Loss of STI1-mediated neuronal survival and differentiation in disease-associated mutations of prion protein.

Cellular prion protein (PrPC ) is widely expressed and displays a variety of well-described functions in the central nervous system (CNS). Mutations of the PRNP gene are known to promote genetic human spongiform encephalopathies, but the components of gain- or loss-of-function mutations to PrPC remain a matter for debate. Among the proteins described to interact with PrPC is Stress-inducible protein 1 (STI1), a co-chaperonin that is secreted from astrocytes and triggers neuroprotection and neuritogenesis through its interaction with PrPC . In this work, we evaluated the impact of different PrPC pathogenic point mutations on signaling pathways induced by the STI1-PrPC interaction. We found that some of the pathogenic mutations evaluated herein induce partial or total disruption of neuritogenesis and neuroprotection mediated by mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinases 1 and 2 (ERK1/2) and protein kinase A (PKA) signaling triggered by STI1-PrPC engagement. A pathogenic mutant PrPC that lacked both neuroprotection and neuritogenesis activities fail to promote negative dominance upon wild-type PrPC . Also, a STI1-α7-nicotinic acetylcholine receptor-dependent cellular signaling was present in a PrPC mutant that maintained both neuroprotection and neuritogenesis activities similar to what has been previously observed by wild-type PrPC . These results point to a loss-of-function mechanism underlying the pathogenicity of PrPC mutations.

Rab5C enhances resistance to ionizing radiation in rectal cancer.

Rectal cancer represents one third of the colorectal cancers that are diagnosed. Neoadjuvant chemoradiation is a well-established protocol for rectal cancer treatment reducing the risk of local recurrence. However, a pathologic complete response is only achieved in 10-40% of cases and the mechanisms associated with resistance are poorly understood. To identify potential targets for preventing therapy resistance, a proteomic analysis of biopsy specimens collected from stage II and III rectal adenocarcinoma patients before neoadjuvant treatment was performed and compared with residual tumor tissues removed by surgery after neoadjuvant therapy. Three proteins, Ku70, Ku80, and Rab5C, exhibited a significant increase in expression after chemoradiation. To better understand the role of these proteins in therapy resistance, a rectal adenocarcinoma cell line was irradiated to generate a radiotherapy-resistant lineage. These cells overexpressed the same three proteins identified in the tissue samples. Furthermore, radiotherapy resistance in this in vitro model was found to involve modulation of epidermal growth factor receptor (EGFR) internalization by Rab5C in response to irradiation, affecting expression of the DNA repair proteins, Ku70 and Ku80, and cell resistance. Taken together, these findings indicate that EGFR and Rab5C are potential targets for the sensitization of rectal cancer cells and they should be further investigated. KEY MESSAGES: • Rab5C orchestrates a mechanism of radioresistance in rectal adenocarcinoma cell. • Rab5C modulates EGFR internalization and its relocalization to the nucleus. • In the nucleus, EGFR can modulate the expression of the DNA repair proteins, Ku70 and Ku80. • Rab5C, Ku70, and Ku80 are overexpressed in tumor tissues that contain tumor cells that are resistant to chemoradiation treatment.

Cellular prion protein modulates defensive attention and innate fear-induced behaviour evoked in transgenic mice submitted to an agonistic encounter with the tropical coral snake Oxyrhopus guibei.

The cellular prion protein (PrP(C)) is a neuronal anchored glycoprotein that has been associated with distinct functions in the CNS, such as cellular adhesion and differentiation, synaptic plasticity and cognition. Here we investigated the putative involvement of the PrP(C) in the innate fear-induced behavioural reactions in wild-type (WT), PrP(C) knockout (Prnp(0/0)) and the PrP(C) overexpressing Tg-20 mice evoked in a prey versus predator paradigm. The behavioural performance of these mouse strains in olfactory discrimination tasks was also investigated. When confronted with coral snakes, mice from both Prnp(0/0) and Tg-20 strains presented a significant decrease in frequency and duration of defensive attention and risk assessment, compared to WT mice. Tg-20 mice presented decreased frequency of escape responses, increased exploratory behaviour, and enhancement of interaction with the snake, suggesting a robust fearlessness caused by PrP(C) overexpression. Interestingly, there was also a discrete decrease in the attentional defensive response (decreased frequency of defensive alertness) in Prnp(0/0) mice in the presence of coral snakes. Moreover, Tg-20 mice presented an increased exploration of novel environment and odors. The present findings indicate that the PrP(C) overexpression causes hyperactivity, fearlessness, and increased preference for visual, tactile and olfactory stimuli-associated novelty, and that the PrP(c) deficiency might lead to attention deficits. These results suggest that PrP(c) exerts an important role in the modulation of innate fear and novelty-induced exploration.

First case of V180I rare mutation in a Brazilian patient with Creutzfeldt-Jakob disease.

Here, we report the first case of V180I rare mutation in a Brazilian woman whose clinical condition started with memory impairment for recent events and insomnia with 2 months of evolution, without any other alterations in neurological examination. Both the electroencephalogram (EEG) and the routine biochemical examination of cerebrospinal fluid (CSF) were normal. CSF 14-3-3 protein search was positive. Magnetic resonance imaging (MRI) of the encephalon showed findings suggestive of Creutzfeldt-Jakob disease, confirmed by sequencing of PRNP gene that reveal V180I mutation also homozygosity for methionine at codon 129 (M129M).

High phenotypic variability in Gerstmann-Sträussler-Scheinker disease.

Gerstmann-Sträussler-Scheinker is a genetic prion disease and the most common mutation is p.Pro102Leu. We report clinical, molecular and neuropathological data of seven individuals, belonging to two unrelated Brazilian kindreds, carrying the p.Pro102Leu. Marked differences among patients were observed regarding age at onset, disease duration and clinical presentation. In the first kindred, two patients had rapidly progressive dementia and three exhibited predominantly ataxic phenotypes with variable ages of onset and disease duration. In this family, age at disease onset in the mother and daughter differed by 39 years. In the second kindred, different phenotypes were also reported and earlier ages of onset were associated with 129 heterozygosis. No differences were associated with apoE genotype. In these kindreds, the codon 129 polymorphism could not explain the clinical variability and 129 heterozygosis was associated with earlier disease onset. Neuropathological examination in two patients confirmed the presence of typical plaques and PrPsc immunopositivity.

Impaired exercise capacity, but unaltered mitochondrial respiration in skeletal or cardiac muscle of mice lacking cellular prion protein.

The studies of physiological roles for cellular prion protein (PrP(c)) have focused on possible functions of this protein in the CNS, where it is largely expressed. However, the observation that PrP(c) is expressed also in muscle tissue suggests that the physiological role of PrP(c) might not be limited to the central nervous system. In the present study, we investigated possible functions of PrP(c) in muscle using PrP(c) gene (Prnp) null mice (Prnp(0/0)). For this purpose, we submitted Prnp(0/0) animals to different protocols of exercise, and compared their performance to that of their respective wild-type controls. Prnp(0/0) mice showed an exercise-dependent impairment of locomotor activity. In searching for possible mechanisms associated with the impairment observed, we evaluated mitochondrial respiration (MR) in skeletal or cardiac muscle from these mice during resting or after different intensities of exercise. Baseline MR (states 3 and 4), respiratory control ratio (RCR) and mitochondrial membrane potential (DeltaPsi) were evaluated and were not different in skeletal or cardiac muscle tissue of Prnp(0/0) mice when compared with wild-type animals. We concluded that Prnp(0/0) mice show impairment of swimming capacity, perhaps reflecting impairment of muscular activity under more extreme exercise conditions. In spite of the mitochondrial abnormalities reported in Prnp(0/0) mice, our observation seems not to be related to MR. Our results indicate that further investigations should be conducted in order to improve our knowledge about the function of PrP(c) in muscle physiology and its possible role in several different neuromuscular pathologies.

Codon 129 polymorphism of prion protein gene in is not a risk factor for Alzheimer's disease.

UNLABELLED: Interaction of prion protein and amyloid-b oligomers has been demonstrated recently. Homozygosity at prion protein gene (PRNP) codon 129 is associated with higher risk for Creutzfeldt-Jakob disease. This polymorphism has been addressed as a possible risk factor in Alzheimer disease (AD). OBJECTIVE: To describe the association between codon 129 polymorphisms and AD. METHODS: We investigated the association of codon 129 polymorphism of PRNP in 99 AD patients and 111 controls, and the association between this polymorphism and cognitive performance. Other polymorphisms of PRNP and additive effect of apolipoprotein E gene (ApoE) were evaluated. RESULTS: Codon 129 genotype distribution in AD 45.5% methionine (MM), 42.2% methionine valine (MV), 12.1% valine (VV); and 39.6% MM, 50.5% MV, 9.9% VV among controls (p>0.05). There were no differences of cognitive performance concerning codon 129. Stratification according to ApoE genotype did not reveal difference between groups. CONCLUSION: Codon 129 polymorphism is not a risk factor for AD in Brazilian patients.

High phenotypic variability in Gerstmann-Sträussler-Scheinker disease / Elevada variabilidade fenotípica na doença de Gerstmann-Sträussler-Scheinker

ABSTRACT Gerstmann-Sträussler-Scheinker is a genetic prion disease and the most common mutation is p.Pro102Leu. We report clinical, molecular and neuropathological data of seven individuals, belonging to two unrelated Brazilian kindreds, carrying the p.Pro102Leu. Marked differences among patients were observed regarding age at onset, disease duration and clinical presentation. In the first kindred, two patients had rapidly progressive dementia and three exhibited predominantly ataxic phenotypes with variable ages of onset and disease duration. In this family, age at disease onset in the mother and daughter differed by 39 years. In the second kindred, different phenotypes were also reported and earlier ages of onset were associated with 129 heterozygosis. No differences were associated with apoE genotype. In these kindreds, the codon 129 polymorphism could not explain the clinical variability and 129 heterozygosis was associated with earlier disease onset. Neuropathological examination in two patients confirmed the presence of typical plaques and PrPsc immunopositivity.

RESUMO A doença de Gerstmann-Sträussler-Scheinker é uma doença priônica genética, cuja mutação mais frequente é p.Pro102Leu. Descrevem-se dados clínicos, moleculares e neuropatológicos de sete indivíduos em duas famílias não relacionadas com p.Pro102Leu. Diferenças notáveis entre os pacientes em relação à idade de início, duração da doença e apresentação clínica foram encontradas. Na primeira família, dois pacientes apresentaram demência rapidamente progressiva e três apresentaram fenótipo de ataxia com idade variáveis de início e duração da doença. Nesta família, a idade de início entre mãe e filha diferiu em 39 anos. Na segunda família, fenótipos diferentes foram observados e idades precoces de início dos sintomas foram associadas à heterozigose no códon 129. Não houve diferença em relação ao genótipo do gene da apoE. O genótipo do códon 129 não foi responsável pela variabilidade clínica; heterozigose no códon 129 esteve associada ao início precoce da doença. O exame neuropatológico em dois pacientes confirmou presença de placas típicas e imunohistoquímica para PrPsc.

Codon 129 polymorphism of prion protein gene in is not a risk factor for Alzheimer's disease / Polimorfismo do codon 129 do gene da proteina prionica nao e fator de risco para doenca de Alzheimer

Interaction of prion protein and amyloid-b oligomers has been demonstrated recently. Homozygosity at prion protein gene (PRNP) codon 129 is associated with higher risk for Creutzfeldt-Jakob disease. This polymorphism has been addressed as a possible risk factor in Alzheimer disease (AD). Objective To describe the association between codon 129 polymorphisms and AD. Methods We investigated the association of codon 129 polymorphism of PRNP in 99 AD patients and 111 controls, and the association between this polymorphism and cognitive performance. Other polymorphisms of PRNP and additive effect of apolipoprotein E gene (ApoE) were evaluated. Results Codon 129 genotype distribution in AD 45.5% methionine (MM), 42.2% methionine valine (MV), 12.1% valine (VV); and 39.6% MM, 50.5% MV, 9.9% VV among controls (p>0.05). There were no differences of cognitive performance concerning codon 129. Stratification according to ApoE genotype did not reveal difference between groups. Conclusion Codon 129 polymorphism is not a risk factor for AD in Brazilian patients.

Polimorfismo do códon 129 do gene da proteína priônica não é fator de risco para doença de Alzheimer A interação entre proteína priônica e oligômeros b-amiloide foi demonstrada recentemente. Homozigose no códon 129 do gene da proteína priônica (PRNP) é fator de risco para doença de Creutzfeldt-Jakob. Este polimorfismo foi estudado como possível fator de risco para doença de Alzheimer (DA). Objetivo Estudar uma possível associação entre o polimorfismo do códon 129 e DA. Métodos Foram investigados 99 pacientes com DA e 111 controles em relação ao polimorfismo do códon 129 e sua associação com desempenho cognitivo. Foram pesquisados outros polimorfismos do PRNP e efeito aditivo do gene da apolipoproteína E (ApoE). Resultados Distribuição no códon 129: 45,5% metionina (MM), 42,2% metionina valina (MV), 12,1% valina (VV) nos pacientes com DA; e 39,6% MM, 50,5% MV, 9,9% VV, nos controles (p >0.05). Não houve diferença no desempenho cognitivo em relação ao códon 129. Estratificação pelo genótipo do ApoE não mostrou diferença entre grupos. Conclusão Polimorfismo do códon 129 não é fator de risco para DA em pacientes brasileiros.

Creutzfeldt-Jakob disease associated with a missense mutation at codon 200 of the prion protein gene in Brazil.

Genetic Creutzfeldt-Jakob disease (gCJD) represents less than 15% of CJD cases, and its clinical picture may be either indistinguishable from that of sporadic CJD (sCJD) or be atypical, usually with younger onset and longer duration. We report a case of 59-year old Brazilian man who presented rapidly progressive cognitive decline and cerebellar ataxia. EEG revealed periodic activity. A brother and a cousin of the patient had CJD. A point mutation at codon 200 (E200K) of the prion protein gene (PRNP) was found and death occurred 11 months after onset of symptoms. Autopsy was not performed. The clinical presentation of gCJD associated with E200K, which is the most frequent PRNP mutation, is quite similar to sCDJ. This is the first report of E200K mutation in Brazil, and it is possible that a more systematic search for its occurrence may show it to be relatively frequent in Brazil.

A forma genética da doença de Creutzfeldt-Jakob (gDCJ) representa aproximadamente 15% dos casos de DCJ e o quadro clínico pode ser indistinguível do observado na forma esporádica (eDCJ) ou pode ser atípico, geralmente com início precoce e maior sobrevida. Relatamos o caso de paciente do sexo masculino, 59 anos, que apresentou declínio cognitivo rapidamente progressivo associado a ataxia cerebelar. EEG revelou atividade periódica. DCJ havia sido diagnosticada no irmão e prima do paciente. A avaliação genética evidenciou mutação de ponto no códon 200 (E200K). Óbito ocorreu 11 meses após o início dos sintomas. Não foi realizada autópsia. O quadro clínico da gDCJ associada a E200K é semelhante ao da eDCJ, sendo esta a mutação mais freqüente no gene da proteína prion (PRNP). Este é o primeiro relato da mutação E200K no Brasil, e é possível que a pesquisa rotineira de mutações no PRNP possa identificar maior freqüência desta mutação em nosso meio.

Prion diseases are undercompulsory notification in Brazil: Surveillance of cases evaluated by biochemicaland/or genetic markers from 2005 to 2007.

The emergence of the new variant of Creutzfeldt-Jakob disease (vCJD) in the United Kingdom has raised concerns over the risks of this prion disease in other parts of the world. Since 2005, human prion diseases have been under compulsory notification in Brazil. It is well known that some polymorphisms within the cellular prion gene (PRNP) have been associated to a higher susceptibility to sporadic CJD (sCJD) and vCJD. OBJECTIVES: To describe the first notified cases and to evaluate the presence of mutations and polymorphisms of the PRNP in these cases. METHODS: Thirty-five notified cases were evaluated by clinical, auxiliary exams and biochemical and/or genetic tests and classified according to the World Health Organization criteria for CJD. A control group (N=202) was included for the purpose of comparing the genetic analyses. RESULTS: Twenty seven cases (74%) were classified as possible sCJD while 51% fulfilled the criteria for probable sCJD. Brain tissue analysis was available in three cases, where two were classified as definite sCJD and one as unconfirmed sCJD. Mutation of the PRNP was not found, and regarding the codon 129 polymorphism, valine in both alleles (Val129Val) was more frequent in patients than in the control group (OR=4.98; 1.55-15.96; p=0.007) when all possible cases were included, but not when only probable cases were considered. CONCLUSIONS: Our data did not show correlation of PRNP polymorphisms with probable sCJD cases. It is necessary to work toward notification of all cases of possible CJD in Brazil and to increase the rate of definitive diagnoses.

O aparecimento da nova variante da doença de Creutzfeldt-Jakob (vDCJ) na Grã-Bretanha causou preocupações quanto aos riscos de doenças por príons em outras partes do globo. Desde 2005, doenças humanas por príons são de notificação compulsória no Brasil. É bem conhecido que alguns polimorfismos do gene da proteína príon celular (PRNP) têm sido associados a maior susceptibilidade a DCJ esporádica (DCJe) e a vDCJ. OBJETIVOS: Descrever os primeiros casos notificados e avaliar a presença de mutações e polimorfismos do PRNP nesses casos. MÉTODOS: 35 casos notificados foram avaliados clinicamente, mediante exames complementares, testes bioquímicos e/ou genéticos e classificados de acordo com os critérios de DCJ da Organização Mundial de Saúde. Grupo controle (N=202) foi incluído para comparação dos dados da análise genética. RESULTADOS: 27 casos (74%) foram classificados como possível DCJe, dos quais 51% preencheram critérios para provável DCJe. Exame neuropatológico do encéfalo foi realizado em apenas 3 casos, dos quais 2 foram classificados como DCJe definida e um como DCJe não confirmada. Mutações do PRNP não foram encontradas e, com respeito ao polimorfismo do códon 129, valina em ambos os alelos (Val129Val) foi mais freqüente em pacientes do que em controles (OR=4,98; 1,55-15,96; p=0,007) quando todos os casos foram investigados, mas não quando apenas casos prováveis foram incluídos. CONCLUSÕES: Nossos dados não mostram correlação dos polimorfismos do PRNP com provável DCJe. É necessário ampliar a notificação de todos os casos de possível DCJ no Brasil e o diagnóstico definitivo.

Papel de prion celular em modelos experimentais de convulsão e detecção de polimorfismos do gene PRNP em pacientes portadores de epilepsias / The role of cellular prion in models of experimental seizure and evaluation of PRNP gene polymorphisms in patients with epilepsy

Prion celular (PrPc) é uma glicoproteína expressa em neurônios e nas células da glia. É muito conservada entre as espécies e sua função celular tem sido intensamente estudada nas últimas décadas. Nosso grupo mostrou que PrPc é capaz de promover adesão e diferenciação neuronais e proteger contra morte celular, através de sua associação a laminina e a STI1. No presente trabalho avaliamos a sensibilidade aos agentes convulsivantes ácido caínico (KA) e pentilenotetrazol (PTZ) em diferentes linhagens de animais knockout e transgênicos para PrPc... A maior sensibilidade foi observada tanto nos animais que não expressam a proteína desde o período embrionário quanto naqueles onde o gene de PrPc foi desligado apenas nos neurônios no período pós-natal, indicando que este fenótipo é causado por uma disfunção neuronal e não por um déficit de desenvolvimento. A presença de apenas uma cópia do gene de PrPc foi capaz de reverter o baixo limiar para convulsão dos animais knockout, enquanto que a superexpressão de PrPc levou a uma alta resistência às convulsões induzidas farmacologicamente... A plausibilidade biológica destes resultados levou-nos a investigar prevalência de variantes alélicas no gene que codifica PrPc (PRNP) em pacientes com epilepsias focais e generalizadas primárias e comparar com controles hígidos. Para isso, validamos a padronização da técnica de DHPLC (cromatografia de fase líquida denaturante) que foi capaz de detectar adequadamente a presença de polimorfismos do gene PRNP em todas as amostras estudadas. A análise preliminar mostrou que há uma maior freqüência do polimorfismo para valina em homozigose no códon 129 entre pacientes do que nos controles. Uma análise detalhada incluindo a estratificação dos pacientes de acordo com o diagnóstico preciso das síndromes epilépticas bem como a correlação do genótipo e variáveis clínicas e demográficas é um ponto a ser investigado futuramente (AU)

Cellular prion protein (PrPc) is a glycoprotein expressed in neurons and glia. It is highly conserved among species and its function is being consistently studied in the last decades. Our group showed that PrPc can promote neuronal adhesion and differentiation and protects against cell death through its association with laminin and STI1. In the present study, we evaluated the sensibility of different Prnp knockout and transgenic mice overexpressig PrPc , to seizures induced by Kainic acid (KA) and Pentylenetetrazol (PTZ). The absence of PrPc leads to a higher sensibility to seizures induced by these two drugs despite of the animal genetic background. The elevated sensibility was observed both in the animals that do not express the protein since the embryonic period as well as in those where the PrPc was switched off only in the neurons at the post-natal period. Thus, indicating that this phenotype is caused by a neuronal dysfunction and not by a development deficit. The presence of just one Prnp allele was capable of reverting de lower seizure threshold observed in Prnp knockout mice, whereas PrPc overexpression leads to a higher resistance to pharmacological-induced seizures. Therefore, the seizure threshold seems to be directly associated to PrPc cellular concentrations. The biological relevance of these results leads us to investigate de presence of PRNP allelic variants in patients with different forms of epilepsy. Firstly, we validated the DHPLC (Denaturing High Performance Liquid chromatography) technique that was able to efficiently detect the PRNP polymorphisms in all samples that were evaluated. The preliminary analysis demonstrated a higher frequency of valine homozygozity at códon 129 when patients were compared to controls. A more detailed evaluation including patients diagnosis, clinical and demographic parameters will be performed in order to correlate them with PRNP variant alleles (AU)