The role of Synphilin-1A/PPP1 complex in Lewy bodies formation

• Autor(a) principal: Fernandes, Emanuel Ferreira
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/12488
• topic: Biomedicina; Doença de Parkinson; Fosfatases

One of the major Parkinson’s disease hallmarks is the development of cytoplasmic inclusions, termed Lewy bodies, mainly within surviving neurons in the brainstem of affected patients. Many proteins have been identified in the Lewy bodies, but their formation mechanism remains unclear. Among the proteins already identified in the Lewy bodies are synphilin-1, a α-synucleininteracting protein, and synphilin-1A, a synphilin-1 splice variant. Synphilin-1 and synphilin-1A have been considered key elements in Parkinson’s disease as their overexpression in human embryonic kidney 293 cells, with or without α-synuclein, leads to the formation of Lewy body-like cytoplasmic inclusions. Therefore, efforts have been made to clarify the regulatory mechanisms behind synphilin-1 and synphilin-1A aggregation as a means to uncover new aspects of Lewy bodies formation. Although kinases able to phosphorylate synphilin-1 have been described, there are no specific data concerning the phosphatases responsible for its dephosphorylation. This gap was filled with the identification of synphilin-1A as a novel phosphoprotein phosphatase 1-interacting protein in human brain, through yeast two hybrid. Hence, in the present work, the physiological role of synphilin-1A/phosphoprotein phosphatase 1 complex is studied, being demonstrated the ability of synphilin-1A to specifically target phosphoprotein phosphatase 1 to inclusion bodies, using immunofluorescence experiments. Moreover, the consequences of disrupting this interaction are explored using a synphilin-1A mutant unable to interact with phosphoprotein phosphatase 1, revealing an enhancement of synphilin-1A aggregative properties. Also, the ability of wild type synphilin-1A and the mutant form to produce aggresomes upon overexpression and without proteasome inhibition is addressed but the results are unclear, does not allowing the classification of the inclusions documented in this work as aggresomes. All together, these results suggest that synphilin-1A is able to affect phosphoprotein phosphatase 1 targeting within cells, being inclusion bodies formation dependent and, most specifically, controlled by phosphoprotein phosphatase 1 activity. It is postulated that decreased phosphoprotein phosphatase 1 recruitment to inclusion bodies produces hyperphosphorylated states that favor protein aggregation.