Publicação
The interplay between alpha-synuclein and ATP13A2 : towards the understanding of the molecular basis of Parkinson’s disease
| Resumo: | Parkinson’s disease (PD) is the most common neurodegenerative disorder with motor impairment. While PD is clinically well characterized, the molecular and cellular basis underlying both the onset and progression of the disorder are still unknown. Gaining deeper knowledge on PD pathophysiology has been hindered by the fact that only a minority of PD patients have a defined genetic cause, with the remaining 90% of the cases being classified as sporadic. Thus far, mutations in more than 20 genes are considered risk factors for developing PD. These PDrelated genes are linked to several distinct intracellular pathways, hardening the quest to pinpoint the exact molecular imbalance responsible for PD onset. One of these pathways, the Endolysosomal, has recently gained notoriety due to its importance in alpha-Synuclein homeostasis (α-Syn). α-Syn is a small protein with unknown function and, perhaps, the most extensively studied in PD context. Several point mutations and gene multiplications in α-Syn gene, SNCA, have been linked to PD and the protein is found in Lewy Bodies (LB), the pathological hallmark of the disease. In the Endolysosomal machinery another PD-associated protein has been under the spotlight: ATP13A2. This protein is a transmembrane ATPase located at the late endosomes and lysosomes, with yet unknown function, that is also present in LB. In the last years important steps have been taken towards understanding the interplay between ATP13A2 and α-Syn, with contradictory results reported. Inarguable though is that ATP13A2 can, at least partially, affect the intracellular fate of α-Syn. Our work confirms that the Endolysosomal pathway plays an important role in α-Syn homeostasis. We start by showing that two proteins members of this pathway, Raba8a and ATP13A2, could alter α-Syn aggregation in a well-established cellular model. Nevertheless, while we found that Raba8a exerts its effect by direct binding to α-Syn, the PD-associated protein ATP13A2 may affect specific cellular mechanisms. We describe that, in human cells, a mutation in ATP13A2, a duplication of 22 base pairs (Dup22), enhances α-Syn aggregation and increases its resistance to proteinase K digestion. The mutated protein could also promote the formation of oligomers and higher α-Syn molecular weight species. In addition, the dynamics between α-Syn and ATP13A2 Dup22 can severely impact cellular homeostasis. Here we report that α-Syn and ATP13A2 Dup22 can be found in a reticular, membranar structure, which we found to be composed by endoplasmic reticulum (ER). This alteration in the ER morphology was correlated with an unmitigated increase in ER stress that culminates with the activation of apoptotic pathways and cell death. Besides ER changes we also identified significant alterations in mitochondria morphology, along with increased susceptibility to oxidative stress. Altogether our work provides novel insights into the effect of Endolysosomal proteins on α-Syn. Additionally we describe that the interaction of two PDassociated proteins, ATP13A2 and α-Syn, may trigger a cascade of deleterious intracellular events that involve ER stress and mitochondria alterations, and ultimately lead to cell death. Most importantly, our findings shed new light on the cellular dyshomeostasis that may underlie the development of PD. |
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| Autores principais: | Fonseca, Tomás Ribeiro da Silva Lopes da, 1987- |
| Assunto: | Alfa-sinucleína Doença de Parkinson Corpos de Lewy Doenças neurodegenerativas Neurociências Teses de doutoramento - 2016 |
| Ano: | 2016 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Parkinson’s disease (PD) is the most common neurodegenerative disorder with motor impairment. While PD is clinically well characterized, the molecular and cellular basis underlying both the onset and progression of the disorder are still unknown. Gaining deeper knowledge on PD pathophysiology has been hindered by the fact that only a minority of PD patients have a defined genetic cause, with the remaining 90% of the cases being classified as sporadic. Thus far, mutations in more than 20 genes are considered risk factors for developing PD. These PDrelated genes are linked to several distinct intracellular pathways, hardening the quest to pinpoint the exact molecular imbalance responsible for PD onset. One of these pathways, the Endolysosomal, has recently gained notoriety due to its importance in alpha-Synuclein homeostasis (α-Syn). α-Syn is a small protein with unknown function and, perhaps, the most extensively studied in PD context. Several point mutations and gene multiplications in α-Syn gene, SNCA, have been linked to PD and the protein is found in Lewy Bodies (LB), the pathological hallmark of the disease. In the Endolysosomal machinery another PD-associated protein has been under the spotlight: ATP13A2. This protein is a transmembrane ATPase located at the late endosomes and lysosomes, with yet unknown function, that is also present in LB. In the last years important steps have been taken towards understanding the interplay between ATP13A2 and α-Syn, with contradictory results reported. Inarguable though is that ATP13A2 can, at least partially, affect the intracellular fate of α-Syn. Our work confirms that the Endolysosomal pathway plays an important role in α-Syn homeostasis. We start by showing that two proteins members of this pathway, Raba8a and ATP13A2, could alter α-Syn aggregation in a well-established cellular model. Nevertheless, while we found that Raba8a exerts its effect by direct binding to α-Syn, the PD-associated protein ATP13A2 may affect specific cellular mechanisms. We describe that, in human cells, a mutation in ATP13A2, a duplication of 22 base pairs (Dup22), enhances α-Syn aggregation and increases its resistance to proteinase K digestion. The mutated protein could also promote the formation of oligomers and higher α-Syn molecular weight species. In addition, the dynamics between α-Syn and ATP13A2 Dup22 can severely impact cellular homeostasis. Here we report that α-Syn and ATP13A2 Dup22 can be found in a reticular, membranar structure, which we found to be composed by endoplasmic reticulum (ER). This alteration in the ER morphology was correlated with an unmitigated increase in ER stress that culminates with the activation of apoptotic pathways and cell death. Besides ER changes we also identified significant alterations in mitochondria morphology, along with increased susceptibility to oxidative stress. Altogether our work provides novel insights into the effect of Endolysosomal proteins on α-Syn. Additionally we describe that the interaction of two PDassociated proteins, ATP13A2 and α-Syn, may trigger a cascade of deleterious intracellular events that involve ER stress and mitochondria alterations, and ultimately lead to cell death. Most importantly, our findings shed new light on the cellular dyshomeostasis that may underlie the development of PD. |
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