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1.
《朊病毒》2013,7(3):172-178
The soluble cellular prion protein (PrPC) is best known for its association with prion disease (PrD) through its conversion to a pathogenic insoluble isoform (PrPSc). However, its deleterious effects independent of PrPSc have recently been observed not only in PrD but also in Alzheimer disease (AD), two diseases which mainly affect cognition. At the same time, PrPC itself seems to have broad physiologic functions including involvement in cognitive processes. The PrPC that is believed to be soluble and monomeric has so far been the only PrP conformer observed in the uninfected brain. In 2006, we identified an insoluble PrPC conformer (termed iPrPC) in uninfected human and animal brains. Remarkably, the PrPSc-like iPrPC shares the immunoreactivity behavior and fragmentation with a newly-identified PrPSc species in a novel human PrD termed variably protease-sensitive prionopathy. Moreover, iPrPC has been observed as the major PrP species that interacts with amyloid β (Aβ) in AD. This article highlights evidence of PrP involvement in two putatively beneficial and deleterious PrP-implicated pathways in cognition, and hypothesizes first, that beneficial and deleterious effects of PrPC are attributable to the chameleon-like conformation of the protein and second, that the iPrPC conformer is associated with PrD and AD.  相似文献   

2.
The soluble cellular prion protein (PrPC) is best known for its association with prion disease (PrD) through its conversion to a pathogenic insoluble isoform (PrPSc). However, its deleterious effects independent of PrPSc have recently been observed not only in PrD but also in Alzheimer disease (AD), two diseases which mainly affect cognition. At the same time, PrPC itself seems to have broad physiologic functions including involvement in cognitive processes. The PrPC that is believed to be soluble and monomeric has so far been the only PrP conformer observed in the uninfected brain. In 2006, we identified an insoluble PrPC conformer (termed iPrPC) in uninfected human and animal brains. Remarkably, the PrPSc-like iPrPC shares the immunoreactivity behavior and fragmentation with a newly-identified PrPSc species in a novel human PrD termed variably protease-sensitive prionopathy. Moreover, iPrPC has been observed as the major PrP species that interacts with amyloid β (Aβ) in AD. This article highlights evidence of PrP involvement in two putatively beneficial and deleterious PrP-implicated pathways in cognition and hypothesizes first, that beneficial and deleterious effects of PrPC are attributable to the chameleon-like conformation of the protein and second, that the iPrPC conformer is associated with PrD and AD.Key words: prion protein, prion disease, cognition, cognitive deficit, insoluble prion protein, Alzheimer disease, variably protease-sensitive prionopathy, dementia, memory  相似文献   

3.
Prion diseases are caused by the conversion of a cellular protein (PrPC) into a misfolded, aggregated isoform (PrPRes). Misfolding of recombinant PrPC in the absence of PrPRes template, cellular factors, denaturing agents, or at neutral pH has not been achieved. A number of studies indicate that dimerization of PrPC may be a key step in the aggregation process. In an effort to understand the molecular event that may activate misfolding of PrPC in more relevant physiological conditions, we tested if enforced dimerization of PrPC may induce a conformational change reminiscent of the conversion of PrPC to PrPRes. We used a well described inducible dimerization strategy whereby a chimeric PrPC composed of a modified FK506-binding protein (Fv) fused with PrPC and termed Fv-PrP is incubated in the presence of a monomeric FK506 or dimerizing AP20187 ligand. Addition of AP20187 but not FK506 to recombinant Fv-PrP (rFv-PrP) in physiological-like conditions resulted in a rapid conformational change characterized by an increase in β-sheet structure and simultaneous aggregation of the protein. Aggregates were partially resistant to proteinase K and induced the conversion of soluble rFv-PrP in serial seeding experiments. As judged from thioflavin T binding and electron microscopy, aggregates converted to amyloid fibers. Aggregates were toxic to cultured cells, whereas soluble rFv-PrP and amyloid fibers were harmless. This study strongly supports the proposition that dimerization of PrPC is a key pathological primary event in the conversion of PrPC and may initiate the pathogenesis of prion diseases.  相似文献   

4.
Prion and Alzheimer diseases are fatal neurodegenerative diseases caused by misfolding and aggregation of the cellular prion protein (PrPC) and the β-amyloid peptide, respectively. Soluble oligomeric species rather than large aggregates are now believed to be neurotoxic. PrPC undergoes three proteolytic cleavages as part of its natural life cycle, α-cleavage, β-cleavage, and ectodomain shedding. Recent evidences demonstrate that the resulting secreted PrPC molecules might represent natural inhibitors against soluble toxic species. In this mini-review, we summarize recent observations suggesting the potential benefit of using PrPC-derived molecules as therapeutic agents in prion and Alzheimer diseases.  相似文献   

5.
蛋白质感染颗粒(PrP)的错误折叠被认为是引起一些神经退化性疾病的主因,但其正常构象(PrPC)的功能却一直不为人所知.近年来研究发现,在正常细胞中,尤其是脑细胞中,细胞膜PrPC可通过内吞作用进入细胞质而将Cu2+载运至SOD1,从而参与调节SOD1 的活性及细胞铜代谢.另有研究表明,Cu2+对于PrPSc(错误构象)的蛋白水解酶K抗性的恢复及不同“病株”的形成也有很重要的作用.  相似文献   

6.
It has been estimated that cerebrospinal fluid (CS F) contains approximately 80 proteins that significantly increase or decrease in response to various clinical conditions. Here we have evaluated the CS F protein PrPC (cellular prion protein) for possible increases or decreases following spinal cord injury. The physiological function of PrPC is not yet completely understood; however, recent findings suggest that PrPC may have neuroprotective properties. Our results show that CS F PrPC is decreased in spinal cord injured patients 12 h following injury and is absent at 7 days. Given that normal PrPC has been proposed to be neuroprotective, we speculate that the decrease in CS F PrPC levels may influence neuronal cell survival following spinal cord injury.Key words: CSF, PrPC, Hsp25, crystallin domain, spinal cord injury  相似文献   

7.
Soluble oligomers of the amyloid-β (Aβ) peptide cause neurotoxicity, synaptic dysfunction, and memory impairments that underlie Alzheimer disease (AD). The cellular prion protein (PrPC) was recently identified as a high affinity neuronal receptor for Aβ oligomers. We report that fibrillar Aβ oligomers recognized by the OC antibody, which have been shown to correlate with the onset and severity of AD, bind preferentially to cells and neurons expressing PrPC. The binding of Aβ oligomers to cell surface PrPC, as well as their downstream activation of Fyn kinase, was dependent on the integrity of cholesterol-rich lipid rafts. In SH-SY5Y cells, fluorescence microscopy and co-localization with subcellular markers revealed that the Aβ oligomers co-internalized with PrPC, accumulated in endosomes, and subsequently trafficked to lysosomes. The cell surface binding, internalization, and downstream toxicity of Aβ oligomers was dependent on the transmembrane low density lipoprotein receptor-related protein-1 (LRP1). The binding of Aβ oligomers to cell surface PrPC impaired its ability to inhibit the activity of the β-secretase BACE1, which cleaves the amyloid precursor protein to produce Aβ. The green tea polyphenol (−)-epigallocatechin gallate and the red wine extract resveratrol both remodeled the fibrillar conformation of Aβ oligomers. The resulting nonfibrillar oligomers displayed significantly reduced binding to PrPC-expressing cells and were no longer cytotoxic. These data indicate that soluble, fibrillar Aβ oligomers bind to PrPC in a conformation-dependent manner and require the integrity of lipid rafts and the transmembrane LRP1 for their cytotoxicity, thus revealing potential targets to alleviate the neurotoxic properties of Aβ oligomers in AD.  相似文献   

8.
《朊病毒》2013,7(6):420-428
ABSTRACT

Converging observations from disparate lines of inquiry are beginning to clarify the cause of brain iron dyshomeostasis in sporadic Creutzfeldt-Jakob disease (sCJD), a neurodegenerative condition associated with the conversion of prion protein (PrPC), a plasma membrane glycoprotein, from α-helical to a β-sheet rich PrP-scrapie (PrPSc) isoform. Biochemical evidence indicates that PrPC facilitates cellular iron uptake by functioning as a membrane-bound ferrireductase (FR), an activity necessary for the transport of iron across biological membranes through metal transporters. An entirely different experimental approach reveals an evolutionary link between PrPC and the Zrt, Irt-like protein (ZIP) family, a group of proteins involved in the transport of zinc, iron, and manganese across the plasma membrane. Close physical proximity of PrPC with certain members of the ZIP family on the plasma membrane and increased uptake of extracellular iron by cells that co-express PrPC and ZIP14 suggest that PrPC functions as a FR partner for certain members of this family. The connection between PrPC and ZIP proteins therefore extends beyond common ancestry to that of functional cooperation. Here, we summarize evidence supporting the facilitative role of PrPC in cellular iron uptake, and implications of this activity on iron metabolism in sCJD brains.  相似文献   

9.

Background

According to the prevailing view, soluble oligomers or small fibrillar fragments are considered to be the most toxic species in prion diseases. To test this hypothesis, two conformationally different amyloid states were produced from the same highly pure recombinant full-length prion protein (rPrP). The cytotoxic potential of intact fibrils and fibrillar fragments generated by sonication from these two states was tested using cultured cells.

Methodology/Principal Findings

For one amyloid state, fibril fragmentation was found to enhance its cytotoxic potential, whereas for another amyloid state formed within the same amino acid sequence, the fragmented fibrils were found to be substantially less toxic than the intact fibrils. Consistent with the previous studies, the toxic effects were more pronounced for cell cultures expressing normal isoform of the prion protein (PrPC) at high levels confirming that cytotoxicity was in part PrPC-dependent. Silencing of PrPC expression by small hairpin RNAs designed to silence expression of human PrPC (shRNA-PrPC) deminished the deleterious effects of the two amyloid states to a different extent, suggesting that the role of PrPC-mediated and PrPC-independent mechanisms depends on the structure of the aggregates.

Conclusions/Significance

This work provides a direct illustration that the relationship between an amyloid''s physical dimension and its toxic potential is not unidirectional but is controlled by the molecular structure of prion protein (PrP) molecules within aggregated states. Depending on the structure, a decrease in size of amyloid fibrils can either enhance or abolish their cytotoxic effect. Regardless of the molecular structure or size of PrP aggregates, silencing of PrPC expression can be exploited to reduce their deleterious effects.  相似文献   

10.
The central event in the pathogenesis of prion diseases involves a conversion of the host-encoded cellular prion protein PrPC into its pathogenic isoform PrPSc 1. PrPC is detergent-soluble and sensitive to proteinase K (PK)-digestion, whereas PrPSc forms detergent-insoluble aggregates and is partially resistant to PK2-6. The conversion of PrPC to PrPSc is known to involve a conformational transition of α-helical to β-sheet structures of the protein. However, the in vivo pathway is still poorly understood. A tentative endogenous PrPSc, intermediate PrP* or "silent prion", has yet to be identified in the uninfected brain7.Using a combination of biophysical and biochemical approaches, we identified insoluble PrPC aggregates (designated iPrPC) from uninfected mammalian brains and cultured neuronal cells8, 9. Here, we describe detailed procedures of these methods, including ultracentrifugation in detergent buffer, sucrose step gradient sedimentation, size exclusion chromatography, iPrP enrichment by gene 5 protein (g5p) that specifically bind to structurally altered PrP forms10, and PK-treatment. The combination of these approaches isolates not only insoluble PrPSc and PrPC aggregates but also soluble PrPC oligomers from the normal human brain. Since the protocols described here have been used to isolate both PrPSc from infected brains and iPrPC from uninfected brains, they provide us with an opportunity to compare differences in physicochemical features, neurotoxicity, and infectivity between the two isoforms. Such a study will greatly improve our understanding of the infectious proteinaceous pathogens. The physiology and pathophysiology of iPrPC are unclear at present. Notably, in a newly-identified human prion disease termed variably protease-sensitive prionopathy, we found a new PrPSc that shares the immunoreactive behavior and fragmentation with iPrPC 11, 12. Moreover, we recently demonstrated that iPrPC is the main species that interacts with amyloid-β protein in Alzheimer disease13. In the same study, these methods were used to isolate Abeta aggregates and oligomers in Alzheimer''s disease13, suggesting their application to non-prion protein aggregates involved in other neurodegenerative disorders.  相似文献   

11.
《朊病毒》2013,7(4):190-194
Alzheimer and prion diseases are neurodegenerative disorders characterised by the abnormal processing of amyloid-b (Ab) peptide and prion protein (PrPC), respectively. Recent evidence indicates that PrPC may play a critical role in the pathogenesis of Alzheimer disease. PrPC interacts with and inhibits the b-secretase BACE1, the rate-limiting enzyme in the production of Ab. More recently PrPC was identified as a receptor for Ab oligomers and the expression of PrPC appears to be controlled by the amyloid intracellular domain (AICD). Here we review these observations and propose a feedback loop in the normal brain where PrPC exerts an inhibitory effect on BACE1 to decrease both Ab and AICD production. In turn, the AICD upregulates PrPC expression, thus maintaining the inhibitory effect of PrPC on BACE1. In Alzheimer disease, this feedback loop is disrupted, and the increased level of Ab oligomers bind to PrPC and prevent it from regulating BACE1 activity.  相似文献   

12.
Prion diseases are characterized biochemically by protein aggregation of infectious prion isoforms (PrPSc), which result from the conformational conversion of physiological prion proteins (PrPC). PrPC are variable post-translationally modified glycoproteins, which exist as full length and as aminoterminally truncated glycosylated proteins and which exhibit differential detergent solubility. This implicates the presence of heterogeneous phenotypes, which overlap as protein complexes at the same molecular masses. Although the biological function of PrPC is still enigmatic, evidence reveals that PrPC exhibits metal-binding properties, which result in structural changes and decreased solubility. In this study, we analyzed the yield of PrPC metal binding affiliated with low solubility and changes in protein banding patterns. By implementing a high-speed centrifugation step, the interaction of zinc ions with PrPC was shown to generate large quantities of proteins with low solubility, consisting mainly of full-length glycosylated PrPC; whereas unglycosylated PrPC remained in the supernatants as well as truncated glycosylated proteins which lack of octarepeat sequence necessary for metal binding. This effect was considerably lower when PrPC interacted with copper ions; the presence of other metals tested exhibited no effect under these conditions. The binding of zinc and copper to PrPC demonstrated differentially soluble protein yields within distinct PrPC subtypes. PrPC–Zn2+-interaction may provide a means to differentiate glycosylated and unglycosylated subtypes and offers detailed analysis of metal-bound and metal-free protein conversion assays.  相似文献   

13.
Proper diagnosis and treatment of traumatic brain injury (TBI) in children is becoming an increasingly problematic issue in China. This study investigated Chinese clinicians to provide information about their knowledge and experiences in diagnosis and treatment of pediatric TBI. We conducted a questionnaire survey among clinicians in the emergency departments and neurosurgery departments at 9 major hospitals in China. The questionnaire included demographic information, and knowledge and experiences regarding the diagnosis and treatment of pediatric TBI. A total of 235 clinicians completed questionnaires. 43.8% of the surveyed clinicians reported children with only scalp hematoma without any other signs and symptoms of concussion as TBI cases. Most clinicians (85.1%) reported no existing uniform diagnostic criteria for children with TBI in China. The majority of clinicians (91.9%) reported that CT scans were performed in all patients with suspected head injury as a routine procedure in their hospitals. Only 20.9% of clinicians believed that radiation from CT scanning may increase cancer risk in children. About 33.6% of the clinicians reported that they ordered CT scans to investigate suspected head injury due to the poor doctor-patient relationship in China, and to protect themselves against any medical lawsuits in the future. About 80% of the clinicians reported that there are no existing pediatric TBI treatment guidelines in China. Instead a senior doctor’s advice is the most reported guidelines regarding treating pediatric TBI (66.0%). All of the surveyed clinicians reported that the lack of diagnosis and/or treatment standard is the biggest problem in effectively diagnosing and treating pediatric TBI in China. Developing guidelines for the diagnosis and treatment of children with TBI is a high priority in China. The extremely high usage of CT for pediatric TBI in China suggests that it is important to establish evidence-based clinical decision rules to help Chinese clinicians make diagnostic and therapeutic decisions during their practice in order to identify children unlikely to have a clinically-important TBI who can be safely discharged without a CT scan.  相似文献   

14.
Transmissible spongiform encephalopathies are fatal neurodegenerative disorders thought to be transmitted by self-perpetuating conformational conversion of a neuronal membrane glycoprotein (PrPC, for “cellular prion protein”) into an abnormal state (PrPSc, for “scrapie prion protein”). Doppel (Dpl) is a protein that shares significant biochemical and structural homology with PrPC. In contrast to its homologue PrPC, Dpl is unable to participate in prion disease progression or to achieve an abnormal PrPSc-like state. We have constructed a chimeric mouse protein, composed of the N-terminal domain of PrPC (residues 23-125) and the C-terminal part of Dpl (residues 58-157). This chimeric protein displays PrP-like biochemical and structural features; when incubated in presence of NaCl, the α-helical monomer forms soluble β-sheet-rich oligomers which acquire partial resistance to pepsin proteolysis in vitro, as do PrP oligomers. Moreover, the presence of aggregates akin to protofibrils is observed in soluble oligomeric species by electron microscopy.  相似文献   

15.
Flotillins are membrane association proteins consisting of two homologous members, flotillin-1 (Flot-1) and flotillin-2 (Flot-2). They define a clathrin-independent endocytic pathway in mammal cells, which are also distinct from some other endocytosis mechanisms. The implicated cargoes of the flotillin-dependent pathway are mainly some GPI-anchored proteins, such as CD59 and Thy-1, which positionally colocalize with flotillins at the plasma membrane microdomains. To see whether flotillins are involved in the endocytosis of PrPC, the potential molecular interaction between PrPC and flotillins in a neuroblastoma cell line SK-N-SH was analyzed. Co-immunoprecipitation assays did not reveal a detectable complex in the cell lysates of a normal feeding situation. After stimulation of Cu2+, PrPC formed a clear complex with Flot-1, but not with Flot-2. Immunofluorescent assays illustrated that PrPC colocalized well with Flot-1, and the complexes of PrPC–Flot-1 shifted from the cell membrane to the cytoplasm along with the treatment of Cu2+. Down-regulating the expression of Flot-1 in SK-N-SH cells by Flot-1-specific RNAi obviously abolished the Cu2+-stimulated endocytosis process of PrPC. Moreover, we also found that in the cell line human embryonic kidney 293 (HEK293) without detectable PrPC expression, the distribution of cellular Flot-1 maintained almost unchanged during Cu2+ treatment. Cu2+-induced PrPC–Flot-1 molecular interaction and endocytosis in HEK293 cells were obtained when expressing wild-type human PrP (PrPPG5), but not in the preparation expressing octarepeat-deleted PrP (PrPPG0). Our data here provide direct evidences for the molecular interaction and endocytosis of PrPC with Flot-1 in the presence of copper ions, and the octarepeat region of PrPC is critical for this process, which strongly indicates that the Flot-1-dependent endocytic pathway seems to mediate the endocytosis process of PrPC in the special situation.  相似文献   

16.
Corruption of cellular prion protein (PrPC) function(s) at the plasma membrane of neurons is at the root of prion diseases, such as Creutzfeldt-Jakob disease and its variant in humans, and Bovine Spongiform Encephalopathies, better known as mad cow disease, in cattle. The roles exerted by PrPC, however, remain poorly elucidated. With the perspective to grasp the molecular pathways of neurodegeneration occurring in prion diseases, and to identify therapeutic targets, achieving a better understanding of PrPC roles is a priority. Based on global approaches that compare the proteome and metabolome of the PrPC expressing 1C11 neuronal stem cell line to those of PrPnull-1C11 cells stably repressed for PrPC expression, we here unravel that PrPC contributes to the regulation of the energetic metabolism by orienting cells towards mitochondrial oxidative degradation of glucose. Through its coupling to cAMP/protein kinase A signaling, PrPC tones down the expression of the pyruvate dehydrogenase kinase 4 (PDK4). Such an event favors the transfer of pyruvate into mitochondria and its conversion into acetyl-CoA by the pyruvate dehydrogenase complex and, thereby, limits fatty acids β-oxidation and subsequent onset of oxidative stress conditions. The corruption of PrPC metabolic role by pathogenic prions PrPSc causes in the mouse hippocampus an imbalance between glucose oxidative degradation and fatty acids β-oxidation in a PDK4-dependent manner. The inhibition of PDK4 extends the survival of prion-infected mice, supporting that PrPSc-induced deregulation of PDK4 activity and subsequent metabolic derangements contribute to prion diseases. Our study posits PDK4 as a potential therapeutic target to fight against prion diseases.  相似文献   

17.
Danielle Beckman 《朊病毒》2016,10(2):131-142
The physiological properties of the native, endogenous prion protein (PrPC) is a matter of concern, due to its pleiotropic functions and links to neurodegenerative disorders and cancer. In line with our hypothesis that the basic function of PrPC is to serve as a cell surface scaffold for the assembly of signaling modules, multiple interactions have been identified of PrPC with signaling molecules, including neurotransmitter receptors. We recently reported evidence that PrPC may modulate monoaminergic neurotransmission, as well as depressive-like behavior in mice. Here, we discuss how those results, together with a number of other studies, including our previous demonstration that both inflammatory and behavioral stress modulate PrPC content in neutrophils, suggest a distributed role of PrPC in clinical depression and inflammation associated with neurodegenerative diseases. An overarching understanding of the multiple interventions of PrPC upon physiological events may both shed light on the pathogenesis of, as well as help the identification of novel therapeutic targets for clinical depression, Prion and Alzheimer's Diseases.  相似文献   

18.
19.
Alzheimer and prion diseases are neurodegenerative disorders characterised by the abnormal processing of amyloid-β (Aβ) peptide and prion protein (PrPC), respectively. Recent evidence indicates that PrPC may play a critical role in the pathogenesis of Alzheimer disease. PrPC interacts with and inhibits the β-secretase BACE1, the rate-limiting enzyme in the production of Aβ. More recently PrPC was identified as a receptor for Aβ oligomers and the expression of PrPC appears to be controlled by the amyloid intracellular domain (AICD). Here we review these observations and propose a feedback loop in the normal brain where PrPC exerts an inhibitory effect on BACE1 to decrease both Aβ and AICD production. In turn, the AICD upregulates PrPC expression, thus maintaining the inhibitory effect of PrPC on BACE1. In Alzheimer disease, this feedback loop is disrupted, and the increased level of Aβ oligomers bind to PrPC and prevent it from regulating BACE1 activity.Key words: alzheimer disease, amyloid-β, Aβ oligomers, amyloid intracellular domain, BACE1, presenilin, prion protein  相似文献   

20.
Prion diseases, or transmissible spongiform encephalopathies (TSEs) are progressive, fatal neurodegenerative diseases with no effective treatment. The pathology of these diseases involves the conversion of a protease sensitive form of the cellular prion protein (PrPC) into a protease resistant infectious form (PrPres). The efficiency of this conversion is predicated upon a number of factors, most notably a strong homology between cellular PrPC and PrPres. In our recently published study, we infected mice with the RML-Chandler strain of scrapie and treated them with heterologous hamster prion proteins. This treatment was seen to reduce clinical signs of prion disease, to delay the onset of clinical symptoms and to prolong survival. In this current article we discuss potential mechanisms of action of treatment with heterologous prion proteins. We also discuss potential extensions of these studies using a heterologous rabbit PrP-based treatment strategy or a peptide based strategy, and improvement of treatment delivery including a lentiviral-based system.  相似文献   

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