Serine 129 Phosphorylation Reduces the Ability of α-Synuclein to Regulate Tyrosine Hydroxylase and Protein Phosphatase 2A in Vitro and in Vivo

Abstract

α-Synuclein (a-Syn), a protein implicated in Parkinson disease, contributes significantly to dopamine metabolism. a-Syn binding inhibits the activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. Phosphorylation of TH stimulates its activity, an effect that is reversed by protein phosphatase 2A (PP2A). In cells, a-Syn overexpression activates PP2A. Here we demonstrate that a-Syn significantly inhibited TH activity in vitro and in vivo and that phosphorylation of a-Syn serine 129 (Ser-129) modulated this effect. In MN9D cells, a-Syn overexpression reduced TH serine 19 phosphorylation (Ser(P)-19). In dopaminergic tissues from mice overexpressing human a-Syn in catecholamine neurons only, TH-Ser-19 and TH-Ser-40 phosphorylation and activity were also reduced, whereas PP2A was more active. Cerebellum, which lacks excess a-Syn, had PP2A activity identical to controls. Conversely, a-Syn knock-out mice had elevated TH-Ser-19 phosphorylation and activity and less active PP2A in dopaminergic tissues. Using an a-Syn Ser-129 dephosphorylation mimic, with serine mutated to alanine, TH was more inhibited, whereas PP2A was more active in vitro and in vivo. Phosphorylation of a-Syn Ser-129 by Polo-like-kinase 2 in vitro reduced the ability of a-Syn to inhibit TH or activate PP2A, identifying a novel regulatory role for Ser-129 on a-Syn. These findings extend our understanding of normal a-Syn biology and have implications for the dopamine dysfunction of Parkinson disease.

Authentically Phosphorylated α-Synuclein at Ser129 Accelerates Neurodegeneration in a Rat Model of Familial Parkinson's Disease

“…These findings may be explainable by an idea that the rapid elevation of Ser129-phosphorylated ␣-syn monomers causes transient damage to dopaminergic neurons in an aggregation-independent manner. Although the normal function of Ser129-phosphorylated ␣-syn remains unclear, Ser129 phosphorylation is reported to reduce the ability of ␣-syn to regulate the tyrosine hydroxylase activity (Lou et al, 2010). The transient damage of Ser129-phosphorylated ␣-syn may be associated with its function in dopamine metabolism.…”

Neuroprotective and Anti-inflammatory Properties of a Coffee Component in the MPTP Model of Parkinson's Disease

“…Nevertheless, altered PP2A methylation by MPP + and its prevention by EHT demonstrated in cultured cells likely contributes to the changes in the inflammatory response seen in vivo as PP2A is intimately involved in inflammatory responses [36]. Additionally, normalization of PP2A function has been hypothesized to be relevant in relation to modulation of tyrosine hydroxylase function [37,38].…”

Mimicking Phosphorylation at Serine 87 Inhibits the Aggregation of Human α-Synuclein and Protects against Its Toxicity in a Rat Model of Parkinson's Disease

“…axonal transport (pS129: McFarland et al, 2008;Lou et al, 2010;Wu et al, 2011), and degradation (pS129: Chau et al, 2009;Machiya et al, 2010), as well as its own aggregation (pS87: Waxman and Giasson, 2008;Paleologou et al, 2010;pS129: Smith et al, 2005, Paleologou et al, 2008 and toxicity (pS129: Sugeno et al, 2008;Kragh et al, 2009). Human ␣-syn within LBs is phosphorylated at S129 and S87, and several groups have reported significant increases in pS87 and pS129 levels in patients with AD, LBD, and MSA (pS129; Fujiwara et al, 2002, Anderson et al, 2006) (pS87; (Paleologou et al, 2010) as well as in Tg mice and rat models of synucleinopathies (pS129: Kahle et al, 2002;Zhou et al, 2008;Khandelwal et al, 2010).…”