Department of Pharmacological Sciences, Elan Pharmaceuticals, South San Francisco, CA 94080, USA.
Department of Pharmacological Sciences, Elan Pharmaceuticals, South San Francisco, CA 94080, USA.
Neuroscience. 2014 Jan 3;256:72-82. doi: 10.1016/j.neuroscience.2013.09.061. Epub 2013 Oct 12.
α-Synuclein is the major component of Lewy bodies. α-Synuclein phosphorylated at Ser 129 (Phospho-α-Syn) is the most common synuclein modification observed in Parkinson's disease pathology and transgenic animal models. Polo-like kinase 2 (PLK2) was previously proposed as an important kinase in α-synuclein phosphorylation at Ser129. To better understand the role of PLK2 in α-synuclein phosphorylation in vivo, we further evaluated the effect of PLK2 genetic knockdown and pharmacological inhibition on Phospho-α-Syn levels in different brain regions of PLK2 knockout (KO), heterozygous (Het) and wild-type (WT) mice. Whereas PLK2 knockdown had no effect on Total-α-synuclein brain levels, it resulted in a gene-dosage dependent, albeit incomplete, reduction of endogenous Phospho-α-Syn levels in all brain regions investigated. No compensatory induction of other α-synuclein kinases (PLK3, casein kinase-2, G-protein-coupled receptor kinase 5 (GRK5) and GRK6) was observed at the mRNA level in the PLK2 KO mouse brain. To determine whether increased activity of another PLK family member is responsible for the residual Phospho-α-Syn levels in the PLK2 KO mouse brain, the pan-PLK inhibitor BI 2536 was tested in PLK2 KO mice. Whereas BI 2536 reduced Phospho-α-Syn levels in WT mice, it did not further reduce the residual endogenous Phospho-α-Syn levels in PLK2 KO and Het mice, suggesting that a kinase other than PLK1-3 accounts for the remaining PLK inhibitor-resistant pool in the mouse brain. Moreover, PLK3 KO in mice had no effect on both Total- and Phospho-α-Syn brain levels. These results support a significant role for a PLK kinase in phosphorylating α-synuclein at Ser129 in the brain, and suggest that PLK2 is responsible for this activity under physiological conditions.
α-突触核蛋白是路易小体的主要成分。在帕金森病病理学和转基因动物模型中，最常见的突触核蛋白修饰是丝氨酸 129 磷酸化的α-突触核蛋白（Phospho-α-Syn）。以前曾提出 Polo 样激酶 2（PLK2）是α-突触核蛋白丝氨酸 129 磷酸化的重要激酶。为了更好地理解 PLK2 在体内α-突触核蛋白磷酸化中的作用，我们进一步评估了 PLK2 基因敲低和药理学抑制对 PLK2 敲除（KO）、杂合子（Het）和野生型（WT）小鼠不同脑区 Phospho-α-Syn 水平的影响。虽然 PLK2 敲低对总α-突触核蛋白脑水平没有影响，但它导致所有研究脑区的内源性 Phospho-α-Syn 水平呈基因剂量依赖性但不完全降低。在 PLK2 KO 鼠脑中，未观察到其他α-突触核蛋白激酶（PLK3、酪蛋白激酶 2、G 蛋白偶联受体激酶 5（GRK5）和 GRK6）的代偿性诱导。为了确定 PLK 家族的另一个成员的活性增加是否导致 PLK2 KO 鼠脑中残留的 Phospho-α-Syn 水平，我们在 PLK2 KO 小鼠中测试了泛 PLK 抑制剂 BI 2536。虽然 BI 2536 降低了 WT 小鼠中的 Phospho-α-Syn 水平，但它并没有进一步降低 PLK2 KO 和 Het 小鼠中残留的内源性 Phospho-α-Syn 水平，这表明除了 PLK1-3 之外，还有其他激酶负责在鼠脑中存在剩余的 PLK 抑制剂抗性池。此外，PLK3 KO 对小鼠的总和 Phospho-α-Syn 脑水平均无影响。这些结果支持 PLK 激酶在大脑中磷酸化α-突触核蛋白丝氨酸 129 中起重要作用，并表明在生理条件下 PLK2 负责该活性。
