Circadian regulation of prion protein messenger RNA in the rat forebrain: a widespread and synchronous rhythm

Excessive replacement changes drive evolution of global sheep prion protein (PRNP) sequences

Sheep prion protein (PRNP) is the major host genetic factor responsible for susceptibility to scrapie. We aimed to understand the evolutionary history of sheep PRNP, and primarily focused on breeds from Turkey and Ethiopia, representing genome-wise ancient sheep populations. Population molecular genetic analyses are extended to European, South Asian, and East Asian populations, and for the first time to scrapie associated haplotypes. 1178 PRNP coding region nucleotide sequences were analyzed. High levels of nucleotide diversity driven by extensive low-frequency replacement changes are observed in all populations. Interspecific analyses were conducted using mouflon and domestic goat as outgroup species. Despite an abundance of silent and replacement changes, lack of silent or replacement fixations was observed. All scrapie-associated haplotype analyses from all populations also showed extensive low-frequency replacement changes. Neutrality tests did not indicate positive (directional), balancing or strong negative selection or population contraction for any of the haplotypes in any population. A simple negative selection history driven by prion disease susceptibility is not supported by the population and haplotype based analyses. Molecular function, biological process enrichment, and protein-protein interaction analyses suggested functioning of PRNP protein in multiple pathways, and possible other functional constraint selections. In conclusion, a complex selection history favoring excessive replacement changes together with weak purifying selection possibly driven by frequency-dependent selection is driving PRNP sequence evolution. Our results is not unique only to the Turkish and Ethiopian samples, but can be generalized to global sheep populations.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Neuroprotective effect and potential of cellular prion protein and its cleavage products for treatment of neurodegenerative disorders part I. a literature review

INTRODUCTION

The cellular prion protein (PrP^C) is well known for its pathogenic roles in prion diseases, several other neurodegenerative diseases (such as Alzheimer's disease), and multiple types of cancer, but the beneficial aspects of PrP^C and its cleavage products received much less attention.

AREAS COVERED

Here the authors will systematically review the literatures on the negative as well as protective aspects of PrP^C and its derivatives (especially PrP N-terminal N1 peptide and shed PrP). The authors will dissect the current findings on N1 and shed PrP, including evidence for their neuroprotective effects, the categories of PrP^C cleavage, and numerous cleavage enzymes involved. The authors will also discuss the protective effects and therapeutic potentials of PrP^C-rich exosomes. The cited articles were obtained from extensive PubMed searches of recent literature, including peer-reviewed original articles and review articles.

EXPERT OPINION

PrP and its N-terminal fragments have strong neuroprotective activities that should be explored for therapeutics and prophylactics development against prion disease, Alzheimer's disease and a few other neurodegenerative diseases. The strategies to develop PrP-based therapeutics and prophylactics for these neurodegenerative diseases will be discussed in a companion article (Part II).

Harnessing the Physiological Functions of Cellular Prion Protein in the Kidneys: Applications for Treating Renal Diseases

A cellular prion protein (PrP^C) is a ubiquitous cell surface glycoprotein, and its physiological functions have been receiving increased attention. Endogenous PrP^C is present in various kidney tissues and undergoes glomerular filtration. In prion diseases, abnormal prion proteins are found to accumulate in renal tissues and filtered into urine. Urinary prion protein could serve as a diagnostic biomarker. PrP^C plays a role in cellular signaling pathways, reno-protective effects, and kidney iron uptake. PrP^C signaling affects mitochondrial function via the ERK pathway and is affected by the regulatory influence of microRNAs, small molecules, and signaling proteins. Targeting PrP^C in acute and chronic kidney disease could help improve iron homeostasis, ameliorate damage from ischemia/reperfusion injury, and enhance the efficacy of mesenchymal stem/stromal cell or extracellular vesicle-based therapeutic strategies. PrP^C may also be under the influence of BMP/Smad signaling and affect the progression of TGF-β-related renal fibrosis. PrP^C conveys TNF-α resistance in some renal cancers, and therefore, the coadministration of anti-PrP^C antibodies improves chemotherapy. PrP^C can be used to design antibody-drug conjugates, aptamer-drug conjugates, and customized tissue inhibitors of metalloproteinases to suppress cancer. With preclinical studies demonstrating promising results, further research on PrP^C in the kidney may lead to innovative PrP^C-based therapeutic strategies for renal disease.

The IDIP framework for assessing protein function and its application to the prion protein

The quest to determine the function of a protein can represent a profound challenge. Although this task is the mandate of countless research groups, a general framework for how it can be approached is conspicuously lacking. Moreover, even expectations for when the function of a protein can be considered to be 'known' are not well defined. In this review, we begin by introducing concepts pertinent to the challenge of protein function assignments. We then propose a framework for inferring a protein's function from four data categories: 'inheritance', 'distribution', 'interactions' and 'phenotypes' (IDIP). We document that the functions of proteins emerge at the intersection of inferences drawn from these data categories and emphasise the benefit of considering them in an evolutionary context. We then apply this approach to the cellular prion protein (PrP^C ), well known for its central role in prion diseases, whose function continues to be considered elusive by many investigators. We document that available data converge on the conclusion that the function of the prion protein is to control a critical post-translational modification of the neural cell adhesion molecule in the context of epithelial-to-mesenchymal transition and related plasticity programmes. Finally, we argue that this proposed function of PrP^C has already passed the test of time and is concordant with the IDIP framework in a way that other functions considered for this protein fail to achieve. We anticipate that the IDIP framework and the concepts analysed herein will aid the investigation of other proteins whose primary functional assignments have thus far been intractable.

Sleep deprivation regulates availability of PrPC and Aβ peptides which can impair interaction between PrPC and laminin and neuronal plasticity

PrP^C is a glycoprotein capable to interact with several molecules and mediates diverse signaling pathways. Among numerous ligands, laminin (LN) is known to promote neurite outgrowth and memory consolidation, while amyloid‐beta oligomers (Aβo) trigger synaptic dysfunction. In both pathways, mGluR1 is recruited as co‐receptor. The involvement of PrP^C/mGluR1 in these opposite functions suggests that this complex is a key element in the regulation of synaptic activity. Considering that sleep‐wake cycle is important for synaptic homeostasis, we aimed to investigate how sleep deprivation affects the expression of PrP^C and its ligands, laminin, Aβo, and mGluR1, a multicomplex that can interfere with neuronal plasticity. To address this question, hippocampi of control (CT) and sleep deprived (SD) C57BL/6 mice were collected at two time points of circadian period (13 hr and 21 hr). We observed that sleep deprivation reduced PrP^C and mGluR1 levels with higher effect in active state (21 hr). Sleep deprivation also caused accumulation of Aβ peptides in rest period (13 hr), while laminin levels were not affected. In vitro binding assay showed that Aβo can compete with LN for PrP^C binding. The influence of Aβo was also observed in neuritogenesis. LN alone promoted longer neurite outgrowth than non‐treated cells in both Prnp^+/+ and Prnp^0/0 genotypes. Aβo alone did not show any effects, but when added together with LN, it attenuated the effects of LN only in Prnp^+/+ cells. Altogether, our findings indicate that sleep deprivation regulates the availability of PrP^C and Aβ peptides, and based on our in vitro assays, these alterations induced by sleep deprivation can negatively affect LN–PrP^C interaction, which is known to play roles in neuronal plasticity.

The Role of the Mammalian Prion Protein in the Control of Sleep

Sleep disruption is a prevalent clinical feature in many neurodegenerative disorders, including human prion diseases where it can be the defining dysfunction, as in the case of the "eponymous" fatal familial insomnia, or an early-stage symptom as in certain types of Creutzfeldt-Jakob disease. It is important to establish the role of the cellular prion protein (PrP^C), the key molecule involved in prion pathogenesis, within the sleep-wake system in order to understand fully the mechanisms underlying its contribution to both healthy circadian rhythmicity and sleep dysfunction during disease. Although severe disruption to the circadian rhythm and melatonin release is evident during the pathogenic phases of some prion diseases, untangling whether PrP^C plays a role in circadian rhythmicity, as suggested in mice deficient for PrP^C expression, is challenging given the lack of basic experimental research. We provide a short review of the small amount of direct literature focused on the role of PrP^C in melatonin and circadian rhythm regulation, as well as suggesting mechanisms by which PrP^C might exert influence upon noradrenergic and dopaminergic signaling and melatonin synthesis. Future research in this area should focus upon isolating the points of dysfunction within the retino-pineal pathway and further investigate PrP^C mediation of pinealocyte GPCR activity.

Physiological Functions of the Cellular Prion Protein

The prion protein, PrP^C, is a small, cell-surface glycoprotein notable primarily for its critical role in pathogenesis of the neurodegenerative disorders known as prion diseases. A hallmark of prion diseases is the conversion of PrP^C into an abnormally folded isoform, which provides a template for further pathogenic conversion of PrP^C, allowing disease to spread from cell to cell and, in some circumstances, to transfer to a new host. In addition to the putative neurotoxicity caused by the misfolded form(s), loss of normal PrP^C function could be an integral part of the neurodegenerative processes and, consequently, significant research efforts have been directed toward determining the physiological functions of PrP^C. In this review, we first summarise important aspects of the biochemistry of PrP^C before moving on to address the current understanding of the various proposed functions of the protein, including details of the underlying molecular mechanisms potentially involved in these functions. Over years of study, PrP^C has been associated with a wide array of different cellular processes and many interacting partners have been suggested. However, recent studies have cast doubt on the previously well-established links between PrP^C and processes such as stress-protection, copper homeostasis and neuronal excitability. Instead, the functions best-supported by the current literature include regulation of myelin maintenance and of processes linked to cellular differentiation, including proliferation, adhesion, and control of cell morphology. Intriguing connections have also been made between PrP^C and the modulation of circadian rhythm, glucose homeostasis, immune function and cellular iron uptake, all of which warrant further investigation.

NCAM1 Polysialylation: The Prion Protein's Elusive Reason for Being?

Much confusion surrounds the physiological function of the cellular prion protein (PrP^C). It is, however, anticipated that knowledge of its function will shed light on its contribution to neurodegenerative diseases and suggest ways to interfere with the cellular toxicity central to them. Consequently, efforts to elucidate its function have been all but exhaustive. Building on earlier work that uncovered the evolutionary descent of the prion founder gene from an ancestral ZIP zinc transporter, we recently investigated a possible role of PrP^C in a morphogenetic program referred to as epithelial-to-mesenchymal transition (EMT). By capitalizing on PrP^C knockout cell clones in a mammalian cell model of EMT and using a comparative proteomics discovery strategy, neural cell adhesion molecule-1 emerged as a protein whose upregulation during EMT was perturbed in PrP^C knockout cells. Follow-up work led us to observe that PrP^C regulates the polysialylation of the neural cell adhesion molecule NCAM1 in cells undergoing morphogenetic reprogramming. In addition to governing cellular migration, polysialylation modulates several other cellular plasticity programs PrP^C has been phenotypically linked to. These include neurogenesis in the subventricular zone, controlled mossy fiber sprouting and trimming in the hippocampal formation, hematopoietic stem cell renewal, myelin repair and maintenance, integrity of the circadian rhythm, and glutamatergic signaling. This review revisits this body of literature and attempts to present it in light of this novel contextual framework. When approached in this manner, a coherent model of PrP^C acting as a regulator of polysialylation during specific cell and tissue morphogenesis events comes into focus.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton

Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer's disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.

Prion Protein Signaling in the Nervous System—A Review and Perspective

Prion protein (PrPC) was originally known as the causative agent of transmissible spongiform encephalopathy (TSE) but with recent research, its true function in cells is becoming clearer. It is known to act as a scaffolding protein, binding multiple ligands at the cell membrane and to be involved in signal transduction, passing information from the extracellular matrix (ECM) to the cytoplasm. Its role in the coordination of transmitters at the synapse, glyapse, and gap junction and in short- and long-range neurotrophic signaling gives PrPC a major part in neural transmission and nervous system signaling. It acts to regulate cellular function in multiple targets through its role as a controller of redox status and calcium ion flux. Given the importance of PrPC in cell physiology, this review considers its potential role in disease apart from TSE. The putative functions of PrPC point to involvement in neurodegenerative disease, neuropathic pain, chronic headache, and inflammatory disease including neuroinflammatory disease of the nervous system. Potential targets for the treatment of disease influenced by PrPC are discussed.

Circadian clocks and neurodegenerative diseases: time to aggregate?

The major neurodegenerative diseases are characterised by a disabling loss of the daily pattern of sleep and wakefulness, which may be reflective of a compromise to the underlying circadian clock that times the sleep cycle. At a molecular level, the canonical property of neurodegenerative diseases is aberrant aggregation of otherwise soluble neuronal proteins. They can thus be viewed as disturbances of proteostasis, raising the question whether the two features - altered daily rhythms and molecular aggregation - are related. Recent discoveries have highlighted the fundamental contribution of circadian clocks to the correct ordering of daily cellular metabolic cycles, imposing on peripheral organs such as the liver a strict programme that alternates between anabolic and catabolic states. The discovery that circadian mechanisms are active in local brain regions suggests that they may impinge upon physiological and pathological elements that influence pro-neurodegenerative aggregation. This review explores how introducing the dimension of circadian time and the circadian clock might refine the analysis of aberrant aggregation, thus expanding our perspective on the cell biology common to neurodegenerative diseases.

Identification of adjacent binding sites for the YY1 and E4BP4 transcription factors in the ovine PrP (Prion) gene promoter

The PrP gene encodes the cellular isoform of the prion protein (PrP(c)) which has been shown to be crucial to the development of transmissible spongiform encephalopathies (TSEs). PrP knock-out mice, which do not express endogenous PrP(c), exhibit resistance to TSE disease. The regulation of PrP gene expression represents, therefore, a crucial factor in the development of TSEs. Two sequence motifs in the PrP promoter (positions -287 to -263 from transcriptional start) were previously reported as being highly conserved, and it was suggested that they represent binding sites for as yet unidentified transcription factors. To test this hypothesis, binding of nuclear proteins was analyzed by electrophoretic mobility shift assays using ovine or murine cells and tissues with radiolabeled DNA probes containing the conserved motif sequences. Specific binding was observed to both motifs, and polymorphic variants of these motifs exhibited differential binding. Two proteins bound to these motifs were identified as the Yin Yang 1 (YY1) (motif 1) and E4BP4 (motif 2) transcription factors. Functional promoter analysis of four different promoter variants revealed that motif 1 (YY1) was associated with inhibitory activity in the context of the PrP promoter, whereas motif 2 (E4BP4) was linked to a slight enhancing activity. This represents the first demonstration of binding of nuclear factors to two highly conserved DNA sequence motifs within mammalian PrP promoters. The action of these factors on the PrP promoter is haplotype-specific, leading us to propose that the prion protein expression pattern and, with it, the distribution of TSE infectivity may be associated with PrP promoter genotype.

Hypothalamic-pituitary-adrenal axis disregulation in PrPC-null mice

As manifestations of prion diseases include disturbances of hypothalamic and pituitary functions, we tested the hypothesis that the cellular prion protein (PrPC) has a role as modulator of the hypothalamic-pituitary-adrenal axis. The level of corticosterone and adrenocorticotropic hormone were compared in PrPC null (PrP 0/0) and wild-type (PrP+/+) mice. PrP 0/0 showed hypercorticism during the dark part of day. After acute stress, corticosterone and adrenocorticotropic hormone increased similarly in PrP+/+ and PrP 0/0 mice. Adrenocorticotropic hormone, however, remained elevated in PrP+/+ 0/0 mice at corticosterone levels that are inhibitory in PrP mice. Pretreatment with corticosterone or dexamethasone inhibited stress-induced elevation of adrenocorticotropic hormone in PrP+/+ but not in PrP 0/0 mice. Thus, PrPC may play a role in the negative feedback regulation of axis.

Physiology of the prion protein

Prion diseases are transmissible spongiform encephalopathies (TSEs), attributed to conformational conversion of the cellular prion protein (PrP(C)) into an abnormal conformer that accumulates in the brain. Understanding the pathogenesis of TSEs requires the identification of functional properties of PrP(C). Here we examine the physiological functions of PrP(C) at the systemic, cellular, and molecular level. Current data show that both the expression and the engagement of PrP(C) with a variety of ligands modulate the following: 1) functions of the nervous and immune systems, including memory and inflammatory reactions; 2) cell proliferation, differentiation, and sensitivity to programmed cell death both in the nervous and immune systems, as well as in various cell lines; 3) the activity of numerous signal transduction pathways, including cAMP/protein kinase A, mitogen-activated protein kinase, phosphatidylinositol 3-kinase/Akt pathways, as well as soluble non-receptor tyrosine kinases; and 4) trafficking of PrP(C) both laterally among distinct plasma membrane domains, and along endocytic pathways, on top of continuous, rapid recycling. A unified view of these functional properties indicates that the prion protein is a dynamic cell surface platform for the assembly of signaling modules, based on which selective interactions with many ligands and transmembrane signaling pathways translate into wide-range consequences upon both physiology and behavior.

Lambs with scrapie susceptible genotypes have higher postnatal survival

Background

Prion protein (PrP) alleles associated with scrapie susceptibility persist in many sheep populations even with high frequencies despite centuries of selection against them. This suggests that scrapie susceptibility alleles have a pleiotropic effect or are associated with fitness or other traits that have been subject to selection.

Methodology/Principal Findings

We genotyped all lambs in two scrapie-free Scottish Blackface sheep flocks for polymorphisms at codons 136, 154 and 171 of the PrP gene. We tested potential associations of the PrP genotype with lamb viability at birth and postnatal survival using a complementary log-log link function and a Weibull proportional hazard model, respectively. Here we show there is an association between PrP genotype, as defined by polymorphisms at codons 154 ad 171, and postnatal lamb survival in the absence of scrapie. Sheep carrying the wild-type ARQ allele have higher postnatal survival rates than sheep carrying the more scrapie-resistant alleles (ARR or AHQ).

Conclusion

The PrP genotypes associated with higher susceptibility to scrapie are associated with improved postnatal survival in the absence of the disease. This association helps to explain the existence, and in many instances the high frequency, of the ARQ allele in sheep populations.

The prion protein family: Diversity, rivalry, and dysfunction

The prion gene family currently consists of three members: Prnp which encodes PrP(C), the precursor to prion disease associated isoforms such as PrP(Sc); Prnd which encodes Doppel, a testis-specific protein involved in the male reproductive system; and Sprn which encodes the newest PrP-like protein, Shadoo, which is expressed in the CNS. Although the identification of numerous candidate binding partners for PrP(C) has hinted at possible cellular roles, molecular interpretations of PrP(C) activity remain obscure and no widely-accepted view as to PrP(C) function has emerged. Nonetheless, studies into the functional interrelationships of prion proteins have revealed an interesting phenomenon: Doppel is neurotoxic to cerebellar cells in a manner which can be blocked by either PrP(C) or Shadoo. Further examination of this paradigm may help to shed light on two prominent unanswered questions in prion biology: the functional role of PrP(C) and the neurotoxic pathways initiated by PrP(Sc) in prion disease.

Lymphoid follicles of the ileal Peyer's patch of lambs express low levels of PrP, as demonstrated by quantitative real-time RT-PCR on microdissected tissue compartments, in situ hybridization and immunohistochemistry

The expression level of normal cellular prion protein (PrPC) is thought to influence the transmission of transmissible spongiform encephalopathies (TSEs) from the peripheral entry site to the site of pathological changes in the central nervous system. In many TSEs, the clinical disease is preceded by a period in which the agent accumulates in lymphoid organs, particularly in association with follicular dendritic cells of lymphoid follicles. As the probable route of entry of the TSE agent is via the gut, the expression profile of PrP was examined in well-developed gut-associated lymphoid tissue of lambs, the ileal Peyer's patch, by laser microdissection and real-time RT-PCR. Lymphoid follicles were found to have very low levels of expression, whilst highest levels were detected in the outer submucosa and the muscular layer. These findings were supported by in situ hybridization and immunohistochemistry, which showed specific labelling in nerve cells in ganglia of the submucosal (Meissner's) and myenteric (Auerbach's) plexi of the enteric nervous system. Based on the assumption that potential sites for conversion to the scrapie-related prion protein (PrPSc) should display high levels of expression of PrPC, this study suggests that the accumulation of PrPSc in the lymphoid follicles of the Peyer's patch is not preceded by PrP conversion in the same tissue compartment.

Prion protein expression in bovine podocytes and extraglomerular mesangial cells

The cellular form of the prion protein (PrP(c)) is thought to be a substrate for an abnormal isoform of the prion protein (PrP(sc)). One emerging hypothesis is that the proposed conversion phenomenon takes place at the site at which the infectious agent meets PrP(c). PrP(c) is abundant in the central nervous system, but little is known about the cell-type-specific distribution of PrP(c) in non-neuronal tissues of cattle. We have studied whether PrP(c), a protein found predominantly in neurons, also exists in bovine podocytes, since neurons and podocytes share a large number of similarities. We have therefore examined the expression of PrP(c) by immunohistochemistry, reverse transcription/polymerase chain reaction and enzyme-linked immunosorbent analysis. Immunostained serial sections and specific antibodies against PrP(c) have revealed that PrP(c) is selectively localized in podocytes and is particularly strongly expressed in extraglomerular mesangial cells but not in endothelial or intraglomerular mesangial cells. The selective expression of PrP(c) in podocytes is of special importance, as it suggests that these cells represent possible targets for peripheral infection with prions and demonstrates that PrP(c) can be added to the list of neuronal factors expressed in mammalian podocytes.

Elevated silver, barium and strontium in antlers, vegetation and soils sourced from CWD cluster areas: do Ag/Ba/Sr piezoelectric crystals represent the transmissible pathogenic agent in TSEs?

High levels of Silver (Ag), Barium (Ba) and Strontium (Sr) and low levels of copper (Cu) have been measured in the antlers, soils and pastures of the deer that are thriving in the chronic wasting disease (CWD) cluster zones in North America in relation to the areas where CWD and other transmissible spongiform encephalopathies (TSEs) have not been reported. The elevations of Ag, Ba and Sr were thought to originate from both natural geochemical and artificial pollutant sources--stemming from the common practise of aerial spraying with 'cloud seeding' Ag or Ba crystal nuclei for rain making in these drought prone areas of North America, the atmospheric spraying with Ba based aerosols for enhancing/refracting radar and radio signal communications as well as the spreading of waste Ba drilling mud from the local oil/gas well industry across pastureland. These metals have subsequently bioconcentrated up the foodchain and into the mammals who are dependent upon the local Cu deficient ecosystems. A dual eco-prerequisite theory is proposed on the aetiology of TSEs which is based upon an Ag, Ba, Sr or Mn replacement binding at the vacant Cu/Zn domains on the cellular prion protein (PrP)/sulphated proteoglycan molecules which impairs the capacities of the brain to protect itself against incoming shockbursts of sound and light energy. Ag/Ba/Sr chelation of free sulphur within the biosystem inhibits the viable synthesis of the sulphur dependent proteoglycans, which results in the overall collapse of the Cu mediated conduction of electric signals along the PrP-proteoglycan signalling pathways; ultimately disrupting GABA type inhibitory currents at the synapses/end plates of the auditory/circadian regulated circuitry, as well as disrupting proteoglycan co-regulation of the growth factor signalling systems which maintain the structural integrity of the nervous system. The resulting Ag, Ba, Sr or Mn based compounds seed piezoelectric crystals which incorporate PrP and ferritin into their structure. These ferrimagnetically ordered crystals multireplicate and choke up the PrP-proteoglycan conduits of electrical conduction throughout the CNS. The second stage of pathogenesis comes into play when the pressure energy from incoming shock bursts of low frequency acoustic waves from low fly jets, explosions, earthquakes, etc. (a key eco-characteristic of TSE cluster environments) are absorbed by the rogue 'piezoelectric' crystals, which duly convert the mechanical pressure energy into an electrical energy which accumulates in the crystal-PrP-ferritin aggregates (the fibrils) until a point of 'saturation polarization' is reached. Magnetic fields are generated on the crystal surface, which initiate chain reactions of deleterious free radical mediated spongiform neurodegeneration in surrounding tissues. Since Ag, Ba, Sr or Mn based piezoelectric crystals are heat resistant and carry a magnetic field inducing pathogenic capacity, it is proposed that these ferroelectric crystal pollutants represent the transmissible, pathogenic agents that initiate TSE.

Prion protein accumulation and neuroprotection in hypoxic brain damage

The function of the normal conformational isoform of prion protein, PrP(C), remains unclear although lines of research have suggested a role in the cellular response to oxidative stress. Here we investigate the expression of PrP(C) in hypoxic brain tissues to examine whether PrP(C) is in part regulated by neuronal stress. Cases of adult cerebral ischemia and perinatal hypoxic-ischemic injury in humans were compared with control tissues. PrP(C) immunoreactivity accumulates within neuronal processes in the penumbra of hypoxic damage in adult brain, and within neuronal soma in cases of perinatal hypoxic-ischemic injury, and in situ hybridization analysis suggests an up-regulation of PrP mRNA during hypoxia. Rodents also showed an accumulation of PrP(C) in neuronal soma within the penumbra of ischemic lesions. Furthermore, the infarct size in PrP-null mice was significantly greater than in the wild type, supporting the proposed role for PrP(C) in the neuroprotective adaptive cellular response to hypoxic injury.

Prion protein (PrPc) immunocytochemistry and expression of the green fluorescent protein reporter gene under control of the bovine PrP gene promoter in the mouse brain

Expression of the cellular prion protein (PrP(c)) by host cells is required for prion replication and neuroinvasion in transmissible spongiform encephalopathies. As a consequence, identification of the cell types expressing PrP(c) is necessary to determine the target cells involved in the cerebral propagation of prion diseases. To identify the cells expressing PrP(c) in the mouse brain, the immunocytochemical localization of PrP(c) was investigated at the cellular and ultrastructural levels in several brain regions. In addition, we analyzed the expression pattern of a green fluorescent protein reporter gene under the control of regulatory sequences of the bovine prion protein gene in the brain of transgenic mice. By using a preembedding immunogold technique, neuronal PrP(c) was observed mainly bound to the cell surface and presynaptic sites. Dictyosomes and recycling organelles in most of the major neuron types also exhibited PrP(c) antigen. In the olfactory bulb, neocortex, putamen, hippocampus, thalamus, and cerebellum, the distribution pattern of both green fluorescent protein and PrP(c) immunoreactivity suggested that the transgenic regulatory sequences of the bovine PrP gene were sufficient to promote expression of the reporter gene in neurons that express immunodetectable endogenous PrP(c). Transgenic mice expressing PrP-GFP may thus provide attractive murine models for analyzing the transcriptional activity of the Prnp gene during prion infections as well as the anatomopathological kinetics of prion diseases.

Does an infrasonic acoustic shock wave resonance of the manganese 3+ loaded/copper depleted prion protein initiate the pathogenesis of TSE?

Intensive exposures to natural and artificial sources of infrasonic acoustic shock (tectonic disturbances, supersonic aeroplanes, etc.) have been observed in ecosystems supporting mammalian populations that are blighted by clusters of traditional and new variant strains of transmissible spongiform encephalopathy (TSE). But TSEs will only emerge in those 'infrasound-rich' environments which are simultaneously influenced by eco-factors that induce a high manganese (Mn)/low copper (Cu)-zinc (Zn) ratio in brains of local mammalian populations. Since cellular prion protein (PrPc) is a cupro-protein expressed throughout the circadian mediated pathways of the body, it is proposed that PrP's Cu component performs a role in the conduction and distribution of endogenous electromagnetic energy; energy that has been transduced from incoming ultraviolet, acoustic, geomagnetic radiations. TSE pathogenesis is initiated once Mn substitutes at the vacant Cu domain on PrPc and forms a nonpathogenic, protease resistant, 'sleeping' prion. A second stage of pathogenesis comes into play once a low frequency wave of infrasonic shock metamorphoses the piezoelectric atomic structure of the Mn 3+ component of the prion, thereby 'priming' the sleeping prion into its fully fledged, pathogenic TSE isoform - where the paramagnetic status of the Mn 3+ atom is transformed into a stable ferrimagnetic lattice work, due to the strong electron-phonon coupling resulting from the dynamic 'Jahn-Teller' type distortions of the oxygen octahedra specific to the trivalent Mn species. The so called 'infectivity' of the prion is a misnomer and should be correctly defined as the contagious field inducing capacity of the ferrimagnetic Mn 3+ component of the prion; which remains pathogenic at all temperatures below the 'curie point'. A progressive domino-like 'metal to ligand to metal' ferrimagnetic corruption of the conduits of electromagnetic superexchange is initiated. The TSE diseased brain can be likened to a solar charged battery on continuous charge; where the Mn contaminated/Cu depleted circadian-auditory pathways absorb and pile up, rather than conduct the vital life force energies of incoming ultra violet, acoustic and geomagnetic radiation. Instead of harnessing these energies for the body's own bio-rhythmic requirements, an infrasonic shock induced metamorphosis of the Mn atom intervenes; initiating an explosive pathogenesis that perverts the healthy pathways of darkness and light; Cu prions are replaced by hyperpolarized Mn 3+ prions that seed self perpetuating 'cluster bombs' of free radical mediated neurodegeneration. TSE ensues.

Selective expression of prion protein in peripheral tissues of the adult mouse

The level of expression of normal cellular prion protein, PrP(c) (cellular prion protein), controls both the rate and the route of neuroinvasive infection, from peripheral entry portal to the CNS. Paradoxically, an overview of the distribution of PrP(c) within tissues outside the CNS is lacking. We have used novel antibodies that recognise cellular prion protein in glutaraldehyde-fixed tissue (in order to optimise immunohistochemical labelling of this conformationally labile protein), in combination with in situ hybridisation, to examine the expression of PrP(c) in peripheral tissues of the adult mouse. We found that although prion protein is expressed in many tissues, it is expressed at high levels only in discrete subpopulations of cells. Prominent amongst these are elements of the "hardwired neuroimmune network" that integrate the body's immune defence and neuroendocrine systems under CNS control. These prion protein-expressing elements include small diameter afferent nerves in the skin and the lamina propria of the aerodigestive tract, sympathetic ganglia and nerves, antigen presenting and processing cells (both follicular and non-follicular dendritic cells) and sub-populations of lymphocytes particularly in skin, gut- and bronchus-associated lymphoid tissues. Prion protein is also expressed in the parasympathetic and enteric nervous systems, in the dispersed neuroendocrine system, and in peripheral nervous system axons and their associated Schwann cells. This selective expression of cellular prion protein provides a variety of alternative routes for the propagation and transport of prion infection entering from peripheral sites, either naturally (via the aerodigestive tract or abraded skin) or experimentally (by intraperitoneal injection) to the brain. Key regulatory cells that express prion protein, and in particular enteroendocrine cells in the mucosal wall of the gut, and dendritic cells that convey pathogens from epithelial layers to secondary lymphoid organs, may be particularly important in the transmission of infection in the periphery.

A marked disparity between the expression of prion protein and its message by neurones of the CNS

Expression of the normal cellular form of prion protein is both necessary and rate-limiting in the spread of prion disease, yet its cellular expression in vivo is poorly understood. To optimise immunohistochemical labelling of this protein in mouse brain, we have developed novel antibodies that recognise cellular prion protein in glutaraldehyde-fixed tissue. Expression was found to be predominantly neuronal, and to differ between different classes of neurone. Thus, neurones immunoreactive for GABA expressed very high levels of normal prion protein; most projection neurones expressed much lower levels, particularly on their axons in the major fibre tracts, and some neurones (e.g. those positive for dopamine) displayed no detectable prion protein. In marked contrast, all neurones, even those that were immunonegative, expressed high levels of message for prion protein, shown by non-radioactive in situ hybridisation. Glia expressed very low levels of message, and undetectable levels of prion protein. We conclude that the steady-state level of prion protein, which differs so markedly between different neuronal types, is primarily controlled post-transcriptionally, possibly by differences in protein trafficking or degradation. These marked differences in the way different neurones produce and/or degrade their normal cellular prion protein may influence the selective spread and neurotoxic targeting of prion diseases within the CNS.

Nonneuronal cellular prion protein

The normal cellular prion protein (PrP(c)) is a membrane sialoglycoprotein of unknown function having the unique property of adopting an abnormal tertiary conformation. The pathological conformer PrP(sc) would be the agent of transmissible spongiform encephalopathies or prion diseases. They include scrapie and bovine spongiform encephalopathy in animals and Creutzfeldt-Jakob disease in humans. The conversion of PrP(c) into PrP(sc) in the brain governs the clinical phenotype of the disease. However, the three-dimensional structure change of PrP(c) can also take place outside the central nervous system, in nonneuronal cells particularly of lymphoid tissue where the agent replicates. In natural infection, PrP(c) in nonneuronal cells of peripheral extracerebral organs may play a key role as the receptor required to enable the entry of the infectious agent into the host. In the present review we have undertaken a first evaluation of compelling data concerning the PrP(c)-expressing cells of nonneuronal origin present in cerebral and extracerebral tissues. The analysis of tissue, cellular, and subcellular localization of PrP(c) may help us better understand the biological function of PrP(c) and provide some information on physiopathological processes underlying prion diseases.

Does an ultra violet photooxidation of the manganese-loaded/copper-depleted prion protein in the retina initiate the pathogenesis of TSE?

Ecosystems supporting clusters of sporadic transmissible spongiform encephalopathy (TSE) are characterized by common properties of high-manganese/low-copper, zinc, selenium mineral status, and high-altitude/snow-covered/pre-cambrian mountain terrain where above-average intensities of ultra violet/ozone oxidants are prevalent. Cell culture trials have confirmed the hypothesis that manganese (Mn) substitutes at Prion Protein's (PrP's) vacated copper (Cu) domain, whereupon PrP loses its Cu-mediated antioxidant function, transforming into a protease-resistant misfolded isoform that aggregates into fibril 'tombstone' structures - the key hallmark distinguishing TSE central nervous system (CNS) pathology. The cellular localisation of PrP suggests PrP serves a 'front line' contributory role in neutralizing radicals generated by incoming environmental oxidants, whilst an intensive expression of PrP messenger ribonucleic acid (mRNA) in the retina, melanocytes, epidermis, etc., suggests PrP performs a key antioxidant role as a 'photooxidative shock absorber'; binding of porphyrin IX, Congo red and other photosensitisers to PrPc suggests PrPc serves as an integral associate of the porphyrin/melanin chromophore electron transfer chain; thereby serving as a quencher of singlet O2/superoxide generated by photoenergised chromophores/xeno photosensitisers. It is proposed that sporadic TSE pathogenesis is initiated in the retina of environmentally/genetically predisposed individuals via a two-stage chronic toxic process - Mn substitution at PrP's Cu domain forming a stable Mn2+-PrP complex, followed by an ultra violet in situ photo-oxidization of the Mn2+ component; whereby the latent 'Jekyll and Hyde' capacity of the Mn2+-PrP conjugate is activated into the fully fledged, 'infectious' lethal auto-oxidizing, Mn3+-PrP 'prion' agent. Thus, PrPc's Cu-mediated antioxidant function is replaced by a Mn3+-mediated autooxidant dysfunction. Could the UK's increased loading of a cocktail of environmental oxidants that penetrated the CNS of the UK bovine (ultra violet microwaves/ozone/systemic cu-chelating insecticides) account for a more virulent Mn4+ mediated acceleration of the TSE degenerative process in Mn-contaminated/genetically predisposed individuals, manifesting as the widespread emergence of new-variant bovine spongiform encephalopathy (BSE)/variant Creutzfeldt-Jacob disease (VCJD)/FSE in younger mammals?