RESUMEN
The cellular prion protein, PrPC , is a copper-binding protein abundantly expressed in the brain, particularly by neurons, and its conformational conversion into the amyloidogenic isoform, PrPSc , plays a key pathogenic role in prion diseases. However, the role of copper binding to PrPC in prion diseases remains unclear. Here, we fed mice with a low-copper or regular diet and intracerebrally inoculated them with two different mouse-adapted RML scrapie and BSE prions. Mice with a low-copper diet developed disease significantly but only slightly later than those with a regular diet after inoculation with BSE prions, but not with RML prions, suggesting that copper could play a minor role in BSE prion pathogenesis, but not in RML prion pathogenesis. We then generated two lines of transgenic mice expressing mouse PrP with copper-binding histidine (His) residues in the N-terminal domain replaced with alanine residues, termed TgPrP(5H > A)-7342/Prnp0/0 and TgPrP(5H > A)-7524/Prnp0/0 mice, and similarly inoculated RML and BSE prions into them. Due to 2-fold higher expression of PrP(5H > A) than PrPC in wild-type (WT) mice, TgPrP(5H > A)-7524/Prnp0/0 mice were highly susceptible to these prions, compared to WT mice. However, TgPrP(5H > A)-7342/Prnp0/0 mice, which express PrP(5H > A) 1.2-fold as high as PrPC in WT mice, succumbed to disease slightly, but not significantly, later than WT mice after inoculation with RML prions, but significantly so after inoculation with BSE prions. Subsequent secondary inoculation experiments revealed that amino acid sequence differences between PrP(5H > A) and WT PrPSc created no prion transmission barrier to BSE prions. These results suggest that copper-binding His residues in PrPC are dispensable for RML prion pathogenesis but have a minor effect on BSE prion pathogenesis. Taken together, our current results suggest that copper could have a minor effect on prion pathogenesis in a strain-dependent manner through binding to His residues in the N-terminal domain of PrPC .
RESUMEN
Conformational conversion of the cellular prion protein, PrPC, into the amyloidogenic isoform, PrPSc, is a key pathogenic event in prion diseases. However, the conversion mechanism remains to be elucidated. Here, we generated Tg(PrPΔ91-106)-8545/Prnp0/0 mice, which overexpress mouse PrP lacking residues 91-106. We showed that none of the mice became sick after intracerebral inoculation with RML, 22L, and FK-1 prion strains nor accumulated PrPScΔ91-106 in their brains except for a small amount of PrPScΔ91-106 detected in one 22L-inoculated mouse. However, they developed disease around 85 days after inoculation with bovine spongiform encephalopathy (BSE) prions with PrPScΔ91-106 in their brains. These results suggest that residues 91-106 are important for PrPC conversion into PrPSc in infection with RML, 22L, and FK-1 prions but not BSE prions. We then narrowed down the residues 91-106 by transducing various PrP deletional mutants into RML- and 22L-infected cells and identified that PrP mutants lacking residues 97-99 failed to convert into PrPSc in these cells. Our in vitro conversion assay also showed that RML, 22L, and FK-1 prions did not convert PrPΔ97-99 into PrPScΔ97-99, but BSE prions did. We further found that PrP mutants with proline residues at positions 97 to 99 or charged residues at positions 97 and 99 completely or almost completely lost their converting activity into PrPSc in RML- and 22L-infected cells. These results suggest that the structurally flexible and noncharged residues 97-99 could be important for PrPC conversion into PrPSc following infection with RML, 22L, and FK-1 prions but not BSE prions.
Asunto(s)
Enfermedades por Prión , Proteínas Priónicas , Priones , Animales , Ratones , Enfermedades por Prión/genética , Proteínas Priónicas/química , Proteínas Priónicas/genética , Priones/patogenicidad , Prolina , Isoformas de Proteínas/genética , Translocación GenéticaRESUMEN
Prion diseases are a group of devastating neurodegenerative disorders, which include Creutzfeldt-Jakob disease (CJD) in humans, and scrapie and bovine spongiform encephalopathy (BSE) in animals [...].
Asunto(s)
Síndrome de Creutzfeldt-Jakob , Encefalopatía Espongiforme Bovina , Enfermedades por Prión , Priones , Scrapie , Animales , Encéfalo/metabolismo , Bovinos , Síndrome de Creutzfeldt-Jakob/etiología , Síndrome de Creutzfeldt-Jakob/patología , Encefalopatía Espongiforme Bovina/patología , Enfermedades por Prión/etiología , Enfermedades por Prión/patología , Priones/metabolismo , Scrapie/patología , OvinosRESUMEN
The cellular isoform of prion protein, designated PrPC, is a membrane glycoprotein expressed most abundantly in the brain, particularly by neurons, and its conformational conversion into the abnormally folded, amyloidogenic isoform, PrPSc, is an underlying mechanism in the pathogenesis of prion diseases, a group of neurodegenerative disorders in humans and animals. Most cases of these diseases are sporadic and their aetiologies are unknown. We recently found that a neurotropic strain of influenza A virus (IAV/WSN) caused the conversion of PrPC into PrPSc and the subsequent formation of infectious prions in mouse neuroblastoma cells after infection. These results show that IAV/WSN is the first non-prion pathogen capable of inducing the conversion of PrPC into PrPSc and propagating infectious prions in cultured neuronal cells, and also provide the intriguing possibility that IAV infection in neurons might be a cause of or be associated with sporadic prion diseases. Here, we present our findings of the IAV/WSN-induced conversion of PrPC into PrPSc and subsequent propagation of infectious prions, and also discuss the biological significance of the conversion of PrPC into PrPSc in virus infections.
Asunto(s)
Orthomyxoviridae , Proteínas PrPC , Enfermedades por Prión , Priones , Animales , Encéfalo/patología , Ratones , Proteínas PrPC/metabolismo , Enfermedades por Prión/metabolismo , Proteínas Priónicas/metabolismo , Priones/metabolismoRESUMEN
Prion diseases are a group of fatal neurodegenerative disorders caused by accumulation of proteinaceous infectious particles, or prions, which mainly consist of the abnormally folded, amyloidogenic prion protein, designated PrPSc. PrPSc is produced through conformational conversion of the cellular isoform of prion protein, PrPC, in the brain. To date, no effective therapies for prion diseases have been developed. In this study, we incidentally noticed that mouse neuroblastoma N2a cells persistently infected with 22L scrapie prions, termed N2aC24L1-3 cells, reduced PrPSc levels when cultured in advanced Dulbecco's modified eagle medium (DMEM) but not in classic DMEM. PrPC levels remained unchanged in prion-uninfected parent N2aC24 cells cultured in advanced DMEM. These results suggest that advanced DMEM may contain an anti-prion compound(s). We then successfully identified ethanolamine in advanced DMEM has an anti-prion activity. Ethanolamine reduced PrPSc levels in N2aC24L1-3 cells, but not PrPC levels in N2aC24 cells. Also, oral administration of ethanolamine through drinking water delayed prion disease in mice intracerebrally inoculated with RML scrapie prions. These results suggest that ethanolamine could be a new anti-prion compound.
Asunto(s)
Encéfalo/metabolismo , Etanolamina/farmacología , Proteínas PrPSc , Enfermedades por Prión , Animales , Línea Celular Tumoral , Ratones , Ratones Endogámicos ICR , Proteínas PrPSc/antagonistas & inhibidores , Proteínas PrPSc/genética , Proteínas PrPSc/metabolismo , Enfermedades por Prión/tratamiento farmacológico , Enfermedades por Prión/genética , Enfermedades por Prión/metabolismoRESUMEN
Conformational conversion of the cellular isoform of prion protein, PrPC, into the abnormally folded, amyloidogenic isoform, PrPSc, is an underlying pathogenic mechanism in prion diseases. The diseases manifest as sporadic, hereditary, and acquired disorders. Etiological mechanisms driving the conversion of PrPC into PrPSc are unknown in sporadic prion diseases, while prion infection and specific mutations in the PrP gene are known to cause the conversion of PrPC into PrPSc in acquired and hereditary prion diseases, respectively. We recently reported that a neurotropic strain of influenza A virus (IAV) induced the conversion of PrPC into PrPSc as well as formation of infectious prions in mouse neuroblastoma cells after infection, suggesting the causative role of the neuronal infection of IAV in sporadic prion diseases. Here, we discuss the conversion mechanism of PrPC into PrPSc in different types of prion diseases, by presenting our findings of the IAV infection-induced conversion of PrPC into PrPSc and by reviewing the so far reported transgenic animal models of hereditary prion diseases and the reverse genetic studies, which have revealed the structure-function relationship for PrPC to convert into PrPSc after prion infection.
Asunto(s)
Síndrome de Creutzfeldt-Jakob/genética , Enfermedad de Gerstmann-Straussler-Scheinker/genética , Gripe Humana/genética , Insomnio Familiar Fatal/genética , Proteínas PrPC/genética , Proteínas PrPSc/genética , Proteínas Priónicas/genética , Animales , Línea Celular Tumoral , Síndrome de Creutzfeldt-Jakob/metabolismo , Síndrome de Creutzfeldt-Jakob/patología , Síndrome de Creutzfeldt-Jakob/virología , Enfermedad de Gerstmann-Straussler-Scheinker/metabolismo , Enfermedad de Gerstmann-Straussler-Scheinker/patología , Enfermedad de Gerstmann-Straussler-Scheinker/virología , Humanos , Virus de la Influenza A/genética , Virus de la Influenza A/crecimiento & desarrollo , Virus de la Influenza A/patogenicidad , Gripe Humana/metabolismo , Gripe Humana/patología , Gripe Humana/virología , Insomnio Familiar Fatal/metabolismo , Insomnio Familiar Fatal/patología , Insomnio Familiar Fatal/virología , Ratones , Ratones Transgénicos , Mutación , Neuronas/metabolismo , Neuronas/patología , Neuronas/virología , Proteínas PrPC/química , Proteínas PrPC/metabolismo , Proteínas PrPSc/química , Proteínas PrPSc/metabolismo , Proteínas Priónicas/química , Proteínas Priónicas/metabolismo , Conformación Proteica , Genética Inversa/métodosRESUMEN
Misfolding of the cellular prion protein, PrPC, into the amyloidogenic isoform, PrPSc, which forms infectious protein aggregates, the so-called prions, is a key pathogenic event in prion diseases. No pathogens other than prions have been identified to induce misfolding of PrPC into PrPSc and propagate infectious prions in infected cells. Here, we found that infection with a neurotropic influenza A virus strain (IAV/WSN) caused misfolding of PrPC into PrPSc and generated infectious prions in mouse neuroblastoma cells through a hit-and-run mechanism. The structural and biochemical characteristics of IAV/WSN-induced PrPSc were different from those of RML and 22L laboratory prions-evoked PrPSc, and the pathogenicity of IAV/WSN-induced prions were also different from that of RML and 22L prions, suggesting IAV/WSN-specific formation of PrPSc and infectious prions. Our current results may open a new avenue for the role of viral infection in misfolding of PrPC into PrPSc and formation of infectious prions.
Asunto(s)
Virus de la Influenza A/fisiología , Gripe Humana/metabolismo , Gripe Humana/virología , Neuroblastoma/metabolismo , Neuroblastoma/virología , Proteínas Priónicas/química , Línea Celular Tumoral , Humanos , Gripe Humana/genética , Neuroblastoma/genética , Proteínas Priónicas/metabolismo , Conformación Proteica , Pliegue de ProteínaRESUMEN
Prions are infectious agents causing prion diseases, which include Creutzfeldt-Jakob disease (CJD) in humans. Several cases have been reported to be transmitted through medical instruments that were used for preclinical CJD patients, raising public health concerns on iatrogenic transmissions of the disease. Since preclinical CJD patients are currently difficult to identify, medical instruments need to be adequately sterilized so as not to transmit the disease. In this study, we investigated the sterilizing activity of two oxidizing agents, ozone gas and vaporized hydrogen peroxide, against prions fixed on stainless steel wires using a mouse bioassay. Mice intracerebrally implanted with prion-contaminated stainless steel wires treated with ozone gas or vaporized hydrogen peroxide developed prion disease later than those implanted with control prion-contaminated stainless steel wires, indicating that ozone gas and vaporized hydrogen peroxide could reduce prion infectivity on wires. Incubation times were further elongated in mice implanted with prion-contaminated stainless steel wires treated with ozone gas-mixed vaporized hydrogen peroxide, indicating that ozone gas mixed with vaporized hydrogen peroxide reduces prions on these wires more potently than ozone gas or vaporized hydrogen peroxide. These results suggest that ozone gas mixed with vaporized hydrogen peroxide might be more useful for prion sterilization than ozone gas or vaporized hydrogen peroxide alone.
Asunto(s)
Peróxido de Hidrógeno/química , Ozono/química , Priones , Acero Inoxidable , Animales , Encéfalo/metabolismo , Encéfalo/patología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Peróxido de Hidrógeno/farmacología , Ratones , Ozono/farmacología , Proteínas PrPC/antagonistas & inhibidores , Proteínas PrPC/química , Enfermedades por Prión/etiología , Enfermedades por Prión/prevención & control , Acero Inoxidable/químicaRESUMEN
Conformational conversion of the cellular prion protein, PrPC, into the abnormally folded isoform, PrPSc, is a key pathogenic event in prion diseases. However, the exact conversion mechanism remains largely unknown. Transgenic mice expressing PrP with a deletion of the central residues 91-106 were generated in the absence of endogenous PrPC, designated Tg(PrP∆91-106)/Prnp0/0 mice and intracerebrally inoculated with various prions. Tg(PrP∆91-106)/Prnp0/0 mice were resistant to RML, 22L and FK-1 prions, neither producing PrPSc∆91-106 or prions in the brain nor developing disease after inoculation. However, they remained marginally susceptible to bovine spongiform encephalopathy (BSE) prions, developing disease after elongated incubation times and accumulating PrPSc∆91-106 and prions in the brain after inoculation with BSE prions. Recombinant PrP∆91-104 converted into PrPSc∆91-104 after incubation with BSE-PrPSc-prions but not with RML- and 22L-PrPSc-prions, in a protein misfolding cyclic amplification assay. However, digitonin and heparin stimulated the conversion of PrP∆91-104 into PrPSc∆91-104 even after incubation with RML- and 22L-PrPSc-prions. These results suggest that residues 91-106 or 91-104 of PrPC are crucially involved in prion pathogenesis in a strain-dependent manner and may play a similar role to digitonin and heparin in the conversion of PrPC into PrPSc.
Asunto(s)
Encefalopatía Espongiforme Bovina/genética , Proteínas PrPC/genética , Proteínas PrPSc/genética , Deficiencias en la Proteostasis/genética , Scrapie/genética , Eliminación de Secuencia , Animales , Baculoviridae/genética , Baculoviridae/metabolismo , Secuencia de Bases , Encéfalo/metabolismo , Encéfalo/patología , Bovinos , Clonación Molecular , Susceptibilidad a Enfermedades , Encefalopatía Espongiforme Bovina/metabolismo , Encefalopatía Espongiforme Bovina/patología , Expresión Génica , Inyecciones Intraventriculares , Ratones , Ratones Transgénicos , Proteínas PrPC/química , Proteínas PrPC/metabolismo , Proteínas PrPSc/administración & dosificación , Proteínas PrPSc/química , Proteínas PrPSc/metabolismo , Deficiencias en la Proteostasis/metabolismo , Deficiencias en la Proteostasis/patología , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Scrapie/metabolismo , Scrapie/patología , Especificidad de la EspecieRESUMEN
Prion protein (PrPC) knockout mice, named as the "Ngsk" strain (Ngsk Prnp0/0 mice), show late-onset cerebellar Purkinje cell (PC) degeneration because of ectopic overexpression of PrPC-like protein (PrPLP/Dpl). Our previous study indicated that the mutant mice also exhibited alterations in cerebellum-dependent delay eyeblink conditioning, even at a young age (16 weeks of age) when neurological changes had not occurred. Thus, this electrophysiological study was designed to examine the synaptic function of the cerebellar cortex in juvenile Ngsk Prnp0/0 mice. We showed that Ngsk Prnp0/0 mice exhibited normal paired-pulse facilitation but impaired long-term depression of excitatory synaptic transmission at synapses between parallel fibres and PCs. GABAA-mediated inhibitory postsynaptic currents recorded from PCs were also weakened in Ngsk Prnp0/0 mice. Furthermore, we confirmed that Ngsk Prnp0/0 mice (7-8-week-old) exhibited abnormalities in delay eyeblink conditioning. Our findings suggest that these alterations in both excitatory and inhibitory synaptic transmission to PCs caused deficits in delay eyeblink conditioning of Ngsk Prnp0/0 mice. Therefore, the Ngsk Prnp0/0 mouse model can contribute to study underlying mechanisms for impairments of synaptic transmission and neural plasticity, and cognitive deficits in the central nervous system.
Asunto(s)
Cerebelo/fisiopatología , Depresión Sináptica a Largo Plazo/fisiología , Proteínas PrPC/genética , Transmisión Sináptica/fisiología , Ácido gamma-Aminobutírico/metabolismo , Animales , Cerebelo/metabolismo , Condicionamiento Palpebral/fisiología , Potenciales Postsinápticos Inhibidores/fisiología , Ratones , Ratones Noqueados , Plasticidad Neuronal/fisiología , Proteínas PrPC/metabolismoRESUMEN
The normal cellular isoform of prion protein, designated PrPC, is constitutively converted to the abnormally folded, amyloidogenic isoform, PrPSc, in prion diseases, which include Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. PrPC is a membrane glycoprotein consisting of the non-structural N-terminal domain and the globular C-terminal domain. During conversion of PrPC to PrPSc, its 2/3 C-terminal region undergoes marked structural changes, forming a protease-resistant structure. In contrast, the N-terminal region remains protease-sensitive in PrPSc. Reverse genetic studies using reconstituted PrPC-knockout mice with various mutant PrP molecules have revealed that the N-terminal domain has an important role in the normal function of PrPC and the conversion of PrPC to PrPSc. The N-terminal domain includes various characteristic regions, such as the positively charged residue-rich polybasic region, the octapeptide repeat (OR) region consisting of five repeats of an octapeptide sequence, and the post-OR region with another positively charged residue-rich polybasic region followed by a stretch of hydrophobic residues. We discuss the normal functions of PrPC, the conversion of PrPC to PrPSc, and the neurotoxicity of PrPSc by focusing on the roles of the N-terminal regions in these topics.
Asunto(s)
Enfermedades por Prión/metabolismo , Proteínas Priónicas/química , Proteínas Priónicas/metabolismo , Animales , Humanos , Mutación , Enfermedades por Prión/genética , Proteínas Priónicas/genética , Conformación Proteica , Dominios ProteicosRESUMEN
The cellular prion protein, PrPC, is a glycosylphosphatidylinositol anchored-membrane glycoprotein expressed most abundantly in neuronal and to a lesser extent in non-neuronal cells. Its conformational conversion into the amyloidogenic isoform in neurons is a key pathogenic event in prion diseases, including Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. However, the normal functions of PrPC remain largely unknown, particularly in non-neuronal cells. Here we show that stimulation of PrPC with anti-PrP monoclonal antibodies (mAbs) protected mice from lethal infection with influenza A viruses (IAVs), with abundant accumulation of anti-inflammatory M2 macrophages with activated Src family kinases (SFKs) in infected lungs. A SFK inhibitor dasatinib inhibited M2 macrophage accumulation in IAV-infected lungs after treatment with anti-PrP mAbs and abolished the anti-PrP mAb-induced protective activity against lethal influenza infection in mice. We also show that stimulation of PrPC with anti-PrP mAbs induced M2 polarization in peritoneal macrophages through SFK activation in vitro and in vivo. These results indicate that PrPC could activate SFK in macrophages and induce macrophage polarization to an anti-inflammatory M2 phenotype after stimulation with anti-PrP mAbs, thereby eliciting protective activity against lethal infection with IAVs in mice after treatment with anti-PrP mAbs. These results also highlight PrPC as a novel therapeutic target for IAV infection.
Asunto(s)
Virus de la Influenza A/metabolismo , Pulmón , Macrófagos , Infecciones por Orthomyxoviridae , Proteínas PrPC/metabolismo , Transducción de Señal , Animales , Anticuerpos Monoclonales de Origen Murino/farmacología , Pulmón/metabolismo , Pulmón/patología , Pulmón/virología , Macrófagos/metabolismo , Macrófagos/patología , Macrófagos/virología , Ratones , Ratones Mutantes , Infecciones por Orthomyxoviridae/genética , Infecciones por Orthomyxoviridae/metabolismo , Infecciones por Orthomyxoviridae/patología , Proteínas PrPC/antagonistas & inhibidores , Familia-src Quinasas/genética , Familia-src Quinasas/metabolismoRESUMEN
Worldwide spread of influenza A virus (IAV) strains, which are resistant to currently available anti- influenza agents such as viral neuraminidase inhibitors, has encouraged identification of new target molecules for anti-influenza agents. Reactive oxygen species (ROS) causing oxidative stress play a pivotal role in the pathogenesis of lung injuries induced by infection with IAVs, therefore suggesting that anti-oxidative therapeutics targeting cellular molecules could be beneficial against IAV infection without inducing drug-resistant IAV strains. We recently found that the normal cellular prion protein, PrPC, whose conformational conversion into the amyloidogenic isoform, PrPSc, in the brain is a key pathogenic event in prion diseases, is expressed by lung epithelial cells and exerts a protective role against IAV infection in mice by reducing ROS in infected lungs. The Cu content and activity of anti- oxidative enzyme Cu/Zn-superoxide dismutase, or SOD1, were lower in the lungs of PrPC-knockout mice, suggesting that the anti-oxidative activity of PrPC is probably attributable to its function of activating SOD1 through regulating Cu content in lungs. Here, we introduce PrPC as a novel modulator of influenza and its potential implication for anti-oxidative therapies for IAV infection. We also introduce other candidate targets reported for anti- oxidative anti-influenza therapies.
Asunto(s)
Antivirales/farmacología , Virus de la Influenza A/efectos de los fármacos , Virus de la Influenza A/fisiología , Gripe Humana/virología , Proteínas Priónicas/farmacología , Animales , Antioxidantes/farmacología , Antivirales/uso terapéutico , Interacciones Huésped-Patógeno , Humanos , Gripe Humana/tratamiento farmacológico , Gripe Humana/genética , Gripe Humana/metabolismo , Oxidación-Reducción/efectos de los fármacos , Sustancias Protectoras/farmacología , Especies Reactivas de Oxígeno/metabolismo , Replicación Viral/efectos de los fármacosRESUMEN
Conformational conversion of the cellular isoform of prion protein, designated PrPC, into the abnormally folded, amyloidogenic isoform, PrPSc, is an essential pathogenic event in prion diseases. However, the exact conversion mechanism remains largely unknown. Lines of evidence indicate that the N-terminal domain, which includes the N-terminal, positively charged polybasic region and the octapeptide repeat (OR) region, is important for PrPC to convert into PrPSc after infection with prions. To further gain insights into the role of the polybasic region and the OR region in prion pathogenesis, we generated two different transgenic mice, designated Tg(PrP3K3A)/Prnp0/0 and Tg(PrP3K3A∆OR)/Prnp0/0 mice, which express PrPC with lysine residues at codons 23, 24, and 27 in the polybasic region mutated with or without a deletion of the OR region on the Prnp0/0 background, respectively, and intracerebrally inoculated them with RML and 22L prions. We show that Tg(PrP3K3A)/Prnp0/0 mice were highly resistant to the prions, indicating that lysine residues at 23, 24, and 27 could be important for the polybasic region to support prion infection. Tg(PrP3K3A∆OR)/Prnp0/0 mice also had reduced susceptibility to RML and 22L prions equivalent to Tg(PrP3K3A)/Prnp0/0 mice. The pre-OR region, including the polybasic region, of PrP3K3A∆OR, but not PrP3K3A, was unusually converted to a protease-resistant structure during conversion to PrPSc3K3A∆OR. These results suggest that, while the OR region could affect the conformation of the polybasic region during conversion of PrPC into PrPSc, the polybasic region could play a crucial role in prion pathogenesis independently of the OR region.
Asunto(s)
Proteínas PrPC/metabolismo , Enfermedades por Prión/metabolismo , Proteínas Priónicas/metabolismo , Priones/metabolismo , Animales , Lisina/metabolismo , Ratones Transgénicos , Eliminación de Secuencia/fisiologíaRESUMEN
The normal cellular prion protein, designated PrPC, is a membrane glycoprotein expressed most abundantly in brains, particularly by neurons, and to a lesser extent in non-neuronal tissues including lungs. Conformational conversion of PrPC into the amyloidogenic isoform is a key pathogenic event in prion diseases. We recently found that PrPC has a protective role against infection with influenza A viruses (IAVs) in mice by reducing reactive oxygen species in the lungs after infection with IAVs. The antioxidative activity of PrPC is probably attributable to its function to activate antioxidative enzyme Cu/Zn-superoxide dismutase, or SOD1, through regulating Cu content in lungs infected with IAVs. Oxidative stress could play a pivotal role in the pathogenesis of a wide range of viral infections. Here, we introduce our and others' studies on the role of PrPC in viral infections, and raise the attractive possibility that PrPC might be a novel target molecule for development of antioxidative therapeutics against not only IAV infection but also other viral infections.
Asunto(s)
Regulación de la Expresión Génica/inmunología , Proteínas de Choque Térmico/inmunología , Pulmón/inmunología , Infecciones por Orthomyxoviridae/genética , Proteínas PrPC/inmunología , Superóxido Dismutasa-1/inmunología , Animales , Cobre/inmunología , Cobre/metabolismo , Activación Enzimática , Células Epiteliales/enzimología , Células Epiteliales/inmunología , Células Epiteliales/virología , Proteínas de Choque Térmico/genética , Virus de la Influenza A/patogenicidad , Virus de la Influenza A/fisiología , Pulmón/enzimología , Pulmón/virología , Ratones , Infecciones por Orthomyxoviridae/enzimología , Infecciones por Orthomyxoviridae/inmunología , Infecciones por Orthomyxoviridae/virología , Estrés Oxidativo , Proteínas PrPC/genética , Factores Protectores , Especies Reactivas de Oxígeno/inmunología , Especies Reactivas de Oxígeno/metabolismo , Superóxido Dismutasa-1/genéticaRESUMEN
The cellular prion protein, designated PrPC, is a membrane glycoprotein expressed abundantly in brains and to a lesser extent in other tissues. Conformational conversion of PrPC into the amyloidogenic isoform is a key pathogenic event in prion diseases. However, the physiological functions of PrPC remain largely unknown, particularly in non-neuronal tissues. Here, we show that PrPC is expressed in lung epithelial cells, including alveolar type 1 and 2 cells and bronchiolar Clara cells. Compared with wild-type (WT) mice, PrPC-null mice (Prnp0/0) were highly susceptible to influenza A viruses (IAVs), with higher mortality. Infected Prnp0/0 lungs were severely injured, with higher inflammation and higher apoptosis of epithelial cells, and contained higher reactive oxygen species (ROS) than control WT lungs. Treatment with a ROS scavenger or an inhibitor of xanthine oxidase (XO), a major ROS-generating enzyme in IAV-infected lungs, rescued Prnp0/0 mice from the lethal infection with IAV. Moreover, Prnp0/0 mice transgenic for PrP with a deletion of the Cu-binding octapeptide repeat (OR) region, Tg(PrPΔOR)/Prnp0/0 mice, were also highly susceptible to IAV infection. These results indicate that PrPC has a protective role against lethal infection with IAVs through the Cu-binding OR region by reducing ROS in infected lungs. Cu content and the activity of anti-oxidant enzyme Cu/Zn-dependent superoxide dismutase, SOD1, were lower in Prnp0/0 and Tg(PrPΔOR)/Prnp0/0 lungs than in WT lungs. It is thus conceivable that PrPC functions to maintain Cu content and regulate SOD1 through the OR region in lungs, thereby reducing ROS in IAV-infected lungs and eventually protecting them from lethal infection with IAVs. Our current results highlight the role of PrPC in protection against IAV infection, and suggest that PrPC might be a novel target molecule for anti-influenza therapeutics.
Asunto(s)
Proteínas PrPC/metabolismo , Proteínas Priónicas/metabolismo , Animales , Encéfalo/patología , Cobre/metabolismo , Susceptibilidad a Enfermedades/metabolismo , Virus de la Influenza A/metabolismo , Virus de la Influenza A/patogenicidad , Pulmón/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Neuronas/metabolismo , Proteínas PrPC/fisiología , Enfermedades por Prión/metabolismo , Proteínas Priónicas/farmacología , Priones/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
Background: Proteolytic processing of the prion protein (PrP
Asunto(s)
Proteína ADAM10/metabolismo , Encéfalo/metabolismo , Neuronas/metabolismo , Proteínas Priónicas/metabolismo , Animales , RatonesRESUMEN
Conformational conversion of the cellular isoform of prion protein, PrPC, into the abnormally folded, amyloidogenic isoform, PrPSc, is a key pathogenic event in prion diseases, including Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy (BSE) in animals. We previously reported that the octapeptide repeat (OR) region could be dispensable for converting PrPC into PrPSc after infection with RML prions. We demonstrated that mice transgenically expressing mouse PrP with deletion of the OR region on the PrP knockout background, designated Tg(PrPΔOR)/Prnp0/0 mice, did not show reduced susceptibility to RML scrapie prions, with abundant accumulation of PrPScΔOR in their brains. We show here that Tg(PrPΔOR)/Prnp0/0 mice were highly resistant to BSE prions, developing the disease with markedly elongated incubation times after infection with BSE prions. The conversion of PrPΔOR into PrPScΔOR was markedly delayed in their brains. These results suggest that the OR region may have a crucial role in the conversion of PrPC into PrPSc after infection with BSE prions. However, Tg(PrPΔOR)/Prnp0/0 mice remained susceptible to RML and 22L scrapie prions, developing the disease without elongated incubation times after infection with RML and 22L prions. PrPScΔOR accumulated only slightly less in the brains of RML- or 22L-infected Tg(PrPΔOR)/Prnp0/0 mice than PrPSc in control wild-type mice. Taken together, these results indicate that the OR region of PrPC could play a differential role in the pathogenesis of BSE prions and RML or 22L scrapie prions.IMPORTANCE Structure-function relationship studies of PrPC conformational conversion into PrPSc are worthwhile to understand the mechanism of the conversion of PrPC into PrPSc We show here that, by inoculating Tg(PrPΔOR)/Prnp0/0 mice with the three different strains of RML, 22L, and BSE prions, the OR region could play a differential role in the conversion of PrPC into PrPSc after infection with RML or 22L scrapie prions and BSE prions. PrPΔOR was efficiently converted into PrPScΔOR after infection with RML and 22L prions. However, the conversion of PrPΔOR into PrPScΔOR was markedly delayed after infection with BSE prions. Further investigation into the role of the OR region in the conversion of PrPC into PrPSc after infection with BSE prions might be helpful for understanding the pathogenesis of BSE prions.
Asunto(s)
Susceptibilidad a Enfermedades , Encefalopatía Espongiforme Bovina/fisiopatología , Proteínas PrPC/química , Proteínas PrPC/fisiología , Enfermedades por Prión/fisiopatología , Priones/patogenicidad , Animales , Encéfalo/patología , Bovinos , Encefalopatía Espongiforme Bovina/prevención & control , Humanos , Ratones , Ratones Transgénicos , Oligopéptidos/química , Oligopéptidos/genética , Proteínas PrPC/genética , Enfermedades por Prión/prevención & control , Priones/química , Priones/genética , Eliminación de SecuenciaRESUMEN
Conformational conversion of the cellular prion protein, PrPC, into the abnormally folded isoform of prion protein, PrPSc, which leads to marked accumulation of PrPSc in brains, is a key pathogenic event in prion diseases, a group of fatal neurodegenerative disorders caused by prions. However, the exact mechanism of PrPSc accumulation in prion-infected neurons remains unknown. We recently reported a novel cellular mechanism to support PrPSc accumulation in prion-infected neurons, in which PrPSc itself promotes its accumulation by evading the cellular inhibitory mechanism, which is newly identified in our recent study. We showed that the VPS10P sorting receptor sortilin negatively regulates PrPSc accumulation in prion-infected neurons, by interacting with PrPC and PrPSc and trafficking them to lysosomes for degradation. However, PrPSc stimulated lysosomal degradation of sortilin, disrupting the sortilin-mediated degradation of PrPC and PrPSc and eventually evoking further accumulation of PrPSc in prion-infected neurons. These findings suggest a positive feedback amplification mechanism for PrPSc accumulation in prion-infected neurons.
Asunto(s)
Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Priones/metabolismo , Animales , Humanos , Lisosomas/metabolismo , Ratones , Proteínas PrPC/metabolismo , Transporte de ProteínasRESUMEN
Prion diseases are a group of fatal neurodegenerative disorders caused by prions, which consist mainly of the abnormally folded isoform of prion protein, PrPSc. A pivotal pathogenic event in prion disease is progressive accumulation of prions, or PrPSc, in brains through constitutive conformational conversion of the cellular prion protein, PrPC, into PrPSc. However, the cellular mechanism by which PrPSc is progressively accumulated in prion-infected neurons remains unknown. Here, we show that PrPSc is progressively accumulated in prion-infected cells through degradation of the VPS10P sorting receptor sortilin. We first show that sortilin interacts with PrPC and PrPSc and sorts them to lysosomes for degradation. Consistently, sortilin-knockdown increased PrPSc accumulation in prion-infected cells. In contrast, overexpression of sortilin reduced PrPSc accumulation in prion-infected cells. These results indicate that sortilin negatively regulates PrPSc accumulation in prion-infected cells. The negative role of sortilin in PrPSc accumulation was further confirmed in sortilin-knockout mice infected with prions. The infected mice had accelerated prion disease with early accumulation of PrPSc in their brains. Interestingly, sortilin was reduced in prion-infected cells and mouse brains. Treatment of prion-infected cells with lysosomal inhibitors, but not proteasomal inhibitors, increased the levels of sortilin. Moreover, sortilin was reduced following PrPSc becoming detectable in cells after infection with prions. These results indicate that PrPSc accumulation stimulates sortilin degradation in lysosomes. Taken together, these results show that PrPSc accumulation of itself could impair the sortilin-mediated sorting of PrPC and PrPSc to lysosomes for degradation by stimulating lysosomal degradation of sortilin, eventually leading to progressive accumulation of PrPSc in prion-infected cells.