RESUMO
FE65 is an adaptor protein that interacts with the cytoplasmic tail of the amyloid precursor protein (APP). In cultured non-neuronal cells, the formation of the FE65-APP complex is a key element for the modulation of APP processing, signalling and beta-amyloid (Abeta) production. The functions of FE65 in vivo, including its role in the metabolism of neuronal APP, remain to be investigated. In this study, transgenic mice expressing human FE65 were generated and crossbred with APP transgenic mice, known to develop Abeta deposits at 6 months of age. Compared with APP mice, APP/FE65 double transgenic mice exhibited a lower Abeta accumulation in the cerebral cortex as demonstrated by immunohistochemistry and immunoassay, and a lower level of APP-CTFs. The reduced accumulation of Abeta in APP/FE65 double transgenics, compared with APP mice, could be linked to the low Abeta42 level observed at 4 months of age and to the lower APP-CTFs levels. The present work provides evidence that FE65 plays a role in the regulation of APP processing in an in vivo model.
Assuntos
Peptídeos beta-Amiloides/antagonistas & inibidores , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/biossíntese , Precursor de Proteína beta-Amiloide/genética , Proteínas do Tecido Nervoso/biossíntese , Proteínas Nucleares/biossíntese , Peptídeos beta-Amiloides/genética , Animais , Encéfalo/metabolismo , Regulação da Expressão Gênica/fisiologia , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares/genética , Processamento de Proteína Pós-Traducional/genéticaRESUMO
Several novel transgenic mouse models expressing different mutant APPs in combination with mutant PS1 have been developed. These models have been analyzed to investigate the formation and progressive alterations of dystrophic neurites (DNs) in relation to Abeta deposits. In the most aggressive model, Abeta deposits appear as early as 2.5 months of age. Maturation of DNs was qualitatively quite similar among models and in some respect reminiscent of human AD pathology. From the onset of deposition, most if not all Abeta deposits were decorated with a high number of APP-, ubiquitin-, and MnSOD-immunoreactive DNs. Phosphorylated Tau DNs, however, appeared at a much slower rate and were more restricted. Mitochondrial dysfunction markers were observed in DNs: the frequency and the density per deposit of DNs accumulating cytochrome c, cytochrome oxidase 1, and Bax progressively increased with age. Later, the burden of reactive DNs was reduced around large compact/mature deposits. In addition, the previously described phenomenon of early intraneuronal Abeta accumulation in our models was associated with altered expression of APP protein as well as oxidative and mitochondrial stress markers occasionally in individual neurons. The present study demonstrates that oxidative and mitochondrial stress factors are present at several phases of Abeta pathology progression, confirming the neuronal dysfunction in APP transgenic mice.
Assuntos
Precursor de Proteína beta-Amiloide/genética , Proteínas de Membrana/genética , Neuritos/patologia , Placa Amiloide/patologia , Animais , Humanos , Imunoensaio , Imuno-Histoquímica , Medições Luminescentes , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Transgênicos , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Mutação/genética , Placa Amiloide/genética , Plasmídeos/genética , Presenilina-1 , Estresse Fisiológico/patologia , Superóxido Dismutase/metabolismo , Fatores de Tempo , Proteínas tau/metabolismoRESUMO
Most early-onset cases of familial Alzheimer's disease (FAD) are linked to mutations in two related genes, ps1 and ps2. FAD-linked mutant PS1 alters proteolytic processing of the amyloid precursor protein and increases vulnerability to apoptosis induced by various cell stresses. In transfected cell lines, mutations in ps1 decrease the unfolded-protein response (UPR), which is the response to the increased amounts of unfolded proteins that accumulate in the endoplamic reticulum (ER), indicating that these mutations may increase vulnerability to ER stress by altering the UPR signalling pathway. Here we report that, in primary cultured neurons from cortices of transgenic mice, overexpression of mutated PS1 (M146L mutation) but not PS1 wild-type (wt) enhanced spontaneous neuronal apoptosis that involved oxidative stress and caspase activation. In PS1M146L cultures, neurons displaying immunoreactivity for human PS1 were threefold more vulnerable to spontaneous apoptosis than the overall neuronal population. In addition, PS1M146L transgenic neurons were more sensitive to apoptosis induced by various stresses, including two ER-Golgi toxins, nordihydroguaiatric acid and brefeldin A (also known to induce UPR), as well as staurosporine. In contrast, PS1 wt transgenic neurons were resistant to apoptosis induced by Golgi-ER toxins but displayed a comparable vulnerability to staurosporine. Our study demonstrates that, as previously reported, overexpression of FAD-linked mutant PS1 enhances neuronal vulnerability to spontaneous and induced apoptosis. In addition, we show that this vulnerability was correlated with mutant PS1 protein expression and that PS1 wt overexpression selectively prevented ER-Golgi stress-induced apoptosis. These data indicate that PS1 interferes with a specific apoptotic pathway that results from a dysfunction of the ER-Golgi compartment.
