Reduction of phosphorylated α-synuclein through downregulation of casein kinase 2α alleviates dopaminergic-neuronal function

Abstract

Among the post-translational modifications of α-synuclein, phosphorylation has been reported to modulate the protein's nuclear localization, gene-expression and cytotoxicity. However, its effect on the functional performance of dopaminergic-neurons is not known. We aimed to evaluate the effect of siRNA-silencing of casein kinase (CK)2α in SH-SY5Y-cells overexpressing A53T α-synuclein, in alleviating phosphorylated α-synuclein serine129 (pSyn-129)-induced changes in intracellular Ca2+ ([Ca2+]i) response to physiological stimuli and vesicular-dopamine release. A53T transfection showed distinct increase in basal pSyn-129 expression with simultaneous nuclear localization, and CK2α siRNA decreased ROS-generation and pSyn-129 levels. A significant reduction was observed in KCl-induced ([Ca2+]i) response and vesicular-dopamine release in the A53T-transfected cells with a corresponding decrease in immunopositive-population of resting-vesicles (VMAT2). CK2α siRNA treatment showed recovery in [Ca2+]i rise with a corresponding upregulation of expression of voltage-gated Ca2+-channels (VGCC) CaV1.3 and CaV2.2 and RyR1 responsible for Ca2+ induced Ca2+ release from ER, VMAT2 expression and vesicular-dopamine release. Thus, using CK2α siRNA to reduce phosphorylation improved cellular-pathology in terms of ROS generation and pSyn-129 levels, as well as functional performance of DA-neuronal cells.