α‐Synuclein up‐regulates expression of caveolin‐1 and down‐regulates extracellular signal‐regulated kinase activity in B103 neuroblastoma cells: role in the pathogenesis of Parkinson's disease

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Abstract
α‐Synuclein accumulation plays an important role in the pathogenesis of Lewy body disease (LBD) and Parkinson's disease (PD). Although the mechanisms are not yet clear, it is possible that dysregulation of the extracellular signal‐regulated kinase (ERK) might play a role. As caveolins form scaffolds onto which signaling molecules such as ERK can assemble, we propose that signaling alterations associated with α‐synuclein accumulation and neurodegeneration, might be mediated via caveolae. Therefore, the objective of the present study was to investigate the potential contribution of alterations in the caveolar system in mediating α‐synuclein effects on the ERK signaling pathway. For this, synuclein‐transfected B103 neuroblastoma cells were used as a model system. In this cell line, caveolin‐1 expression was up‐regulated, whereas, ERK was down‐regulated. ERK was weakly but consistently co‐immunoprecipitated with α‐synuclein but caveolin‐1 did not co‐immunoprecipitate with α‐synuclein. Moreover, treatment of α‐synuclein‐ overexpressing cells with caveolin‐1 antisense oligonucleotides resulted in stimulation of ERK activity, with amelioration of the neuritic alterations. Transduction of α‐synuclein‐overexpressing cells, with an adenoviral vector directing the expression of ERK, resulted in suppression of caveolin‐1 expression and re‐establishment of the normal patterns of neurite outgrowth. These results suggest that α‐synuclein may also interfere with ERK signaling by dysregulating caveolin‐1 expression. Thus, the caveolin‐1/ERK pathway could be a therapeutic target for the α‐synuclein‐related neurodegenerative disorders.