RESUMO
The paradoxical appearance of aggregated α-synuclein (αsyn) in naive transplanted embryonic stem cells in Parkinson's disease (PD) brains has recently been reported, highlighting the possibility of neuron to neuron transmission of αsyn in PD. Here, we demonstrate in a cellular model the presence of αsyn oligomers in the extracellular space, their uptake by neurons, retrograde axonal transport to cell soma, and detrimental effects on neighboring cells. Moreover, we demonstrate that Hsp70 chaperones αsyn in the extracellular space and reduces extracellular αsyn oligomer formation and related toxicity. These novel findings provide evidence that extracellular αsyn oligomers may represent a crucial player in the propagation of pathology in PD, with their modulation by Hsp70 representing a potential new target for therapeutic interventions.
Assuntos
Proteínas de Choque Térmico HSP70/metabolismo , Neurônios/fisiologia , Transmissão Sináptica/fisiologia , alfa-Sinucleína/metabolismo , Animais , Axônios/metabolismo , Benzoquinonas/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Técnicas de Cocultura , Meios de Cultivo Condicionados/farmacologia , Dependovirus/genética , Espaço Extracelular/metabolismo , Vetores Genéticos/genética , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HEK293 , Proteínas de Choque Térmico HSP70/antagonistas & inibidores , Proteínas de Choque Térmico HSP70/genética , Humanos , Lactamas Macrocíclicas/farmacologia , Luciferases/genética , Luciferases/metabolismo , Camundongos , Neurônios/citologia , Neurônios/metabolismo , Multimerização Proteica , Transfecção , alfa-Sinucleína/química , alfa-Sinucleína/genéticaRESUMO
Tau protein is present in six different splice forms in the human brain and interacts with microtubules via either 3 or 4 microtubule binding repeats. An increased ratio of 3 repeat to 4 repeat isoforms is associated with neurodegeneration in inherited forms of frontotemporal dementia. Tau over-expression diminishes axonal transport in several systems, but differential effects of 3 repeat and 4 repeat isoforms have not been studied. We examined the effects of tau on mitochondrial transport and found that both 3 repeat and 4 repeat tau change normal mitochondrial distribution within the cell body and reduce mitochondrial localization to axons; 4 repeat tau has a greater effect than 3 repeat tau. Further, we observed that the 3 repeat and 4 repeat tau cause different alterations in retrograde and anterograde transport dynamics with 3 repeat tau having a slightly stronger effect on axon transport dynamics. Our results indicate that tau-induced changes in axonal transport may be an underlying theme in neurodegenerative diseases associated with isoform specific changes in tau's interaction with microtubules.
Assuntos
Transporte Axonal/fisiologia , Mitocôndrias/fisiologia , Neurônios/fisiologia , Tauopatias/fisiopatologia , Proteínas tau/genética , Proteínas tau/metabolismo , Animais , Linhagem Celular Tumoral , Córtex Cerebral/citologia , Glioma , Proteínas de Fluorescência Verde/genética , Humanos , Camundongos , Técnicas Analíticas Microfluídicas , Neurônios/citologia , Transporte Proteico/fisiologia , Sequências Repetitivas de Ácido Nucleico/fisiologia , Tauopatias/genética , Tauopatias/metabolismo , TransfecçãoRESUMO
The ability of the low density lipoprotein receptor-related protein (LRP) to form homo-dimers was studied in mouse neuroblastoma and human neuroglioma cells as well as in primary cortical cultures from adult mouse brain. Homo-dimerization of LRP light chain (LC) was shown by several methods including co-immunoprecipitation, fluorescence lifetime imaging microscopy, and bimolecular fluorescence complementation assay. The requirement of intact NPXY motifs of LRP LC for homo-dimerization was ruled out by co-immunoprecipitation assay.