP-(23-231) and constructs in which the octarepeat region has been removed, or His95 and His110 is replaced by alanine residues, have been used to elucidate the order and mode of Cu2+ coordination to PrP-(23-231). We have built on our understanding of the appearance of visible CD spectra and EPR for various PrP fragments to characterize Cu2+ coordination to full-length PrP. At physiological pH, Cu2+ initially binds to full-length PrP in the amyloidogenic region between the octarepeats and the structured domain at His95 and His110. Only subsequent Cu2+ ions bind to single histidine residues within the octarepeat region. Ni2+ ions are used to further probe metal binding and, like Cu2+, Ni2+ will bind individually to His95 and His110, involving preceding main chain amides. Competitive chelators are used to determine the affinity of the first mole equivalent of Cu2+ bound to full-length PrP; this approach places the affinity in the nanomolar range. The affinity and number of Cu2+ binding sites support the suggestion that PrP could act as a sacrificial quencher of free radicals generated by copper redox cycling. [ABSTRACT FROM AUTHOR]

The cellular prion protein is known to be a copper-binding protein. Despite the wide range of studies on the copper binding of PrP, there have been no studies to determine the affinity of the protein on both full-length prion protein and under physiological conditions. We have used two techniques, isothermal titration calorimetry and competitive metal capture analysis, to determine the affinity of copper for wild type mouse PrP and a series of mutants. High affinity copper binding by wild type PrP has been confirmed by the independent techniques indicating the presence of specific tight copper binding sites up to femtomolar affinity. Altogether, four high affinity binding sites of between femto- and nanomolar affinities are located within the octameric repeat region of the protein at physiological pH. A fifth copper binding site of lower affinity than those of the octameric repeat region has been detected in full-length protein. Binding to this site is modulated by the histidine at residue 111. Removal of the octameric repeats leads to the enhancement of affinity of this fifth site and a second binding site outside of the repeat region undetected in the wild type protein. High affinity copper binding allows PrP to compete effectively for copper in the extracellular milieu. The copper binding affinities of PrP have been compared with those of proteins of known function and are of magnitudes compatible with an extracellular copper buffer or an enzymatic function such as superoxide dismutase like activity. [ABSTRACT FROM AUTHOR]

The continuous emergence of antibiotic resistance demands that novel classes of antibiotics continue to be developed. The division machinery of bacteria is an attractive target because it comprises seven or more essential proteins that are conserved almost throughout the bacteria but are absent from humans. We describe the development of a cell-based assay for inhibitors of cell division and its use to isolate a new inhibitor of FtsZ protein, a key player in the division machinery. Biochemical, cytological, and genetic data are presented that demonstrate that FtsZ is the specific target for the compound. We also describe the effects of more potent analogues of the original hit compound that act on important pathogens, again at the level of cell division. The assay and the compounds have the potential to provide novel antibiotics with no pool of pre-existing resistance. They have provided new insight into cytokinesis in bacteria and offer important reagents for further studies of the cell division machinery. [ABSTRACT FROM AUTHOR]

The prion protein (PrP) is a Cu2+ binding cell surface glyco-protein. Misfolding of PrP into a β-sheet rich conformation is associated with transmissible spongiform encephalopathies. Here we use Ni2+ as a diamagnetic probe to further understand Cu2+ binding to PrP. Like Cu2+, Ni2+ preferentially binds to an unstructured region between residues 90 and 126 of PrP, which is a key region for amyloidogenicity and prion propagation. Using both 1H NMR and visible-circular dichroism (CD) spectroscopy, we show that two Ni2+ ions bind to His96 and His111 independently of each other. 1H NMR indicates that both Ni2+ binding sites form square-planar diamagnetic complexes. We have previously shown that Cu2+ forms a paramagnetic square-planar complex in this region, suggesting that Ni2+ could be used as a probe for Cu2+ binding. In addition, competition studies show that two Cu2+ ions can displace Ni2+ from these sites. Upon Ni2+ addition 1H NMR changes in chemical shifts indicate the imidazole ring and amide nitrogen atoms to the N terminus of both His96 and His111 act as coordinating ligands. Use of peptide fragments confirm that PrP(92-96) and PrP(107-111) represent the minimal binding motif for the two Ni2+ binding sites. Analysis of Cu2+ loaded visible-CD spectra show that as with Ni2+, PrP(90-115) binds two Cu2+ ions at His96 and His111 independently of each other. Visible CD studies with PrP(23-231Δ51-90), a construct of PrP(23-231) with the octarepeat region deleted to improve solubility, confirm binding of Ni2+ to His96 and His111 in octarepeat deleted PrP(23-231). The structure of the Cu/Ni complexes is discussed in terms of the implications for prion protein function and disease. [Copyright &y& Elsevier]

The recently described doppel protein (Dpl) is a homologue of the prion protein (PrPc). This protein, expressed in the brains of mice that lack the expression of PrPc, causes neuronal death as the mice age. Previous studies have suggested this neuronal damage is caused by oxidative assault and changes in the activity of NOS proteins. We investigated the toxicity of Dpl in cell culture models and showed that Dpl was toxic to neurons. This toxicity was inhibited by the expression of PrPc and possibly involved direct interaction between the two proteins. The mechanism of toxicity involved stimulation of nitric oxide production via activation of the nitric oxide synthases, nNOS and iNOS. This mechanism of toxicity is quite different from that of PrPSc and does not require the protein to change conformation. These results provide the first evidence for the mechanism of Dpl toxicity. [Copyright &y& Elsevier]

Examines the role of prion protein (PrP) in plasminogen activation. Characteristic features of prion diseases; Expression of normal PrP in plasma membranes; Mechanism of PrP-dependent activation of plasminogen; Association of prion diseases with normal PrP conversion.

To address the need for new antibacterials, a number of bacterial genomes have been systematically disrupted to identify essential genes. Such programs have focused on the disruption of single genes and may have missed functions encoded by gene pairs or multiple genes. In this work, we hypothesized that we could predict the identity of pairs of proteins within one organism that have the same function. We identified 135 putative protein pairs in Bacillus subtilis and attempted to disrupt the genes forming these, singly and then in pairs. The single gene disruptions revealed new genes that could not be disrupted individually and other genes required for growth in minimal medium or for sporulation. The pairwise disruptions revealed seven pairs of proteins that are likely to have the same function, as the presence of one protein can compensate for the absence of the other. Six of these pairs are essential for bacterial viability and in four cases show a pattern of species conservation appropriate for potential antibacterial development. This work highlights the importance of combinatorial studies in understanding gene duplication and identifying functional redundancy. [ABSTRACT FROM AUTHOR]