Study of pro-apoptotic protein RTP801 homeostasis and its regulation by NEDD4 in Parkinson's disease
Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons of the Substantia Nigra pars compacta (SNpc) and the presence of cytoplasmic protein inclusions named Lewy Bodies. Current treatments are directed principally to ameliorate the clinical manifestations of the disease rather...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2016 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/398915 |
| Acceso en línea: | http://hdl.handle.net/10803/398915 |
| Access Level: | acceso abierto |
| Palabra clave: | Malalties neurodegeneratives Enfermedades neurodegeneratives Neurodegenerative Diseases Malaltia de Parkinson Enfermedad de Parkinson Parkinson's disease Ubiqüitina Ubicuitina Ubiquitin Ciències de la Salut 616.8 |
| Sumario: | Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons of the Substantia Nigra pars compacta (SNpc) and the presence of cytoplasmic protein inclusions named Lewy Bodies. Current treatments are directed principally to ameliorate the clinical manifestations of the disease rather than suppressing the underlying neuron degeneration and death. This is due, in part, to an incomplete understanding of the pathways that lead to neurodegeneration in PD. RTP801 is induced in cellular and animal models of Parkinson's disease (PD) and is elevated in neuromelanin positive neurons in the Substantia Nigra (SN) of PD patients. In a variety of neuronal systems, RTP801 overexpression or upregulation is sufficient to trigger cell death. This involves a sequential mechanism in which it sequentially inactivates mTOR and survival kinase Akt. RTP801 is a protein with a very short half-life (2-7 minutes), so it should be strictly and dynamically controlled at post-translational level to precisely modulate mTOR pathway. Hence, elucidating which proteins mediate RTP801 degradation would be a stepping-stone to design new therapies to block neurodegeneration. NEDD4, is an E3 ubiquitin ligase highly expressed in mammalian neurons that has been directly linked to PD pathogenesis since it has been reported to promote α-synuclein degradation and to be protective against its toxicity. In this work, we report that NEDD4 contributes to RTP801 protein degradation. We show in neuronal cells that there is a pool of RTP801 degraded via lysosomal pathway. We also demonstrate that both proteins interact and that NEDD4 enhances RTP801 polyubiquitination by preferentially conjugating K63 ubiquitin chains. Importantly, NEDD4 regulates RTP801 protein levels in cultured cells and in a conditional knockout mouse model. We also provide evidence that NEDD4 protects against RTP801 toxicity by mediating its polyubiquitination. Furthermore, NEDD4 levels are decreased in the 6-OHDA PD cellular model and its restoration protects against 6-OHDA-induced cell death by reducing RTP801 protein levels. Moreover, NEDD4 loss of function is toxic in neurons due to RTP801 elevation and the subsequent mTOR/Akt inactivation. A role for NEDD4 in PD is supported by observation of diminished NEDD4 in nigral neurons from postmortem sporadic PD brains. In line with these findings, the NEDD4 signaling inducer NAB2 reduces RTP801 protein levels in control and in 6-OHDA-treated cortical neurons. However, NAB2 is not sufficient to confer protection against 6-OHDA toxicity, because the compound itself represses mTOR signaling pathway compromising cell survival. |
|---|