α-Synuclein activation of protein phosphatase 2A reduces tyrosine hydroxylase phosphorylation in dopaminergic cells
α-Synuclein activation of protein phosphatase 2A reduces tyrosine hydroxylase phosphorylation in dopaminergic cells
复制标题
DOI：
10.1242/jcs.02481
复制
发表时间：
2005-08-01
影响因子：
4
通讯作者：
Perez, RG
中科院分区：
文献类型：
--
作者：
Peng, XMM;Tehranian, R;Perez, RG
突触核蛋白是一种丰富的突触前蛋白，与神经元可塑性和神经退行性疾病有关。虽然α -synuclein的功能尚未完全阐明，但我们发现α -synuclein通过结合并抑制酪氨酸羟化酶来调节多巴胺的合成，酪氨酸羟化酶是多巴胺合成的限速酶。了解α -突触核蛋白在多巴胺能细胞中的功能应该会增加我们对这种与帕金森病和其他疾病有关的关键蛋白的认识。在此，我们报告了α -突触核蛋白在稳定转染的多巴胺能细胞中减少酪氨酸羟化酶磷酸化和活性的机制。酪氨酸羟化酶的短期调控依赖于蛋白氨基末端调控区域关键丝氨酸残基的磷酸化。其中，Ser40对酪氨酸羟化酶激活和多巴胺合成有重要作用。我们观察到α -突触核蛋白过表达导致MN9D细胞和诱导型PC12细胞Ser40磷酸化降低。Ser40主要被环amp依赖性蛋白激酶PKA磷酸化，几乎完全被蛋白磷酸酶PP2A去磷酸化。因此，我们测量了α -突触核蛋白过表达对我们细胞中PKA和PP2A水平和活性的影响。PKA不受-突触核蛋白的影响。PP2A蛋白水平也没有变化，但PP2A的活性随着α -突触核蛋白的表达而增加。抑制PP2A显著增加Ser40磷酸化，仅在α -synuclein过表达蛋白中，α -synuclein也被发现与PP2A共免疫沉淀。总之，这些数据揭示了α -synuclein和PP2A之间的功能相互作用，导致PP2A激活，并强调了α -synuclein在蛋白质磷酸化中的关键作用。
alpha-Synuclein is an abundant presynaptic protein implicated in neuronal plasticity and neurodegenerative diseases. Although the function of alpha-synuclein is not thoroughly elucidated, we found that alpha-synuclein regulates dopamine synthesis by binding to and inhibiting tyrosine hydroxylase, the rate limiting enzyme in dopamine synthesis. Understanding alpha-synuclein function in dopaminergic cells should add to our knowledge of this key protein, which is implicated in Parkinson's disease and other disorders. Herein, we report a mechanism by which alpha-synuclein diminishes tyrosine hydroxylase phosphorylation and activity in stably transfected dopaminergic cells. Shortterm regulation of tyrosine hydroxylase depends on the phosphorylation of key seryl residues in the amino-terminal regulatory domain of the protein. Of these, Ser40 contributes significantly to tyrosine hydroxylase activation and dopamine synthesis. We observed that alpha-synuclein overexpression caused reduced Ser40 phosphorylation in MN9D cells and inducible PC12 cells. Ser40 is phosphorylated chiefly by the cyclic AMP-dependent protein kinase PKA and dephosphorylated almost exclusively by the protein phosphatase, PP2A. Therefore, we measured the impact of alpha-synuclein overexpression on levels and activity of PKA and PP2A in our cells. PKA was unaffected by alpha-synuclein. PP2A protein levels also were unchanged, however, the activity of PP2A increased in parallel with alpha-synuclein expression. Inhibition of PP2A dramatically increased Ser40 phosphorylation only in alpha-synuclein overexpressors in which alpha-synuclein was also found to co-immunoprecipitate with PP2A. Together the data reveal a functional interaction between alpha-synuclein and PP2A that leads to PP2A activation and underscores a key role for alpha-synuclein in protein phosphorylation.