Analysis of a cell model of neurodegeneration induced by herpes simplex virus 1 and oxidative stress. Implication of the lysosomal pathway
- Autores: Hernike Kristen
- Directores de la Tesis: María Jesús Bullido Gómez -Heras (dir. tes.), Jesús Aldudo Soto (dir. tes.)
- Lectura: En la Universidad Autónoma de Madrid ( España ) en 2017
- Idioma: inglés
- Número de páginas: 140
- Tribunal Calificador de la Tesis: Jesús Ávila de Grado (presid.), Lourdes Ruiz Desviat (secret.), Ángel Cedazo Minguez (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: Biblos-e Archivo
- Resumen
Alzheimer’s disease (AD), the single most common cause of dementia, is characterized by massive neuronal damage leading to cerebral atrophy and the loss of cognitive function. Most AD cases (˃95%) are sporadic. Sporadic AD is a highly complex disease for which neither the causal agent(s) nor the molecular mechanisms behind are well known. Among the environmental risk factors, persistent brain infections, particularly those induced by Herpes simplex virus type 1 (HSV-1), seem to play a key role in AD pathogenesis. Another factor is oxidative stress (OS), intimately linked to aging and, therefore, thought to be crucial to the onset and development of the disease. Our group works with both factors to simulate the sporadic form of AD in vitro. The objective of the present study was the identification of genes and pathways associated with AD to provide novel diagnostic tools predicting the risk and/or the progression of the symptoms, and to establish possible therapeutic targets for the disease. Gene expression studies of the human neuroblastoma cell line SK-N-MC have identified a set of OS-regulated genes in infected cells and in cells harbouring APP with the Swedish mutation (APPswe), a cell model of familial AD. Analysis of these genes revealed that the main pathway altered was the lysosomal system suggesting that the interaction of OS with both HSV-1 and APPswe affects lysosomal function. These data support earlier findings and those of other authors highlighting the role of lysosomal pathway in early stages of AD neurodegeneration. To strengthen this hypothesis, we focused on the lysosomal pathway in our cell models and found that HSV-1 infection and OS led to an increase of lysosomal content, decreased activity of several lysosomal hydrolases, inhibition of the endocytosis-mediated degradation of the EGF receptor, and accumulation of intracellular cholesterol. Taken together, these results confirm that the lysosomal pathway is severely impaired. The lysosomal-associated membrane protein 2 (LAMP2) gene was one of the most strongly modulated ones in the differential expression analysis. In addition, LAMP2 has been functionally involved in the export of cholesterol out of lysosomes and in the final stages of autophagy. Both processes are essential for lysosome function and have been reported to be deeply altered in AD. All these evidences point to LAMP2 as a strong candidate to mediate the lysosomal alterations observed in our models. Indeed, the case/control studies revealed LAMP2 genetic variants to be associated with AD risk suggesting that LAMP2 is involved in the disease. To study the role of this candidate in the neurodegenerative events induced by HSV-1, human neuroblastoma cell lines with a stable knockdown for LAMP2 were generated in-house and two additional murine LAMP2-deficient cell lines—MEFs and N2a—were used. LAMP2 deficiency induced a less effective HSV-1 infection in both cell lines suggesting a functional role of LAMP2 in viral cycle. Preliminary results indicate that the absence of LAMP2 does not affect HSV-1-induced neurodegenerative events like tau phosphorylation, accumulation of intracellular Aβ42 and inhibition of Aβ secretion. In conclusion, the results of the current project point to alterations in the lysosomal pathway as a potential common pathogenic mechanism underlying the different forms of AD (familial and sporadic) and suggest that pharmacological modulation of this pathway might be beneficial for AD.
